Naturalization of Developed Floodplains: An Integrated Analysis
Authors: Sparks Richard E. , Braden John B. 
Published: August 2010

Summary

Reducing future flood damages and restoring natural services provided by floodplains is not as simple as buying levee districts from willing sellers and then breaching the levees. Removing agriculture from the floodplain can have a significant negative impact on the local economy, unless outdoor recreation, tourism or other activities are developed that are compatible with the naturalized floodplain. The value of the area for these activities depends in turn on the quality of the naturalization. We evaluated the potential for naturalization using a simulation model for an indicator group of plants, the moist‐soil plant community, that depends on the natural flooding cycle and provides food and shelter for a variety of valued species. Existing conditions and two alternative scenarios were evaluated by analyzing the frequency of successful growing seasons for moist soil plants using a 47‐year record of daily water levels and a hydraulic simulation model (for the scenarios). Results were expressed as color‐coded probabilities of plant success overlain on 3‐D maps of the floodplains—a visualization of results that was readily understood by stakeholders.

One of the stakeholders, The Nature Conservancy, subsequently funded a more detailed study by our scientists of the Emiquon Floodplain Restoration Project, a 2,125‐ha agricultural drainage and levee district purchased for $18.3 million in 2000 by the Conservancy and located within our study reach on the Illinois River. Based on the results, the Conservancy plans to undertake a managed reconnection of the river and the floodplain at Emiquon, using gates in the levee to admit river water (and aquatic organisms) during the spring flood, but to exclude the unnatural, frequent summer floods that drown moist‐soil plants. The Conservancy intends the Emiquon Restoration to be a model not only for its floodplain restorations in the Upper Mississippi River Basin, but also a model for naturalization projects undertaken by state and federal agencies. Three papers from this project are cited extensively in the U.S. Army Corps of Engineers' Illinois River Basin Restoration Comprehensive Plan and Integrated Environmental Assessment and the plan includes recommendations for naturalizing the hydrology of the river and restoring moist‐soil vegetation (USACE 2006).

The results from the project are also used in an introductory lecture for summer interns at the National Great Rivers Research and Education Center and have been the basis of the development of an economic module for the NSF curriculum development project on Interdisciplinary Modeling of Aquatic Ecosystems (Saito et al. 2005). Our co‐PIs and project information were among the resources used by graduate students in a project in Urban and Regional Planning at the University of Illinois to: (1) analyze the evolution of planning efforts on the Illinois River; (2) compare these efforts to planning efforts elsewhere; and (3) develop a framework for improved, integrated planning for the Illinois River (Fassero et al. 2001).