Roadway water management

Technical guide Roadway water management October 2006 Translate August 2007

The Technical Department for Transport, Roads and Bridges Engineering and Road Safety (Service d'études techniques des routes et autoroutes - Sétra) is a technical department within the Ministry of Transport and Infrastructure. Its field of activities is the road, the transportation and the engineering structures. The Sétra supports the public owner The Sétra supplies State agencies and local communities (counties, large cities and urban communities) with informations, methodologies and tools suited to the specificities of the networks in order to: improve the projects quality; help with the asset management; define, apply and evaluate the public policies; guarantee the coherence of the road network and state of the art; put forward the public interests, in particular within the framework of European standardization; bring an expertise on complex projects. The Sétra, producer of the state of the art Within a very large scale, beyond the road and engineering structures, in the field of transport, intermodality, sustainable development, the Sétra: takes into account the needs of project owners and prime contractors, managers and operators; fosters the exchanges of experience; evaluates technical progress and the scientific results; develops knowledge and good practices through technical guides, softwares; contributes to the training and information of the technical community. The Sétra, a work in partnership The Sétra associates all the players of the French road community to its action: operational services; research organizations; Scientific and Technical Network (Réseau Scientifique et Technique de l'equipement RST), in particular the Public Works Regional Engineering Offices (Centres d'études techniques de l'equipement CETE), companies and professional organizations; motorway concessionary operators; other organizations such as French Rail Network Company (Réseau Ferré de France RFF) and French Waterways Network (Voies Navigables de France - VNF); Departments like the department for Ecology and Sustainable Development The Sétra regularly exchanges its experience and projects with its foreign counterparts, through bilateral co-operations, presentations in conferences and congresses, by welcoming delegations, through missions and expertises in other countries. It takes part in the European standardization commissions and many authorities and international working groups. The Sétra is an organization for technical approval, as an EOTA member (European Organisation for Technical Approvals).

Technical guide Roadway water management This document is the translation of the work "Assainissement routier" published in october 2006 under the reference 0632.

This technical guide on road improvements has been prepared by a working group set up by representatives of the Scientific and Technical Network of the Ministry of Infrastructure and consulting engineers. It was technically validated by (Sétra). Members of the working group: David Gaillard (Sétra), J. Ranchet (DREIF - LREP), Jean Béréterbide (CETE Sud-Ouest), Marc Valin (CETE Nord-Picardie), Jacques Hurtevent (CETE Méditerranée), Alain Costille (DDE (District-level Offices for Infrastructure) 95), Gilles Cartoux (DDE 58), René Marcaud (Sté SILENE), Alain Limandat (SEEE). Editing and layout were carried out by: Marie Odile Cavaillès (Sétra). Serge Criscione (DREIF - LREP), Jacques Hurtevent (CETE Méditerranée), Marc Valin (CETE Nord-Picardie), Bruno Van-Hauwaert (CETE Nord-Picardie) prepared the diagrams. On reading the guide the glossary, in appendix 4.3 gives the definitions of main special terms (marked with *) used; the abbreviations and symbols encountered in the text are clarified in appendix 4.4; bibliographic references: in the text, the numbers in brackets [ ] correspond to the documents listed in the bibliography in appendix 4.6. Collection «Les outils» Sétra 4 September 2007

Contents The Sétra supports the public owner...2 The Sétra, producer of the state of the art...2 The Sétra, a work in partnership...2 Contents... 5 Preamble... 7 1 - Technical design of structures... 8 1.1 - Re-establishment of natural flows (catchment areas < 100 km 2 )... 8 1.1.1 - General principles...9 1.1.2 - Determination of the project flow...11 1.1.3 - Design of hydraulic structures...18 1.1.4 - Maintenance and operation of the hydraulic structures...19 1.2 - Surface drainage of the platform... 20 1.2.1 - General principles...20 1.2.2 - Nature and function of systems...20 1.2.3 - Choice of drainage structures and hydraulic design calculation...26 1.1.4 - Maintenance and operation of the structures [11]...26 1.3 - Road structure drainage... 27 1.3.1 - Definition...27 1.3.2 - Who does what?...27 1.3.3 - Summary of the effects of water on the road...27 1.4 - Controlling road pollution... 27 1.4.1 - Definition...27 1.4.2 - Who does what?...27 1.4.3 - Summary of risks and challenges...28 2 - Sequence of studies... 29 2.1 - Preliminary studies... 29 2.1.1 - Hydraulics*...29 2.1.2 - Protection of Water Resources...29 2.2 - Outline Preliminary Project (APS) studies... 30 2.2.1 - Choice of scales for the plans of the routes studied...30 2.2.2 - Road surface drainage at the Outline Preliminary Project (APS) study stage30 2.3 - Project studies... 33 2.3.1 - Height setting constraints...33 2.3.2 - Validation of the general principles...33 2.4 - Water Law Dossiers (DLE) or water police [police de l eau] dossier... 35 2.4.1 - At the project study stage...35 2.4.2 - At the Outline Preliminary Project (APS) level...35 3 - Study quality approach... 36 3.1 - Notions of process and progression, of inputs, outputs and tasks... 38 3.1.1 - Process...38 3.1.2 - Progression...38 3.1.3 - Required "inputs" and expected "outputs"...39 3.1.4 - Main tasks...39 3.2 - Issuing an order... 41 3.2.1 - General principles...41 Collection «Les outils» Sétra 5 September 2007

3.2.2 - Progression of studies...41 3.3 - Traceability of choices/decisions, archives... 55 3.4 - Validating the production... 55 4 General technical appendices... 56 4.1 - General elements of hydrology... 56 4.1.1 - Rainfall data...56 4.1.2 - Numerical example of application for the calculation of a project flow of a natural catchment area...58 4.2 - Elements of general hydraulics... 65 4.2.1 - On the theory of flows...65 4.2.2 - ABAC design charts for small hydraulic structures for re-establishing natural flows...74 4.2.3 - Constructional arrangements and protection of hydraulic structures...84 4.2.4 - Dimensioning of a hydraulic structure for re-establishing natural flows - application example...86 4.2.5 - Surface drainage of the platform - calculation method...94 4.2.6 - Surface drainage of the platform - hydraulic calculations - application examples 97 4.3 - Glossary... 105 4.4 - Abbreviations and symbols... 108 Abbreviations (French)...108 Symbols...108 4.5 - Table summarizing principle formulae... 110 4.6 - Bibliography (non-exhaustive list)... 112 Technical documents:...112 Regulatory texts:...112 For information...112 Collection «Les outils» Sétra 6 September 2007

Preamble Road construction hydrology covers the re-establishment of natural flows, the drainage of roadways, drainage and the control of road pollution. The recommendation on road improvements of 1982 dealt essentially with the first two fields. The collection of guides "Water and road construction" deals with the protection of water resources and aquatic environments in the context of road infrastructure. A working group made up of hydraulic experts was set up by Sétra to collect up-to-date knowledge in the field of hydrology and take account of environmental protection-related impacts. This work took shape in a guide in three main sections: the technical design of structures; studies; the quality procedure. General technical appendices give calculation examples and ABAC calculation charts to be used. It was devised to meet the needs and expectations of prime contractors. Its primary purpose is as a tool that assists in the design of drainage structures for new road projects and improvement planning studies on existing roads. This guide puts forward a methodological approach to the technical design of structures to re-establish natural run-offs, drain the platform and drain off road use generated pollution. It can also provide assistance in drawing up an improvement project and in applying the quality approach at the study level. In must be noted that this document deals only with the re-establishment of natural flows in small catchment areas (catchment area smaller than 100 square kilometers or so). For larger catchment areas or where there are specific hydraulic problems, a specialist must be consulted. It is for the project designer to co-ordinate the various aspects to be taken into account in the design of structures (road safety, signage, multi-functional structures etc.). The present document includes the aspects of maintenance, operation and management of structures at the project design stage. The chapters dealing with internal drainage and road pollution are summarized in the present document, as these topics are the subject of specific guides, one on drainage and the other on pollution management, to be published by Sétra at the same time as this one. Collection «Les outils» Sétra 7 September 2007

1 - Technical design of structures Roadway water management covers the following aspects: the re-establishment of natural flows, the collection and evacuation of surface water within the footprint of the road, the collection and evacuation of internal water i.e. internal drainage, the management of road pollution. 1.1 - Re-establishment of natural flows (catchment areas < 100 km 2 ) The re-establishment of natural flows consists in ensuring the continuity of surface run-off in catchment areas through which the road passes. This re-establishment must be commensurate with local risks, conditions and requirements (flooding, erosion or sedimentation, durability of the infrastructure, safety of users and respect for the aquatic environment), which should be identified, and must be designed in accordance with the regulations in force. The road can present an obstacle to natural water flows and, conversely, these can cause damage to the road (see diagram No. 1). The hydraulic structures re-establishing natural flows must therefore be correctly sized to limit the risks of flooding and submersion of or damage to the road within acceptable limits, of flooding upstream of the road, of breaches in the road structure. We can distinguish three cases of interaction between a water course and the road: a part of the road line encroaches on the flood plane or high water channel of a significant water course; a specific study is required, which goes beyond the scope of the present document, the road line crosses a water course that is significant or poses specific hydraulic problems; here, too, a study by a specialist is required, the road line crosses a water course with a catchment area not exceeding some hundred square kilometers, with no particular challenges, which is the subject of the present chapter; above this limit, the study requires the intervention of specialists in hydrology, hydraulics and hydrogeomorphology. Initially the water concentration point was downstream of point A The realization of the infrastructure displaced this point upstream of point B Cours d'eau = water course Ouvrage hydraulique de rétablissement=hydraulic structure re-establishing flow Diagram No.1: displacement of the point of concentration of run-off Collection «Les outils» Sétra 8 September 2007

1.1.1 - General principles The hydraulic re-establishment of natural flows is one of the greatest constraints on road projects, especially on the longitudinal section. Consequently, particular attention should be paid to it at the pilot project stage. Apart from the regulatory aspect, which requires checking, the various stages in determining the hydraulic structure to be installed are: the estimation of the project flow as a function of a recurrence interval and an exceptional flow, the dimensioning, selection and setting of the hydraulic structure (checks of upstream water level, flow speeds, free space, hydrological impact and, where required, the free movement of the icthyofauna). Choice of the recurrence interval (T).The recurrence interval, T, to be taken into account must, in each case, be the subject of an analysis setting the infrastructure investment costs against the consequences of an overflow for users, landowners adjacent to the road and the water course, road structures (local and temporary traffic perturbations and risk situations) and, finally, on the natural environment. In all cases, knowledge of the regulations and consultation with the water authorities (water police and the Mission Inter-Service de l Eau [Inter-department Water Mission] (MISE)) will be necessary. In the absence of this type of analysis, it is recommended to adopt the following values for recurrence intervals: under motorways: 100 years, under roads or restored communication links: 100 years, 50 years or even 25 years for catchment areas where floods are limited in time and subject to a low or zero incidence of overflow, depending on the case, roads and motorways in flood zones: the height of the infrastructure must take account of the risks and challenges connected with the flood zone. For each type of infrastructure, the run-off conditions and the effect of an exceptional flood level must be assessed. Upstream water level (H AM ) and speed of flow (Ve) in hydraulic structures The upstream water level must be compatible with the height setting of the infrastructure and the flood risk. In all cases, the upstream water level must not exceed 1.2 times the height of the structure for the project flow for structures with an opening of ð 2 m. The speeds must meet the following criteria with regard to the durability of the structures: concrete structures: 4 m/s, metal structures: 2.5 m/s => see appendix 4.6 [8]. To take account of the fish population, lower speeds must be demonstrated (approximate speed of 1 m/s). If it is impossible to satisfy these conditions, protective arrangements should be considered. Free space (TA) of the hydraulic structure The free space corresponds, strictly speaking, to the free height between the water line and the upper generatrix of the structure (see diagram No. 2). In our case, it is measured with respect to the notional water level ye + H AM 2 For an opening 2.00 m: to be assessed according to the nature of the catchment area. For an opening > 2.00 m: TA of 0.50 to 1.50 m. The fill ratio of the hydraulic structure for the project flow must not exceed 0.75. Collection «Les outils» Sétra 9 September 2007

Diagram No. 2: free space of the hydraulic structure Collection «Les outils» Sétra 10 September 2007

Impact of the hydraulic structure The rise in the water line upstream of the hydrological structure relative to the existing situation and the speed of flow out of the structure are to be assessed with respect to the local risks and challenges. Open channel flow within the hydraulic structure must be ensured for the project flow. Free movement of the ichthyofauna The minimum water level with limited speed of flow must make adequate provision for the upstream migration of fish during low-water periods. It is often necessary to arrange for the base of the structure to reconstitute a natural river bed. Reference should be made to the works "facteurs biologiques à prendre en compte dans la conception des ouvrages de franchissement" ("biological factors to be taken into account in the design of bridging structures") [1] and "Passes à poissons : expertise, conception des ouvrages de franchissement" ("Fish-passes: appraisal, design of bridging structures") [2]. Location of the hydraulic structure In plan, the hydraulic structure is generally located on the axis of the low-level bed of the water course; its opening must be at least equal to that of the low level bed. It may, nevertheless, be necessary to straighten the natural course of flow beneath the infrastructure to achieve a more direct crossing. It is a question of establishing its feasibility in both environmental and regulatory respects. The continuity of flow must be respected and protection must be provided in areas susceptible to erosion. In longitudinal elevation, the setting of the hydraulic bridging structure is conditional on the natural topography of the terrain and the flow conditions (gradient of bed). So far as possible, the hydraulic structure should be set to follow the gradient of the natural bed of the water course. Evaluation of the project flow and the exceptional flow The following chapter sets out some simple methods that can be used to evaluate the project flows. The exceptional flow to be taken into account is at least equal to 1.5 times Q 100. An evaluation of its impact (with the hydraulic structure dimensioned for the project flow) on the safety of users, on the durability of the infrastructure and on the environment must be carried out with a view to assessing the measures to be taken. 1.1.2 - Determination of the project flow (an application example of the calculation of the project is given in appendix 4.1.2) The project flow corresponds to the peak flow for a given recurrence interval, on the basis of which the dimensions of the hydraulic structure are determined. The calculation methods proposed below use the "rational" and "crupidex" formulae with a "transition" formula to make the link between the two. They are simple and can be applied to natural catchment areas. They were developed by experts for the realization of the Mediterranean TGV. The same applies for the run-off coefficient, the concentration time* and the transition formula. Other proven methods can also be applied. Whatever the chosen method, the results of project flow calculations for a natural catchment area are subject to uncertainties (precipitation values, complexity of phenomena etc.). An investigation in the field must be carried out to ensure that the calculation results are consistent with reality. Rational formula Range of validity Its range of validity is as follows: up to 1 km 2 in mainland France, except for the Mediterranean sea-board, Collection «Les outils» Sétra 11 September 2007

up to 10 km 2 on the Mediterranean sea-board (zone with rainfall intensities similar to the regions of PACA, Corsica, Languedoc Roussillon). Formula where: : recurrence interval project flow m 3 /s : run-off coefficient* weighted for the recurrence interval, T : rainfall intensity in mm/h for the recurrence interval* T during the concentration time* t C : total area of the catchment area in km 2. A J : partial area of the natural catchment area with coefficient C J in km 2 t c : concentration time* t c in minutes where L j : length of flow (in m) on a section where the speed of flow is V j (en m/s). The Montana coefficients, a and b are obtained by statistical adjustment from the water levels observed during a given time. The base data or the reconstituted Montana coefficients can be obtained from the weather service. Run-off coefficient, C 10 For T = 10 years (indicative values) (see table No. 1) Variability of the run-off coefficient* The values of the coefficients increases with the intensity of the precipitation but this variation differs with the degrees of permeability and retention of the ground making up the catchment area. Thus, a highly impermeable natural catchment area will have a high coefficient C (10) and this will increase little with the recurrence interval under consideration. Conversely, a highly permeable natural catchment area or one with a high retention capacity will have a run-off coefficient* of almost zero until a threshold is reached and then increase very rapidly and may reach values comparable with those for an impermeable catchment area. This behavior is characteristic of natural catchment areas with a threshold effect. The variability of the run-off coefficient is a function of the initial retention, P o of the natural catchment area: For C (10) < 0.8 on a P 0 in mm and P 10 = the 10-year daily rainfall in mm If C (10) 0.8, we generally take: P 0 = 0 and C (T) = C (10) Run-off coefficient C T for a recurrence interval, T > 10 years P (T) = daily rainfall of the recurrence interval, T Collection «Les outils» Sétra 12 September 2007

An application example of the variation of the run-off coefficient* of the rain is given in appendix 4.1.2. Rainfall parameters These parameters (see appendix 4.1.1) can be obtained from Météo France (the French weather service). These are the Montana coefficients a (T) and b (T) of the rain i (T) = a (T) x t b c (T) with i in mm/h and t c in minutes Ten-year daily rainfall of the recurrence interval Daily rainfall of a given recurrence interval P T in mm. Vegetation cover Morphology Gradient % Sandy coarse terrain Alluvial terrain Clayey terrain Wooded almost flat undulating mountainous p < 5 5 p < 10 10 p < 30 0,10 0,25 0,30 0,30 0,35 0,50 0,40 0,50 0,60 Grazing almost flat undulating mountainous p < 5 5 p < 10 10 p < 30 0,10 0,15 0,22 0,30 0,36 0,42 0,40 0,55 0,60 Arable almost flat undulating mountainous p < 5 5 p < 10 10 p < 30 0,30 0,40 0,52 0,50 0,60 0,72 0,60 0,70 0,82 Table No. 1: run-off coefficient for T = 10 years Collection «Les outils» Sétra 13 September 2007

Determination of the concentration time*, t c, for T = 10 years The determination of this parameter requires the evaluation of the speed of run-off of the water on the natural catchment area*. The run-off can be : very gentle: run-off in a surface layer (see diagram No. 3), characterized by run-off spread out over the natural catchment area or more rapid: concentrated run-off (see diagram No. 4), characterized by talwegs* and ravines fed by the valley slopes and by the low-water beds of the water courses. Diagram No. 3: run-off in a surface layer Diagram No. 4: concentrated run-off The speeds shown in tables 2 and 3 could be used. These values are determined from: V in m/s p in m/m V = k x p 1 / 2 x R h 2 / 3 (see appendix 4.2.1) Table No. 3 below was drawn up for k = 15 and R h =1, values generally accepted for pilot projects. Slope in m/m Speed in m/s 0.01 0.02 0.03 0.05 0.1 0.15 0.2 0.30 0.14 0.20 0.24 0.31 0.44 0.54 0.62 0.76 Table No. 2: evaluation of the speed of run-off in a surface water layer Slope in m/m 0.00 3 0.00 5 0.00 7 0.01 0.01 5 0.02 0 0.03 0 0.04 0 0.05 0 0.07 0 0.10 0 0.15 0 0.20 0 Speed in m/s 0.8 1.1 1.2 5 1.5 1.8 5 2.1 2.6 3 3.3 5 4 4.7 5 5.8 6.7 Table No. 3: evaluation of the speed of concentrated water run-off Determination of the concentration time* for a recurrence interval > 10 years where: tc (T) : concentration time* for the ten-year recurrence interval, in minutes. Tc 10 : ten-year concentration time*, in minutes. P (T) : daily rainfall of recurrence interval T, in mm. P 10 : ten-year daily rainfall, in mm. P 0 : initial retention, in mm. Collection «Les outils» Sétra 14 September 2007

