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’ catchment solutions to fluvial flooding :-

  1.  Routine GIS feature-creation from Lidar point-cloud to describe the catchment digitally (Globalmapper being hard to beat)
  2.  Moderated pragmatic stream Bathymetry to 1M grid from stage 1 (Atrepo point-smoothing methodology being critical to bed-interpolation)
  3.  2D Terrain-Mesh creation and channel-flow computation  (HECRAS 5-2D courtesy USACE)

g40-ap40-varch1-gis  g40-ap40-varch2-bathym  g40-varch3-mesh

In this way, alternative channel features can be tested in software against extreme rainfall set as calibrated input to the 2D hydraulic model.


Q1:

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 gaw1@cantab.net)

gb40-pkfm-varch2

Q2:

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.)

Q3:

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

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RAS-Flood Methodology        More on Virtual Case Study        Acknowledgements

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Download tests:   canal map                          g40-fbridges

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