This simulation represents the 5-year design storm event for the KCDA area. The event is based on the August 2016 historical tropical storm scaled to the 5-year 48-hour design storm precipitation volume. The storm critical duration was determined by modeling the gridded precipitation over the KCDA area and identifying the peak flow leaving the KCDA area for a variety of storm lengths. To match the design storm volume, the August 2016 historical storm was configured with a 0.65 scale factor for KCDA ME_MERI_50_UG. The model simulation was created in HEC-RAS Version 6.5. This represents the 2017 to 2019 existing conditions Mermentau geometry with calibration regions configured for validation as an average of calibration events. The simulation includes: a constant boundary inflow hydrograph for the Mermentau River based the 50th percentile flow of 500 cfs; design storm precipitation based on scaling of the August 2016 storm event; a constant mean high high water variable downstream tidal boundary condition; a constant downstream stage hydrograph of constant 50th percentile of 2.49 ft (NAVD88) at the Gulf Intracoastal Water Way derived from USACE Gage #76800, and infiltration over the watershed. The initial simulation time step is 5 seconds with the control by courant condition option enabled, allowing HEC-RAS to adjust the timestep as condition warrant during the simulation. This model is most applicable from river station 50 (ungaged) of Mermentau River to river station 5 of Bayou Queue de Tortue and associatted upper watershed for Mermentau River.
SCENARIO
5SEC