Interior Drainage Analysis for the Coeur d’Alene Flood Works Certification 

Client: City of Coeur d’Alene/Ruen-Yeager & Associates (2013-2014)


HMH Engineering was subcontracted by Ruen-Yeager to perform the Interior Drainage Analysis for the City’s flood protection works which protects the North Idaho College campus and the historic Fort Grounds neighborhood.  The Interior Drainage Analysis is a necessary component for certification of the flood works (or levee) for the National Flood Insurance Program.  The analysis must identified potential flooded areas in the levee’s interior based on a 100-year design storm and the capacity of the City and the College’s drainage facilities.  Without certification, the area protected by the levee would revert to a flood zone, forcing many residents to purchase flood insurance.

Mapping of existing drainage facilities
⦁    Delineation of subcatchments (mini-watersheds) 
⦁    Research of historical rainfall events, previous reports, and selection of an appropriate design storm
⦁    Modeling of drainage facilities in EPA-SWMM
⦁    Modeling of existing storm sewers
⦁    Modeling of grass swales and drywells
⦁    Calibration of the EPA-SWMM model to observed events
⦁    Determination of improvements required to alleviate flooding of depths greater than one foot