An automated technique for delineating and characterizing valley-bottom settings

Accurate delineation and characterization of valley-bottom settings is cruc ial to the assessment of the biological and geomorphological components of riverine systems; yet, to date, most valley-bottom mapping endeavors have b een done manually. To improve this situation, we developed automated techni ques in a Geographic Information System (GIS) for delineating and character izing valley-bottom settings in river basins ranging in size from approxima tely 1,000-10,000 km(2). All procedures were developed with ARC/INFO GIS so ftware and fully automated in Are Macro Language (AML). The GRID module is required for valley-bottom delineation and slope calculations: whereas char acterization (i.e., measuring the width of the valley-bottom zone) requires Coordinate Geometry (COGO) in the ARCEDIT module. The process requires thr ee inputs: a polygon coverage of the analysis area; an are coverage of its hydrography, and a grid representing its digital elevation. The AML is desi gned to operate within a wide range of computer memory/disk space options, and it allows users to customize several procedures to match the scale and complexity of a given analysis area with available computer hardware.