MODELING NUTRIENT-ENRICHED SEDIMENTS
TRANSPORT
DURING COASTAL EROSION PROCESSES
Sponsor: Lake Erie Commission
Project period: 1999-2000
Principal Investigator: Dr. Ron Li
Project Team: Tarig A Ali
Description
This project will develop a new approach to characterize and monitor the transport of nutrient-enriched sediments during coastal erosion processes. The project site will be selected in Lake Erie coastal areas where farming using heavy phosphorus based fertilizer is practiced and severe coastal erosion has been taking place. The information of landuse/farming and phosphorus distribution on the land will be managed in a GIS. A new innovative model that quantitatively models soil transport in the coastal area during erosion processes will be developed. In this model the soil with a varying concentration of phosphorus and other agrochemicals is divided into triangular patches.
Coastal erosion and sedimentation are one of primary sources of nonpoint source pollution. Such contaminants include oxygen demanding organic wastes, phosphorus and nitrogen, toxic chemical from manufacturing and industrial processes, pesticide and herbicide residues and heavy metals. Coastal eroding process transports large quantity of the sediments, for example from upland/farmland practices within coastal environment, and/or away to the water body. Understanding of the eroding process is absolutely crucial to track nutrient-enriched sediment movement and its impact on the coastal ecosystem. Three of the four severely eroding sites in the Great Lakes area are along the Lake Erie coastline; two of them are within Ohio. 95% of Lake Erie shore in Ohio is eroding Some eroding stretches have an annual erosion rate as high as 110 feet. Farming is one of major industries in Ohio. Phosphorus loading into Lake Erie is most intensive in the Great Lakes Basin, among which a great amount of phosphorus (adhesion to soil particles) is discharged into Lake Erie by erosion of forming land along the shoreline and riverbanks. The related water quality impacts have been severe, including extensive algae blooms, accumulation of organic debris, reduced oxygen levels, loss of fish and wildlife habitats and introduction of toxic chemicals into the ecosystem. Erosion in such a freshwater coastal environment has its unique characteristics and affects the ecosystem in a different way.
The loss of the soil within patches is modeled using the Revised Universal Soil Loss Equation and considering erosion process terms and others special for Lake Erie, such as storm surge factor, winter ice process factor, and sediment concentration. The soil transport and coastline changes caused by erosion processes are monitored by periodic high resolution satellite imagery (0.82 meter) and airborne images (centimeters) and used to calibrate the soil/contaminated sediment loss model. Nutrient-enriched sediments loaded into the lake can thus be estimated through the model. This estimation of the loaded sediments will be further verified by water quality tests using coring data. This model can be used as a fundamental basis for water quality management and coastal protection.
Furthermore, wave and tidal action in Lake Erie are generally limited. Storm surges are one of the driving forces of erosion, which can quickly raise the local lake level by more than one meter. In winter much of Lake Erie and its beaches are frozen, inhibiting the formation of storm waves and reducing erosion. Icesheets absorb nearshore and lakebed sediments and transport them when starting melt. Therefore, during ice formation in early winter and icemelt in spring thaw, ice processes can accelerate erosion. The spring rains, snowmelt, and low evaporation rates cause Lake Erie’s average water in June to be 30 centimeters above the typical January level. Several years of above normal precipitation, e.g. in the mid-1980’s, can cause Lake Erie’s water level to rise significantly above its long- term average, increasing the likelihood of erosion.
Objectives of this research:
To study and quantify characteristics of coastal erosion processes that transport soils from farmland/bluff to berms and further to lake bottom in Lake Erie ecosystem, considering nontidal wave effects including storm surges and winter ice processes;
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