Using a GIS-Based Solution for Watershed Analysis and Automation: A Case Study

A GIS application called GISHYDRO is being used by the Maryland State Highway Administration (MdSHA). The GIS application is being used to save time in developing the hydrologic parameters for a drainage area with a size of approximately 150 square kilometers. To be more specific, GISHYDRO was used to develop RCN numbers for existing and ultimate land use conditions as well as provide initial estimates for times of concentration and to develop a TR-20 model. The use of GISHYDRO saved the project a significant amount of time by automating the process of developing RCN numbers, drainage areas, slopes, stream lengths and times of concentration. Also the results show that it provided this automation with a great deal of accuracy. The watershed is a rural watershed consisting primarily of forested and agricultural lands. The watershed's slopes are between 0.005 and 0.010 m/m, there are no major reservoirs, and the valleys are narrow and provide little storage for attenuation. The watershed is dendric and has a relatively high drainage density. The subwatersheds range from 8.26 square kilometers to 29.16 square kilometers, with the average subwatershed around 15.54 square kilometers.