ARCADIS joined with two other firms to complete the first stormwater capital improvement study for Cobb County. Priority area No. 1 consisted of the central and western segments of the county. We completed a full study of the Noses Creek watershed, which is approximately 48 square miles in area, the largest segment of priority area No. 1. The Noses Creek watershed has a wide range of development densities and types. Land uses within the basin range from the densely developed urban and residential areas of western Marietta, through large residential subdivisions and open land.

We completed a full scope of stormwater master planning for the Noses Creek watershed. Our engineers and surveyors completed field reconnaissance of all accessible streams within the watershed to assess problem areas, evaluate stream quality, and identify significant structures. A structure inventory was then completed, with all stormwater structures carrying flow from areas of 125 acres or more (smaller structures were inventoried as appropriate) surveyed and inventoried. This data was compiled into an interactive database for easy access by the county. Relevant data was then applied to develop hydrologic and hydraulic models of the watershed, using the HEC-1 and HEC-2 model packages. Existing land use was established through overlaying the Atlanta Regional Commission's EDIS database to basin maps within ArcViewâ. Once calibrated, these models were then applied to evaluate known and potential flooding and erosion problems under both existing and future land uses. The models were then used to evaluate a number of alternative improvements to mitigate the modeled problem.