Designing a Basic White Water Canoe/Kayak Course using InfoWorks ICM

Transcription

1 Designing a Basic White Water Canoe/Kayak Course using InfoWorks ICM Adam Cambridge Hydrologist, Sinclair Knight Merz Robert Morden Senior Hydrologist, Sinclair Knight Merz Summary A functional design for a basic white water canoe/kayak course was prepared using InfoWorks ICM s 2D package. InfoWorks ICM was selected as the tool for the job, as it uses an unstructured mesh approach, is stable, is quick to build, and therefore balanced the technical understanding required with cost (flow conditions such as this would typically warrant CFO and/or physical modelling). The 2D model was successfully verified to a number of spot gaugings taken of water level and velocity along the full length of the course and was used to efficiently test different course arrangements using the functional requirements developed in conjunction with the working group. The functional requirements will be of use for engineers designing white water courses on rivers in the future and when used in combination with InfoWorks 2D provides an efficient means for preparing concept and functional designs, as well as communicating results through the use of themes and avi animations that can easily be created. InfoWorks ICM Case Study 1 October 2012

2 Introduction A basic white water canoe/kayak course on the Yarra River has been under consideration for some time by Parks Victoria, Melbourne Water, and key stakeholders, including Canoeing Victoria, the Melbourne Canoe Club and the Victorian Slalom Technical Committee (hereafter referred to as the working group). During an initial study it was identified that a reach of river just upstream of the Fitzsimons Lane Bridge, Templestowe would be most suitable, as the site: has existing good vehicle and pedestrian access, including a car park area is nearby to an existing canoe/kayak training facility (canoe store and boat ramp); and has a number of existing small riffles caused by rock bars (refer to Figure 1 below) Figure 1 Existing riffle features Parks Victoria commissioned SKM to prepare a functional design for a course at the proposed site following the completion of a feasibility study and a concept design phase. With few courses constructed in Australia let alone those built on a section of river, SKM developed a performance criteria for the course during the concept design phase and then used InfoWorks ICM along with environmental criteria to prepare a functional design. InfoWorks ICM was selected as the tool for the job, as it balanced the technical understanding required with cost (such flow conditions typically would warrant CFO and/or physical modelling) and also because InfoWorks ICM s 2D package: uses an unstructured mesh approach is most suitable for rapidly varying flows; can represent varying boundary conditions; can internally create TIN ground models ; can easily be amended to represent course arrangements through the use of mesh polygons defining heights or changes in level; and is stable and quick to build. Basic White Water Canoe/Kayak Design Criteria for Rivers There are few, if any, publically available guidelines to assist in the design of white water courses on rivers. To develop a basis for designing a course two workshops were held with Parks Victoria and the working where constraints and requirements of the course were openly discussed. Aspects considered included, appearance, experience/skill level, paddle/boat requirements, course features and alignment, viewing areas, course safety, as well as environmental requirements such as, flood InfoWorks ICM Case Study 2 October 2012

3 risk, fish passage, aquatic ecology, and scour/erosion. The performance criteria developed for designing a basic white water canoe/kayak course from a user s perspective for the river is summarised in Table 1 below. Table 1 Performance criteria for a basic white water canoe/kayak design from a user s perspective for rivers Component Requirement Appearance Experience/skill level The course should have a natural appearance. Large (>1m) smooth natural rocks are preferred. An example is provided in Figure 2. The course will be targeted at the basic entry level the course should be operational for the maximum period that can be achieved, Paddle and boat requirements depths of flow should be greater than 0.6m and ideally be 1.0m, foot and hand entrapments should be avoided, refuge areas should be provided near bank areas. The course should have one defined deeper flow channel. Structures should be tapered towards the deeper flow channel In channel course features Structures should be prominent and only become inundated during higher design flows Runs should be 5m wide as a minimum, as this will allow a standard canoe/kayak to pass through sideways Slalom features Slalom poles slots should be provided along both of the banks so that cables and slalom gates can be erected. Access should extend from the start of the course to just beyond the Fitzsimmons Lane Bridge in effect the full length of the course on the southern bank The access path should be approximately 2m to 3m wide, but minimum standard Access path widths will be confirmed during detailed design. Access paths should use hard surface techniques such as concrete to ease maintenance. Three existing access points on the southern bank should be formalised. Access to the northern bank (e.g. for erecting the poles) will be through the existing track used to access the flow gauge. Boat access should be provided at the start and end of the course Viewing areas The course should provide formal areas for spectators. A series of large steps would be the preferred appearance for seating areas. This could either be provided by timber decking or through a series of steps cut into the bank. An example is provided in Figure 2. InfoWorks ICM Case Study 3 October 2012

