Hydrologic simulation of storm water detention storage in an urbanizing flood-plan
Smith, David Paxton
Bedient, Philip B.
Master of Science
Emerging concepts of urban flood control consider the use of storage detention, especially where channel capacities are being overtaxed by urban runoff. Particular problems exist where high rainfall intensities and low topographic relief combine with rapid urban development to produce potential flooding. Traditional approaches to flood control emphasize channelization of main streams and laterals to speed urban runoff out of developed areas. However, in low relief areas where the effect of urban drainage may be to greatly increase the peak flow rate and decrease the time to peak, flood control solutions of the 195's cannot handle the increasing development of the 197's. This has been experienced in rapidly growing coastal cities such as Houston, Texas. The purpose of the present study is to analyze the effect of detention storage placement and design on downstream flood flows in an urbanizing watershed. Effects of rainfall frequency, land use condition, and storage policy are directly considered in the methodology. The approach can be applied to any urban watershed in which historical rainfall data and streamflow data as well as land use information is available. The U.S. Army Corps of Engineers HEC-1 Model forms the basic tool for analysis of flood flows. A storage detention model is used in conjunction with empirical unit hydrographs which are derived as functions of land use. Storage detention is tested in both existing urban areas as well as projected future developments to discover effects on flood frequency flows. It is concluded that the ability to reduce the flooding potential of a rapidly urbanizing watershed with detention storage is limited by topography, remaining open space, and the presence of downstream development.