EXTRACTION AND REPRESENTATION OF NESTED CATCHMENT AREAS FROM DIGITAL ELEVATION MODELS IN LAKE-DOMINATED TOPOGRAPHY

This paper presents a new method for extracting flow directions, contr ibuting (upslope) areas, and nested catchments from digital elevation models in lake-dominated areas. Existing tools for acquiring descripti ve variables of the topography, such as surface flow directions and co ntributing areas, were developed for moderate-to steep topography. The se tools are typically difficult to apply in gentle topography owing t o limitations in explicitly handling lakes and other flat areas. This paper addresses the problem of accurately representing general topogra phic features by first identifying distinguishing features, such as la kes, in gentle topography areas and then using these features to guide the search for topographic flow directions and catchment marking. Lak es are explicitly represented in the topology of a watershed for use i n water routing. Nonlake flat features help guide the search for topog raphic flow directions in areas of low signal to noise. This combined feat-Lire-based and grid-based Search for topographic features yields improved contributing areas and watershed boundaries where there are l akes and other flat areas. Lakes are easily classified from remotely s ensed imagery, which makes automated representation of lakes as subsys tems within a watershed system tractable with widely available data se ts.