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United States Department of Agriculture

Agricultural Research Service

Title: Differentiating the Impact of Parameter Lumping from the Impact of Geometric Simplification in Modeling Runoff and Erosion 1584

item Canfield, Howard
item Goodrich, David

Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2005
Publication Date: January 15, 2006
Citation: Canfield, H.E., Goodrich, D.C. 2006. Differentiating the impact of parameter lumping from the impact of geometric simplification in modeling runoff and erosion. J. Hydrological Processes. 20(1):17-35.

Interpretive Summary: Computer models are used to predict how much flooding, erosion and sedimentation will occur. In order for these computer models to be accurate, accurate data must be put into the model. However, we don't really know how much spatial detail is needed in the input data to produce an accurate model estimate. This study began with data input values estimated on a 2.5 x 2.5 meter grid over a 4.4 ha watershed, and then looked at the effect of averaging these input values on predicted flooding and erosion. It also looked at the effect of using a less complex channel network representation than the actual field conditions. It concluded that there are not statistically-significant differences in predicted floods from moderate or large storms (which are usually the most important) as a result of either introducing more less channel networks or using averaged model input values. The study found, however, that for large storms the effect of averaging was to predict different amounts of sediment eroded from hillslopes and channels than the more spatially complex case. Therefore, the study concluded that using data that was not highly spatially-detailed was good enough for modeling runoff, but that the degree of spatial detail changed the erosion modeling, so that more spatially-varied data is better for modeling erosion.

Technical Abstract: There have been many studies of hydrologic processes and scale. However, some researchers have found that predictions from hydrologic models may not be improved by attempting to incorporate the understanding of these processes into hydrologic models. This paper quantifies the effect of simplifying watershed geometry and averaging the parameter values on simulations generated using the KINEROS2 model. Furthermore, it examines what these changes in model input have on model output. The model was applied on a small semiarid rangeland watershed. The study concludes that averaging input parameter values has little impact on runoff volume and peak in simulating runoff. However, geometric simplification does have an impact on runoff peak and volume, but it is not statistically significant. In contrast, both averaging input parameter values and geometric simplification have an impact on model-predicted sediment yield.

Last Modified: 4/23/2014
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