Submitted to: Annual American Geophysical Union Hydrology Days
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 1999
Publication Date: June 1, 1999
Technical Abstract: Distributed models of rainfall-runoff and soil erosion often use Geographic Information Systems (GIS) to describe the landscape topography on which runoff and erosion processes take place. Identification of drainage boundaries and channels, including channel properties, is the traditional forte and main contribution of GIS systems to distributed modeling. The identification of distributed properties for subcatchments from digital Elevation Models (DEM) is a new area of exploration. Contrary to the uniquely identifiable topographic properties of drainage divides and channels, distributed properties require a model to reduce the distributed information into a representative value for the subcatchment. Thus, a representative subcatchment property can have different values depending on the underlying model representation. Numerical algorithms are presented to approximate subcatchment area, length and slope for irregularly shaped subcatchments. Subcatchment area is calculated as a simple summation of al raster cells within the subcatchment. However, different models can be used to compute representative subcatchment length and slope. The length and slope values from several alternative models are evaluated and significant differences between the models are found. The differences are not the result of approximation errors, but result from the different interpretation and model representation of the property under consideration. These differences can have important implication for distributed rainfall-runoff and erosion modeling. The selection of the underlying model for subcatchment length and slope calculations from DEMs and the resulting differences in the representative length and slope values are discussed.