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HEC-RAS Flood Model + Dam Break
I am a structural engineer given the task of completing an Emergency Action Plan for a small pond dam in Maryland. I have reviewed many methods on how to do this and tried to figure the best way to model this and perform the EAP/Dam Break analysis. If anyone wants to see my thought process here and comment on anything that I might have missed or if I am on the right path to completing such a dam break/flood inundation model – please feel free as it would be much appreciated. (I hope it is clear enough as I wrote this pretty quickly to sum up this effort)
Given
As-Built Plans of small area around pond dam – no electronic version or CAD files.
Hand calcs & TR-20 calcs containing discharge quantities, storage/elevation graphs, runoff curve numbers and runoff, time runoff charts, storage curve tables…etc.
To do:
From the State of Maryland Requirements:
Perform HEC-1 to develop & route hydrographs.
Fail dam with NWS Dam Break (which apparently doesn’t exist in its free state)
Route breach hydrograph downstream
Basic Assumptions
The post development calculations were performed by another engineering consultant years ago. The calculations assume that the existing RCP is clogged for the rainfall events: 2-Year Storm, 100-Year Storm, Brim-up condition, ½ PMF, and PMF.
Analysis Performed
The initial calculations were reviewed. The As-Built Plans from September, 1993 were referenced to and I created cross-sections along the south, west, and southwest directions of the pond dam (the areas susceptible to flooding). Based on the previous information, appropriate input values were determined and entered into a HEC-1 program to determine outflows. The HEC-1 results were then entered into a HEC-RAS flood modeling program to route the flood. A dam breach calculation was performed from the State of Maryland Department of Environment’s Simple Dam Break spreadsheets. The US Army Corps of Engineers dam break program is not supported anymore due to unavailable funds. From the results produced in HEC-RAS, a flood danger reach map was prepared.
Potential Impacted Area
From the results produced in HEC-RAS, a flood danger reach map was prepared based on the HEC-RAS results and a satellite image of the area. The impacted areas were drawn over the image in AutoCAD.
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Linear Mode