The value of the concentration time* is an approximate value, which depends, in part, on the precipitations and the morphology of the natural catchment area. In the interests of simplification, it is generally accepted that, for studies up to the pilot project stage, the empirical formulae in appendix 4.5 can be applied. Collection «Les outils» Sétra 15 September 2007

Crupedix formula This comes from the Ministry of Agriculture (Cemagref, 1980). Range of validity: from 10 km 2, except for the Mediterranean sea-board (50 km 2 ), and up to 100 km 2, formula valid only for the ten-year flow, the interval (Q/2-2Q) represents confidence interval with a probability of more than 80 % of including the calculated value. Formula: The flow where: Q 10 : ten-year flow, in m 3 /s, R : regional coefficient reflecting the aptitude for run-off P 10 : daily rainfall of ten-year recurrence interval, in mm S BV : area in km 2 Evaluation of the hundred-year flow from the ten-year flow of the Crupedix formula We obtain the hundred-year flow from the correlation: Q 100 = b. Q 10 a priori: 1.4 b 4 The parameter b depends on the area of the catchment area: up to 20 km 2, b is determined using the rational formula (calculation of Q 10 and Q 100 as if the rational formula were applicable), above 20 km 2, b is determined from data obtained from gauged water courses on catchment areas near the project. Failing this, b = 2 minimum. Choice of the parameter R The regional coefficient, R, is to be checked locally. If this is not possible (absence of gauged water courses in representative catchment areas near the project), the following coefficient values can be used: R = 0.2 for permeable areas (Champagne, Beauce), R = 1.5 to 1.8 for impermeable areas (Lorraine plateau, Vendée), R = 1 for intermediate areas. Evaluation of the flow, Q T, of recurrence interval*, T The evaluation of a flow of recurrence interval, T, between 10 and 100 years can be obtained from the following formula, assuming that the statistical distribution of the observed values follows Gumbel's law: where Δ Q = Q 100 Q 10 y = (-ln (-ln (1-1 T if T = 20 years y = 2.97 if T = 30 years y = 3.38 Transition formula This formula can be justified to the extent that the ten-year flow yielded by the rational formula can sometimes be twice that yielded by the Crupedix formula. The flow yielded by the transition formula is written: ))) Collection «Les outils» Sétra 16 September 2007

where: : project flow with recurrence interval T, : flow yielded by the rational formula, recurrence interval T, : flow yielded by the Crupedix formula, recurrence interval T, α, β : weighting coefficients α varies linearly from 1 to 0 as the surface area (S) increases from 1 to 10 km 2, from which: α = France except Mediterranean sea-board and β = 1 - α α varies linearly from 1 to 0 as the surface area (S) increases from 10 to 50 km 2 α = Mediterranean sea-board and β = 1 - α The ranges of applicability of the three formulae presented above are as follows: (see table No. 4). An application example is shown in appendix 4.1.2 on a fictional natural catchment area. Area of catchment (in km 2 ) 1 10 50 100 France except Mediterranean sea-board Rational formula Transition formula Crupedix formula Crupedix formula Mediterranean sea-board Rational formula Rational formula Transition formula Crupedix formula Table No. 4: ranges of applicability for each of the three formulae Collection «Les outils» Sétra 17 September 2007

1.1.3 - Design of hydraulic structures Structures are generally classified in 5 families: circular ducts, box culverts*, arched culverts*, large arched structures and major structures. So far as possible, production stock items should be chosen rather than the more costly structures cast in place. Reinforced concrete structures, provided they are correctly designed and built with due care, are assured of excellent strength and longevity. The structural design of proposed structures is a task for civil engineering consultants. Factors influencing the choice of hydraulic structures In choosing the structure to be used, the longevity of the road, the safety of users, investment costs and methods for subsequent maintenance of the structure must always be borne in mind. The factors influencing the choice are: the quantity of the flow to be discharged, which fixes the flow cross-section and the type of structure, the hydraulic characteristics of the structure: roughness factor (K), funneling coefficient (K e ) creating a loss of head at the entry, shape of the flow section, the width of the bed; a unique structure, adapted to the flow to be discharged and the width of the bed of the water course is generally preferable to multiple structures, which increase head losses and obstruct the passage of floating bodies, the available height between the project height and the talweg*, the static and dynamic loads acting on the hydraulic structure, the foundation conditions of the structures, the speed and ease of implementation: production stock items supplied in transportable sections and assembled on site can be an interesting solution for reducing completion times and in cases where site access is difficult, the resistance to chemical agents, the shock resistance: massive structures withstand best the shocks and abrasion from solid materials carried by the current. Protection of hydraulic structures (see appendix 4.2.3) Consideration can be given to setting the invert* of the structure 0.30 m or more below the deepest part of the water course to allow the reconstitution of a natural bed in the structure (ascent of fish). The raised upstream level of flows and the increased speed of flow at the exit from the structure most frequently require protective measures both upstream and downstream of the structure. Any straightening of the course will require: continuity of flow, effective protection of the banks against changes of direction by durable techniques with a priority on vegetation based systems [10] "Protection des berges de cours d eau en techniques végétales [Protection of the banks of water courses by means of vegetation]". Reinforcement techniques using rock lining and gabions* should be used only on sections other wise heavily eroded by the current if there are significant risks to personal safety or high value-added assets, flows on steep gradients, p = 4%, pose special problems (determination of the upstream water level, speed in the structures etc.) that are not discussed in this guide. Calculating the structures Calculation of the structures can only be carried out after determining the constraints on natural flow up to at least 100 m downstream of the hydraulic structure. Furthermore, the openings of the hydraulic re-establishment structures are generally narrower than the current section of the stream or talweg* for reasons of cost. This narrowing is not without consequences for its operation, especially when discharging the peak flood flow. What must be borne in mind: Collection «Les outils» Sétra 18 September 2007

the structure must be able to discharge the flood quantity corresponding to the project flow* with an upstream water level* (H AM ) of the structure compatible with the setting of the project and the preservation of private property, the verification for an exceptional flow must be examined, in the context of the present guide, the upstream water level (H AM ) is confused with the total energy head line, the setting of the longitudinal section requires knowledge of the rise in the water line inherent in this narrowing of the flow; it is therefore necessary to determine the flow régime, the setting of the structure must not engender a hydraulic jump*, the calculation is carried out from downstream to upstream, i.e. the first thing to look for is the flow régime in the stream downstream of the hydraulic structure, the speed of flow must not exceed 4 m/s for concrete structures and 2.5 m/s for metal pipes. The method presented in the present guide is a simplified method (simplified Bernoulli theorem). It draws on the basic notions of hydraulics* (taking account of the flow régimes). The basic data required to understand the calculation method are shown in appendix 4.2.1. The principle of the method consists in determining, in the first place, the flow régime downstream of the proposed structure in order to calculate the upstream water level, H AM, of the structure: if the flow is in fluvial régime*, the proposed structure must be set in fluvial régime (application of ABAC charts 1 to 5 see appendix 4.2.2), if the flow is in torrential régime*, the proposed structure can be set in fluvial régime* (application of ABAC charts 1 to 5 see appendix 4.2.2), The general relationship giving H AM is the following: where: y e = water level at the entry and immediately inside the hydraulic structure, in meters. V e = speed at the entry to the structure in meters per second under y e. K e = head loss coefficient at the entry to the hydraulic structure (function of the type of head). G = acceleration due to gravity in m/s 2 and V e = S EM = stream cross-section at the entry to the hydraulic structure under y e in m 2 A numerical application example is shown in appendix 4.2.4. 1.1.4 - Maintenance and operation of the hydraulic structures Access to the hydraulic structures must take account of the operating constraints. An annual inspection and an inspection after a flood event are necessary in order to plan, if needed, maintenance of the structure and clearance of any silt. The minimum diameter of hydraulic structures under motorways is 800 mm. This dimension should, in all scenarios, be compatible with the managing body's maintenance capabilities. For 2 or 3-lane roads, this diameter may be reduced to 600 mm while still guaranteeing the operating conditions. Collection «Les outils» Sétra 19 September 2007

1.2 - Surface drainage of the platform This is the collection and evacuation of surface water within the footprint of the road. An essential component of the road project, the three objectives of the platform drainage are: the safety of users through the evacuation of water from the roadways and embankments, the longevity of the infrastructure, by collecting the water and evacuating it from the road, the management of road pollution. A badly designed network will lead to surface disorders (system overflows, floods etc.) and major structural disorders of the roadway in the medium term. These situations are aggravating factors for the safety of users and the integrity of the road. Furthermore, any road run-off transferred off the platform is not environmentally neutral. 1.2.1 - General principles The environmental constraints (outfalls*, environmental vulnerability), the hydrogeology*, the engineering geology (nature of the ground) and the mapping of the project (high and low points, banked roadways) and the safety of users all come into the overall design of the systems. It is recommended to adopt the following principles: In questions of road design: in grazing profile, the longitudinal profile must be set so that the roadway and subgrade structures are embanked and platform run-off can be evacuated by gravity in the drainage system, avoid gradients less than 0.5 % as they may lead to water stagnating at changes of crossfall, avoid deep excavated sections (cuttings); these are often critical points for drainage and sometimes subject to drawdown of surface water, proscribe low points in cuttings. In questions of drainage: respect the criteria for the placing of structures with regard to the safety of users (see Guide sur le traitement des obstacles latéraux [Guide on dealing with lateral obstacles] [6]), adapt sealing of the collector structures to the requirement to protect water resources (see Guide sur le traitement de la pollution routière [Guide on the management of road pollution] [13]), equip the tops of cutting banks of longitudinal structures in the case of run-off in a natural catchment area (bank erosion and overload of the system at the foot of the bank), proscribe pumping stations (reversing or lifting stations) except in exceptional cases (costly installations, complex to operate and maintain), always try to keep water moving under gravity and on the surface, use as many discharge points as possible to avoid flow concentrations to be weighed against environmental considerations, study the possibility that infiltrations overflow (if this is consistent with the protection of water resources) and of downstream flows (water meadows*, intermediate holding basins etc.), dimension systems for rainfall with a recurrence interval of at least ten years (T = 10 years), check that the roadway will not be submerged for a recurrence interval of 25 years; on the contrary, this can be permitted for the shoulder for T = 25 years, avoid discharging into the road platform* drainage system any water from natural catchment areas or surface water layers, plan for a clad structure if the gradient is 1 % or if the speed of flow is likely to cause erosion (the critical gradient is often of the order of 3.5 %), in regions subject to frost, give the preference to concrete or masonry structures, turfed structures slow the downstream passage of flows, favor infiltration and tend to reduce pollution. 1.2.2 - Nature and function of systems The drainage network must collect the run-off water from roads and their enclosing Collection «Les outils» Sétra 20 September 2007

banks/embankments to evacuate them towards the outfalls*. The main development of its architecture is along the infrastructure, using gravity driven hydraulics (between a high point and a low point), by assembling unitary structures (linear or at points, buried or superficial). The platform* systems have the peculiarity of mainly being linear systems, parallel to the axis of the road (a distinction must, however, be made between off-platform systems and systems on the platform). Diagram No. 5 shows the situation of these systems on the transverse section of a two-lane dual roadway. The architecture of a drainage system can, conventionally, be broken down into 5 main parts: the longitudinal collection system, the transverse structures, the connecting structures, the containing and pollution control structures and the outfalls*. Longitudinal collection system Cutting bank top system The role of the cutting bank top system (see diagram No. 6) is to avoid erosion of the bank and feed run-off to the system at the foot of the bank. Generally, this structure is clad to avoid its erosion and infiltrations that might jeopardize the stability of the bank. It intercepts the run-off water of the natural catchment area as modified by the road construction. It is set back somewhat (1 to 2 m) from the crest of the bank. This structure should dimensioned for an adequate capacity of each contiguous section. Arrangements for its maintenance should be planned. Diagram No. 5: situation of the systems on the transverse section of a four-lane bidirectional highway. Réseau du TPC Descente d'eau Traversée ou 1/2 traversée Réseau de crête de talus de remblai Réseau de pied de talus de remblai Raccordement bourrelet/descente Regard avaloir Raccordement descente/cunette Raccordement fossé/descente Réseau de crête de talus de déblai Réseau de pied de talus de déblai Ouvrage longitudinal de crête de talus de déblai Cunette de réception de la chaussée et du talus de déblai Diagram No. 6: position of the cutting bank top system Median system Downdrain Crossing or half-crossing Embankment top system Embankment foot system Ridge/downdrain connection Drainage opening Downdrain/channel connection Ditch/downdrain connection Cutting bank top system Cutting bank foot system Cutting bank top Roadway and cutting bank reception channel Cutting bank foot system The function of this system is to collect the run-off water from the cutting bank, the roadway, the emergency lane and the verge*. As a general rule and in current sections, a gully* is made, grassed or lined depending on the constraints (gradient). In its design, the gully* must not compromise the safety of users. It must be watertight to an extent compatible with the required level of protection of water resources. At regular intervals, the gully* must be connected to a buried collector. The latter could serve to recover, via the manholes, the clear drainage water. Collection «Les outils» Sétra 21 September 2007

Hydraulic dimensioning has been shown to be indispensable. Depending on the size of the intake area* formed by the bank, a double system might be considered: a system collecting only the bank run-off with direct discharge to the outfall*, a system bringing together run-off from the roadway and passing it to a treatment arrangement before discharge to the outfall*. Median (TPC) system The function of the median system is to collect and evacuate water from the median and the banked up roadway. Although not used by traffic, this part of the platform* must be carefully designed and constructed to prevent run-off from the higher roadway reaching the lower (risk of aquaplaning) and to protect the roadways from infiltration (case of unlined medians): case of unlined medians: on straight sections, the run-off shall be channeled by a longitudinal transport structure (clad or not) of type flat ditch* or prefabricated gutter. To complete this surface collector, drainage provision shall be made to protect the body of the roadways from the migration of water through the median towards the pavement structures and the roadbed (see diagram No. 7). In banked curves, a concrete gutter* along the edge of the median can intercept, if necessary, run-off from the banked up roadway. Depending on the position of the safety barrier, if there is one, this gutter* should be covered (with a slit grill or openwork concrete). So far as possible, this structure should not be beneath the barrier for practical reasons of access and maintenance (see diagram No. 8). case of lined medians: on straight sections ("roof" cross-section) gravity run-off from each roadway will be towards the outer edges of the road. In banked curves, a concrete gutter* should be installed in a position to drain the maximum possible area of the banked up roadway. In the case of successive resurfacing of the roadways (apart from the median), an outfall at the low point of the longitudinal elevation should be planned in from the project stage. Collection «Les outils» Sétra 22 September 2007

Diagram No. 7: unlined median Diagram No. 8: banked curve: a surface structure completes the arrangement. Its location must take account of the safety devices and subsequent resurfacing of the roadway TPC non revêtu > 3m - Bande médiane en "V" - Bande médiane en "V" équipée d'un fil d'eau revêtu Bande médiane géomembrane éventuelle Drain Fil d'eau revêtu type fossé plat symétrique En alignement droit: Le TPC doit être assaini pour protéger la chaussée des infiltrations. Le positionnement du drain doit tenir compte de l'implantation des équipements de sécurité et des zones plantées Caniveau à grille si apports importants Dans le cas contraire fossé plat type "CC" Unpaved median> 3m - V-shaped median strip - V-shaped median strip with a lined gutter Median strip geomembrane as required Drain Symmetrical lined ditch-type gutter On straight sections: The median must be drained to protect the roadway from infiltration. The position of the drain must take account of the layout of safety equipment and planted areas Grated drainage channel if significant inflows Otherwise a flat ditch CC type Embankment top system The function of this part of the longitudinal system is to channel run-off water from the roadway to avoid its being discharged to the embankment slope. It thus protects the road embankment from any alteration (formation of gullies, erosion and, in the limit, collapse). As a general rule, this type of structure is to be provided: where the height of the embankment is 4 m; this limit value is reduced to 2 m in regions exposed to intense rainfall (Mediterranean region in particular), to evacuate run-off from the platform* at a favorable point along the road. In running section, the structure can consist of ridged elements* (bituminous concrete, hydraulic concrete) or of concrete borders type T1 or T2. The profiles must be compatible with safety rules. Downdrains must be provided to discharge the run-off to the foot of the embankment (Embankment foot system). Except in special cases, the spacing of these downdrains is generally: 50 m in oceanic and continental regions, 30 m in regions of intense rainfall, 30 m when the gradient of the longitudinal elevation is 0.5 % or 3.5 %. Collection «Les outils» Sétra 23 September 2007

In all cases, the following points should be taken into account: the hydraulic saturation of this system for rainfall with a recurrence interval of ten years must not lead to submersion of the roadway (submersion of the emergency lane or lay-by tolerated for T = 25 years), the toe of a concrete retaining device can serve as a gutter in certain road configurations (provide water passages or absorption grid), to take account of the protection of water resources, a gutter* or a collector to evacuate the run-off at a given point would replace the ridge*. Embankment foot system Located at natural ground level, this system must collect all the water from the road intake area by gravity and direct it towards the outfall* without posing a threat to lower ground. On certain stretches, this system also intercepts the run-off water of a natural catchment area to direct to crossing structures. This part of the system also protects the foot of the embankment against erosion. The structure is generally a grassed, trapezoidal ditch with high hydraulic capacity, or a lined ditch* where there is risk of erosion (the critical gradient is often of the order of 3.5 %). Transverse structures Classified under this heading are structures for transferring run-off from one longitudinal system to another. Classically, this family of structures includes surface structures, such as tiled downdrains as well as transverse structures beneath the roadway (buried collectors). Their location is subject to examination of the following points: the mapping of the road, the direction of run-off (from the platform and the associated catchment areas), the flows to be carried and the positions of outfalls*. A few rules to apply: the water from a cutting bank must be discharged, as soon as possible, off the platform via a crossdrain under the roadway, where the infrastructure includes a median, an inspection hatch for the cross-drain should be provided in the median, tiled downdrains are to be preferred to pipes (significant risk of obstruction), the feet of tiled downdrains must be connected to the ditch* in such a way as to avoid erosion (concrete molding). Connecting structures These are the manholes and the various connections between longitudinal and transverse structures, the proper execution of which is critical to the correct operation of the drainage system and its longevity. Most frequently, these structures are prefabricated but may sometimes be cast in situ. These are: inspection manholes, required for the inspection and maintenance of buried collectors, drainage openings to into which the water falls, pipe header walls to funnel the water and retain the earth, various connections (ridges* / downdrains, downdrains / ditches etc.), others. A few rules to apply: a manhole is obligatory at any change in direction of the line of the collector, at a change in gradient in the longitudinal elevation or at a change in collector diameter, in these structures, provide decantation channels (at least 10 cm deep) to trap sand and gravel. Retaining and pollution control structures Retaining structure refers to balancing tanks (surge limiting, storm or retaining), the main function of which is to store and delay downstream flows towards the outfall. They play a multiple role: desedimentation and the minimization of accidental pollution. The retaining and pollution control Collection «Les outils» Sétra 24 September 2007

structures are a matter for the specialist. Outfalls* The outfalls* to which the discharge can be directed in terms of quantity and quality must be identified before designing the system. Collection «Les outils» Sétra 25 September 2007

