Floodplain Restoration and Nutrient Retention

Project Title: Floodplain restoration and nutrient retention in the Wabash River Basin

Principal Investigator: Dr. Sara K. McMillan, Purdue University, Department of Agricultural & Biological Engineering

Project Staff/Co-Investigator(s): Dr. Venkatesh Merwade, Purdue University, Lyles School of Civil Engineering

Dates: March 2016-February 2017

Total Federal Funds:  Total Non-Federal Funds:

Project Reports
Project Factsheet

Dr. Gary Lamberti

Floodplains occupy a small fraction of the total landscape, yet they retain a disproportionate amount of nutrients and sediment. During high flow events, riverine water overtops the channel banks, flowpaths widen causing velocities to slow and retention times to increase, which are critical to sediment and nutrient trapping. Rapidly changing flow conditions directly impact the spatial extent of inundation as well as the magnitude and direction of flow velocities. High resolution of local controls (e.g., topography, vegetation and groundwater flow) are required to accurately predict these changes. Further, in the areas of sustained wetness and high inputs of organic matter, nutrient transformations are maximized. While nitrogen removal via microbial processes is greatest under these conditions, the mechanisms controlling phosphorus removal are highly variable and poorly understood. Floodplain restoration and breaching of levees to re-establish natural flood pulsing is a strategy that shows great promise. In fact, the Natural Resources Conservation Service in Indiana has restored nearly 30,000 acres of riverine floodplains in the Wabash River Basin to improve water quality and other ecosystem functions. However, characterization and prediction of the environmental factors driving successful restoration is needed to find optimal locations that achieve the greatest impact per dollar invested. Therefore, our goal is to develop a robust predictive tool to quantify river floodplain connectivity and its impact on sediment and nutrient retention at the confluence of the Wabash and Tippecanoe Rivers. We will build a 2-dimensional hydrodynamic model of the system and measure rates of nitrogen and phosphorus transformations in floodplain sediments. We will scale results temporally and spatially to estimate the net impact of floodplain processes on nutrient retention in the Wabash River Basin. Collectively, this will build the foundation for an integrated and interdisciplinary analysis of the complex environmental controls on nutrient retention in river-floodplain ecosystems.