Automated Geoprocessing Workflow for Watershed Delineation and Classification for Flash Flood Assessment.

Abstract

The characteristics of a drainage basin have a major effect on the risk potential for flash floods. For a detailed study on the risk potential detailed topographic, geological, soil related, meteorological, and historical data is needed, which is not available in many regions of the world. On the other hand, high resolution Digital Elevation Models are ready to use, from which topographic parameters of a watershed related to the risk potential can be extracted. In this study a complete automated workflow based on ArcGIS ModelBuilder using standard tools will be introduced and discussed. Some additional tools have been implemented to complete the overall workflow. These tools have been programmed using Python and Java in the context of ArcObjects. The model has been applied to the upper reach of the Akhangaran river south-east of Tashkent in Uzbekistan, which covers a total area of about 3600 km2. For the study area according to Strahler order 4 sub-basins of 6th order, 20 of 5th order, 71 of 4th order , 326 of 3rd order, and 1559 of 2nd order have been classified. The sub-basins have been evaluated according to the stream bifurcation ratio, the drainage density, the stream frequency, the circular ratio, the elongation ratio, and some other parameters.