1.2.3 - Choice of drainage structures and hydraulic design calculation Choice of drainage structures There is, a priori, no ready-made and reproducible solution for all road projects. However, there are four main criteria to be satisfied in the choice of a drainage structure: its hydraulic capacity, its insertion in the longitudinal and transverse sections of the road project and thus its mapping, which must also take account of the user safety aspect, its level of protection with regard to water resources, the ease of operation and maintenance of its structures. Hydraulic design calculation of the structures The method of dimensioning the drainage structures is based on the application of the rational formula. Equation 1 where: Q = flow in l/s produced by the road catchment for a frequency equal to the frequency of i C = dimensionless run-off* coefficient of the de platform i = intensity in mm/h for a chosen frequency A = surface area in ha of the platform The calculation principle is thus to determine the drainage structure with the capacity to evacuate this flow. o this end, the flow capability* of the structure Q c (full-bore flow) given by the Manning Strickler* formula (see appendix 4.2.1): where: Q : flow in m 3 /s K : roughness coefficient R h : hydraulic radius with: in meters S m : wetted cross-section in m 2 P m : wetted perimeter in m p : gradient in m/m is compared with the run-off flow found from equation 1 above. Appendix 4.2.5 explains the principle of the calculation method and appendix 4.2.6 shows the calculation of classical structures, namely, the dimensioning of a grassed gully*, of a median channel, of a succession of two collecting structures and of the feed to a basin by association of system branches. The calculation is carried out by iteration. 1.1.4 - Maintenance and operation of the structures [11] Some recommendations must be taken into account at the preliminary project design: surface structures are to be preferred to buried structures, reduce as far as possible the different types of structures, choose simple and accessible structures and durable materials, do not use diameters of less than 600 mm for cross-drains under the full road width and 400 mm for cross-drains under half the road width for reasons of maintenance and desedimentation as well as to cope with settlement problems. Do not forget that these structures are generally seated on the natural terrain and subject to high loads (embankment, traffic etc.) and can be deflected out of their installation line, in cases where the outlet is down a grassy bank, provide a tiled downdrain, as cross-drains under the roadway are subject to high loads (static and dynamic loads), use suitable pipes; as a minimum, select a pipe in reinforced concrete, series 135A (see fasc. 70 [4]). Provide for its protection in the building phase. Provide access to the structures for their maintenance (tracks, stairs, refuges etc.), Collection «Les outils» Sétra 26 September 2007

in straight sections, the spacing between manholes can be increased to 80 m, taking account of the performances of jetting maintenance equipment, it is essential to place visitable manholes along the line of the system; smaller accesses for maintenance can, where appropriate, be placed between the visitable manholes, when locating the structures, always bare in mind the safety of the operating personnel and minimize any nuisance to the user. 1.3 - Road structure drainage The reader should refer to the technical guide "Drainage routier [Road drainage]" [12], which deals with the subject. 1.3.1 - Definition Road drainage consists in the collection and evacuation of water within the substructure of the road. 1.3.2 - Who does what? The decision to drain lies within the competence of geotechnicians and roadway mechanical engineers. The main consideration of road drainage is to set all the structures so as to ensure the evacuation of all the drains. 1.3.3 - Summary of the effects of water on the road It is an illusion to think that a roadway will be free of water. It is, however, possible to make drainage provisions that collect water from the road surface and channel it off the road platform* as quickly as possible. A Road drainage system is not necessarily a part of all new road projects (roadways with low traffic, absence of heavy good vehicles, favorable hydrogeological* and hydrological* conditions, quality of materials etc.). However, rigorous analysis and detailed investigations must first be carried out with roadway specialists regarding the following: water infiltration into/under a roadway (lack of substructure drainage or surface drainage) can soon provoke structural damage, the effect of alternating expansion and contraction due to freeze-thaw cycles can degrade materials performance and lead to long-term breakdown of the structure, flexible roadways are particularly sensitive to the water content, especially those surfaced with untreated gravel, road surfaces in bituminous concrete are not watertight; imperfect routine maintenance and the ageing of coatings increase the permeability, interfaces between materials and roadway boundaries are critical area, variations in the water content of the materials making up the body of the roadway have a considerable influence on its mechanical characteristics. 1.4 - Controlling road pollution The reader should refer to the technical guide "Traitement de la pollution routière [Dealing with road pollution]" [13], which sets out all the procedures to be followed in order to take proper account of the protection of water resources in road projects. 1.4.1 - Definition The management of road pollution consists in the provision of all measures to be implemented to meet water resource protection requirements. 1.4.2 - Who does what? The environmental specialists define and rank the risks with respect to water resources (RE). Collection «Les outils» Sétra 27 September 2007

The designer dimensions the structures to achieve the water resource protection objectives. 1.4.3 - Summary of risks and challenges Work site, chronic, seasonal and accidental pollution can adversely affect water quality, water habitats and its use. Furthermore, it should not be forgotten that the management of road pollution imposes environmental obligations on the project manager. Any failure to meet these obligations can lead to disputes that may involve the responsibility of the project owner. Collection «Les outils» Sétra 28 September 2007

2 - Sequence of studies The establishment of a surface drainage project must not take priority over the definitive mapping and setting of the road. The required procedure, therefore, is one of joint iteration with the geometric study of the road line, the geological study and the environment. It is advisable to involve the regional environmental directorate [DIREN] and the water police at the start of the study procedures or no later than the stage at which environmental studies are carried out in detail. The main objective is to establish the constraints on the altitude of the road line relative to the reestablishments of natural run-off, the protection of water resources, surface drainage and drainage of the platform. The future operating company shall be associated with the project team (design of structures, working methods, operation, maintenance and management). This procedure shall be initiated from the preliminary study stage and be applied up to the definitive project. 2.1 - Preliminary studies Circular No. 94-56 of May 5, 1994 states: "the purpose of the preliminary studies is to determine the functions to be satisfied and to verify the technical and financial feasibility of the proposed infrastructure. The main aim of these studies is thus to define not only the road planning option but also its forecast budget". They are generally prepared from plans at a scale of 1:50,000 or 1:100,000. With regard to road surface drainage, the preliminary studies must make clear any constraints relating to hydraulics* and water resource protection having a significant financial impact on the project. This type of issue is raised by an expert assessment. The project should give particular attention to the hydraulics and the protection of Water Resources. 2.1.1 - Hydraulics* By planning: the location of outfalls* (flow, qualitative and quantitative aspects), the definition of flood planes (environmental study) and listing of the flood zones (expansion, depth of flooding, duration, frequency), the proposal of structures for bridging water courses and their flood areas, the analysis of sections crossing flood planes and their approximate heading up (estimation of embankment and protection work). 2.1.2 - Protection of Water Resources From the listing of the water resources with high asset value (environmental study), the impact of the presence of these resources on the mapping of the road line. The types of protection measures must then be defined. Apart from the "hard point" zones, estimates are based on ratios. Collection «Les outils» Sétra 29 September 2007

2.2 - Outline Preliminary Project (APS) studies "The purpose of these studies is to define more precisely the chosen option, choosing the solution and setting a ceiling on costs. The content of these studies is limited to what is necessary to start the public inquiry procedure". The Outline Preliminary Project (APS) is complete with the "description of the route variants and the justification of the proposed choice (300-m strip for a new interurban route, precise route for developments in an urban or suburban environment so that the footprint can be included in townplanning documentation)". The proposed choice is justified on the basis of a multi-criterion analysis of the variants studied. 2.2.1 - Choice of scales for the plans of the routes studied studies of variants: - in rural areas: 1:10,000 (1:5,000 for difficult sectors) - in urban areas: 1:5,000 (1:2,000 for difficult sectors) proposed variant: - in rural areas: 1:5,000 to 1:10,000 - in urban areas: 1:1,000 to 1:2,000 These indications do not exclude the use of larger scales at the level of certain "hard points". 2.2.2 - Road surface drainage at the Outline Preliminary Project (APS) study stage The road surface drainage study consists, in the first place, of: precisely locating the outfalls* with their specific characteristics, within the boundary of the chosen study zone, investigate the environmental data relating to surface and ground water, in particular those that may cause future difficulties. These data can represent a constraint or introduce obligations. At this stage, the hydrological* and hydrogeological* investigations should have been started, as these must be summarized in the dossier, list the setting constraints on all the routes studied, defined in table No. 5. These constraints are established from plans to the scales already mentioned. In the majority of cases, the engineering consultancy will base its work on existing information with regard to flood planes or on summary calculations. Modeling shall be used only for hard points. The delays, sometimes considerable, in completing these studies imply that they should be undertaken very early. The analysis of the constraints connected with road surface drainage (and other aspects of the road) can be used to optimize the settings of the routes. These can then be used as a basis for the definitive road surface drainage study. They can then be classified on the basis of the equipment, the costs, the modifications imposed on run-offs and the impact of the project on water resources for each of the variants. Collection «Les outils» Sétra 30 September 2007

The dimensioning of the water protection structures shall be refined for the proposed solution 1 in plan in longitudinal elevation in transverse section natural runoffs water course crossing points, flood planes Establish the height setting constraints by defining H AM Links with the nomenclature of the Water Act Platform surface drainage Discharge points or constraints Determine steep gradient zones, height settings for median discharges, low points Zones requiring large-scale structures Ground drainage of the platform Zones requiring ground drainage (see laboratory study) Setting outfall height of the drains Protection of water resources From the vulnerability ranking of water resources along the route Low points to be prohibited, direction of gradients Types of structures Types of structures off platform See appendix 4.4 for abbreviations and symbols Table No. 5: height setting constraints for all routes 1 Note, the threshold of 1,830,000 Ä for the overall cost of the project conditions the way in which the public inquiry is started (cost of project < 1,830 kä: common law inquiry, cost of project > 1,830 kä: inquiry under Bouchardeau rules [law No. 83-630, 12 July, 1983]). Collection «Les outils» Sétra 31 September 2007

Contraintes liées à la protection de la RE Esquisse de tracé ou fuseau d'étude Etude de labo définissant les sols sensibles à l'eau Contraintes de calage du tracé - établissement des EN - protection de la RE - assainissement/drainage Remise d'un nouveau tracé par le MO Propositions d'aménagements par le BE Validation par le MO - Analyse et chiffrage des propositions retenues - Définition de la procédure d'enquête publique -Choix du tracé soumis à l'enquête d'utilité publique Enquête d'utilité publique Avis favorable Etude de projet Oui Non Constraints linked to the protection of the water resources Outline route proposal or design envelope Laboratory study defining soils sensitive to water Routing constraints - re-establishment of natural flows - protection of water resources - drainage Submission of a new route by the project owner Development proposals by the consultants Approval by the project owner - Analysis and costing of retained proposals - Definition of the public inquiry procedure - Choice of route submitted to public inquiry Public inquiry Favorable opinion Project design Yes No See appendix 4.4 for abbreviations and symbols Diagram No. 9: summary of the sequence of Outline Preliminary Project (APS) studies Collection «Les outils» Sétra 32 September 2007

2.3 - Project studies The purpose of the project studies is to define the solution in detail, make the technical choices and fix the cost ceiling for the project. They lead up to the individual land inquiries and the execution studies. The overall plan of the project is generally studied at a scale of from 1:500 to 1:2000. 2.3.1 - Height setting constraints At this point in the studies, the height setting constraints of the route must be defined precisely: for the re-establishment of natural flows, HAM is defined as a function of the flow régime downstream and in the proposed structure (height setting of proposed structures at 1:500 horizontally and 1:100 vertically), the influence of off-platform* structures for water protection is assessed by dimensioning the structures and including the height calculations on the water streams from sub-platform* discharges. The longitudinal elevation of the infrastructure is also to be adjusted according to the heights assigned to the low points (preferred discharge points), The surface drainage of the platform must include any safety arrangements on the footprint required for the surface drainage as well as discharge from the median(s). Particular attention must be paid to setting the heights of the streams of water at intersections, depending on banking and equipment. The drains must be able to empty by gravity. 2.3.2 - Validation of the general principles it is desirable, where appropriate, for the principles of the re-establishment of natural flows and water resource protection to be validated by the water police services at this stage in the study, analysis of the overall constraints relating to road surface drainage makes it possible to optimize the height settings of the routes; exchanges (on the level or with change of level) must also be set in height from these constraints, for this height setting, the main contractor should also include the other constraints (environment, geology, ground stability, road safety etc.). The road surface drainage consultants must then check that the height setting proposed by the main contractor (this height setting most frequently results from a compromise between the various constraints) causes no major difficulties for the road surface drainage (design, impact on the natural environment, safety, servicing, access and maintenance aspects). The main contractor must then be informed of these difficulties (example: installation of a pumping station, risk of flooding of the infrastructure and (or) adjoining land, risk of aquaplaning, unsatisfactory operation of the drainage system, difficulties of access to a basin etc.). once the route is validated by the main contractor, the "applicative" surface drainage study can be carried out. Collection «Les outils» Sétra 33 September 2007

Contraintes liées à la protection de la RE Esquisse de tracé ou fuseau d'étude Etude de labo définissant les sols sensibles à l'eau Définition des principes de protection de la RE Définition des principes de rétablissement des EN Definition des zones à drainer en liaison avec les "terrassements et chaussées" en fonction de la nature des ouvrages d'assainissement de PF Validation par services de PE Calage "fin" du projet en fonction (points de rejets, types) Calage "fin" du projet lié aux rétablissements des EN Calage "fin" du projet pour assurer le drainage et l'assainissement de PF avec les exutoires Remise des contraintes d'ar au MO Prise en compte de l'ensemble des contraintes par le MO Remise d'un tracé calé au BE AR par le MO Vérification du calage par BE AR Faire part au MO de l'incidence du calage sur AR Nouveau calage éventuel du tracé Etude du projet d'ar d'après la géométrie validée par le MO Oui Non Constraints linked to the protection of the water resources Outline route proposal or design envelope Laboratory study defining soils sensitive to water Definition of water resource protection principles Definition of principles of re-establishment of natural flows Definition of areas to be drained in conjunction with "roads and earthworks" according to the type of platform surface drainage structures. Approval by the water police "Fine" setting-out of project according to discharge points, types "Fine" setting-out of project according to re-establishment of natural flows "Fine" setting-out of project to ensure drainage of the platform with the outfalls Submission of roadway water management constraints to the project owner Consideration of all constraints by the project owner Submission of route setting-out to the road surface drainage consultants by the project owner Checking of layout by the road surface drainage consultants Advise project owner of the implications of the setting-out on the road surface drainage scheme Further adjustment of the route setting-out if necessary Design of a road surface drainage scheme based on the geometry approved by the project owner Yes No (1) or refinement relative to the Outline Preliminary Project (2) it also concerns constraints other than those connected with the road surface drainage (geology, countryside, noise etc.) See appendix 4.4 for abbreviations and symbols Diagram No. 10: summary of the sequence of project studies Collection «Les outils» Sétra 34 September 2007

2.4 - Water Law Dossiers (DLE) or water police dossier The guide "Nomenclature de la loi sur l eau application aux infrastructures routières [Nomenclature of the Water Act application to road infrastructures]" [9] summarizes the regulatory and legislative framework of the Water Act and gives details of the use of the main topics in the field of linear infrastructures. 2.4.1 - At the project study stage At the project study stage, the line of all projected roadways (links, interchanges, rerouted roads, access roads) is fixed. Incidentally, the project level supplies the definitive nature and characteristics of the structures and certain points of detail that may prove necessary for drawing up the Water Law Dossier (DLE). Furthermore, at the level of the project, taking the Water Act into account in the realization of the road works [14] is realistic (provisional installations, site tracks, need for a water drawing point etc.). The inclusion of site impacts in the Water Law Dossier (DLE) must be taken into account. Depending on the risks and challenges with regard to water resources and the complexity of the structures to be planned or the level of detail to be supplied, the Water Law Dossier (DLE) can be drawn up: from the completed project study, in which case the delay for drawing up the Water Law Dossier (DLE) is added to the time taken to complete the project study, in anticipation of the project study, in which case the principles will be supplied (for example, schematic position of basins on a plan, basin type, table giving the characteristics of each basin etc.). A contact with the water police services is desirable in the event of any query on the feasibility of the second case. In all cases, the Water Law Dossier (DLE) presented must be drawn up with an eye to clarity, transparency and technical readability by a wide public. 2.4.2 - At the Outline Preliminary Project (APS) level Strictly speaking, the Outline Preliminary Project (APS) level does not correspond to the Water Law Dossier (DLE) level. Indeed, the project route is not fixed (ink, interchange etc.) and the scale of the Outline Preliminary Project (APS) (1:5000 in general) is too small to respond to points of detail where necessary. It is also "difficult" to deal with the site aspect in the Water Law Dossier (DLE) at the Outline Preliminary Project (APS) level. However, in the event of a tight deadline for the launch of an operation (or "in place" improvement operation where the route is already fixed), experience shows that the Water Law Dossier (DLE)s can be drawn up at the Outline Preliminary Project (APS) level, at the same time as the public utility inquiry (DUP). In such cases, it is appropriate to carry out two simultaneous but separate inquiries (the public utility and Water Law Dossier (DLE)s are separate, as are the inquiry registers). Such a case can be envisaged where there is no serious problem with regard to the impact of the project on water resources, where the projected road line is relatively fixed or where a change in the route of the road does not lead to problems different from those presented in the Water Law Dossier (DLE). This does not exclude a detailed study of certain aspects. For example, the re-establishment of a runoff in which there are fish runs can be affected, as might the modeling of a flood plane and the structures for re-establishing this flood plane for a given constraint on the maximum flood level. These studies are not necessarily carried out in the Outline Preliminary Project (APS) at a topographic scale compatible with the Water Law Dossier (DLE). This being the case, when the Water Law Dossier (DLE) is drawn up at the Outline Preliminary Project (APS) level, the applicant is exposed, in particular, to the application of article 15 of order No. 93-742 of Mar 29, 1993 (new application for authorization with public enquiry where appropriate). The advice is to contact the water police service to jointly assess the feasibility of a Water Law Dossier (DLE) at the Outline Preliminary Project (APS) level. Collection «Les outils» Sétra 35 September 2007

