This tutorial is an illustration of a stepwise procedure for resolving errors in calculated channel travel times that occur when processing watershed parameters in HEC-GeoHMS. Channel travel time errors occur when a GIS-defined channel slope value during preprocessing of the Digital Elevation Data (DEM) is zero or negative (Adalikwu, 2021). The tutorial is intended to assist a relatively experienced ArcMap user resolve channel travel time errors that are documented in the TR55 Worksheet. Particularly, this tutorial is useful if the Muskingum method is selected by the watershed modeler as the river routing method. The K parameter value in the Muskingum routing method is the channel travel time (Song, Kong, & Zhu, 2011). This value can be obtained from the TR55 Worksheet under the channel flow characteristics. According to the TR55 methodology, a watershed’s time of concentration is a hydrologic parameter estimated as the sum of travel times for channel flow, concentrated shallow flow and sheet flow (Fleming & Doan, 2013; McCuen & Okunola, 2002). Therefore, errors in channel travel times will result in incorrect computed time of concentration. The step-by-step approach in this tutorial begins with the preprocessing of GIS data in HEC-GeoHMS up until when channel errors are encountered and how the errors are resolved.
South Dakota State University (SDSU), Jerome J. Lohr College of Engineering, Civil and Environmental Engineering Department
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Adalikwu, Philip A. and Burckhard, Suzette R., "How to Resolve Channel Travel Time Errors in the TR-55 Worksheet Using Arc Hydro Tools, HEC-GeoHMS and HEC-HMS" (2021). Civil and Environmental Engineering Reports and Manuals. 3.