REVISITING WATERSHED DRAINAGE DENSITY: NEW CONSIDERATIONS FOR HYDROLOGIC PREDICTION
Here we revisit the long-standing conceptualization of drainage density as a good predictor of flow behavior at the landscape level. We depict drainage density (Dd) heterogeneity as a probability distribution function (pdf) of individual drainage densities within a watershed. Rather than limiting Dd to a single number (mean), we use standard quantitative descriptors of the pdf to explore landscape-level controls on flow regime. Two watersheds with similar mean values may have dramatically different pdfs and therefore exhibit variations in flow dynamics. We assert that some of the inconsistent results applying Dd as a predictive variable may be due to the accuracy with which a mean value can capture the behavior of a drainage network. In watersheds where drainage density is homogeneous, mean Dd may provide a good approximation of drainage behavior, but in watersheds where drainage density is heterogeneous, quantitative descriptors of the pdf can provide additional insight into flow dynamics.