At the project study level (in parallel) Project study completed (1) (2) or details or degree of precision (3) where appropriate See appendix 4.4 for abbreviations and symbols Diagram No. 11: summary of the sequence of drawing up the Water Law Dossier (DLE) At the Outline Preliminary Project (APS) level The Outline Preliminary Project (APS) study, approved solution, is concluded. During the study, the Water Police services have been consulted on the proposals for re-establishment of natural flows and the protection of water resources and have been able to react. (1) (2) or details complete the Outline Preliminary Project (APS) dossier if it is "not of a sufficient level". For example: with typical sections of re-establishment of natural flows (covering the various cases of re-establishment), describe the types of bank protection at the structure outlet (vegetation etc.), use typical Contraintes liées à la protection de la RE Constraints linked to protection of water resources Géométrie globale du projet Overall geometry of the project Collection «Les outils» Sétra 36 September 2007

Définition des principes de rétablissement des EN et de protection de la RE Définition du contenu et du niveau technique du DLE Validation par le service de PE Elaboration du DLE Compléments topographiques de "détail" et études complémentaires de "détail" Non Definition of principles of re-establishment of natural flows and protection of water resources Definition of the content and technical level of the Water Law Dossier Approval by the water police Elaboration of the Water law Dossier Additional "detailed" topographical information an additional "detailed" design studies. No Collection «Les outils» Sétra 37 September 2007

3 - Study quality approach The circular of December 22, 1992, which deals with road quality, that each phase in the process of elaborating a road project must be complete in order not to compromise the later stages. This requires sufficient knowledge of the field of road surface drainage and of the interactions with other fields (mapping of the route, environment, geotechnics, safety, operation, maintenance etc.). With regard to road surface drainage, each phase (or study level) of the elaboration process calls on a progression that uses elementary data (called inputs), applies tasks and produces results (called outputs). The approaches presented hereafter are deliberately simplified in the interests of clarity. The end points mentioned in the tables that follow are so-called "technical" end points and not procedural. They do not exclude possible additions from various guides dealing with the quality of studies. These approaches must serve as a guide for drawing up the specifications to be submitted to consultant offices with a view to making an order. 3.1 - Notions of process and progression, of inputs, outputs and tasks 3.1.1 - Process The process represents all those study levels that take place one after the other to arrive at a project meeting the needs expressed by the project owner. 3.1.2 - Progression In the context of the present guide, at each study level, the progressions apply to the four following fields (see diagram No. 12): re-establishment of natural flows, protection of water resources, platform surface drainage, ground drainage of the platform. Note: the term progression applies here to the macro-tasks necessary to successfully complete each technical stage at each road project study level. It differs from the term of chapter 2 "Sequence of studies", which, in this chapter, dealt with "collective entities" (e.g. setting the longitudinal elevation). Collection «Les outils» Sétra 38 September 2007

Diagram No. 12: progression of studies Processus Progression Entrées Sorties Etudes préliminaires APS Etude de projet Dossier loi sur eau Process Progression Inputs Outputs Preliminary studies Outline Preliminary Project Project study Water law dossier (DLE) 3.1.3 - Required "inputs" and expected "outputs" The inputs consist of all the documents that must be to hand in order to proceed with the technical study. The outputs consist of all the documents expected at the end of the technical study: plans, calculation notes, functional diagrams, technical notes. The inputs are supplied by the main contractor and the outputs are supplied by the design consultancy. 3.1.4 - Main tasks The tasks are carried out by the design consultancy. As it is not the purpose of the guide to constitute a training manual, the description of the tasks is limited the essential "macro-tasks" without going into all the details of the elementary tasks. The interest of this presentation is to: draw attention to the "unavoidables", facilitate the programming of the designer's work, encourage uniformity of practices, identify the most pertinent stages at which to carry out the various checks. Table No. 6 gives an example of the main tasks. Inputs (Project owner) Tasks (Design consultancy) Outputs (Design consultancy) 1. Geometry of project validated 1. Evaluation of project flows 1. Note 2. Studies: - geological and geotechnical - environmental 2. Choice of type and characteristics of the hydraulic structure (as a function of the characteristics of the project of the water course, of the project quality and respect for the hydraulic characteristics of the run-off) and of the layout. 2. Catchment area plan with number of catchments, position of hydraulic structures, specialized information regarding geology and the environment Collection «Les outils» Sétra 39 September 2007

3. Recurrence interval of project flow and constraints relating to the hydraulic structure Water protection orders if the Water Law Dossier (DLE) was prepared at the pilot project level 3. Technical drawings Tentative bill of quantities / estimate 3. Technical drawings defining all proposed measures Tentative bill of quantities / estimate See appendix 4.4 for abbreviations and symbols Table No. 6: example of a natural flow at the project level Collection «Les outils» Sétra 40 September 2007

3.2 - Issuing an order 3.2.1 - General principles The operational principles of issuing an order remain the same, whether the order is issued internally to a specialist department or CETE [TECHNICAL ENGINEERING CENTERS FOR INFRASTRUCTURE], to teams working in partnership or to a private consultant engineering office. Only the legal procedure is different. The deadline for submitting the study is counted from the "letter of order". It must take account of the end points and the deadlines for submission of inputs by the project owner. The inputs and basic guidelines required for satisfactory progress of the study are indicated in tables 7, 8, 9 and 10 and diagram No. 13 with the tasks and required outputs for each study level. 3.2.2 - Progression of studies Elaboration of the Outline Preliminary Project (At the level of re-establishing natural flows) Inputs (Project owner) Tasks (Design consultancy) Outputs (Design consultancy) 1. Mapping of the proposed project (with Natural Terrain) - plans - longitudinal evaluation typical longitudinal and transverse sections. 2. Environmental study: summary of aspects having an influence on the re-establishment natural flows and aquatic environments, PPRN [Natural risk prevention plan]. 3. PLU [Local town plan] 4. Recurrence interval of project flow (Q p ) 5. Account taken of exceptional flows (Q ex ) 6. Minimum characteristics of structures and account taken of maintenance and operation aspects 7. Validation by the Water Police services of the selected options (optional: can apply, for example, to the assumptions made regarding the raising of zones liable to flooding) 8. Validated definitive mapping - plan representing all reestablished roadways with positions of the structures... - typical longitudinal and transverse sections Delimitation of the Catchment Areas Field investigation (verification of critical catchment area limits, census of existing hydraulic structures, flood levels and flood planes, operation of these hydraulic structures in flood periods, type of bed, obstacles etc.) and collection of data and information (regional environmental directorate, district agricultural and forestry directorate) Knowledge of rainfall Evaluation of Q p and Q ex, Q MNA5, Q annual average Types of projected hydraulic structures Pre-dimensioning of hydraulic structures with definition of values of H AM Passage of Q ex through the projected hydraulic structures Recommendations for line and elevation of the route in plan and longitudinal elevation submitted to the project owner End point* Re-adjustment: - of the limits and areas of catchment areas - of Q p values - of Q ex values Pre-dimensioning of structures Supporting measures (recalibrations, falls, protections etc.) Tentative bill of quantities Estimates Catchment area maps with positions of hydraulic structures, zones liable to flooding etc. Plans and longitudinal elevation: Brief note showing, in particular: - summary of inputs - assumed pattern of rainfall - calculation of Q p and Q ex, Q MNA5, Q annual average - principles of re-establishment of natural flows underlying the types of structures - Consequences of Q ex - the hard points (e.g. request to substantially raise the longitudinal elevation and the consequences of not doing so) Note: for the constraint on setting the height of the road, the outputs can be submitted to the project owner in the form of a working document (documents, minutes). Catchment area maps with positions of hydraulic structures - Plans and longitudinal elevation of the road with positions and characteristics of the hydraulic structures, Q p, Q ex and H AM Justificatory technical note with, in particular, a listing of the inputs Estimate Collection «Les outils» Sétra 41 September 2007

See appendix 4.4 for abbreviations and symbols Table No. 7: elaboration of the Outline Preliminary Project (APS) at the level of re-establishment of natural flows Collection «Les outils» Sétra 42 September 2007

Elaboration of the Outline Preliminary Project At the level of re-establishment of natural flows Inputs (Project owner) Tasks (Design consultancy) Outputs (Design consultancy) 1. Mapping of the proposed project 2. Environmental studies: vulnerability of receiving surface environments, water course quality targets, position of harnessing points and protection perimeters, SAGE [Water development and management scheme] guidance, general measures aimed at protecting water resources etc. 3. Geological: - nature of subsoils thickness of ground water protection - vulnerability of ground water resources, see appendix 4.6 [13] 4. Road traffic 5. On-site intervention times in the event of Accidental Pollution, and account taken of maintenance and operation aspects 6. Validation by the Water Police services of the measures taken to protect water resources (optional) 7. Definitive mapping of all roadways - plans- typical longitudinal and transverse sections. Classification over the length of the projected mapping of the vulnerability of water resources Assignment of a type of water resource protection structure to each class of resource with an inadequacy recurrence interval associated with the structure. Recommendations for setting the height of the road (plan and longitudinal elevation) End point* Application of water resource protection measures - Tentative bill of quantities - Estimate Graphical documentation of the ranking of the vulnerability of water resources Diagrams of typical water resource protection structures Plans and longitudinal elevation showing recommended changes of route Brief note explaining the proposals Positions of harnessing points and their protection perimeters on the catchment area plan (or a separate plan) Water course quality target (Catchment area plan) Classification of water resource vulnerability Typical water resource protection structures Project plans longitudinal elevation - positions of discharge points - positions of off-platform watercourse protection structures Zones of application of the projected measures on the platform (zones to be sealed) Evaluation of the pollution loads (if necessary) and the resulting concentrations - Technical note - Tentative bill of quantities - Estimate See appendix 4.4 for abbreviations and symbols Table No. 8: elaboration of the Outline Preliminary Project (APS) at the water resource protection level Collection «Les outils» Sétra 43 September 2007

Elaboration of the Outline Preliminary Project At the platform surface drainage level Inputs (Project owner) Tasks (Design consultancy) Outputs (Design consultancy) 1. Geometry of the proposed project of all roadways - plan - typical longitudinal and transverse sections 2. Study of water resource protection - ranking of the vulnerability of water resources - discharge points 3. Geological study - nature of subsoils (sensitivity to water) - nature of permeability of subsoils (protection of ground water against accidental pollution) 4. Account taken of maintenance an operation aspects 5. Definitive mapping of all roadways - plans - typical longitudinal and transverse sections. Definition by uniform classes of the nature and first order characteristics of the surface drainage Appreciation of the specific zones having an impact on the project footprint or (and) a significant cost increase of the structures and on the height setting of the road. Recommendations for the height setting of the road End point* Adaptation of previously defined measures - Tentative bill of quantities - Estimate Typical clad sections with typical surface drainage structures Plan with discharge points and zones of application of the typical sections Brief note explaining the proposals Technical note - Tentative bill of quantities - Estimate See appendix 4.4 for abbreviations and symbols Table No. 9: elaboration of the Outline Preliminary Project (APS) at the platform surface drainage level Collection «Les outils» Sétra 44 September 2007

Elaboration of the Outline Preliminary Project At the platform surface drainage level Inputs (Project owner) Tasks (Design consultancy) Outputs (Design consultancy) 1. Mapping of the proposed project 2. Regional climate (freeze/thaw aspect) account taken for the roadway structures 3. Geological and geotechnical study - nature of subsoils (sensitivity to water) - drainage of banks 4. Typical transverse sections with - nature of surface drainage structures (Project owner or design office) and - roadway structures 5. Account taken of maintenance and operation aspects 6. Definitive mapping of all roadways - plans- typical longitudinal and transverse sections. Identification of zones requiring ground drainage as a function of: - guidance provided by the geological study - the climate - the nature of the surface drainage structures (platform sealing aspect) Depth of draining devices as a function of the thickness of the roadway structures and capping layer Recommendations for setting the height of the project longitudinal elevation End point* Definition of ground drainage zones Position of type of drainage on typical transverse sections - Tentative bill of quantities - Estimate Zones of longitudinal elevation to be raised Brief note explaining the proposals Plan and (or) longitudinal elevation with zones to be drained and application Typical transverse sections with position of the drainage systems - Technical note - Tentative bill of quantities - Estimate See appendix 4.4 for abbreviations and symbols Table No. 10: elaboration of the Outline Preliminary Project (APS) at the platform ground drainage level Summary of the progression of Outline Preliminary Project (APS) studies This progression relates to the technical aspects. The design office should, in any case, keep within the context of the study level and concentrate, in particular, on aspects that weigh significantly in the estimate. The design office's investigation must therefore remain at the scale of the study and not overreach itself by seeking after an illusory level of precision. Let it be remembered that the main impact of road surface drainage on the project costs results from resetting the height of the road. This re-adjustment can affect the amounts of cutting and banking to an extent that is not negligible and for which an estimation from the ratios is difficult. Collection «Les outils» Sétra 45 September 2007

This summary uses the elements from the four preceding tables. PROJECT OWNER DESIGN OFFICE Re-establishment of natural flows Geometry of the proposed project 1 Environmental study 2 Recurrence interval Q p Account taken of Q ex Protection of water resources 1 + 2 Traffic Geological study 2 Intervention time in the event of accidental pollution Platform surface drainage 1 + 2 + 3 + result of B Platform ground drainage 1 + 3 + result of C Climatic conditions See appendix 4.4 for abbreviations and symbols Diagram No. 13: summary of the progression of Outline Preliminary Project (APS) studies BV Enquête Terrain et recueil d'infos Pluviométrie Evaluation Qp Choix typologie des OH Prédimension OH avec Ham, Qp "passage" Q ex dans OH Hiérarchisation de la vulnérabilité de la RE Affectation d'un type d'ouvrage par classe de vulnérabilité Définition d'une typologie d'ouvrage d'assainissement par zone Vérification de la faisabilité des points de rejet Recommandation pour le calage du projet Point d'arrêt Géométrie validée Etude proprement dite - Zone nécessitant un drainage - Profondeur du dispositif de drainage - Vérification des possibilités de rejets des drains (exutoires) Catchment area Field survey and collection of information Rainfall Evaluation of Qp Choice of type of hydraulic structures Initial design of hydraulic structures with Ham and Qp "passage" of Q ex in hydraulic structures Classification of vulnerability of water resources Assignment of a type of structure for each vulnerability class Definition of a surface water drainage structure type per zone Verification of feasibility of discharge points Recommendation for project setting out Stop point Geometry approved Design - Area requiring to be drained - Depth of drainage structure - Verification of drain discharge options (outfalls) Collection «Les outils» Sétra 46 September 2007

Note: the progression described for the Outline Preliminary Project (APS) applies for the variants and the proposed solution. This progression relates to the technical aspects. The design office should, in any case, keep within the context of the study level and concentrate, in particular, on aspects that weigh significantly in the estimate. The design office's investigation must therefore remain at the scale of the study and not overreach itself by seeking after an illusory level of precision. Let it be remembered that the main impact of road surface drainage on the project costs results from resetting the height of the road. This re-adjustment can affect the amounts of cutting and banking to an extent that is not negligible and for which an estimation from the ratios is difficult. Collection «Les outils» Sétra 47 September 2007

Elaboration of the project La progression of the project studies is similar to that of the Outline Preliminary Project (APS) studies The inputs, tasks and outputs are, however, more closely defined. Tables 11, 12, 13 and 14 and diagram No. 14 mention that which is to be supplied in addition in the project study progression as compared with that of the Outline Preliminary Project. Project/additional requirements as compared with the Outline Preliminary Project (APS) at the level of the re-establishment of natural flows Inputs (Project owner) Tasks (Design consultancy) Outputs (Design consultancy) As for Outline Preliminary Project (APS) plus: 1. Geometry - plan with ground interface of all roadways. Water courses, streams and talwegs* must also be shown, enabling transverse sections to be read off. - transverse and longitudinal sections 2. PLU [Local town plan] 3. Outline Preliminary Project (APS) study and observations on the Outline Preliminary Project (APS) study 4. Water Law Dossier (DLE) and Water Police orders (if Water Law Dossier (DLE) drawn up in Outline Preliminary Project) 5. Details of mixed passages - hydraulic structure / fauna - hydraulic structure / tractor passage - hydraulic structure with fish passage - etc. 6. Additional topographic readings on water course (on request from the design office) 7. Situation in sections 8. Lifting of end point* As for Outline Preliminary Project (APS) plus: Longitudinal elevation of water course (CE) with the project of all roadways concerned Choice of the type of structure Characteristics of the structure (OH) Dimensioned section of the hydraulic structure (shown on the longitudinal elevation of the watercourse with the project) Hydraulic flow characteristics upstream of the hydraulic structure, in the structure and downstream of the structure (height of flow, speeds, régimes) Information from the project owner if incompatibility with the road height setting and end point Protection of the water course (bed and banks) against erosion Detail drawings Typical drawings of upstream and downstream heads Addition to the project plan view of - the hydraulic structure - types of head - types of protection - resizing of the water course As for Outline Preliminary Project (APS) plus: Longitudinal elevation of water course with dimensioned longitudinal section of the hydraulic structures and roadways (see sheet) - resized zones of the water course - zones where bed and bank protections are applied Additional reconnaissance of the terrain Sections and definitions of the protections and resizing Typical head drawings Plan (at study scale) with: - the position of the hydraulic structures - the typical heads - types of protection - resizing of the water course Technical note with, in particular, list of inputs. See appendix 4.4 for abbreviations and symbols Table No. 11: elaboration of the project at the level of re-establishment of natural flows Collection «Les outils» Sétra 48 September 2007

