Published: 1999
Total Pages: 91
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The Ashtabula River flows north into Lake Erie at the city of Ashtabula in northeast Ohio. The Federal navigation project in the lower Ashtabula River contains a breakwater protected harbor in Lake Erie and a navigable waterway extending about 3.2 km upstream to a point approximately 300 m downstream of the 24th Street Bridge. Sediments in the harbor and lower 600 m of the waterway are classified as suitable for open-lake disposal, whereas sediments upstream are classified as unsuitable for open-lake disposal. In the harbor and lower 600 m of the waterway, dredging operations are conducted as required to permit commercial navigation. Dredging operations in the remainder of the waterway were suspended in the 1970s, closing the channel to commercial navigation, in response to the increased cost of safe removal and disposal of sediments contaminated with heavy metals, chlorinated hydrocarbons, and polynuclear aromatic hydrocarbons. The waterway is heavily used for recreational navigation. Limited dredging operations were conducted in the reach upstream of the 5th Street Bridge in 1993 to maintain safe navigation conditions for recreational traffic. Numerical hydraulic and sedimentation models of the lower Ashtabula River were developed using the TABS-MD modeling system. The objective of the model study described herein was to estimate the potential magnitude and spatial distribution of scour that may occur during an extreme event, such as the 100-year return period flood, potentially causing exposure and dispersal of contaminants buried in the channel bed sediments. Other reports in this series describe field data collections and laboratory erosion experiments conducted in support of the model investigation. The model study revealed that a 100-year return period flood event coincident with Lake Erie stage held at the low-water datum has the potential to scour 80,000 cu m of bed sediments from the lower Ashtabula River producing scour depths generally less than 1 m.c