4 Figure Error! No text of specified style in document.2 Typical functional requirements for the course Flow gauging at the nearby Warrandyte Gauge was then used to establish the current flow behaviour for the stretch of river (percentiles), as well as those rates which should be used for assessing key environmental considerations, such as flood risk, fish passage, and aquatic ecology. Design flow rates for course users were established by reviewing known river levels published on the Whitehorse Canoe Club website ( which are rated in terms of Poor (stay home), Low (acceptable), and Good to determine corresponding rates of flow. This process established that for the Yarra River: good canoeing conditions typically require about 800ML/day to 1200ML/d; and the lower limits of acceptable canoeing typically are around 200ML/day where after there is not enough water to negotiate small rapids without grounding the canoe/kayak on the bottom. With a design criteria established in terms the project moved onto preparing a functional design using InfoWorks ICM s 2D packaged. The basis of design and approach to defining the performance criteria can be re used and built upon by engineers in the future. Model Build To develop a 2D domain of the current river arrangement a ground model TIN was generated internally by InfoWorks ICM using point type shapefiles of the terrain and the river bed bathymetry (topographic survey and LiDAR). A 2D mesh zone was then drawn around the study extent, defined as a normal boundary type, set with a representative roughness, and set to minimum and maximum triangles of 1m 2. Mesh zones were then included to the north and south of the banks with default triangle areas specified for maximising the computational time of the model. A 2D boundary InfoWorks ICM Case Study 4 October 2012

5 polyline was then snapped along the upstream boundary of the model, so that the 2D model could simulate flow entering the 2D domain. The general layout of the model is summarised in Figure 3 below. Inflow boundary Study extent Detailed mesh Course mesh TIN Ground Model Figure 3 Model Schematic Model Verification To ensure the model developed could be used reliably in the design of a basic white water canoe/kayak course spot gaugings of water levels and velocities were taken along the full length of reach of river. Corresponding flow gauging obtained from the nearby Warrandyte was then simulated using an inflow associated to the 2D boundary and used to critically evaluate the model. During this process it was found that the model originally developed only required a few minor adjustments to the representation of the bathymetry for it to be verified and the in built TIN surface functionality included within InfoWorks ICM made this process significantly more efficient. The performance of the model is summarised in Figure 4 below where it can be seen that the model is reproducing very comparable velocities and water levels. InfoWorks ICM Case Study 5 October 2012

6 Designingg a Basic White Water Canoe/Kayak Course using InfoWorks ICM Figure 4 Verification of the InfoWorks ICM model Recorded water levels and velocities Modelled water levels andd velocities Comments The model is reproducing the recorded water levels at the upstream and downstream extents of the model. In thee central areas of the study extent the model is predicting slighter higher water levels (e.g. recorded = 14.15m AHD modelled = 14.24m AHD) than that was recorded, but it is predicting very comparable velocities (e.g. recorded r = 0.8m/s modelled = 0.86m/s). The modelled velocities at thee upstream extent are also very comparable. At the downstream extent, while the water level is being reproduced by the model, it is predicting a much lowerr velocity (recorded = 0.9m/s modelled = 0.4m/s). Having visited the site it is felt that this recording may be erroneous, as this is a location by the bank where flows in the river expand and reducee in velocity. With this inn mind the model has been deemed to t be suitable for use. InfoWorks ICM Case Study 6 October 2012

7 Functional Design The functional design was prepared by simulating the verified model with the range of design flows identified and then amending the model to include course features as mesh polygons defining course features. Depths of flow and velocity were compared to the existing situation and used to ensure that the flow conditions created by the course would not significantly increase flood risk, would uphold fish passage, and not significantly affect upstream and downstream pool levels and thus littoral vegetation. The scenario tool within InfoWorks ICM was particularly useful in this regard, as it allowed the model amendments to be easily tracked and later audited by reviewers. The ability of mesh polygons to quickly adjust the 2D domain also allowed course configurations to be easily evaluated and amended to prepare a functional design. The final preferred course arrangement includes a series of higher level groyne features that are tapered towards the channel and raised areas along the bank which provide protection against scour and erosion. The functional design is shown in Figure 5 below which has elements and vectors themed as outlined in Tables 2 and 3. The themes and animations that were prepared were found to be particularly useful in communicating results to the working group. Table 2 Depth Theme Depth (m) 0.10 Minimum depth for riffles 0.30 Minimum depth for small sized fish 0.40 Minimum depth for small and medium sized fish 0.60 Minimum depth for course users 1.00 Ideal depth for course users > 2.50 Table 3 Velocity Theme Description Depths exceeding fish passage and course users requirements Velocity (m/s) Description Maximum velocity for small sized fish passage Maximum velocity for large sized fish passage 1.00 Instability velocity for access Desirable velocity for basic course users > 1.50 Desirable velocity for more advanced course users 1 Note: instability velocities will vary with time, body shapes, and weights. The adopted velocity is meant to be representative of instability which can occur due to moment instability ( toppling when the flow exceeds the moment due to weight of the body) and friction instability ( sliding when the flow exceeds the frictional resistance between the substrate and the persons feet). InfoWorks ICM Case Study 7 October 2012

8 Figure 5 Functional Design Functional Design 200ML/Day (Average Low Flow) Functional Design 1000ML/Day (Average Flow) Functional Design 360ML/Day (Median Summer Flow) Functional Design 2000ML/Day (Maximum Flow) InfoWorks ICM Case Study 8 October 2012

9 Conclusions The following can be concluded: While the design of a basic white water course would typically be undertaken using 3D and/or physical modelling, InfoWorks ICM s 2D package is a robust and efficient tool to use for preparing concept and functional designs. The performance criteria developed for designing a basic white water canoe/kayak course for rivers provided in Table 1 can be re used and built upon by engineers in the design of subsequent courses. The in built TIN ground model tool within InfoWorks ICM was found to be particularly useful in developing a bathymetry for the model The in built scenario functionality provides an effective quality management tool allowing modellers to better track and later audit models developed InfoWorks ICM Case Study 9 October 2012