Field studies of the storm event hydrologic response in an urbanizing watershed

Abstract

Dead Run is a 14.3 km² urban drainage basin, which is a tributary to the Gwynns Falls, the principal study watershed of the Baltimore Ecosystem Study. Hydrologic response in urban watersheds is examined through analyses of rainfall and discharge observations from the Dead Run watershed during a 6 month period beginning in June of 2003. Rainfall variability for flash flood–producing storms in Dead Run can be quite large when viewed from a Euclidean perspective. When viewed from the perspective of a distance metric imposed by the drainage network of Dead Run, however, the spatial variability of rainfall is small. The drainage network structure diminishes the effects of spatial rainfall variability for storm event hydrologic response, resulting in Dead Run exhibiting striking uniformity of response to storms with contrasting spatial distribution of rainfall. There is large storm-to-storm variation in the event water balance of Dead Run. Variation is linked to antecedent soil moisture (from the pervious portion of the watershed underlain by urban soils), rainfall variability, and spatial heterogeneity of runoff production.