EXAMINING THE EFFECTS OF URBANIZATION ON STREAMS USING INDICATORS OF GEOMORPHIC STABILITY

Abstract

Understanding the response of a watershed to urbanization is important for future land use management and preserving or restoring aquatic habitat. Previous geomorphic studies of urbanization primarily consist of case studies documenting changes in hydrologic response and channel morphology, but offer limited predictive capabilities. However, channel-stability assessment methods have been developed to distinguish between stable and degrading or aggrading sites. Such measures allow possible prediction of urbanization impacts and offer possibilities of better preservation tools. Preservation or restoration of urban channels may be approached using stability measures as preliminary guidelines, and their applicability to various scenarios is important to assess. Seven stream-channel sites, with drainage areas between 15.9 and 72.1 km2 and high density urbanization ranging from 0% to 32%, were studied for geomorphic stability. Two qualitative and seven quantitative stability measures were tested for distinguishing between stable and degrading sites; quantitative measures were generally more successful than qualitative measures. Urbanization was not a distinguishable causal factor in channel instability, although some measures of channel instability were associated with higher levels of urbanization. [Key words: urbanization, channel stability, stream restoration.]