Flood risk assessment through a detailed 1D/2D coupled model

Transcription

1 CORFU Project Barcelona Case Study Final Workshop 19 th of May 2014 Flood risk assessment through a detailed 1D/2D coupled model Beniamino Russo Aqualogy Urban Drainage Direction

2 Introduction and general information Budget: 4.7 M Duration: 4 years Number of partners: 18 Main structure: 4 WP Coordinator: Prof. S. Djordjevic (Exeter University). Main objective: improve urban flood management increasing cities resilience 8 case studies: European and Asian cities will learn from each other through the development, investigation and dissemination of strategies that aim to improve flood resilience.

3 Barcelona Case study Collserola mountain Besós River Llobregat River High gradients Runoff preferred direction LowWell-channeled gradients and critical rivers points FLOODS Mediterranean sea

4 Barcelona Case study Location: Mediterranean Area, NE Spain Inhabitants/Area/People Density: 1,621,000 inhab. within an area of Km 2 with a density of 15,980 inhab./ Km 2 (19,200 inhab./ Km 2 not considering Collserola mountain). Morphology and land use: high slopes in the upper part of the city and flat and impervious areas near the cost. Climatology/Rainfall patterns: Average annual precipitations: 600 mm. Heavy rainfall with high intensities (Maximum intensity in 5 min is 205 mm/h for a 10 yr return period and 50% of annual precipitation can occur in only 2 or 3 events causing flash flood events). Raval District: Very vulnerable district with a people density of 44,000 inhab./km 2. Spot susceptible to flooding as demonstrated by historical data. Traditional 1D sewer models do not detect flooding problems as demonstrated by historic data

5 Detailed 1D/2D coupled model Type of model: Detailed 1D/2D coupled model (1D for sewer flow and 2D for overland flow) developed using Infoworks ICM Analyzed domain: 5 catchments Main characteristics of the model: 241 Km of pipes, 3286 manholes, 6 storage tanks with a total capacity of 170,000 m 3 Innovations of the model: Introduction of main and secondary network and micro-catchment definition in critical areas; DTM with a resolution of 1m2 and a precision of 15 cm in terms of ground level; 2D domain with more than 400,000 triangular cells

6 Results of sewer flow calibration Sewer system calibration (Flow depths time series in pipes, manholes and storage tanks) Situation for a monitored manhole (P-AV65) in Parallel Street Measured Simulated

7 Results of sewer flow calibration Sewer system calibration (Flow depths time series in pipes, manholes and storage tanks) Situation for a monitored pipes (P-IV35.1) in Diagonal Avenue (close to Balmes Street) Measured Simulated

8 Results of sewer flow calibration Sewer system calibration (Flow depths time series in pipes, manholes and storage tanks) Situation for several monitored storage tanks Bori i Fontestá Escola Industrial Joan Miró Measured Simulated

9 Results of sewer flow validation Sewer system validation (Flow depths time series in pipes, manholes and storage tanks) Situation for several monitored sewer system infrastructures Manhole BR-CL205 Parallel Street Manhole P-AV65 Parallel Street Pipe P-IV35.1 Balmes Street Diagonal Avenue Urgell storage tank Measured Simulated

10 Results of surface flow validation Validation of surface flow Comparison between flow depths provided by model simulations and youtube video recorded during the event of 30/07/ m

11 Results of surface flow validation Surface flow validation Diagonal Avenue with Casanova Street: Analysis of sewer profile focusing on the surcharged manholes. Comparison with a photo taken during the event of 30/07/2011

12 Flood risk assessment Following the literature, a risk map could be seen as the combination between a hazard map and a vulnerability map. Need to assess flood hazard and vulnerability.

13 Flood risk assessment For the Barcelona case study, flood risk assessment and, consequently, flood hazard and vulnerability assessment, was focused on the following targets for current and future scenarios: Flood risk concerning pedestrian circulation Flood risk concerning vehicular circulation Flood risk concerning goods and properties

14 Flood modeling scenarios For the case of Barcelona, and more specifically for the Raval District, a combination of different future scenarios of climate, adaptive capacity and socioeconomic aspects was developed. One of the considered scenarios was a business-as-usual (BAU)scenario, in which no adaptation strategies was implemented and it was associated to medium growth. In addition, 3 levels of adaptive capacity that could be reached were considered. In order to be able to compare the efficiency of the different adaptation measures, they were related to the same climate scenario (pessimistic scenario) and the medium socioeconomic scenario for the horizon 2050.

15 Future scenarios Summary of the combination of the scenarios and their main characteristics

16 Adaptation scenario 1: Non-structural measures Early warning systems Sliding panels across the entrances to prevent floodwater entry to properties Lift goods at risk

17 Adaptation scenario 1: Non-structural measures An early warning systems based on weather forecast is currently implemented in Barcelona (HIDROMET) Sliding panels constitute a common measure in the Raval District to cope with flood impacts

18 Adaptation scenario 2 (Green roofs) Sensitive topic for the Public Administrations Specific study carried out by Urban Ecology Agency of the Barcelona Municipality

19 Adaptation scenario 2 (Green roofs) Public areas Private areas

20 Adaptation scenario 3 (Structural measures)

21 Flood risk assessment for pedestrian circulation Flood hazard assessment

22 Flood hazard assessment for pedestrian circulation Flood hazard assessment was carried out for the Raval district according to specific criteria achieved for flooded streets during heavy storm events High hazard conditions were defined for velocities above 1.88 m/s and flow depths above 10 cm, while for moderate hazard, 1.5 m/s and 6 cm were considered as thresholds. Hazard level High Moderate Low Flow conditions (for flow depths between 9 and 16 cm) v 1.88 m/s 1.51 v < 1.88 m/s v < 1.51