Project / additions relative to Outline Preliminary Project (APS) at the Water Resources Protection level Inputs (Project owner) Tasks (Design consultancy) Outputs (Design consultancy) As for Outline Preliminary Project (APS) plus: 1. Geometry of the project - plan with ground interface of all roadways - footprints (if already determined) - equipped transverse sections (noise protection dykes etc.) - longitudinal elevation 2. PLU [Local town plan] 3. Outline Preliminary Project (APS) study and observations on the Outline Preliminary Project (APS) study - vulnerability ranking of water resources and type of structure assigned to each vulnerability rank - forbidden discharge points 4. Water Law Dossier (DLE) and Water Police orders (if Water Law Dossier (DLE) drawn up in Outline Preliminary Project) 5. Additional topographic readings on water course (on request from the design office) 6. In sections 7. All elements required for structuring the systems for platform surface drainage (definition of the discharge points, structure of the surface drainage system, evaluation of the characteristics of the intake area at each discharge point) and ground drainage (any drainage discharge into basins, for example) (see infra "Project / Surface drainage and Project / Ground drainage") 8. Landscape constraints 9. Possibility of evacuation other than by gravity? 10. Lifting of end point* As for Outline Preliminary Project (APS) plus: Structuring of platform systems as a function of the possible discharge points Discharge points of the ground drainage system Location and dimensioning of the off-platform water resource protection structures Note: the foregoing tasks must be worked on in the context of surface drainage if the project is "complex". Information from the project owner if incompatibility with the road height setting and end point Plans defining the off-platform water resource protection structure with NGF [French National Survey heights] - longitudinal section - transversal sections - inputs - outputs - access ramp - screens - structure of bed and banks - degassing - drainage - access - etc. Plans defining pumping stations As for Outline Preliminary Project (APS) plus: Plan view: - platform discharge points - off-platform water resource protection structures with earth inputs - hydraulic junctions between platform discharge points and the structures - access to structures Plans defining structures (see tasks) Plans defining junctions between discharge points and structures Plans defining pumping stations Technical note: - list of inputs - assumptions - rainfall data - recurrence intervals of inadequacy of the structures - calculation of structures - calculation of residual loads at structure outputs and concentrations (if necessary) - description constructional provisions and structures - justification for pumping peak flow or of overflow from each accumulation section etc. See appendix 4.4 for abbreviations and symbols Collection «Les outils» Sétra 49 September 2007

Table No. 12: elaboration of project at water resource protection level Collection «Les outils» Sétra 50 September 2007

Project / additions relative to Outline Preliminary Project (APS) at the platform surface drainage level Inputs (Project owner) Tasks (Design consultancy) Outputs (Design consultancy) As for Outline Preliminary Project (APS) plus: 1. Mapping of the project - plan with ground interface, positions and types of noise protection, of civil engineering structures, tunnels, borders in islands, roundabouts, retaining walls (including type), landscaping with artificially created high and low points - typical cross-sections with sections of the roadways and all equipment (safety devices, borders, lighting, noise protection etc.) - pebble traps, verges - cross-sections, current types with equipment - longitudinal elevations with indication of banking - dimensioned plans of intersections - dimensioned plans of the various existing or projected networks - the footprints (if already determined) 2. For memory: - structuring of the measures taken for water resource protection - definition of the structures for re-establishing natural flows 3. recurrence interval of project flow of the surface drainage systems 4. Possibility of evacuation other than by gravity? 5. Lifting of end point* As for Outline Preliminary Project (APS) plus: Elaboration of the structural constraints on plan by position: - of the high and low points of the longitudinal elevation and in intersections - direction of banking by lane - points of change of banking by lane - gradient classes (ex. intermediate gradients < 0.5 %, > 3.5 %) - height classes of embankments (ex. h ² 2 m, h > 4 m, h intermediate) - zones sensitive to water - zones ranked by water resource vulnerability - points (or zones) of forbidden discharge Choice of structures and fine structuring of systems (taking account of water resources) Hydraulic calculation Information from the project owner if incompatibility with the road height setting and end point Plans defining structures: - route in plan with positions and characteristics of the various isolated systems and structures - dimensioning of the structures (plan or (and) longitudinal elevation) - typical structures - typical transverse sections with typical positions of surface drainage structures Plans defining pumping stations As for Outline Preliminary Project (APS) plus: Defining plans as defined in the column "Tasks" with the structural constraints Technical note: - list of inputs - rainfall data - project flow - recurrence interval of inadequacy of the structures - structuring of systems - choice and calculation of structures - description of constructive measures - justification of pumping peak flow or overflow per accumulation cistern etc. See appendix 4.4 for abbreviations and symbols Table No. 13: elaboration of the project at the platform surface drainage level Collection «Les outils» Sétra 51 September 2007

Project / additions relative to Outline Preliminary Project (APS) at the platform surface drainage level Inputs (Project owner) Tasks (Design consultancy) Outputs (Design consultancy) As for Outline Preliminary Project (APS) plus: - elements enumerated for the platform surface drainage at the project level As for Outline Preliminary Project (APS) plus: Details of the zones to be drained Choice of drainage devices Typical drawings of drainage devices and manholes Transfer to plan of the various types of drainage devices and their manholes As for Outline Preliminary Project (APS) plus: Plan with positions of the various drainage devices and manholes, suppliers quotes where appropriate Typical drawings Memo with, in particular, listing of inputs and decision parameters Supplier's quotation for drainage devices (if necessary) See appendix 4.4 for abbreviations and symbols Table No. 14: elaboration of the project at the platform surface drainage level Collection «Les outils» Sétra 52 September 2007

Summary of the progression of project studies This summary is in addition to the "summary of the progression of Outline Preliminary Project (APS) studies" (diagram No. 13) and goes into more detail on certain aspects. PROJECT OWNER DESIGN OFFICE Re-establishment of natural flows - Mapping of the project of all roadways and interchanges with ground interfaces 1 - Observations on the Outline Preliminary Project - Details of: mixed structures hydraulic + fauna... 1 + footprints + equipped transverse sections + landscape constraints + structures of surface an ground drainage systems (if from another design office) 2 2 + all equipment - safety, borders, noise protection... - positions and plans of civil engineering structures - positions and plans of walls + typical transverse sections with equipment and roadway structures + current transverse sections with equipment and top bedding of earthworks + dimensioned plans of the various existing or projected systems Platform ground drainage (les zones of terrain sensitive to water are assumed to be defined in the Outline Preliminary Project (APS) 3 See appendix 4.4 for abbreviations and symbols Diagram No. 14: summary of project studies PL du CE avec projet routier et OH projeté Caractéristiques hydrauliques de l'écoulement Recommandation pour le calage fin de projet Point d'arrêt Géométrie validée Etude proprement dite Longitudinal elevation of water course with road scheme and projected hydraulic structure Hydraulic flow characteristics Recommendation for detailed project setting-out Stop point Geometry approved Design Collection «Les outils» Sétra 53 September 2007

Altimétrie des points de rejet Calage des ouvrages hors PF Elaboration des contraintes structurelles Choix des ouvrages Applications au projet Calculs hydrauliques Cotes f.e aux points de rejet Choix des dispositifs drainants Application au projet Cotes f.e aux points de rejet Discharge point levels Setting-out of works outside the platform Elaboration of structural constraints Choice of structures Applications to the project Hydraulic calculations Gutter levels at discharge points Choice of drainage devices Application to the project Gutter levels at discharge points Collection «Les outils» Sétra 54 September 2007

3.3 - Traceability of choices/decisions, archives The various phases of the study (setting the road height and studies as such) are carried out by iteration. Each document drawn up and the choices of the project owner to proceed to the next iteration must be available for consultation at any time. The working documents, design office proposals and choices made to arrive at the final height setting of the project must be kept by making up usable archive files. 3.4 - Validating the production This is a question of being able to draw up a "certification of service rendered" (in the case of a study for which an external design office is engaged) or carry out a "project review" (if the study is carried out internally). The validation elements are described, non-exhaustively, hereafter: number of paper dossiers submitted, reproducible format (paper and/or computer medium), geometric format of the study (A3 landscape for example), graphic chart, documents making up each dossier, consistency between documents, consistency of references to various documents, appendices, paragraphs etc, account taken of inputs, scales of plans, format and content of computer media, presence of all documents making up the dossier, suitable format of software used. Collection «Les outils» Sétra 55 September 2007

4 General technical appendices 4.1 - General elements of hydrology 4.1.1 - Rainfall data The rainfall characteristics enter into the estimation of the input flows from the road catchment area and the natural catchment area crossed by the road by means of the various calculation methods, the most frequently used being the rational formula and the Crupedix method (see 1.1 and 1.2). The rainfall information used for road projects is of two types: Intensity-duration relationships of the rain for given frequencies (IDF curves) Drawn up from rain gage readings (height of water per time interval), these are used to calculate runoff flows using the rational formula. The average intensity i (T,tc) of the rainfall over the concentration time tc for a recurrence interval T is represented by the Montana formula: i (T,tc) = a (T) x tc b(t) (tc in minutes). The values of the coefficients a and b depend, for each station, on the recurrence interval (T) and the range of validity corresponding to an interval of duration of precipitation (D). The relationship i (T,tc) = a (T) x tc b(t) is generally adjusted for the following time intervals: 6 to 30 minutes (couple a (T) and b (T) ), 15 to 360 minutes (couple a (T) et b (T) ), 360 to 24 minutes (couple a" (T) and b" (T) ), For the calculations, the values of the coefficients a and b should thus be taken for the time interval that corresponds to the concentration time of the catchment area under consideration. Remarks: the coefficients a and b must not be used outside their range of validity, in all cases, it is advisable to use local rainfall data, the rainfall data values change with time, altering the coefficients a and b. They can be obtained from the national meteorological service (METEO-FRANCE), in each study, the location of the reference rain gage used, the observation period and the units of the coefficients a and b with their recurrence interval must be shown for each range of validity (D) applied in the study. Daily water heights for a given frequency These values P (T) come from the operation of the rain gages and represent a height of uncentered water falling in 24 hours as a function of a recurrence period. They are used essentially in the formulae for calculating the input flows of natural catchment areas. As in the previous paragraph, knowledge of the local values of P (T) can be obtained from the national meteorological service. Collection «Les outils» Sétra 56 September 2007

As an example, table No. 15 gives the values of the Montana coefficients obtained from the Météo France office of Lille-Lesquin (59) for the period: 1955-1997 (years 1989, 1991, 1992 and 1993 incomplete). Remark: the use of these values in the Montana formula: i (T,tc) = a (T) x tc b(t) gives the result of the intensity i in mm/minute with a concentration time tc expressed in minutes). To obtain a result in mm/hour, value a must be multiplied by 60. Table No. 16 gives the daily water heights for a given frequency. Recurrence intervals Height in mm 10 years 47.5 20 years 53.6 25 years 55.5 50 years 61.3 75 years 64.7 100 years 66.4 Table No. 16: daily water heights for a given frequency T (recurrence intervals) D (validity ranges of the Montana coefficients) a b a b a b 2 years 3.276 0.586 5.842 0.766 5.417 0.756 5 years 4.727 0.596 9.194 0.804 6.152 0.738 10 years 5.669 0.600 11.417 0.819 6.686 0.730 20 years 6.592 0.603 13.699 0.832 7.249 0.725 25 years 6.864 0.603 14.391 0.835 7.397 0.723 50 years 7.749 0.604 16.700 0.845 7.891 0.718 75 years 8.319 0.607 17.977 0.849 8.208 0.716 100 years 8.650 0.606 18.992 0.853 8.390 0.714 Table No. 15: values of Montana coefficients from Météo France, Lille-Lesquin, for the period: 1955-1997 Collection «Les outils» Sétra 57 September 2007

4.1.2 - Numerical example of application for the calculation of a project flow of a natural catchment area Characteristics of the natural catchment area crossed by the project Essentially, information about the natural environment is collected, together with the characteristics of the catchment area concerned. To the extent that there is no rain gage station on the stream in question, this work is based essentially on map data, a reconnaissance on foot of the terrain and the collection of information from the various services and locally. The first step is to delimit the catchment area upstream of the projected road. From this delimitation and a reconnaissance on the ground, the principal characteristics of the catchment area concerned can be obtained. The map below shows the natural catchment area of the Quievelon stream, crossed by the road project that links the communes of Quievelon and Colleret. It gives the future location of the hydraulic structure required to re-establish natural flows. Incidentally, it is important to note that there is no ichthyofauna present in this stream. Consequently no special provision need be made for the transit and reproduction of species. Diagram No. 15 shows the cross-section at the level of the crossing point (point c). Description of the catchment area The project is in the south of the northern district in the region of Avesnes. The catchment area crossed is part of the Sambre river basin and is drained by the Quievelon stream. It consists essentially of hedgerows, wet meadows, arable land and small wooded areas. The presence of a small conurbation should also be noted. Collection «Les outils» Sétra 58 September 2007

Map of the natural catchment area crossed and location of the re-establishment structure Zone urbanisée Zones boisées Cultures Pâturages Projet Limite de bassin versant Ecoulement concentré Ecoulement en nappe Point A TN Distance AB Pente AB Urbanized areas Wooded areas Crops Pasture Project Catchments area boundary Concentrated flow Sheet flow Point A natural terrain Distance AB Slope AB Collection «Les outils» Sétra 59 September 2007

In photo No. 1, we note the presence of a structure located 0.6 km downstream of the project. This stonework structure has never been subject to overflow, according to evidence collected in the neighborhood. The hydraulic cross-section of this existing structure (see diagram No. 16), which is of the order of 5.70 m 2, gives us a good indication of the size of the structure to be installed (all the more so since inquiries in the neighborhood indicate that it has never overflowed, making this a ceiling cross-section for the structure in the project). Photo No. 1: Quievelon stream Morphology of the catchment area The nature of the ground encountered shows a sedimentary facies. The principal characteristics of the catchment area are as follows: Surface area: S = 2.53 km 2 Diagram No. 15: cross-section of the stream at the level of the crossing point (point C) Average gradient: = 0.0191 m/m or 2 % with: ΔΗ: height difference between high point and low point of the catchment area equal to 49 m L: length of water course equal to 2565 m from A to C Ground use wooded areas S B = 0.71 km 2 built-up areas S U = 0.17 km 2 grazing areas S P = 0.98 km 2 arable land S C = 0.67 km 2 Diagram No. 16: existing structure Profil chaussee Roadway profile profil tn Natural terrain profile Rainfall parameters used For the purposes of the study, we obtained the necessary rainfall data from the Météo France service of the Lille-Lesquin station (59), which are representative and close to the project. They give us the values of the coefficients a and b used in the Montana formula with i intensity in mm/minute and t temps in minutes (see table No. 17). The ten-year and hundred-year daily rainfalls in mm are: P (10) = 48 mm and P (100) = 67 mm Recurrence intervals Ranges of validity of the Montana coefficients Period: 1955-1997 (1) 6 min< t <30 min 15 min< t <360 min a b a b 10 years 340,14 0,600 685,02 0,819 100 years 519,00 0,606 1139,52 0,853 (1) Years 1989, 1991, 1992 and 1993 incomplete Collection «Les outils» Sétra 60 September 2007

Table No. 17: ranges of validity of the Montana coefficients as a function of the recurrence interval Collection «Les outils» Sétra 61 September 2007

Determination of the project flow of the natural catchment area By application of the rational method 1) for T = 10 years evaluation of the run-off coefficient C (10) (with the aid of table No. 1, section 1.1.2); C (10) : calculated by considering a gradient of less than 5 % (almost flat) with sedimentary soils. For the built-up area, we took the ration of the sealed surface area to the total area. The elementary coefficients obtained were as follows: - wooded areas (S B = 0.71 km 2 ): 0.30 - built-up areas (S U = 0.17 km 2 ): 0.55 - grazing areas (S P = 0.98 km 2 ): 0.30 - arable areas (S C = 0.67 km 2 ): 0.50 from which calculation of the concentration time tc (10) (method described in section 1.1.4), tc (10) : calculated bearing in mind that on the upstream section (section AB) there is little or no run-off (layer run-off) and on the downstream section (section BC) the run-off is almost continuous and more marked (concentrated run-off). - Section AB: (run-off in layer) Heights: point A = 227.00 NGF, point B = 197.00 NGF Length L AB = 1210 m, gradient p AB = 0.025 m/m - Section BC: (concentrated run-off) Heights: point B = 197.00 NGF, point C = 178.00 NGF Length L AB = 1355 m, gradient p AB = 0.014 m/m which gives a concentration time Collection «Les outils» Sétra 62 September 2007

calculation of the critical intensity i (10) i (10) : determined from the Montana equation using the rainfall parameters, a and b, of the region of the study for a recurrence interval of 10 years as a function of the range of validity that includes the concentration time tc (10) of the natural catchment area, i.e: from which ten-year peak flow Q (10) 2) for T = 100 years summary of known parameters for: T = 10 years P (10) = 48 min C (10) = 0.37 tc (10) = 104 min for: T = 100 years P (100) = 67 min calculation of the initial retention P 0 (method described in section 1.1.4) As we have C (10) = 0.37 < 0.8 we have evaluation of the run-off coefficient C (100) (method described in section 1.1.2) calculation of the concentration time tc (100) (method described in section 1.1.4), calculation of the critical intensity i (100) i (100) : determined from the Montana equation using the rainfall parameters, a and b, of the region of the study for a recurrence interval of 100 years as a function of the range of validity that includes the concentration time tc (100) of the natural catchment area i.e: from which hundred-year peak flow Q (100) We see that the ration obtained is Q (100) / Q (10) = 8.5 / 4.0 = 2.12. This value reflects the threshold effect on a small catchment area (excepting overflow into zones subject to flooding). Collection «Les outils» Sétra 63 September 2007

By application of the Crupedix formula summary of known parameters Surface area of the natural catchment area: S BV = 2.53 km 2 Ten-year uncentered daily rainfall: P (10) = 48 mm Regional coefficient: R = 1 (the nature of the ground being semi-permeable, the selected value is that for intermediate subsoils, as recommended in section 1.1.4). ten-year peak flow Q (10) hundred-year peak flow Q (100) Using the ratio Q (100) /Q (10) = 2.12 obtained using the rational method, we obtain: By application of the transition formula Results of calculation by the rational method: Q R(10) = 4.0 m 3 /s Q R(100) = 8.5 m 3 /s Results of calculation by the Crupedix method: Q R(10) = 0.8 m 3 /s Q R(100) = 1.7 m 3 /s Surface area of the natural catchment area: (S BV ) = 2.53 km 2 calculation of parameters α and β and ten-year peak flow Q (10) hundred-year peak flow Q (100) For dimensioning the hydraulic structure to re-establish the Quievelon stream under the project, we therefore take the project flow Q (100) = 7.4 m 3. By way of comparison, the flow Q (100) = 7.4m 3 /s corresponds to a water level of 1.40 m in the existing structure located downstream of the project (by using the Manning Strickler formula with an estimated roughness coefficient, K, of 40 and a gradient p = 0.0030 m/m). To the extent that this structure permits a water level of up to 2 m, the selected flow seems consistent. The inquiries made in the neighborhood confirmed that this structure has never shown itself inadequate, making the result of our calculation acceptable. Collection «Les outils» Sétra 64 September 2007

