Hydraulics & Waterways

Oral

394998 - Gauge-Adjusted Radar Rainfall Analysis for Sugar and Johnson Creeks, Iowa

Thursday, June 7
8:30 AM - 10:00 AM
Location: Regency Room

A hydrologic and hydraulic analysis was performed for both Johnson Creek and Sugar Creek within the City of West Des Moines, Iowa, (City) jurisdiction as part of the City of West Des Moines Grand Technology Gateway Location and Environmental Study. To evaluate mitigation alternatives which reduce flood damage potential and define a more efficient floodway, a more detailed hydraulic analysis of the area for existing and future conditions, was required. Additionally, a significant flood occurred in the Sugar and Johnson Creeks watersheds on June 25, 2015. This resulted in flooding on Sugar and Johnson Creeks in the study area. To confirm the GTG hydrologic model and the 2D hydraulic model, HDR performed a high-resolution gauge-adjusted radar rainfall analysis for the flood and updated the hydrologic model of the Sugar and Johnson Creeks watersheds to determine flow hydrographs for each stream at the bridges of interest in the study. The probability associated with the flood was estimated and the peak runoff from the hydrologic model was compared to the peak runoff resulting from the reconstructed June 25 flood. After the June 25 flood, HDR gathered rainfall data, visited the study area during the flood, and used high water marks gathered by the City of West Des Moines after the flood to confirm the 2D hydraulic model. This was done by executing the 2D hydraulic model with the hydrographs that resulted from the flood reconstruction and hydrologic model update after the June 25 flood.

Andrew William McCoy


HDR Engineering Inc

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394998 - Gauge-Adjusted Radar Rainfall Analysis for Sugar and Johnson Creeks, Iowa



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