Floodplain Restoration and Bankfull Wetlands for Watershed-Scale Benefits: Insights from Model-Informed Design Case Studies in Ohio and Kentucky
Sarah M. Wallentine
Robert Hawley, PhD, PE
Sustainable Streams, LLC
Louisville, KY
Authors: Wallentine, S.M., Raetz, A.E., Hawley, R.J., Korth, N.L.
North American stream ecosystems have been subject to anthropogenic impacts for millennia. Impacts that have been amplified throughout four centuries of European settlement include widespread floodplain drainage, watershed deforestation and development, stream channelization, and beaver extirpation. As a result, streams have become more straight, incised, and disconnected from floodplains, thus altering ecosystems and ecological services afforded to nature and humans alike.
While many approaches to restore stream ecosystems and ecological services have developed over the last half-century, floodplain restoration has more recently been shown to be a leading cost-effective strategy to provide watershed-scale benefits. A relatively simple approach involves removal of ~1-3 meters of post-settlement alluvium and re-establishment of the native seedbank, which work together to restore a more natural connection of the stream or river to its floodplain. Benefits include increased flood storage, decreased flood stage, reduced channel erosion, improved water quality, and restored habitat for fish, birds, mussels, and macroinvertebrates.
This presentation will use multiple case studies to provide insights on modeling, design, construction, and benefits of recent floodplain restoration projects in Ohio and Kentucky. Model-informed design will be showcased, specifically, how hydrologic and hydraulic modeling, including HEC-RAS 2D, can be leveraged to improve designs and achieve sustainable restoration objectives. For example, when sufficient and reliable ground truth data are available, 2D hydraulic modeling can improve confidence in estimating runoff volume that will enter a bankfull wetland during flood events. Further, a 2D hydraulic model enables designers to better understand flow interaction between stream or river and wetland, thus providing insight into flow dynamics entering/exiting and within the wetland. This can illuminate key design features such as: placement, sizing, and grading of inflow/outflow features to effectively convey runoff for flood storage while mitigating blockage by sedimentation; and sizing, grading, and planting of the bankfull wetland to provide sufficient residence times for nutrient assimilation (e.g. to meet TMDLs) and habitat for local fauna. As floodplains are often the last available open spaces in urban and suburban watersheds, understanding cost-effective and sustainable restoration approaches is important in uplifting communities and the ecosystems on which they rely.
About Sarah M. Wallentine
Ms. Wallentine has 14 years of experience as a research engineer, project and program manager. In 2023, Sarah left her career as a research aerospace engineer and began her formal education in wetlands, streams, stormwater, groundwater, water resources, and ecological engineering at Ohio State University. Sarah earned her M.S. in Environmental Engineering in 2025, completing a research thesis titled Quantifying Treatment Effectiveness and Modeling Hydrologic and Hydrodynamic Complexities in a Constructed Riparian Wetland System Treating Riverine Storm Flows in Southwest Ohio. Sarah has expertise in 2D HEC-RAS, and has experience with several engineering tools and methods for watersheds, streams, wetlands, groundwater, and water resources.
About Robert Hawley, PhD, PE
Robert J. Hawley is a licensed Professional Engineer in five states and the Principal Scientist at Sustainable Streams in Louisville, KY, a company dedicated to stream and watershed science, service, and solutions. Dr. Hawley uses his professional and research projects to make stream restoration and stormwater management more ecologically and socioeconomically sustainable. He has more than 120 miles of stream restoration experience and stormwater management experience in watersheds that collectively drain over 70,000 square miles, with more than $100M in constructed projects. Dr. Hawley has authored more than 30 peer-reviewed publications with over 1,000 citations and tens of thousands reads/downloads.