What is RAS-Flood
RAS-Flood is an assembly of three complementary generic software utilities which map and assess, by virtual case study, ‘in-channel’ OWC catchment solutions to fluvial flooding :-
- Routine GIS feature-creation from Lidar point-cloud to describe the catchment digitally (Globalmapper being hard to beat)
- Moderated pragmatic stream Bathymetry to 1M grid from stage 1 (Atrepo point-smoothing methodology being critical to bed-interpolation)
- 2D Terrain-Mesh creation and channel-flow computation (HECRAS 5-2D courtesy USACE)
In this way, alternative channel features can be tested in software against extreme rainfall set as calibrated input to the 2D hydraulic model.
How long does it take to produce indicative hydrographs from catchment rainfall (for comparison of alternative intervention and landuse measures) ?
Allow a day per 10 sq km for stage-1 (2.5 GHz x 8GB hardware) and 15 minutes per stream for stage-2. Stage-3 mesh creation within the GIS perimeter and with breaklines from stage-1 is automated and takes only a few minutes. However allow an hour or so to check over terrain-geometry manually.
Then, with terrain-geometry, bathymetry & (initially say) 24 hour rainfall loaded, hydraulic flow to yield indicative hydrographs can be tested in less than an hour (per 100 sq km). A cloud server, running the flow analysis code more quickly, is available on request (email email@example.com)
Will catchment flood alleviation measures be considered by policy-makers to provide ‘public good’ and thereby eligible for ‘public funds’ ?
Hard to say, but there is talk of the 2018 Agriculture Act putting a solid value per cubic metre of ‘blue-green’ extreme-event flood-water-storage. (In 2015, the Eden catchment required additional catchment storage in the region of 20,000,000 cubic metres – ie approx 10,000 cubic metres per square kilometre of catchment.)
What does ‘RAS-Flood’ cost and is there a limit to catchment size ?
Data and code are free to download – thereby to provide a steer on stream bathymetry and hydraulic flow. No size limit – useful results to date from 2 sqkm to 1000 sqkm catchments
RAS-Flood Methodology More on Virtual Case Study Acknowledgements
Download tests: canal map g40-fbridges