Speaking

Nitrogen and phosphorus are common nutrients of concern in Ohio’s rivers, ponds and streams after large rain events. In high concentrations, they have been noted to lead to eutrophication, which has resulted in the development of algal blooms and oxygen depletion in the receiving water bodies. With the understanding that elevated nitrogen and phosphorus concentrations can be realized from fertilizer runoff from agricultural fields, lawns and other industrial sources entering a water body, the Ohio Department of Natural Resources’ H2Ohio program has been developed to assist entities in developing methods of lowering these nutrient concentrations in our waterways.

Wetland treatment system design is an effective method to capture and treat high nutrient loads after a storm event. Through utilization of river flow data, key flood elevations can be calculated and used to design the wetland flooding frequency. Native plant species and residence time facilitate the removal of nutrients and turbidity. Hydraulic modeling of the treatment wetland ensures that it is functioning and flooding as intended.

This case study showcases a project undertaken by Columbus and Franklin County Metro Parks at their Walnut Woods Metro Park along the Walnut Creek, which was identified to be an at-risk waterway for high nutrient loads and selected to receive the H2Ohio grant. It outlines the methodology employed in the wetland design and modeling of the stream and wetland to increase flood frequency.