ISEP: AUTOMATED, WEB-GIS BASED HYDROGRAPH SEPARATION TOOL - APPLICATION IN STUDYING HYDROLOGICAL CHANGES DUE TO URBAN SPRAWL

A web based, Geographical Information System (GIS) enabled hydrograph separation tool (iSep) that uses a simple graphical filter method, has been developed and tested here. The iSep model separates baseflow from stream flow record by identifying minimum flow records and connecting minimum flow points using linear interpolation technique. A comparison of iSep results with that of one of the widely used hydrograph separation model, HYSEP, developed by United States Geological Survey (USGS) shows that iSep predictions are consistent with HYSEP.

iSep can be accessed via Internet through any commonly used web browsers at http://www.ecn.purdue.edu/runoff/iSep. The GIS interface provides a way to choose USGS stream gage stations and retrieve stream flow data directly for hydrograph analysis. iSep also provides the users the ability to upload their own stream flow data and get hydrograph separation performed. The output interface provides several options to get the results, including plotting of the hydrograph and getting the results e-mailed to the user. The example application presented demonstrates the use of iSep in studying hydrological impacts of urban sprawl. Little eagle creek watershed, which is one of the rapidly developing watersheds in the northeastern part of Indianapolis, IN has been studied to reveal that hydrograph separated stream flow data can be used as an indicator of urban sprawl related growth.