A Case Study of Channel Change during Urbanization: The San Antonio River from 1830-2004

The lower San Antonio River basin presents the opportunity to study channel planform change during urbanization in the study reach. Using a GIS framework, channel migration is measured over the period from 1838–2004. While the bulk of the watershed area remains rural, the effects of a large, urbanizing core extend throughout the reach. The physical processes governing river morphology in the watershed have a strong spatial component. The upper and lower portions of the study area respond differently to changes in the flow and sediment regimes related to increased impervious cover. By examining morphology change over a long time frame, the affect of urbanization on natural channel change can be determined. This research was motivated by the need to establish minimum in-stream flows for the San Antonio River. Significant alterations to the River are best understood when examined over large spatial and temporal scales, illustrating the need to understand the physical processes governing channel change.