The impact of urban development on hydrologic regime from catchment to basin scales

This study examines the role of urban spatial development on hydrologic response at both catchment (sub-grid) and river basin (between grid) scales in central Indiana. At the catchment scale, effective impervious area (EIA) was estimated using high density urban area and the patch size of low density urban area. The impact of urban spatial arrangement on floods was investigated using the estimated EIA for the entire White River basin, Indiana, as input to the Variable Infiltration Capacity (VIC) hydrology model with urban representation. A geographic information systems (GIS)-based routing scheme was introduced to the VIC model to route the total runoff. Seven theoretical scenarios were developed with equal urban area distributed in different isochrone zones. For return periods up to and including 100-year, the flood peaks at the basin outlet are largest if the travel time from urban cells is approximate to the mode of all pixels' travel time (plus the time for runoff rate to reach its maximum in a storm event) of the basin. Flood peaks tend to be smaller and arrive earlier with urbanization if development occurs in areas with shorter travel time, so the largest impacts of urbanization are not necessarily seen immediately downstream of the development. This research demonstrated that the spatial pattern of urban development can affect the hydrologic regime by influencing the hydrologic connectivity of urban area at a catchment scale, while at the river basin scale it is the travel time of urban location that controls flood patterns. (C) 2011 Elsevier B.V. All rights reserved.