Riprap Basin Design for a Small Catchment
This research study is to examine the hydrologic and hydraulic conditions in an ungagged site. A dangerous drop was formed in the stream bed at the downstream of a bridge and it got moved upstream due to soil erosion. During this analysis, it was just 35 ft. downstream from a local bridge which serves a residential area. It is causing a serious concern. Streambed erosion causes damage to bridge and hydraulic structures. To design a suitable structure to remediate this problem, hydrologic analysis was performed initially. Hydrologic analysis was carried out by developing a watershed rainfall runoff model using HEC HMS (hydrologic Modeling System) software. Needed preliminary watershed processing were done using USEPA BASINS software. Hydraulic modeling of the channel was done using HEC RAS (River Analysis System) software. Field cross section surveys were conducted to develop a hydraulic model. Both models were also used to simulate the known storm data from the 2008 Ike initially to perform calibration. The ungagged watershed models were also fine-tuned using three nearby watersheds which are hydrologically similar to the considered ungagged watershed (Hart Ditch, Deep River, and Little Calumet River). These simulations were also compared to the National Streamflow Statistic (NSS) software relevant to the Northwest Indiana region. Using a fuzzy based approach, peak flow ranges were divided into High, Medium, and Low flow ranges. Optimal design flow volume was derived for the existing site conditions for the recommended return period. This work was very field data intensive, which includes field cross sectional surveys and soil sample analysis. Using these results, the final design of a drop structure was completed with components such as embankments, riprap energy dissipater with feasible alternative options.
Viswanathan, Purdue University.
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