Stafford Run Creek
CobbFendley created detailed hydrologic and hydraulic models of the Stafford Run Creek watershed as it exists in the present day condition to provide a more accurate computation of the existing condition water surface elevations. This study also recommended improvements to the channel in order to result in lower water surface elevations. A HEC-HMS model was created to develop storm runoff hydrographs to represent the present day condition. LiDAR data was used to provide a representation of the terrain within each sub-basin in order to provide a measurement for overland slope, length of the longest watercourse and average slope along the watercourse. This information was utilized to calculate new time of concentration and storage (“TC&R”) values for each sub-basin and ultimately allowed for quantification of runoff contributing to the channel for each sub-basin.
An Unsteady HEC-RAS model was also created to determine the existing condition water surface elevations within the channel which result from the flow contributed from each of the sub-basins within the watershed. Once the existing condition 100-year water surface elevation was established, proposed improvements were iteratively added and removed from the model until a solution was reached in which water surface elevations were reduced to an acceptable level. CobbFendley developed two individual alternatives for improvements to the channel and recommended the alternative which resulted in the best cost/benefit solution.