THE IMPACT OF URBANIZATION ON BASIN EVOLUTION AND ISOLATED WETLANDS: A STUDY FROM THE RITCHEY WOODS NATURAL AREA, HAMILTON COUNTY, INDIANA

The role of time in drainage-basin evolution has long been studied. Ruhe documented that in glaciated terrains, drainage density tends to increase with time. Schumm identified that with time the zone of intense erosion migrates from the basin mouth to the headwater region. Now, throughout the glaciated Midwest, investigators are recognizing that urbanization appears to impact drainage-basin evolution by accelerating these processes. With urbanization, overland-flow times tend to decrease while total stream discharge tends to increase. These flow-characteristic changes, that are associated with urbanization, often lead to a period of channel adjustment and may accelerate channel growth and basin dissection. While many of the processes associated with a basin's response to urbanization have been studied, the long-term implications of accelerated basin response and dissection must be recognized.

Currently, states are grappling with how to protect “isolated” wetlands. In Indiana, the Indiana Department of Environmental Management (IDEM) is trying to assure the functional replacement of isolated wetlands by requiring mitigation when isolated wetlands are destroyed. Unfortunately however, it is being seen that the development and urbanization that leads to the need for wetland mitigation frequently triggers the expansion of 1st order streams and accelerated dissection of the impacted basin. This expansion of the drainage network may make it very difficult for small isolated wetlands to persist on the landscape. Here we will demonstrate the impact of accelerated basin evolution on isolated wetlands in the Ritchey Woods Natural Area, Hamilton County, Indiana.