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Design Storm Flooding in GIS Pro

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01-15-2025 07:24 AM
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maryk43
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New Contributor
‎01-15-2025 07:24 AM

Hi,

I'm currently trying to model design storm flooding (10, 50, 100 yr storms) in GIS Pro. I have been learning the ArcHydro (and Spatial Analyst>Hyrdo) tools and this is really helpful, but it's still one step away from being able to turn this into a design storm flood map. Ideally, I'd like to model this storm flood without having to switch programs. I'm using GISPro and can't use geoHec-RAS within the gis platform. My company is working to upgrade to the newest GIS Pro which should have the simulation tool. However, I can't find how this rainfall depth is applied - is it applied with a unit hydrograph?

Is there any tools or processes I have missed that might be helpful for this goal? Thanks all for your help!

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MarkBoucher
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Honored Contributor
‎01-16-2025 08:11 AM

I come at this from the engineering/hydrologist side. I've been learning GIS and Arc Hydro as I go.

I don't know of any tools for ESRI GIS programs (ArcMap/ArcGIS Pro) that will take rainfall and transform it into runoff (flow). [aka rainfall runoff (RR) transformation ]. I found this article in a quick search but it is academic and may not be ready for real-world application:  

https://www.sciencedirect.com/science/article/abs/pii/S235293852100063X. 

 

If someone knows how to do all of the hydrology and hydraulic (H&H) calculations inside an ESRI GIS program, let everyone know.

 

In using GIS to do this in our agency below are the general steps I am aware of. I have done all of these, but not yet from start to finish on one project.

  1. Use Arc Hydro to delineate watersheds and gather input parameters for HEC-HMS. (HEC-HMS has some GIS capabilities built in, but it does not seem to have fully functional GIS tools yet. For example, it will tell you what the centroidalflowpath distance is, but will not display the centroidalflowpath for you to confirm - at least that was my limited experience. It may be possible to do the whole watershed characteristics and RR transformation in HEC-HMS. HEC-HMS will also deal with routing flows through reservoirs and down long reaches of streams/rivers.
  2. Use HEC-HMS to calculate the flows (hydrology)
  3. Use GIS to create inputs for HEC-RAS, likely using GeoRAS. (HEC-RAS has some very good GIS like functions in a sub-application that is started w/in HEC-RAS called RAS Mapper. HEC-RAS is also needed to model bridges.
  4. Run model in HEC-RAS. (hydraulics) HEC-RAS can run a 1D using (cross sections: cross sections can be input from survey information or cut from a terrain model. The careless use of a terrain model should be avoided. [caution: LiDAR based terrain of a creek under tree cover can be very poor.] or a 2D model using a terrain model [note same caution]. The model is run and the output can be in a put in a form (layer/raster) that is readable by ESRI GIS programs.
  5. Add the HEC-RAS output into GIS.

We have created flows in HEC-HMS and, using the standard HEC-DSS format for the HMS output, read from the DSS file directly into HEC-RAS (1D model) to run an unsteady hydraulic model to evaluate the creek capacity.

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