4.2 - Elements of general hydraulics 4.2.1 - On the theory of flows The re-establishment of natural flows calls on the theory of free surface flow*. A flow is said to be "free surface" if the upper surface is open to atmospheric pressure (for a pipe, the flow water line does not reach the top of the pipe). Flows are classified into two types: Uniform flows A flow is uniform if the flow, the gradient, the cross-section (form and nature of the walls) are constant (see diagram No. 17). The flow in the platform surface drainage structures is nevertheless considered as uniform. In such conditions, the Manning Strickler formula can be applied: where: Q : flow in m 3 /s K : roughness coefficient Rh : hydraulic radius in m where Sm : wetted cross-section in m 2 Pm : wetted perimeter in m p : gradient in m/m This formula can be used to determine the height of the waterline at a point of flow through a given section. This water level is then called the normal level* (it is symbolized as yn in the case of a hydraulic structure and hn in the water course) Choice of the roughness coefficient* K The usual values of roughness coefficient for road surface drainage structures, mentioned in table No. 18, take account of the aging of the structure and the architecture of the system. These are values commonly used for roads. For the types of structure not mentioned in table No. 18, refer to the data sheets produced by the manufacturers and include the aspects of aging and architecture of the system. Recurrence intervals Flat, grassed in, shallow structures h ð 0.15 m h ð 0.20 m h: height of water in the structure in m Grassed in ditches (trapezoidal and triangular ditches) Surface structures in concrete (ditches, gullies and gutters) Smooth pipes (concrete, PVC, PEHD etc.) Height in mm Diagram No. 17: cross-section of a surface drainage structure Table No. 18: roughness coefficients, K, in surface drainage structures 10 15 25 70 80 Collection «Les outils» Sétra 65 September 2007

Gradually varying flows A flow is gradually varying if its various parameters (gradient, cross-section and speed) vary in a continuous, progressive and slow fashion. In the context of the present guide, it is considered that the flow passing from a water course to a reestablishment structure (via the head of the structure) takes place in a gradually varying flow and that the fluid is perfect. Bernoulli's equation Under the conditions defined above, BERNOULLI'S equation applies on a flow line at each section of the free flow: where: H : total head in meters z : level of bed relative to a reference plan in meters y : pressure head in meters (real height of the flow level) V : speed of flow in m/s g : acceleration due to gravity = 9.81 m/s 2 (usually rounded up to 10 m/s 2 ) : represents the kinetic energy in m Taking account of the drop in head along the flow, Bernoulli's equation (see diagram No. 18) is written: ( H drop in head in m) Applying Bernoulli's theorem at the entry to the projected structure, the water level, H AM, upstream of the structure can be evaluated: y e : water level at immediate entry to the structure (in m) K e : funneling coefficient V e : speed at the entry to the structure in m/s Specific head Specific head is the value Replacing, we obtain The variation of H s, as a function of y for a constant flow is represented by the curve (diagram No. 19): The specific head passes through a minimum for a water level called the critical level*. The specific head is then called the critical specific head. The level yc satisfies the equation: L c is the width at the water surface for the water level y c. if the water level y of the flow < y c, the flow is in torrential régime*, if the water level y of the flow = y c, the flow is in fluvial régime *. if the water level y of the flow = y c, the flow is in critical régime *. The waterline in fluvial régime* rises in an upstream direction, which is not the case in torrential régime*. The critical régime* along the flow in the structure is to be proscribed. Collection «Les outils» Sétra 66 September 2007

For the flow régime within the structures, the following configurations are aimed at (see table No. 19): Régime downstream of the structure Fluvial Torrential Régime within the structure Fluvial Fluvial or torrential Table No. 19: configurations for the flow régime within the structure Note: when the régime changes from torrential to fluvial, a jump* is created which is prejudicial for the longevity of the projected structure. This configuration must be the exception. Collection «Les outils» Sétra 67 September 2007

Diagram No. 18: representation of Bernoulli's equation Diagram No. 19: variation of Hs as a function of y Ligne de charge Ligne piézométrique Fond Plan de référence Critique Torrentiel Fluvial Constante Energy line Pressure line Bottom Reference plane Critical Torrential Fluvial Constant Collection «Les outils» Sétra 68 September 2007

Diagram No. 22: procedure for hydraulic dimensioning Dimensionnement hydraulique Hydraulic design Débit de projet Project flow Régime a l'aval de l'oh par calcul de hn et hc abaques 1 et 2 Regime downstream of the hydraulic structure by calculation of hn and hc design charts 1 and 2 Comparaison de hn et hc Compare hn and hc Régime fluvial Fluvial regime Régime torrentiel Torrential regime Calage de l'oh en fluvial Hydraulic structure designed for fluvial flow Calage de l'oh en torentiel Hydraulic structure designed for torrential flow Recherche caractéristiques de l'oh: Section,... Find hydraulic structure characteristics: Cross section Abaques 1 à 5 Design charts 1 to 5 Collection «Les outils» Sétra 69 September 2007

Tels que hauteur OH Comparaison yn et hn Such that height of hydraulic structure Compare yn and hn Collection «Les outils» Sétra 70 September 2007

Procedure for dimensioning the structures The procedure consists in finding: the downstream flow régime. Diagrams 20 and 21 summarize the possible scenarios, namely: - fluvial régime* downstream (structure designed for fluvial), - torrential régime* downstream (structure designed for fluvial or torrential), the design of the structure for the régime appropriate to the downstream régime (which determines the water level y e at the entry to the structure), the upstream water level* H AM of the structure. The flow chart of diagram No. 22 summarizes this procedure: Diagram No. 20: case of fluvial régime downstream of the structure Diagram No. 21: case of torrential régime downstream of the structure 1er (2eme, 3eme) calcul Calculation 1 (2, 3) Recherche du régime du ruisseau aval Find the regime of the downstream stream OH Hydraulic structure FLUVIAL FLUVIAL Cas de la figure ye=yn Case shown in the figure ye=yn si hn avait été supérieur à yn alors ye=hn if hn had been greater than yn, then ye=hn TORRENTIEL TORRENTIAL Collection «Les outils» Sétra 71 September 2007

Si l'oh est calé en torrentiel (cas de la figure ci-dessus) alors ye=yc Si l'oh est calé en torrentiel (yn>yc) alors (ye=yn) If the hydraulic structure is designed for torrential flow (case shown in the above figure) then ye=yc If the hydraulic structure is designed for torrential flow (yn>yc) then (ye=yn) Collection «Les outils» Sétra 72 September 2007

Funneling coefficient* Ke This coefficient varies according to the type of entry to the structure. Take the values from table No. 20: These funneling coefficients K e of table No. 20 do not take account of the sometimes important narrowing of the flow due the embankment of the road and the structure. Also, for these more complex scenarios, other equations must be used that are given in specialist works not mentioned in this document. Type of entry Ends cut on the slope (diagram No. 23) End with head wall and wing walls (diagram No. 24) Ke 0.7 0.5 Table No. 20: pummeling coefficient* K e as a function of the type of entry to the structure Diagram No. 23: ends cut on the slope Mur en retour Mur parafouille Radier facultatif Diagram No. 24: end with head wall and wing walls Return wall Cut-off wall Optional raft Collection «Les outils» Sétra 73 September 2007

4.2.2 - ABAC design charts for small hydraulic structures for re-establishing natural flows Trapezoidal channels, box culverts (m=0) ABAC design chart No. 1: determination of the normal water level Calculer N = avec Q en m3/s l et h en m p en m/m Déterminer m (dalots rectangulaires m=0) lire X sur l'abaque En déduire hn=l/x Canal rectangulaire Calculate N = where Q in m3/s l and h in m p in m/m Determine m (rectangular box culverts m=0) Read X from the design chart Deduce hn=l/x Rectangular channel ABAC design chart No. 2: determination of the critical level Calculer N = avec Q en m3/s l et h en m g ~ 10m.s2 Déterminer m (dalots m=0) lire X sur l'abaque En déduire hc=l/x Canal rectangulaire Calculate N = where Q in m3/s l and h in m g ~ 10m.s2 Determine m (box culverts m=0) Read X from the design chart Deduce hc=l/x Rectangular channel Collection «Les outils» Sétra 74 September 2007

Arched culverts*. Passes. Arches (ABAC design charts 3, 4 and 5) Determination of normal and critical water levels and the flow section. To use these ABAC design charts, the dimensionless parameters must be calculated from the characteristics of the chosen structure. The shape of the arched culverts and passages has been approximated with a semicircle crowning a semi-ellipse (see diagram No. 25). The error relative to the real cross-section is very small once the fill factor exceeds 0.50. P 0 : span of the arched culvert, F: overall height of the culvert, R = (different from the hydraulic radius) Fill ratio τ = The flattening coefficient of the pipe is defined by the relationship = F R (semi-minor axis of the ellipse) from which - circular pipes: λ = 1 - arched culverts and passages: λ varies from 1.25 to 5 - semi-circular arches: we include λ = Diagram No. 25: arched culvert λ λ 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 1.62 1.55 1.49 1.44 1.39 1.35 1.32 1.28 1.25 1.23 1.20 1.18 1.16 1.14 1.12 1.10 1.09 1.08 1.07 1.05 2.75 2.64 2.55 2.46 2.39 2.33 2.27 2.22 2.18 2.14 2.10 2.07 2.04 2.01 1.98 1.96 1.94 1.92 1.90 1.88 2.34 2.26 2.20 2.14 2.09 2.05 2.01 1.98 1.95 1.92 1.89 1.87 1.85 1.83 1.81 1.79 1.78 1.76 1.75 1.74 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0 1.04 1.03 1.02 1.01 1.00 0.99 0.99 0.98 0.97 0.96 0.96 0.95 0.94 0.94 0.93 0.93 0.92 0.92 0.91 1.86 1.85 1.83 1.82 1.80 1.79 1.78 1.77 1.76 1.75 1.74 1.73 1.72 1.71 1.71 1.70 1.69 1.68 1.68 1.72 1.71 1.70 1.69 1.68 1.67 1.67 1.66 1.65 1.64 1.64 1.63 1.62 1.62 1.61 1.61 1.60 1.60 1.59 Collection «Les outils» Sétra 75 September 2007

Table No. 21: interpolation elements for ABAC design charts 3, 4 and 5 for τ = 0.75 Collection «Les outils» Sétra 76 September 2007

ABAC design chart No. 5: determination of yn (normal water level) Calculate ; τn is read off from ABAC design chart No. 5 yn = τn x F Remarks: the oblique straight line indicates the practical limit of the fill ratio in fluvial régime (). Any increase in flow beyond the value corresponding g to et risks fully loading the structure, where the flattening coefficient of the pipe does not appear in the ABAC, table No. 21 gives, pour τ = 0.75, the elements for interpolation. Draw the curve corresponding to the closest to that of the pipe in the region of the value τn = 0.75, if τn < 0.5: try a smaller structure. ABAC design chart No. 5: determination of the normal water level (yn) ABAC design chart No. 3: determination of yc (critical water level) The procedure is the same as for ABAC No. 5; here we calculate the value of: ; from which τc and yc =τc x F. Q en m3/s : débit du projet R en m : demi-portée p en m/m : pente de l'ouvrage K : coef de Manning Stricler Buses métalliques Buses béton Q in m3/s: project flow R in m : half span p in m/m: slope of the structure K: Manning Stricler coefficient Metal culverts Concrete culverts ABAC design chart No. 3: determination of the critical water level (yc) Collection «Les outils» Sétra 77 September 2007

ABAC design chart No. 4: determination of the wetted section (Sm). S en m2 R en m S in m2 R in m ABAC design chart No. 4: determination of S (flow cross-section) for the water level (or, more simply, for the fill ratio) determined previously. From this we deduce the average speed for this level V = Collection «Les outils» Sétra 78 September 2007

Cylindrical pipes (ABAC design charts 6 to 11) ABAC design charts 6, 7 and 8 relate to concrete pipes. ABAC design charts 9, 10 and 11 relate to cylindrical metal pipes. These ABAC design charts apply where the flow downstream of the hydraulic structure does not provoke a downstream reaction (see diagram No. 26) Method of use: For the chosen structure, calculate the ratio ou = where Compare this ratio with the index numbers shown on the two curves (full and dashed) corresponding to each diameter. There are three possible cases: 1. upstream index (full line curve). The upstream water level is read off from the full curve. 2. upstream index < downstream index (dashed curve). Find a curve linearly interpolated between the two curves of the ABAC to determine the upstream H. 3. > downstream index. These ABAC design charts are unusable. Proceed as for arched culverts and box culverts. Diagram No. 26: application of ABAC design charts 6 to 11 for a flow downstream of the hydraulic structure not creating a downstream reaction Remark: the horizontal dotted lines on ABAC design charts 6 to 11 indicate, for each curve, the precision limits not to be exceeded. These limits are essentially located at the upstream water level equal to two diameters (H AM = 2 ), the flow must be free at the exit from the pipe (Hdownstream < ), These ABAC design charts correspond to simple head structures. The use of a profiled upstream head, an assumption different from that of the ABAC design charts, is possible: refer to the methodology explained for arched culverts and box culverts. Collection «Les outils» Sétra 79 September 2007

ABAC design chart No. 6: concrete pipes from 0.40 to 1.50 m in diameter. Upstream check. ABAC design chart No. 7: concrete pipes from 0.40 to 1.50 m in diameter. Upstream check. Mètres Courbe "amont" Courbe "aval" Q en L/sec. Meters "Upstream" curve "Downstream" curve Q in L/sec. Collection «Les outils» Sétra 80 September 2007

ABAC design chart No. 8: concrete pipes from 1.80 to 4.50 m in diameter. Upstream check. Mètres Meters Extension du graphe inférieur Extension of the lower graph Q en L/sec. Q in L/sec. Collection «Les outils» Sétra 81 September 2007

ABAC design chart No. 9: concrete pipes from 0.45 to 1.80 m in diameter. Upstream check. ABAC design chart No. 10: concrete pipes from 0.45 to 1.80 m in diameter. Upstream check. Mètres Meters Q en L/sec. Q in L/sec. Collection «Les outils» Sétra 82 September 2007

ABAC design chart No. 11: concrete pipes from 2.10 to 4.60 m in diameter. Upstream check. Mètres Meters Extension du graphe inférieur Extension of lower graph Q en L/sec. Q in m 3 /sec. Collection «Les outils» Sétra 83 September 2007

4.2.3 - Constructional arrangements and protection of hydraulic structures Setting A structure is set, as a priority, in the bed of a water course. If this is not possible (sinuous course, pronounced oblique angle), attention must be given to: maintenance of a good hydraulic flow upstream and downstream of the structure (diversion of the bed may prove necessary), protection of bends in the new bed and of the filled parts of the old bed. If the flow is permanent, the project must also take account of the provision of a temporary deviation of the water course or, where appropriate, construction of the structure alongside the existing bed (see diagram No. 27). The setting of the structure is linked with the gradient of the bed and the possible constraints relating to the level of the longitudinal elevation of the road. If the gradient of the bed is low (0.5 % to 6 %) and there are no constraints relating to the level of the longitudinal elevation of the road, the structure shall be set in line with the longitudinal elevation of the water course (bottom at about -0.20 m relative to this theoretical longitudinal elevation). In all scenarios, the setting of the structure should take account of the ichthyofauna. If the gradient of the bed is too steep, other types of solution are possible: make arrangements to slow the water (energy dissipaters) while keeping to the longitudinal elevation of the bed (see diagram No. 28); This solution, only usable in box culverts, may require anchoring of the structure (see diagram No. 29), set the structure with a lower gradient than that of the water course with its outlet part way up the embankment or its inlet excavated below normal ground level (see diagram No. 30). Diagram No. 27: diversion of the bed to reduce the obliqueness of the crossing Diagram No. 29: anchoring of the structure Diagram No. 28: energy dissipating arrangements Ecoulement d'origine Solution économique A éviter Protections Voie franchie Ancrage sur assise en béton Dispositifs dissipateurs d'energie Dalots uniquement Radier en escalier Radier muni de plots Diagram No. 30: solutions for reducing the gradient in the absence of ichthyofauna Original flow Economical solution To be avoided Protections Road crossed Anchored on concrete base Energy dissipaters Box culverts only Stepped raft Raft with blocks Collection «Les outils» Sétra 84 September 2007

The choice between these solutions depends on the flow and the nature of the terrain. If the gradient is small or zero, the structure shall be set with the maximum gradient permitted by deepening of the bed by washing out (see diagram No. 31). If the longitudinal elevation of the road requires deepening of the structure, we may consider: low structures: arched culverts or box culverts *, several structures of smaller capacity (less satisfactory solution hydraulically), deepening of the bed if downstream dredging will permit evacuation of the water, in extreme cases, a siphon or an aqueduct after studying all other solutions, including an adaptation of the longitudinal elevation of the infrastructure. Protections These are, essentially, those placed at the inlet and outlet of the structure. The upstream end is protected by a cutoff and a head wall, the embankment by wing walls and a head wall up to the previously determined upstream water level (taking account of exceptional flood levels). The downstream end is also protected by a cutoff and a head wall. Furthermore, the bed and banks are to be protected, preferably by vegetation or, if required by a cladding or rip-rap where the water speed at the outlet is such that there is risk of erosion (V> 2 to 4 m/s, depending on the ground), or where there is an elbow in the water course downstream of the structure. It is essential that the road or motorway embankment crossed by the hydraulic structure is protected up to the project upstream water level or exceptional flood level. Diagram No. 31: gradient too low Approfondissement Deepening Collection «Les outils» Sétra 85 September 2007

