CRWR Online Report 2001-7

 
 

GIS Algorithms for Large Watersheds with Non-contributing Areas

By Melissa Jane Figurski, M.S.E and David R. Maidment

ABSTRACT

The Texas Natural Resources Conservation Commission is creating water availability models to plan and manage long-term use of the Texas water supply. The development of these models requires watershed attributes for control points in Texas river basins. Previous researchers developed a procedure in GIS to determine attributes on small basins in which all the drainage area contributes. This procedure proved inefficient for larger basins and basins with pits that do not allow runoff to flow to the drainage system. This thesis presents an algorithm to develop watershed parameters for large basins in which parameters are developed in subbasins and then mathematically updated to reflect contributions from upstream or downstream subbasins. Additionally, an algorithm is presented to remove non-contributing areas from a GIS analysis in which a pit depth is defined and removed from the flow direction grid created from the digital elevation model (DEM). The drainage area is delineated and compared to reported stream gage contributing areas from the U.S. Geological Survey, and, if necessary, the pit depth is redefined. A comparison of the drainage areas for DEM-delineated watersheds to reported U. S. Geological Survey values validates the algorithm for subdividing large basins, but in non-contributing regions, the comparison suggests that a finer resolution terrain representation is required.

CRWR Online Report 2001-7

 

GIS Algorithms for Large Watersheds with Non-contributing Areas

By Melissa Jane Figurski, M.S.E and David R. Maidment

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