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FLOOD PLAIN EVALUATION Upon completion of the hydrologic investigation, a flood plain evalua- tion was made on each of the drainageways within the Basin for each of the storm frequencies and conditions. The evaluation procedure involved the use of the Corps of Engineers HEC-2 Water Surface Profile Computer Program. This program was developed by the Corps of Engineers at the Hydrologic Engineering Center in Davis, Cal ifornia, and has been accepted as one of the most thorough and comprehensive methodologies for cal- culating water surface profiles in natural channels. This program has been used in other drainage studies in the Denver Metropolitan Area for the Urban Drainage and Flood Control District. Cri teria In the evaluation of the Basin, approximately 380 digitized drainageway cross sections were taken from the 1" = 100' scale mapping completed for the project. I nput to the HEC-2 water surface profi Ie program included the drainageway flows, cross section data along the drainageways, control data of drainage structures and obstructions such as building, vegetation, and manmade embankments, and channel roughness coeff i c i ents. The Mann i ngs roughness factors used in the computation of water surface profiles varied from 0.04 to 0.05 in the channel and overbanks, except on Coon Creek at Leawood Dr. where 0.07 was used. Transition coefficients used to denote changes in the channel cross section causing energy losses were 0.3 for expansion and 0.1 for contraction. Structures along the channel were analyzed concurrently with the drainage- way evaluation. Street crossing structure capacities were computed along with rating curves for significant crossings using the HEC-2 Water Surface Profiles Computer Program. Particular examination was made of culverts under Kipling Street, Wadsworth Boulevard and Pierce Street which are 9