Use of the Basin Development Factor to Evaluate Urban Watershed Response

The Basin Development Factor (BDF) is a reasonably straightforward categorical variable that has promise for estimating urban hydrologic response. The objective of this study is exploratory — the goal is to learn whether the BDF improves the explanation of the rainfall and runoff responses of watersheds. This particular metric is attractive as an alternative to other metrics in use. The BDF was determined for more than 100 watersheds in Texas and then used to generate estimates of unit hydrograph timing characteristics and peak discharge characteristics. Simulated responses using these values are compared to both observed and prior simulated responses for the same watersheds. Inclusion of BDF as an explanatory variable in the regression analyses in this study to generate hydrologic responses did not materially reduce, or enhance performance in models of selected watersheds. This finding indicates that use of BDF cannot make estimates worse, but does not improve estimates either (and thus BDF as implemented here could be ignored). The result was discouraging, but the particular effort overlooked that the regression models used could estimate zero discharges, when, in fact, the actual database did not contain zero values. Despite the discouraging result, the authors believe that the BDF bears further study and suggestions for such studies are offered.