Estimating Impacts of Storm Surge on Inland Flooding Along Rivers Using HEC-RAS 2D
Wednesday, April 25, 2018
2:30 p.m. - 3 p.m. EDT
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Coastal storms generate surge flood impacts along coastlines. River flooding results from those impacts. Commonly used models for coastal storm surge such as Advanced CIRCulation (ADCIRC) and coupled wave models such as Simulation of WAves in the Nearshore (SWAN) have limited ability to model coastal inlets and river channels. While these models work well in large water bodies, their limited resolution of inland floodplain areas can lead to overestimation of flood impacts along smaller inlets and channels. Since they are two-dimensional (2D) models, it became obvious that porting data to a 2D riverine model would provide enhanced depiction of coastal influenced river flooding.
This presentation explores utilization of a publically available 2-D model, HEC-RAS 5.03. This version from the US Army Corps of Engineers has both 1-D and 2-D capability. It can ingest a coastal storm surge hydrograph as a downstream boundary condition while simultaneously incorporating inflow discharge hydrographs for upstream boundaries. Our example is a summary of the results developed for floodplains of the Buffalo River in the City of Buffalo, NY.
Downstream boundary conditions included both one percent annual and 0.2 percent annual exceedance coastal storm conditions. A HEC-RAS 2D representation of the Buffalo River floodplain was developed. This model generated flood elevations associated with 1-percent-annual-chance and 0.2-percent-annual-chance exceedance storm surges from Lake Erie for the downstream portion of the river. Results compare favorably to existing modeling.
Bill Nechamen, firstname.lastname@example.org