Assessing dam pool sediment for understanding past, present and future watershed dynamics: An example from the Cuyahoga River, Ohio

Abstract

Abstract Dams can trap a stream's sediment load and create a sediment record of anthropogenic watershed impacts and stream sediment load variability. We demonstrate the usefulness of dam pool sediments in assessing past, present, and future watershed dynamics in this study of the Gorge Dam Pool, Cuyahoga River, Ohio. The 17.4-m-tall Gorge Dam was constructed in 1912 and subsequently trapped the sediment load of the Middle Cuyahoga River. 210 Pb dating of the impoundment sediment allowed past anthropogenic impacts to be assessed. Mud accumulating between 1912 and 1926 has high trace metal content from industrial activities upstream of the impoundment. Between 1926 and 1978 mud having abundant coal combustion products (CCP) and high but variable metal content accumulated. During this period, sediment accumulation increased due to urbanization in the watershed. Since 1978 CCP and trace metals decline, reflecting the effectiveness of environmental regulations. Sediment accumulation increased dramatically between 2004 and 2008 and again in 2011 as a result of increased extreme flow events. An impoundment sediment accumulation of 7520 tonnes yr −1 for the 210 Pb-dated year 2006 is similar to a watershed model estimate of 7490 tonnes yr −1 determined from year 2006 landcover and supports the use of watershed modeling to estimate sediment load. Dam removal to reestablish river connectivity also eliminates the impoundment sediment trap. The impoundment sediment load record allows for a projection to the downstream sediment load following dam removal. The potential removal of the Gorge Dam will result in a minimal increase to the Lower Cuyahoga River sediment load.