Floodplain Modeling Manual: HEC-RAS Procedures for HEC-2 ...
HEC-RAS flood modeling Little River basin with animation slides
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Transcript of HEC-RAS flood modeling Little River basin with animation slides
EVALUATING SEA LEVEL RISE AND CLIMATE CHANGE ON FLOODINGCase study: Little River basin, Newburyport, MAPrepared by: River Hydraulics, January 2017
Determine potential flood impacts associated with:
1. sea level rise;2. climate change;3. altering watershed infrastructure.
Problem statement
Opportunity New: HEC-RAS 2-dimensional unsteady flow
“bare earth” LiDAR terrain, free, accuracy in inches
Seamlessly combine LiDAR terrain with surveyed channel bathymetry
HEC-RAS modeling of river and tidal flows throughout a flood event
HEC-RAS automated floodplain delineation on aerial or topo maps
HEC-RAS evaluation of changes associated with culvert and bridge modifications
HEC-Hydrologic Modeling System (HEC-HMS)
Rainfall-runoff modeling for model calibration and determination of flood flow frequencies
Historic precipitation modified to reflect impacts of climate change
Drainage areas, runoff curve numbers, and times of concentration determined using Quantum GIS
The next four slides were produced by River Hydraulics using Quantum Geographical Information System (QGIS)
HEC-RAS model
cell size of 250’ x 250’ selected (large size OK with slope of water surface changes slowly)
Finer mesh with smaller cells along road and railroad embankments
Culverts modeled
One single 2D flow area
Overbank terrain from LiDAR seamlessly merged with previously-surveyed channel bathymetry
Calibration using Mothers Day flood of May 2006 (15” rain over 4 days)
HEC-RAS model parameters
Next Steps
Calibration of HEC-RAS Model
Determine flood boundaries, depths, velocities for various flood frequencies or events using HEC-RAS
• Determine impacts of proposed changes at culverts and bridges to upstream and downstream areas using HEC-RAS