4.2.4 - Dimensioning of a hydraulic structure for re-establishing natural flows - application example Following the calculation of the flow from the natural catchment area, a project flow, Q (100), of 7.40 m 3 /s is retained for dimensioning of the hydraulic structure. The verification of the flow conditions is also carried out for an exceptional flow equal to 1.5 x Q (100), i.e. a flow of 11.10 m 3 /s, with the purpose of evaluating the impacts on the longevity of the infrastructure and the safety of adjacent property owners and users. It is thus a question of determining the nature and size of the hydraulic structure and the associated upstream water level (H AM ) permitting re-establishment of the natural flow through the embankment and the emplacement of the necessary protective measures, taking account of the following elements: Mapping data of the terrain in the proximity of the crossing: Longitudinal elevation of the stream at the crossing point (see diagram No. 32) Cross-section of the stream at the crossing point (see diagram No. 33): The representative cross-section (diagram No. 33) of the Quievelon stream downstream of the crossing can be represented as a trapezium (see diagram No. 34). In line with the nature of the walls consisting of grassy earth, we took a roughness coefficient K = 25 (see table No. 18 appendix 4.2.1). The estimated gradient of the banks is 1/1 (45 degrees), which gives m = cotg 45 = 1 The current gradient of the stream downstream of the crossing is 0.004 m/m or 0.4 %. The permissible upstream level has been fixed at 179,75 NGF, which represents the overflow limit of the low-level bed. The exceptionally permissible upstream level has been fixed at 182.00 NGF. This level corresponds to the threshold of the closest dwellings and ensures that the roadway structure is above water. Diagram No. 32: longitudinal elevation of the stream at the level of the crossing point Diagram No. 33: cross-section of the stream at the level - of the crossing point Diagram No. 34: representative cross-section of the stream trapezium approximation Largeur au droit de l'ouvrage Chaussée Talus AMONT AVAL profil moyen des berges actuelles profil du lit de la rivière pente moyenne Profil chaussée Profil TN Width at structure Roadway Slope UPSTREAM DOWNSTREAM Mean profile of the existing banks Profile of the river bed Mean slope Roadway profile Profile of natural ground Collection «Les outils» Sétra 86 September 2007

Flow régime downstream of the hydraulic structure The first task is to define the flow régime of the stream downstream of the hydraulic structure. Determination of the normal water level hn (use of ABAC design chart No. 1) Value of where: Q = Q (100) = 7.4m 3 /s, K = 25 (roughness of the stream bed), p = 0.004 m/m (stream gradient downstream of the crossing), l = 3.80 m (width at bottom of the ditch) and m = cotg 45 = 1 (slope of walls) From ABAC design chart No. 1, we read off: X = 3.4 The normal level is: Example of the use of ABAC design chart No. 1 Calculer N = avec Q en m3/s l et h en m p en m/m Déterminer m (dalots rectangulaires m=0) lire X sur l'abaque En déduire hn=l/x Canal rectangulaire Calculate N = where Q in m3/s l and h in m p in m/m Determine m (rectangular box culverts m=0) Read X from the design chart Deduce hn=l/x Rectangular channel Collection «Les outils» Sétra 87 September 2007

Determination of the critical level hc (using ABAC design chart No. 2) Value of where: Q = Q (100) = 7.4m 3 /s, l = 3.80 m (width at bottom of the ditch), m = cotg 45 = 1 and g acceleration due to gravity = 9.81m/s 2 From ABAC design chart No. 2, we read off: X = 5.8 The critical water level is: Example of the use of ABAC design chart No. 2 Calculer N = avec Q en m3/s l et h en m g ~ 10m.s2 Déterminer m (dalots m=0) lire X sur l'abaque En déduire hc=l/x Canal rectangulaire Calculate N = where Q in m3/s l and h in m g ~ 10m.s2 Determine m (box culverts m=0) Read X from the design chart Deduce hc=l/x Rectangular channel Flow régime of the stream downstream of the hydraulic structure The flow régime of the stream is determined by comparison of the normal (hn) and critical (hc) water levels: hn = 1.12 > hc = 0.66 so the flow régime is fluvial. Since the flow régime of the stream is fluvial, the hydraulic structure must be designed for fluvial régime. Collection «Les outils» Sétra 88 September 2007

General characteristics of the hydraulic structure A hydraulic structure must be defined such that its geometric characteristics, its installation and its hydraulic operation ensure a fluvial régime in this structure while respecting the general conditions of upstream level for the project flow, the exceptional flow and the free space. Choice of hydraulic structure From these data, it must be checked whether the flow conditions are satisfactory (fluvial régime, speed, proportions between normal water level yn and the critical water level yc and upstream water level H AM ). If the chosen structure is not satisfactory, the calculation process must be repeated with different characteristics for the structure. In our case, the hydraulic structure chosen for an initial approach is a concrete box culvert 3 m wide and 2 m high with a roughness coefficient K = 70 (by analogy with the existing structure downstream from the project, see appendix 4.1.2). The choice was for a rectangular box culvert as this allows a low water level for the magnitude of flow and meets the geotechnical constraints (foundation conditions of the structure, height of embankment). To facilitate flow, we decided to place a head wall and wing walls at each end of the structure. Determination of the critical level yc (using ABAC design chart No. 2) Value of where: Q = Q (100) = 7.4m 3 /s, l = 3 m (width of box culvert), m = cotg 90 = 0 (vertical walls) and g acceleration due to gravity = 9.81m/s 2 From ABAC design chart No. 2, we read off: X = 3.5 The critical water level is: Example of the use of ABAC design chart No. 2 Calculer N = avec Q en m3/s l et h en m g ~ 10m.s2 Déterminer m (dalots m=0) lire X sur l'abaque En déduire hc=l/x Canal rectangulaire Calculate N = where Q in m3/s l and h in m g ~ 10m.s2 Determine m (box culverts m=0) Read X from the design chart Deduce hc=l/x Rectangular channel Collection «Les outils» Sétra 89 September 2007

Determination of the normal water level yn to give to the hydraulic structure Since the structure must operate in fluvial régime, we shall take yn = 1.2 x yc (according to the general rules, the normal level yn should be at least 20 % higher than the critical level yc) From knowledge of the critical level: yc = 0.86 m, we obtain, for the normal level: yn = 1.2 x 0.86 = 1.032 m Flow régime in the hydraulic structure The flow régime in the structure is determined by comparison of the normal (yn) and critical (yc) water levels: yn = 1.032 m > yc = 0.86 m Consequently, the structure operates in fluvial régime, which is consistent with the régime downstream in the Quievelon stream. Calculation of the gradient to be given to the hydraulic structure (using ABAC design chart No. 1). The normal level so From ABAC design chart No. 1, we read off: N = 0.12 Since, we can obtain the value of the gradient: where Q = Q (100) = 7.4m 3 /s, l = 3.00 m (width of culvert), m = cotg 90 = 0 (vertical walls), K = 70 (roughness of culvert) and N = 0.12 (obtained using ABAC design chart No. 1). Collection «Les outils» Sétra 90 September 2007

We can thus give the hydraulic structure a gradient of 0.0022 m/m. Example of the use of ABAC design chart No. 1 Calculer N = avec Q en m3/s l et h en m p en m/m Déterminer m (dalots rectangulaires m=0) lire X sur l'abaque En déduire hn=l/x Canal rectangulaire Calculate N = where Q in m3/s l and h in m p in m/m Determine m (rectangular box culverts m=0) Read X from the design chart Deduce hn=l/x Rectangular channel Collection «Les outils» Sétra 91 September 2007

Calculation of the speed of flow in the hydraulic structure Situation: the flow régime in the stream is fluvial: hn downstream = 1.12 m, the flow régime in the structure is fluvial: yn =1.03 m. The normal water level in the structure (yn) and the water level at the entry to the structure (ye) is equal to the normal water level (hn) downstream in the Quievelon stream, i.e. 1.12 m (see diagram No. 22). We have the case of a structure in fluvial régime with a downstream reaction. Calculation of the wetted section and the speed of flow in the hydraulic structure The water line being at 1.12 m and the width of the box culvert: l = 3 m, we can calculate the wetted section (Sm) in the structure: Sm = hn downstream x l = 1.12 x 3 = 3.36 m 2 We obtain the speed of flow in the structure: where, Q = Q (100) = 7.4m 3 /s et Sm = 3.36 m 2 This speed of 2.20 m/s is acceptable as it is well below 4 m/s and does not require the installation of any special protection in the structure. Calculation of the upstream water level (H AM ): It must be ensured that the upstream water level (H AM ) is acceptable with respect to the project constraints. We have a fluvial régime in the structure and in the stream with a downstream water level: hn downstream in the stream higher than the normal water level: (yn) in the structure (case of a structure in fluvial régime with a downstream reaction, see section 4.2.1). The funneling head loss coefficient Ke is taken as equal to 0.5 (use of a classical head to the structure with wing walls) from which: The upstream altitude is 178.10 + 1.49 = 179.59 m. The permissible level being 179.75 m NGF, setting the structure with a gradient of 0.22 % is suitable. Verification of the free space (TA): The free space is measured from the water level to the upper generatrix of the structure. The water level is calculated by considering this level to be equal to the mean of the upstream water level of the structure: H AM = 1.49 m and the level at the entry to the structure: hn downstream = 1.12 m, which gives 1.30 m. The structure has an opening of 2 m; the free space (TA) is therefore 0.70 m. The fill ratio is 0.65, which does not exceed the value of 0.75 (see section 1.1.2). Verification of the hydraulic structure for an exceptional flow For an exceptional flow equal to 1.5 x Q (100) = 11.10m 3 /s, the calculation procedure remains similar and leads to the following results: Flow régime downstream of the hydraulic structure: - normal water level hn: 1.41 m - critical water level hn: 0.93 m hn = 1.41 > hc = 0.93 so the flow régime is fluvial in the stream Collection «Les outils» Sétra 92 September 2007

Flow régime in the hydraulic structure: - normal water level hn: 1.40 m - critical water level hn: 1.13 m yn = 1.40 > yc = 1.13 so the flow régime is fluvial in the structure Speed of flow in the hydraulic structure: The normal water level hn downstream (1.41 m) being higher than the normal water level yn in the structure (1.40 m), the water line in the structure will establish itself at the same level as the normal water level hn downstream, which is 1.41 m - wetted section Sm: 4.23 m 2 - speed of water in the structure: 2.63 m/s Calculation of the upstream water level: - funneling head loss: 0.53 m - upstream water level (H AM ): 180.04 The exceptionally permissible upstream level, fixed at 182.00 NGF, is respected. The level (H AM =180.04 m) reached corresponds to a slight overflow of the stream, which remains acceptable. free space: - free space: 0.23 m - fill ratio: 0.83 The fill ratio exceeds the recommended value of 0.75. To comply with this value, a box culvert 2.30 m high will have to be installed. Diagrammatic representation of the water line in the crossing From the results of the calculations carried out, we can produce a diagrammatic representation of the water line for this re-establishment (see diagram No. 35). Collection «Les outils» Sétra 93 September 2007

4.2.5 - Surface drainage of the platform - calculation method The purpose of the systems is to collect and evacuate water from a linear "geometric" impluvium* of which the surface area can be approximated by S = L x l (see diagram No. 36). They are calculated for a recurrence interval T = 10 years. Having organized the systems to comply with the structural constraints (high points, low points, discharge point, change of banking ), the minimum points of calculation are known (break in slope, discharge to another system from a transverse structure...). The general approach to dimensioning thus consists in verifying that the flow to be evacuated is less than or equal to the flow capability of the chosen structure along the whole length of flow. Flow capability* of the structure (at saturation) symbol Q c : The structure is saturated when it runs full bore. The MANNING STRICKLER equation gives the full bore flow capability, Q c, of the structure: Qc = 1000.K.rh 2/3.p. 1/2.Sm Q c = full bore flow capability in l /s K = roughness coefficient* (see table No. 18) R h = hydraulic radius in m where S m = wetted section in m 2 p = gradient in m/m V = full bore flow speed in m/s where V = Q c S m (at saturation) Diagram No. 35: longitudinal section of the hydraulic structure Largeur au droit de l'ouvrage Chaussée de 7 m AMONT AVAL Talus Ligne d'eau pour Width at structure Roadway 7m wide UPSTREAM DOWNSTREAM Bank Waterline for Collection «Les outils» Sétra 94 September 2007

Calculation of flow to be evacuated (symbol Qev): The flow to be evacuated is obtained by the rational method: Q ev is expressed in l/s C = weighted run-off coefficient of the impluvium C = 1 for the carriage ways and surfaced/clad parts C = 0.8 for verges in treated, stabilized gravel C = 0.5 for verges in untreated, stabilized gravel C = 0.7 for grassed soil receiving water from the roadway C = 0.3 for soil not receiving water from the roadway and for embankments outside the Mediterranean region. C = 0.5 for soil not receiving water from the roadway and for embankments in the Mediterranean region. At the Outline Preliminary Project (APS) stage, the embankments can be neglected in most cases. We can also take C = 1 for the whole impluvium to pre-dimension the systems. i = average intensity of the ten-year rainfall in mm/h, corresponding to the concentration time at the point of calculation and given by the MONTANA formula: A = area of the impluvium in ha (A = length of project x width) i = a x tc -b (t c in minutes). At a given point of calculation, we observe that, once the structure is chosen, the only unknown is the intensity i; which is a function of the concentration time t c at this point. The concentration time in minutes t c is calculated as follows: where - t 1 = time required for the water from the platform to reach the collecting structure. In practice, t 1 is taken as equal to 3 minutes: - t 2 = time in minutes taken for the flow in the structure to cover a length L L = length of the structure in m, V = projected full bore speed of the structure in m/s, at the point of calculation, 0.85 is a coefficient of reduction of V to take account of unequal filling of the structure between the origin of the system and the point of saturation. Comparison of Q ev and Q c The procedure consists in first choosing a structure up to a certain length and calculating whether its characteristics are sufficient, insufficient or excessive for the evacuation of the arriving flow. In the latter two cases, a structure with a larger or smaller capacity should be proposed: if Q ev > Q c, the capacity of the selected structure is insufficient: the length L of the structure should be reduced and a structure of larger capacity should be inserted between this structure and the outfall, if Q ev = Q c, the structure is suitable, the flow to be evacuated being equal to the flow capability of the structure, if Q ev < Q c, the structure has an excessive capacity. For reasons of economy, it is appropriate to assess whether the structure can be reduced by one or more classes. Collection «Les outils» Sétra 95 September 2007

Diagram No. 36: impluvium Chaussée point de calcul Roadway Design point Collection «Les outils» Sétra 96 September 2007

4.2.6 - Surface drainage of the platform - hydraulic calculations - application examples Gully at cutting bank foot The characteristics of the project are as follows (see diagram No. 37): "roof" cross-section: - cutting 200 m long: L = 200 m - width of platform: l = 13.50 m - gradient of longitudinal elevation: p = 0.01 m/m - weighted run-off coefficient of the platform: - grassed gully 2 m wide and 0.25 m deep (with K = 15); this structure is imposed by the cross-section, - I.D.F. curve of the region of study for T =10 years: i in mm/h and tc in minutes. The first iteration for the structure at saturation leads to the following results: 1) calculation of the flow capability of the structure: 2) calculation of the flow to be evacuated: where: from which tc 13.66 minutes where: Q ev (69 l/s) < Q c (92 l/s): the structure is suitable but is not saturated where it leaves the cutting. Diagram No. 37: gully at cutting bank foot TPC revêtu Chaussée Accotement engazonné Ouvrage engazonné Paved median Roadway Grass-verge Grass-covered structure Collection «Les outils» Sétra 97 September 2007

If we wish to gain "more precise" knowledge of the flow at the end of the cutting area, a second iteration is required, taking as input parameter Q c = Q ev = 69 l/s. We require to know the speed of the water in the structure for a flow of 69 l/s, using the MANNING STRICKLER formula. The results are obtained by constructing the graphs 1 and 2 (or by using a computer program). It is also interesting to know the level of water generated in the structure (general principle for assessing whether the characteristics of the structure can be reduced). For a grassed gully 2 m wide, 0.25 m deep, gradient 1 %, we have: Graph No. 1: flow / level ABAC design chart Graph No. 2: flow / speed ABAC design chart Thus, for a flow of 69 l/s, we obtain a water level of 22.50 cm with a speed of 0.343 m/s in the gully. From this, we can calculate a new value of t c. where which gives t c 14.43 minutes Q ev =2.78 x 89 x 103 x 0.27 = 67 l/s In conclusion, the ten-year peak flow at the end of the half platform in cutting is 67 l/s. Note: this iteration is given by way of a possible step; in our scenario, the difference in flow is negligible. This procedure can prove interesting in other situations. Graph No. 1: flow / level ABAC design chart of the gully Graph No. 2: flow / speed ABAC design chart of the gully Débit en l/s Hauteur en m Vitesse en m/s Courbe Débit/Hauteur Courbe Débit/Vitesse Flow in l/s Height in m Velocity in m/s Curve of Flow against Height Curve of Flow against Velocity Collection «Les outils» Sétra 98 September 2007

Ditch at foot of embankment The characteristics of the project are as follows: (see diagram No. 38) "roof" cross-section: - embankment 400 m long: L = 400 m - width of platform: l = 14.00 m - gradient of longitudinal elevation: p = 0.01 m/m - weighted run-off coefficient of the platform: C = 0.88 - grassed, trapezoidal ditch, 1.5 m wide at the top, 0.5 m at the bottom and 0.5 m deep with roughness coefficient K = 25 - I.D.F. curve of the region of study for T =10 years: i in mm/h and t c in minutes. The first iteration for the structure at saturation leads to the following results: 1) calculation of the flow capability of the structure: Q c = 1000.K.Rh 2/3.p. 1/2.Sm = 1000 x25 x 0.261 2/3 0.01 1/2 x 0.5= 510 l/s 2) calculation of the flow to be evacuated: where: tc» 10.69 minutes Q ev =2.78 x 0.88 x 117 x 0.56 (A = 400 m x 14 m = 5600 m 2 = 0.56 ha) Q ev = 160 l/s Q ev (160 l/s) < Q c (510 l/s): the structure is suitable but is not saturated where it leaves the embankment. If we wish to gain "more precise" knowledge of the flow at the end of the embanked section, we can, as in the previous example, proceed to a second iteration, taking as input parameter Q c = Q ev = 160,l/s. For a grassed, trapezoidal ditch, 1.5 m wide at the top, 0.5 m at the bottom and 0.5 m deep with a gradient of 1 %: see graphs 3 and 4. Thus, for a flow of 160 l/s, we obtain a water level of 27.5 cm with a speed of 0.75 m/s in the ditch. From this, we can calculate a new value of t c. from which tc» 13.46 minutes where V = 0.75 m/s Q ev =2.78 x 0.88 x 104.1 x 0.56 = 143 l/s Collection «Les outils» Sétra 99 September 2007

In conclusion, the ten-year peak flow at the end of the half platform in embankment is 143 l/s. Diagram No. 38: ditch at foot of embankment TPC revêtu Chaussée Accotement engazonné Talus Fossé engazonné Paved median Roadway Grass verge Slope Grass-lined ditch Collection «Les outils» Sétra 100 September 2007

Graph no. 3: flow / level ABAC design chart for a trapezoidal ditch Graph no. 4: flow / speed ABAC design chart for a trapezoidal ditch Débit en l/s Flow in l/s Hauteur en m Height in m Vitesse en m/s Velocity in m/s Courbe Débit/Hauteur Curve of Flow against Height Courbe Débit/Vitesse Curve of Flow against Velocity Collection «Les outils» Sétra 101 September 2007

