SEDIMENTATION RATES IN HOVEY LAKE, AN OXBOW ON THE OHIO RIVER FLOODPLAIN, POSEY COUNTY, INDIANA: CONTROLLING FACTORS AND IMPLICATIONS FOR LAKE MANAGEMENT

Hovey Lake is a 1,400-acre oxbow within a Fish and Wildlife Area managed by the Indiana Department of Natural Resources, located on the floodplain of the Ohio River in southern Posey County, Indiana. Although the natural lake formed about 700 years ago, damming in 1975, associated with development of the John T. Myers Locks and Dam on the Ohio River, increased the size and depth of the lake. The lake and surrounding wetlands are home to a significant northern occurrence of bald cypress (Taxodium distichum) and serve as a critical waterfowl migration area. Since 2010, recreational boaters have reported significant shallowing in parts of the lake, along with observations of encroaching perennial vegetation.

In October 2022, nine 30 cm by 30 cm concrete pavers and thirty-two 1 cm diameter, 120 cm-long dowls with attached steel washers were used to delineate nine transects at Hovey Lake in two areas: (1) near inlet channels to determine siltation from channelized flow; and (2) northeast margin of the lake to assess floodplain sedimentation. The pavers and washers were seated at ground level, and their locations pinpointed by GPS. In October 2023, the pads and dowls were re-located, and thickness of accumulated sediment measured. Sedimentation rates near the inlet channels ranged from 0.0 to 3.9 cm/year with an average of 1.6 cm/year, and along the northeast margin, 0.5 to 2.4 cm/year with an average of 1.3 cm/year. The sedimentation rates in this study are greater than historic values (pre-1830s: 0.74 cm/year), but less than those from the early 1970s (2.45 cm/year). The decrease in sedimentation rate since the early 1970s may be due to: (1) increasing acreage of wetlands compared to agricultural lands adjacent to the lake; and/or (2) inundation associated with damming in 1975. Lateral migration of perennial vegetation averaged 4.5 m/year, with a maximum of 30 m/year as determined by comparing aerial photographs, drone imagery, and field observations from 2022 to 2023.

Although sediment infilling of Hovey Lake is inevitable, management options to prolong the longevity of the lake include: (1) continue to convert agricultural lands to wetlands in areas adjacent to the lake; (2) hinder the advancement of invasive perennial vegetation along the eastern shoreline, and/or (3) raise the lake level by additional artificial damming.