Wetland Function for Mitigating Floods in a Downstream Level Controlled River

Abstract

In this study, we present a case study to assess backwater effects induced by hydraulic structures and restored stream vegetation on wetland flood reduction (peak discharge attenuation and peak time delay). A coupled surface-groundwater model, HydroGeoSphere, is applied for the subwatershed including the Yahara River, Cherokee Marsh and downstream Lake Mendota, where the Tenney dam and the Highway 113 bridge constriction are located. The effects with and without hydraulic structures on hydrological connectivity and flood storage capacity are compared. Furthermore, we examine the potential benefit of flood reduction for a large scale stream vegetation restoration at the study site. Results show that hydraulic structures and restored stream vegetation induced backwater can increase hydrological connectivity between river and wetlands. The total flood storage capacity dramatically increases for the integrated backwater wetland system. Overall it is suggested that the backwater wetland provide an optimal flood reduction by keeping the hydraulic structures and restoring the stream vegetation.