USING NONCONTRIBUTING AREA TO ASSESS LANDFORM DEVELOPMENT IN THE CENTRAL LOWLANDS OF NORTH AMERICA

To explore natural drainage network development prior to modifications made by artificial drainage, a soil-based approach for identifying noncontributing areas was utilized. Fluvial network development has commonly been studied using drainage density changes across different landform regions. During early network extension, drainage density usually increases with time, and consequently landscape age is often reflected in drainage network character and extent. In the glaciated Central Lowlands, however, low topographic relief and abundant closed upland basins complicate this relationship. Agricultural drainage tiles and ditches have modified hydrological routing and channel extent in these settings, thereby inhibiting a more complete understanding of Quaternary landscape change. Here, we describe a soil-based approach for exploring drainage network development that is less impacted by drainage engineering. The US Soil Survey has mapped hydrologic and topographic characteristics of closed basins as they relate to indicative soil properties, allowing clear differentiation between closed basins and other landforms. The area that drains to these closed basins does not connect through surface waters to streams and is referred to here as noncontributing area (NCA). The catchment areas for the upland closed basins identified using soil maps were delineated in a geographic information system (GIS). Landform regions were delineated by combining information from available surficial geology, soil survey, and digital elevation maps. The percent NCA of the respective landform regions was then compared in relation to landform region characteristics such as age and type. Results indicate that noncontributing area decreases with increasing age of landform. NCA shows an inverse relationship with drainage density due to stream integration.