Urban development significantly alters the hydrologic and morphologic characteristics of stream channels. Previous research cites impervious surface cover as a primary driving force behind fluvial geomorphic alterations associated with urban development, yet questions remain about the amount of total impervious area (TIA) responsible for subsequent geomorphic modifications of stream systems and about the nature of those modifications. This research compares selected characteristics of 29 rural and 23 urban streams in northern Georgia to determine significant differences in stream hydrology and morphology associated with the expansion of impervious surface cover.
Compared to rural (pre-urban) streams, urban streams were found to exhibit greater mean and flood discharges, but no difference in flood stage recurrence interval was found between the two sample groups. Analysis of the urban stream data suggests that a watershed TIA of 14-16% may be an amount of impervious surface cover above which channels become unstable. It is important to establish the level of impervious surface cover associated with alterations to the fluvial system in an attempt to offset the negative fluvial effects of urban development.