Lake Erie Coastal Erosion
Lake Ontario Coastal Erosion
Beach Erosion Investigation
What's happening?
The Canadian section of the south shore of the Lake Ontario shoreline is largely within the Niagara Peninsula and is generally classified as a major bluff shoreline. (A bluff is a short cliff with a broad face and a steep incline.) The bluffs between Niagara-on-the-Lake and Stoney Creek vary from areas that are eroding slowly to sites that are eroding at upto 1.4 cu.m. per metre of land per year.
What are some causes of coastal erosion?
The rate of erosion of these bluffs is dependent on several factors:
q Type of material from which the bluffs are formed: Some of the bluffs are made up of a very hard rock called shale. These bluffs do erode but at a very slow rate of about 0.1 to 0.3 metres per year. In comparison, bluffs made of till erode at a higher rate of about 1.0 metres per year. (Till is a soft material, usually a mixture of clay, silt and sand, which may have been deposited by glaciers or brought down by rivers.)
q Waves and currents which impact the shoreline. Shoreline which is continuously exposed to direct currents erodes at a faster rate than that which is not. In the same manner, shoreline which is exposed to either strong waves (as when during a storm) or to tide swells deteriorates more rapidly than a sheltered coast.
q Fluctuations in water levels (as during a dry summer or a wet spring) and extreme deviations from normal levels. However, the International Joint Commission on the Great Lakes acts to limit much of this damage by regulating the water that flows into these lakes by the use of dams and canals (e.g. those along the St. Laurence Seaway).
q Freezing and thawing cycles act to fissure even the hardest of rocks: flaking it off and allowing the waves to force into the cracks and remove the material.
q Urbanisation and development along the shoreline: lake-side homes and marinas are very desirable properties and the huge demand for such sites has meant, not only an interference with the natural topography of the beaches, but also, an interference with the natural ground water seepage and surface run-off due to rain and snow.
q Winter storms and hurricanes: Lake Erie is fortunate in that it is not hammered by the strong hurricanes and storms which regularly hit other parts of this continent. For example, the province of Prince Edward Island loses an area of its soft, marine coastland to hurricanes every year. The Southern United States is losing its coastal land at a catastrophic rate (more on this later).
q Moving ice: to a small degree, erodes bluffs, however, ice acts to protect the shore from winter storms.
What's at risk?
Damage to property to the Lake Erie north shore. Considerable damage to cottages and recreational facilities. Remember that one of the Niagara region's biggest sources of income is from the tourism industry.
Damage to infrastructure, e.g., roads, bridges which may cause billions of dollars to repair.
Damage to natural freshwater habitats: Fish like the pugnose shiner and the gravel chub inhabit such waters off the coastlines of the Great Lakes.
Damage to wetlands: Wetlands are very important because they provide habitat to many animals like migrating birds (the red-necked grebe and the double-crested cormorant) and to mammals like the Virginia opossum and southern bog lemming. They often contain fragile ecosystems containing rare plants (e.g., pin oak) and amphibians such as the wood turtle and blackrat snake.
Beach Erosion Investigation
The purpose of this investigation is to determine the effects of gentle and strong waves on beach erosion.
Materials
1. Plexi-glass/ plastic clear stream table or other large rectangular container
2. Ruler
3. Watch or clock with second hand
4. Clean sand
5. Wooden block
6. Paper and pencils for students to sketch on.
Procedure
1. Tape or plug the drain / outlet of the stream table
2. Pour approximately 2.5 cm of water in the container.
3. Add clean sand to one end to simulate a beach.
4. Looking through the sides of the stream table, sketch Beach Profile 1.
5. Place block in end of stream table opposite the "beach".
6. Move block very slowly to create small waves for 3 minutes. The waves should be just large enough to move the sand a little bit.
7. Stop motion of the block after 3 minutes. Observe and sketch Beach Profile 2.
8. Leave new beach in place.
9. Now move block rapidly for 3 minutes to create large waves.
10. Observe and sketch Beach Profile 3.
Observations
Beach Profile 1 Beach Profile 2
Beach Profile 3
1. What differences are there between how a small and large wave erodes a beach?
2. What differences would you expect in the profile of a beach in summer and winter?
3. What other factors might effect beach erosion?
Extension
Design an experiment to test the effects of one factor on the rate of beach erosion.