PARENT SESSION
Oral Session #25: River and Riparian Restoration I.
Presiding: M.A. Madej
Tuesday, August 6. 8:00 AM to 11:30 AM. Mohave Meeting Room, TCC.
Predicting responses of moist-soil plants to flood regime: A simulation model to support restoration of the Illinois floodplain-river ecosystem.
AHN, CHANGWOO*,1, SPARKS, RICHARD1, WHITE, DAVID1, 1 University of Illinois at Urbana-Champaign, Urbana, Illinois
ABSTRACT- Moist-soil plants grow on mud flats left when seasonal floods recede, and the seeds, rhizomes and tubers of these plants are an important food source for waterfowl during their spring and fall migrations in the Mississippi Flyway. Productivity has declined because of unnaturally frequent small floods that inundate the mud flats and drown the plants during the summer growing season. These small floods are caused by operation of the navigation dams on the main channel and by alterations of the floodplain and tributary watersheds and channels. One approach to restoring productivity has been to build low levees to keep small floods off the mud flats. Other alternatives could include changing the operation of the dams and restoring hydraulic retention in the tributary watersheds and the mainstem floodplain. Predictive models are needed to evaluate the most cost-effective combination of approaches. Our moist-soil plant model simulates plant growth and seed production on 1m2 in response to daily water levels during the summer growing season. The model responds to daily water depth, flood timing (within the growing season), and flood duration, and is calibrated using historical (1940-1959) water levels and moist-soil plant coverage for five areas along the Illinois River, a major tributary of the Upper Mississippi River. At a relatively high land elevation within the floodplain (where floodplain forests normally grow because flooding during the summer is relatively infrequent), the model predicts moist soil plant production of ~500-600 g m-2 yr-1 and plant heights of 140 cm by the end of the growing season (mid October). As expected, growth declines with decreasing land elevation or with more frequent flooding at the same elevation. The model is one component of an integrated hydrological-ecological-economic assessment of alternative restoration scenarios for the Illinois floodplain-river ecosystem.
KEY WORDS: moist-soil plant, floodplain restoration, hydrology, ecological modeling