HYDROGEOLOGY AND SUBSURFACE GEOLOGY OF A MODIFIED WETLAND, LIBERTY PARK, TWINSBURG, OHIO

The hydrogeology of a degraded, invasive species dominated, wetland in Liberty Park, Twinsburg, Ohio, was investigated. This wetland, along with Pond Brook, the major stream in the park, has been selected for a comprehensive restoration. The park in located within the glaciated Allegheny Plateau region. Recent hydrologic manipulations such as ditching, dredging and channelization of Pond Brook adversely affected the hydrology of the natural riparian wetland. Sixteen shallow monitoring wells were installed in the 39 acre wetland cell. Continuous data loggers that record water level every hour were installed in Pond Brook and five monitoring wells in the degraded wetland. The remaining wells were hand-monitored with a water-level indicator. Average depth to water in May was 94 cm. Hydrographs show that immediately after a precipitation event, the water level of Pond Brook rises rapidly, and then returns to normal base flow in 2-4 days. Rapid fluctuations in water level were also observed in the monitoring wells and reflect those of the stream. These results indicate that the wetland is hydrologically linked directly to Pond Brook. The shallow subsurface geology is mainly clays and diamicts. Discontinuous lenses of peat and sand were observed in the upper 2 m. The hydrologic connection is attributed to the permeable sand and peat intercalations and fractures in the clays and diamicts. The shallow geology of the area is interpreted to be a glacial topography that was drowned in a post-glacial lake. The design of the restoration constructional works should take into account the direct hydrologic connection between Pond Brook and the modified wetland.