23 Flood hazard assessment for pedestrian circulation Hazard map for the historic validation event ( ) High hazard: 14 % of the total 2D area

24 Flood hazard assessment for pedestrian circulation Baseline scenario Flood hazard maps for synthetic design storms (T1, T10, T100) High hazard areas: 0.05 Km2 (T1), 0.18 Km2 (T10), 0.40 Km2 (T100) High hazard: 5.4% of the total 2D area High hazard: 19.6% of the total 2D area High hazard: 43.5% of the total 2D area

25 Flood hazard assessment for pedestrian circulation Business as usual (BAU) and Adaptation 1 scenarios Flood hazard maps for synthetic design storms (T1, T10, T100) High hazard areas: 0.06 Km2 (T1), 0.24 Km2 (T10), 0.50 Km2 (T100) High hazard: 6.5% of the total 2D area Relative increase: 20% High hazard: 26.1% of the total 2D area Relative increase: 33% High hazard: 20.4% of the total 2D area Relative increase: 25%

26 Flood hazard assessment for pedestrian circulation Adaptation 2 Scenario Flood hazard maps for synthetic design storms (T1, T10, T100) High hazard areas: 0.01 Km2 (T1), 0.07 Km2 (T10), 0.18 Km2 (T100) High hazard: 1.1% of the total 2D area High hazard: 7.6% of the total 2D area High hazard: 20.5% of the total 2D area Relative decrease respect to BAU: 90% Relative decrease respect to BAU: 71% Relative decrease respect to BAU: 64%

27 Flood hazard assessment for pedestrian circulation Adaptation 3 Scenario Flood hazard maps for synthetic design storms (T1, T10, T100) High hazard areas: Km2 (T1), 0.02 Km2 (T10), 0.11 Km2 (T100) High hazard: 0.7% of the total area High hazard: 2.2% of the total 2D area High hazard: 12.0% of the total 2D area Relative decrease respect to BAU: 84% Relative decrease respect to BAU: 92% Relative decrease respect to BAU: 78%

28 Flood risk assessment for pedestrian circulation Flood risk assessment

29 Flood risk assessment Risk is defined as the probability or threat of hazard that is caused by a vulnerability and that may be avoided or minimised through preemptive actions. Risk Matrix Hazard So the risk maps were created multiplying the vulnerability index (1, 2 or 3, corresponding to low, moderate and high vulnerability) by the hazard index (1, 2 or 3, corresponding to low, moderate and high hazard). Finally the total risk varies from 1 to 9 where higher levels indicate higher risk. This methodology is summarized in the following Risk Matrix Vulnerability According to this definition, flood risk in Barcelona Raval District can be assessed through the combination of a hazard map and a vulnerability map

30 Flood risk assessment for pedestrian circulation Flood risk was defined for each census area and represented for all scenarios and return periods Baseline scenario Adaptation 1 scenario Business as usual scenario Adaptation 2 scenario Adaptation 3 scenario

31 Flood risk assessment for vehicular traffic Flood hazard assessment

32 Flood hazard assessment for vehicular traffic Baseline scenario Flood hazard maps for synthetic design storms (T1, T10, T100) High hazard areas: Km2 (T1), Km2 (T10), Km2 (T100) High hazard: 0.05% of the total area High hazard: 0.9% of the total area High hazard: 9.3% of the total area

33 Flood risk assessment for vehicular traffic Flood hazard was defined for each cell and represented for all scenarios and return periods Baseline scenario Adaptation 1 scenario Business as usual scenario Adaptation 2 scenario Adaptation 3 scenario

34 Flood risk assessment for vehicular traffic The risk was defined for each cell considering previous matrix for the return periods T1, T10 and T100 Baseline scenario Adaptation 1 scenario Business as usual scenario Adaptation 2 scenario Adaptation 3 scenario

35 Conclusions In the framework of 7th FP CORFU project, the hydraulic behavior of a critical area of Barcelona (Raval District) have been analyzed. A 1D/2D coupled model was developed using Infoworks ICM (by Innovyze) and the interface between the two drainage layers was characterized through empirical expressions related to hydraulic performance of surface drainage systems. Calibration and validation of the model were based on the data (rain gauge data, time series of flow depths recorded by water level gauges, reports and videos concerning flooded areas) related to 4 heavy storm events occurred in The obtained results show that it is possible to reproduce the effects of urban floods in a more realistic way than traditional 1D sewer flow simulations. A specific analysis on the computational time proved that it is possible to carry out simulations in few minutes using Infoworks ICM code. This aspect allows to use simulation results for real time strategies and early warning systems.

36 Conclusions Flood hazard maps concerning pedestrian circulation, vehicular circulation and goods and properties have been elaborated for historical heavy storms and several synthetic project storms (T1, T10, T11) for current and future scenarios considering climate change impacts and different adaptation measures. The methodology carried out and described can be implemented in the elaboration of future Drainage Master Plans (DMPs). In these DMPs flood impacts in terms of social and economical losses should use to justify or to prioritize structural and non-structural measures. Finally, according to the spirit of the Flood Directive 2007/60/CE and the Real Decreto 903/2010, hazard, vulnerability and risk maps can be used to have a comprehensive knowledge of flood-prone areas. These maps represent a basic tool for the development of flood risk management plans focused prevention, protection and preparedness (to be completed and published by Member States by 22 December 2015).

37 Thanks for your attention Beniamino Russo Aqualogy Urban Drainage Direction

38 CORFU Team

39 Acknowledgements Research on the CORFU (Collaborative research on flood resilience in urban areas) project was funded by the European Commission through Framework Programme 7, Grant Number Innvoyze and the Spanish support with InfoWorks ICM