Ashlee Vargo, (Ashlee.L.Vargo@us.mw.com)

and

Aaron A. Jennings, Professor (aaj2@po.cwru.edu)

Department of Civil Engineering

Case Western Reserve University

Cleveland, OH 44106-7201

Lower Shaker Lake is a small, highly impacted man-made lake in the Doan Brook watershed of Cleveland, Ohio. Fear that the lake was "rapidly filling in" with sediment led to a "dry dredging" project that required draining the lake so that sediments could be removed by an excavation operation. However, a pre-draining baseline survey indicated that there was a submerged channel structure within the lake that probably served a hydraulic role in the lake under storm flow conditions, and probably would not survive the dredging project. Laboratory sediment drying experiments also indicated that it was probably unrealistic to think that the sediments would dry sufficiently to support construction equipment in the allotted time.

Ultimately Lower Shaker Lake was drained, but little sediment was removed. As the water level declined, the sediment fields "slumped" into the submerged channel feature. The surface of the sediment fields also dried yielding a "crust" with significantly different physical properties. This poster presents results of hydraulic modeling and sediment scour testing that was conducted to determine what impact these changes would have on the future of Lower Shaker Lake. Hydraulic modeling indicated that under low-flow conditions sediments accumulate in the lake but that under storm flow conditions they should be scoured from the bottom and flushed out of the lake. Unfortunately, experiments indicate that drying the existing sediments probably armored them against scour by increasing their strength and substantially advancing their scour threshold. It would take very unusual hydraulic conditions to remove the sediments that underwent drying-hardening.