Development of Sediment Transport Tools for Assessing Current and Future Sedimentation in Great Lakes River Mouth Systems

摘要

Background/Objectives. Sediment management is a significant challenge in many GreatLakes harbors, where frequent dredging maintenance of navigational systems is typicallyrequired. Toledo Harbor, which provides navigational access from Lake Erie through thelower 10 miles of the Maumee River, provides a prominent example of these challenges.The navigation channel in Toledo Harbor is subject to significant rates of sedimentationresulting from the combined effects of suspended sediment loading from the MaumeeRiver and wind-wave resuspension and redistribution of bed sediments in Maumee Bay.The U.S. Army Corps of Engineers (USACE) performs dredging maintenance each yearin the Harbor at an annual cost of approximately $5 million. However, even thissignificant investment is insufficient to keep pace with dredging needs. Confined andopen-lake disposal of dredged sediments is also a significant issue. The capacity of theexisting confined disposal facility is nearly exhausted, and current/future open-lakedisposal has the potential to release phosphorus and other pollutants into the watercolumn.Approach/Activities. The recent Great Lakes Research Initiative (GLRI) Action Planincludes a target metric for a 2.5% reduction in sediment deposition in Toledo Harbor by2014. A significant need for Toledo Harbor and other Great Lakes river mouth systems isthe development of quantitative tools to assess current and future projected watershedsediment loadings and resulting sedimentation patterns to inform such managementtargets. Evaluating potential reductions in sedimentation for complex harbor systemssuch as Toledo Harbor requires the integration of all pertinent sediment data into apredictive sediment transport modeling tool. Such an integrated assessment is currentlybeing conducted on behalf of the USACE for Toledo Harbor. Sediment data available toconstruct and constrain a sediment transport model for the Harbor include bathymetricdata collected as part of pre- and post-dredge surveys, surficial particle size distributiondata, total suspended solids concentration data for Maumee River and Maumee Bay, andremote sensing maps of suspended solids distribution. A previously developed sedimenttransport model is being calibrated to data-based estimates of seasonal and annualaccretion rates. Daily measurements of suspended solids concentration and load deliveredvia the Maumee River are available and are being used to estimate reductions inwatershed sediment loading through the 2008-11 period. The calibrated model will beapplied in conjunction with these data-based loading reductions to estimate the reductionin navigation channel accretion that has occurred as a result of GLRI management actionsin the watershed.Results/Lessons Learned. Model development and calibration efforts are in progress,and it is anticipated that application results will be available at the time of presentation.