n the southern shore of Lake Ontario, the sediment transport processes are complex due to a highly dynamic environment, complex shoreline configuration, and large range of sediment fractions which includes silt/clay to cobbles and boulders. Generally, the nearshore environment is supplied by sediments released through the natural erosion and retreat of the bluffs which are found in long stretches along the shoreline ranging from several hundred meters to kilometers in length. The retreat of these shoreline bluffs can result from a variety of processes that operate at different rates and that respond to different triggering mechanisms. For example, wave erosion at the toe of the bluff is a primary cause of bluff retreat, and brief, intense storms that generate large waves can trigger large amounts of bluff retreat in a matter of a few hours or days. Longer term basin-wide or eustatic increases in lake water level can also increase long-term rates of bluff erosion and recession by exposing bluffs more directly to wave action. Surface erosion at the bluff crest from overland runoff can also contribute to bluff recession. Once eroded from the bluffs the material is naturally sorted by the waves and nearshore hydrodynamics and subsequently these materials are transported both in an alongshore and cross-shore direction. Eroded materials are distributed throughout littoral cells and sub-cells or alternatively permanently lost from the system in offshore environment. Depending on the sediment fraction, the response in the nearshore environment differs.
To improve the understanding of coastal processes on the southern shore of Lake Ontario, the New York State Department of Environmental Conservation (DEC) initiated a Project titled: Engineering & Analysis for Coastal Resilience & Ecosystem Restoration Projects. The Project’s primary focus is to study the coastal processes to better inform coastal planning to reduce the risk from flooding and erosion while protecting the coastal ecosystem.
To support the Project, a detailed understanding of hydrodynamics, waves and sediment transport is required. As such, the Project involves a range of activities such as research and data analysis; field services to investigate physical processes, material properties, and shoreline features; desktop assessments; geographic information system analysis (GIS); and a comprehensive numerical modelling program of coastal processes. The key outcomes from the study include wave, hydrodynamic and sediment transport models as well as a detailed sediment budget from Great Sodus Bay to Oswego, which considers fine sediment (silt and clay), sand, and the coarse sediment fractions (pebbles and cobbles) which has not been done in the past due to the lack of data relating to the coarse sediment fractions.
This presentation will describe the overall Project and the latest results with a focus on the numerical modelling including waves, hydrodynamics, and sediment transport. In particular, the presentation will discuss the various sediment sources and sinks, the estimated rate of sediment bypassing at the long jetty structures at Sodus Bay and Little Sodus Bay, and how this information feeds into the sediment budget for the reach of shoreline from Great Sodus Bay to Oswego.