Succession of two structures Considering the two previous examples placed end to end (the part in cutting upstream and followed by the part below the embankment) (see diagram No. 39), the calculations can be carried out as follows: From the point of calculation P0 (high point of road impluvium) to point P1 (change of embanked side), the section is in cutting (as in 1 st calculation example with collection by a grassed gully over 200 m) and we have the following results: Q ev = 67 l/s, A = 0.27 ha, C = 0.89, t c 1 = 14.43 minutes From the point P1 up to the point of calculation P2, the section is embanked (2 nd example with collection by a grassed, trapezoidal ditch over 400 m). The calculation data are as follows: Total area of impluvium (part in cutting + embanked part): 0.27 + 0.56 = 0.83 ha, weighted run-off coefficient: ditch at foot of embankment of which the flow/level and flow/speed laws are given by graphs 3 and 4. To find the flow to be evacuated at point P2, the new concentration time at this point must be calculated; it is equal to: t c = t c1 + t c2 t c1 is known and corresponds to the time of transfer between the high point haut of the road impluvium up to point P1 to cover the 200 m of the part in cutting, i.e. 14.43 minutes t c2 corresponds to the time of transfer between P1 and P2 to cover the 400 m of the embanked part, i.e: where: - V 1 speed at start of ditch at point P1 for 67 l/s, => V 1 = 0.60 m/s (value obtained by calculation or by using graph No. 4), - V 2 speed at saturation at point P2 for 510 l/s, => V 2 = 1.02 m/s. We obtain an average speed: Note: in our case, the average speed found is lower than 0.85 V. At the practical level, this calculation procedure is accepted. The concentration time t c2 is: t c 14.43 + 8.23 = 22.66 minutes i 10 = 392 x 22.66-0.51 = 79.8 mm / h Q ev =2.78 x 0.88 x 79.8 x 0.83 = 162 l/s Q ev (162 l/s) < Q c (510 l/s): the structure is suitable but is not saturated where it leaves the embankment. Making a second iteration using graph 4, we obtain, for a flow of 162 l/s a speed of 0.76 m/s. from which an average speed:, which gives: tχ» 14.43 + 9.80 = 24.23 minutes Collection «Les outils» Sétra 102 September 2007

Q ev =2.78 x 0.88 x 77.1 x 0.83 = 156 l/s In conclusion, the ten-year peak flow at the end of the half platform in embankment is 156 l/s. Note: in our case, the ditch used has a very large evacuation capacity (510 l/s) relative to the inflow (156 l/s); however, as it is a conventional ditch, this structure is retained. Diagram No. 39: succession of two structures point haut BVR point de transition déblai/remblai point de rejet partie en déblai sur 200 m partie en remblai sur 400 m Utilisation d'une cunette enherbée pente 1% Utilisation d'une fossé trapézoïdal enherbé pente 1% High point of road catchments area Cut/fill transition point Discharge point Cut section 200 m long Fill section 400 m long Use a grass-lined channel at a 1% fall Use a grass-lined trapezoidal ditch Collection «Les outils» Sétra 103 September 2007

Association of several systems (in the neighborhood of a low point, for example) The low point at the level of the crossing is the result of two interchange slip roads. Branch 1 has the characteristics mentioned in the preceding example, branch 2 has a larger impluvium than branch 1 and branches 3 and 4 are the symmetrical slip roads of the interchange (see diagram No. 40 ). The characteristics of the branches studied separately are as follows: Branche = Branch Knowledge of the input flow to the basin requires summation of the contributions from the four branches: this is not a simple sum of the separate contributions, which would give a flow of 503 l/s. In fact, the rational method being based on the longest transit time where there is an association of catchment areas, the concentration time to be considered in our case is the longest concentration time, i.e. t c = 34.50 minutes (branch No. 2). The input parameters to the rational formula become: weighted C = 0.91 i 10 = 64.4 mm/h A = 2.49 ha (sum of impluvia) Q ev =2.78 x 0.91 x 64.4 x 2.49 406 l/s (flow less than the sum of elementary contributions) In conclusion, the ten-year aggregate peak flow is 406 l/s. Note: in some rare cases, the resultant flow can be less than the contribution of one branch alone; the highest contribution should be retained in such cases. Diagram No. 40: symmetrical interchange slip roads Bassin Branche Traversée Basin Branch Crossing Collection «Les outils» Sétra 104 September 2007

4.3 - Glossary Roadway water management: All constructional measures contributing to the clearance of the road in three respects, namely: - the collection and evacuation of surface water, - the drainage of internal water (ground drainage), - the re-establishment of natural flows. Sedimentation: Accumulation of earth, sand or other sediment carried by water courses or the sea. Alluvium, sediment. Catchment area: Area of a form such that any water falling within it flows to a single point: the discharge point of the catchment area. Retaining basin: Generic term for a structure installed in series or parallel with a system for the temporary storage of run-off water. Other terms used: buffer, storage, holding etc. basin/tank. Verge: Unsurfaced strip either side of a road Containment ditch: Linear storage structure intended to contain accidental pollution. Ridge gutter: Small linear constructional device placed at the top of an embankment, generally made of concrete or bituminous concrete serving to guide a runoff water along the side of the road to a downdrain. Arched culvert: Concrete or metallic hydraulic structure for the re-establishment of natural flows and characterized by its span and its peak height. Pipe: Family of structures for the collection and longitudinal transport of run-off water from the road (see Acsare). Funneling coefficient K e : Parameter characterizing the transition into the hydraulic structure and characterizing head loss at the upstream end of the structure. Roughness or Manning Strickler coefficient: Coefficient indicating the impediment to flow presented by a hydraulic structure. Run-off coefficient: Theoretical fraction of the gross rainfall that appears as run-off. As a first approximation, it is the ratio of the sealed surface area to the total area of a catchment area (sealing coefficient). Water course: No technical criterion. The existence of a water course is recognized only if the following 3 conditions are satisfied: - persistent natural character of the bed, - a certain flow that depends on the local climatic conditions without necessarily being permanent, - normal route for run-off water. Flood: Phenomenon characterized by a more or less abrupt rise in the level of a water course with an increase in flow to a maximum level. This phenomenon can be accompanied by an overflow of the low-water bed. Floods are part of the régime of a water course. Floods are also characterized by their recurrence interval. The hundred-year flood has a recurrence interval of 100 years. Gully: Shallow, grassed or clad ditch with a gentle shape in the interests of user safety. Box culvert: Hydraulic structure of rectangular section, prefabricated or cast in place and with a high capacity. Flow capability: Maximum flow through a structure running full bore. Collection «Les outils» Sétra 105 September 2007

Project flow: Flow value used for the dimensioning of hydraulic structures. In general, hundred-year flows are used for hydraulic structures re-establishing natural flows and ten-year flows for platform surface drainage. Free surface flow: Term referring to a flow with the upper surface in contact with the air. Closed conduit flow: As opposed to free surface flow, this term refers to, for example, full bore flow in a pipe, i.e. with no remaining air space. Edge effect: Lateral movement of water in the ground at the edge of the surfaced part of the road. Outfall: In general, point of discharge of water outside the road footprint. Also refers to the downstream end of a drainage structure. Ditch: Simple, longitudinal hydraulic structure for the collection of run-off water dug in the ground beyond the shoulder, characterized by its cross-section and gradient. Gabion: Structural element consisting of a metal mesh basket filled with pebbles or small pieces of rock and used to stabilize loose ground and the banks of water courses. Geomembrane: Product suitable for civil engineering, thin flexible, continuous and impervious to liquids, even under working loads. Upstream water level: H AM, height of the waterline at the entry to a hydraulic structure. Downstream water level: H AV, height of the waterline immediately downstream of a hydraulic structure. Its value depends on the régime downstream of the structure. (see 4.2.1 On the theory of flows). Critical water level: Theoretical value determined from an ABAC design chart to define the flow régime (fluvial, torrential or critical). Normal water level: as above. Hydraulics: Study of the flow of liquids and of water in particular. Hydrogeomorphology: Scientific discipline consisting in the detailed study of the morphologie of alluvial planes and identifying on the ground the physical limits associated with the various ranges of floods that have formed them. Hydrogeology: Scientific discipline that concerns itself with the movements of ground water and the behavior of surface water. Hydrology: Scientific discipline that concerns itself with the water cycle. Aquaplaning: Loss of road adhesion due to the intrusion of a thin layer of water between the tire and the road surface. Impluvium: Delimited area receiving rainfall (sometimes synonymous with catchment area). Water meadow: Rich, wet ground often at the end of a backwater. Platform: In the geometric sense, road surface, including roadways and shoulders. Permeability: Ease with which the ground (or other material) allows the passage of a fluid. Wetted perimeter: In a flow section, length of contact between the water and the wall of the structure. Recurrence interval: Average time interval between two occurrences of a specific event. Symbol T, it is the inverse of frequency. Daily rainfall: Uncentered rainfall measured from 06:00 (UTC) on day D to 06:00 (UTC) on day D+1. Rain gage: Apparatus for recording rainfall. It yields data from which, in particular, intensity-duration rainfall curves can be obtained for various frequencies. End point: Point defined in an appropriate document beyond which an activity must not continue without the agreement of an organ or a designated authority. Collection «Les outils» Sétra 106 September 2007

Bearing capacity: Radier (rd): Hydraulic radius: Critical régime: Ability of ground, prepared or not, to withstand loads without deformation beyond a required limit. French term for the bottom (floor/bed) of a hydraulic structure. Ratio of the wetted area to the wetted perimeter. Theoretical boundary régime between fluvial and torrential (Froude number = 1). Fluvial régime: Free surface flow with a Froude number less than 1 (a perturbation can propagate against the current). In fluvial régime, a head loss leads to a fall in the waterline. Torrential régime: Free surface flow with a Froude number greater than 1 (a perturbation cannot propagate against the current). In torrential régime, a head loss leads to a rise in the waterline. Hydraulic jump (or Jump): Rise in the waterline due to a change from torrential to fluvial régime. Wetted section: Cross-sectional area of a structure occupied by the flow. Substratum: Rock underlying and more or less masked by surface deposits. Fill ratio: Ratio between the water level and the nominal water level or the nominal diameter of a hydraulic structure. Concentration time: Time taken by water to cover the distance between the point furthest from an outfall and the outfall. Talweg: Line joining the lowest points of a valley (valley line). Free space: Free height between the waterline and the high point of a conduit-like hydraulic structure. Collection «Les outils» Sétra 107 September 2007

4.4 - Abbreviations and symbols Abbreviations (French) AEP: APS: AR: BAU: BE: Adduction d Eau Potable [drinking water supply] Avant Projet Sommaire [Outline Preliminary Project] Assainissement Routier [roadway water management] Bande d Arrêt d Urgence [emergency lane] Bureau d Etudes [design office, consultancy] BV, BVR, BVN: Bassin Versant, Bassin Versant Routier, Bassin Versant Naturel [catchment area, road catchment area (impluvium), natural catchment area] CE: CETE: DIREN: DDAF: DLE: DUP: EN: GNT: MISE: MO: NGF: OA: OH: PDC: PE: PF: PL: PIPO: PPRN: PT: PLU: RE: SAGE: TPC: Symbols Cours d Eau [water course] Centre d Etudes Techniques de l Equipement [Technical Engineering Centers for Infrastructure] Direction Régionale de l Environnement [regional environmental directorate] Direction Départementale de l Agriculture et de la Forêt [district agricultural and forestry directorate] Dossier Loi sur l Eau [water law dossier] Déclaration d Utilité Publique [declaration of public utility] Écoulement Naturel [natural flow] Grave Non Traitée [untreated gravel] Mission Inter-service de l Eau [inter-district water mission] Maître d Ouvrage [project owner] Nivellement Général de la France [French national survey / national height datum] Ouvrage d Art [civil engineering structure] Ouvrage Hydraulique [hydraulic structure] Perte de Charge [head loss] Police de l Eau [water police] Plate-forme [platform] Profil en Long [longitudinal elevation] Passage Inférieur à Portique Ouvert [open-ended underpass] Plan de Prévention des Risques Naturels [natural risk prevention plan] Profil en Travers [transverse elevation/section] Plan Local d Urbanisme [local town plan] Ressource en Eau [water resources] Schéma d Aménagement et de Gestion des Eaux [water development and management scheme] Terre-Plein Central [median] A: area of catchment area a et b: Rainfall or Montana coefficients α et β: Weighting coefficients in the transition formula b : Regional coefficient for the calculation of Q 100 Collection «Les outils» Sétra 108 September 2007

C (T) : Run-off coefficient for recurrence interval T F: Height, vertical axis f.e: Fil d eau, channel g: Acceleration due to gravity m/s² H AM : Upstream water level h C : Critical water level outside structure h n : Normal water level outside structure h r : Fill level i (T) : Rainfall intensity for recurrence interval T I.D.F: Intensity Duration Frequency curve K: Roughness coefficient* or Manning Strickler coefficient K e : Funneling coefficient* L: Length of longest hydraulic path m: Value of cotg ø (ABAC design charts 1 and 2) N: Input calculation parameter to ABAC design charts 1 and 2 λ: Flatness coefficient of an arched culvert p: Gradient, slope P 0, P 10, P 100 : Daily rainfall for indicated recurrence intervals Po: Span of an arched culvert P m : Wetted perimeter Q c : Flow capability Q ev : Flow to be evacuated Q 10 : Ten-year flow Q 100 : Hundred-year flow Q ex : Exceptional flow Q MNA5 : Average monthly dry season flow with a recurrence interval of 5 years Q P : Project flow R: Regional coefficient in the Crupedix formula R d : Radier [bottom/floor of hydraulic structure] R h : Hydraulic radius S: surface area of catchment area S, S EM : Section of ac structure Wetted section T: Recurrence interval TA: Free space TN: Natural terrain τ: Fill ratio t c : Concentration time V e : Speed of flow X: Index (calculation of hn and hc ABAC design charts 1 and 2) y c : Critical water level in hydraulic structure y e : Water level at entry to hydraulic structure y n : Normal water level in hydraulic structure Collection «Les outils» Sétra 109 September 2007

4.5 - Table summarizing principle formulae Formulae Designation Fundamental formula of hydraulics Manning Strickler formula Bernoulli's equation Rational formula Montana formula Crupedix formula Empirical formulae for the calculation of concentration time Passini Ventura Collection «Les outils» Sétra 110 September 2007

Speeds method Collection «Les outils» Sétra 111 September 2007

4.6 - Bibliography (non-exhaustive list) Technical documents: [1] M. Larinier. Facteurs biologiques à prendre en compte dans la conception des ouvrages de franchissement [biological factors to be taken into account in the design of crossing structures], Bulletin Français de la Pêche et de la pisciculture [French bulletin of fishing and pisciculture] (BFPP) 1992 vol 65 No. 326-327. [2] C. Gosset, M. Larinier, J.P. Porcher, F. Travade. "Passes à poissons: expertise, conception des ouvrages de franchissement [Fish passes: expertise, design of crossing structures]" (compilation) available from Conseil Supérieur de la Pêche, 134, avenue de Malakoff, Paris. [3] Guide L eau et la route [Guide to water and roads] - Sétra - 1994 to 1999. Volume 1: problems of aquatic environments, volume 2: elaborating the project, volume 3: management of the road, volume 4: Impacts on aquatic environments, volume 5: laws and regulations on water resources, volume 6: accidental pollution on large infrastructures, volume 7: arrangements for the treatment of rainwater. [4] CCTG - ouvrages d assainissement [water management structures] - leaflet 70. Title I: réseaux [systems] title II: ouvrages de recueil, de restitution et de stockage des eaux pluviales [structures for the collection, return and storage of rainwater] November 2003. [5] Réhabilitation des voies rapides urbaines: thème assainissement [Rehabilitation of urban freeways: topic water management] Sétra technical guide 2001- Ref. D 0025 [6] Traitement des obstacles latéraux [Treatment of lateral obstacles] Sétra technical guide 2002 Ref. E0233 [7] Aide au Choix des Solutions d Assainissement et de drainage des Routes Existantes (ACSARE) [Selection aid for solutions for the improvement and drainage of existing roads] - Sétra technical guide 1993 Ref. D9232 [8] Buses métalliques: recommandations et règles de l art [Metal culverts: recommendations and engineering rules] Guide technique Sétra/LCPC technical guide September 2001, Ref. F8105 [9] Nomenclature de la loi sur l eau: application aux infrastructures routières [Nomenclature of the water law: application to road infrastructures] Sétra guide June 2004, Ref. 0412 [10] B. Lachat. Protection des berges de cours d eau en techniques végétales [Protection of the banks of water courses using vegetation techniques] Ministry of the Environment Editions 1994. [11] L entretien courant de l assainissement de la route [Running maintenance of road surface drainage]. Sétra practical guide 1998 - Ref. D9841 [12] Drainage routier [Road drainage] Sétra technical guide 2006, Ref. 0605 [13] Traitement de la pollution routière [Treatment of road pollution] Sétra technical guide to be published shortly. Regulatory texts: Law No. 92-3 of January 3, 1992 on water (included under title I of book II of the Code of the Environment) and its implementation orders. Order No. 93-742 of March 29, 1993 regarding the authorization and declaration procedures provided by the article of the law No. 92-3 of January 3, 1992 on water. Circular No. 94-56 of May 5, 1994 defining the procedures for drawing up, instruction and approval of investment operations in the unassigned national road network. Roads Directorate Circular No. 18 581 of December 22, 1992 on road quality available from Sétra Ref. A 9353. For information Technical instruction regarding drainage systems in agglomerations interministerial circular 77.284/INT of June 22, 1977 replaced by "la ville et son assainissement [the town and its drainage]" from Certu June 2003. Collection «Les outils» Sétra 112 September 2007

Ouvrages routiers et inondations: «des idées pour mieux gérer les écoulements dans les petits bassins versants» [Road structures and floods: "ideas for the better management of flows in small catchment areas"] Sétra information note No. 56, économie environnement conception [economy environment design] June 1998 (available for download from the Sétra Web-site). Collection «Les outils» Sétra 113 September 2007

This technical guide on roadway water management proposes a methodical approach to the technical design of structures to accommodate natural flows, for surface drainage of the platform and for internal ground drainage. This guide is intended for project owners and main contractors and for design offices and consultants concerned in the design of water management structures for new road projects and in rehabilitation studies for existing roads. This document is available and can be downloaded from the Sétra Web-site: http://www.setra.equipement.gouv.fr The Sétra belongs to the scientific and technical network of the French Public Works Ministry (RST) The Sétra authorization is required for reproduction of this document (all or even part) 2007 Sétra - Reference: 0744A - ISRN: EQ-SETRA--07-ED41--FR+ENG