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Work Order 16423

Due to occasional flooding of a low water crossing and the possible interruption of emergency services to residences, the City of Waco requested a floodplain analysis of Harris Creek in western Waco to determine the feasibility of a bridge. The Wallace Group’s surveying services included cross-sectional surveying along 1,450 feet of the existing natural channel. An accurate delineation of the drainage area was accomplished by importing and compiling digital USGS images into AutoCAD’s Land Development program. The time of concentration was determined and a composite SCS curve number was used to accurately reflect the existing conditions. The HEC-HMS Hydrologic Program was utilized to determine the 100-year runoff based upon a Type II Storm.

The existing natural channel was modeled within the HEC-RAS River Analysis Program developed by the US Army Corps of Engineers. Based upon the determined water surface elevation, a bridge was determined to be impractical due to the required span length and the location of existing houses. A future street extension was proposed to resolve the existing problem.