Optimized Pit Removal
Extracting hydrologic features such as stream centerlines and watershed extents from a Digital Elevation Model (DEM) typically requires first hydrologically conditioning the DEM. In this process the elevations are modified in order to clearly establish flow directions. One downside of the standard ArcGIS Fill method of removing pits is that it tends to obscure meaningful elevation data for wide areas upstream of any dam-like feature. This is especially prevalent when the terrain is flat and when working with high resolution data such as LiDAR.
The Optimized Pit Removal tool uses a combination of cut and fill to remove all undesired pits while minimizing the overall changes to the landscape. The user can choose to either minimize the absolute change in landscape elevation summed across all cells, or to minimize the net change in landscape elevation (effectively balancing cut and fill). An option is also provided to exclusively use cut.
The tool also allows users to mark specific depressions to be left unmodified by setting the lowest cell to have a value of No Data. This feature can be used to establish reservoirs as well as known drainage features such as storm sewer inlets.
Compatibility:
The tool was designed for ArcMap 10.1 and Windows 7 64-bit and has not been tested in other environments. Most hydrologic conditioning workflows also require the ArcGIS Spatial Analyst Extension.
The current maximum grid size is approximately 50,000,000 cells, with a practical limit of approximately 25,000,000 cells (5 square km. at 1 meter resolution). This file size limit will be expanded in future versions of the tool.
Feedback, including interesting case studies and suggested improvements for future versions of the tool, can be directed to Stephen Jackson (srj9@utexas.edu).
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