Shoreline
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Shorelines

Water: Shorelines

Shorelines

From beaches and dunes to bluffs and wetlands, shorelines are already being shaped by our changing climate.

They are constantly subjected to the whims of waves, wind, rain, snow, ice and human activity—all factors that are also affected by the Earth’s rising temperature.

The Environmental Law and Policy Centre notes that there are two types of shorelines seen on southern Lake Huron that may be significantly affected by climate change in the next century: soft rock shorelines with bluff coasts and sandy beach/dune coasts. [10]

Changes to Lake Huron’s water level and wave characteristics, in addition to increased precipitation patterns, have the potential to impact bluff and beach erosion on these shores. Hard rock shorelines, such as the Niagara Escarpment that forms the northeastern side of the Bruce Peninsula, will likely not be affected quite as much.

Calling your bluff

A bluff is steep shoreline slope, similar to a cliff but made of sediment instead of rock. There are between six and seven kilometers of bluffs on the shores of Lake Huron between Sarnia and Tobermory, the majority of which are found in Huron County. The bluffs on Lake Huron’s southeastern shores are made of 86% silt and clay, and 14% sand, gravel and cobbles.

Water: Bluffs

Erosion is a natural and important process for a coastline. Beach and dune systems rely on the erosion of bluffs to provide new sand and material. In turn, beaches and dunes protect the shoreline from storm waves and further erosion. [11]

Development and human activity tend to be concentrated along coastal regions. Unfortunately, erosion can pose a serious threat to this infrastructure, particularly if it was built before people had enough information to locate their buildings safely away from erosion- and flooding-prone areas.

Water: Erosion

North Shore Trail between Port Elgin and Southampton Ont. on June 3, 2020. (Scott Miller/CTV London)

Shoreline Processes (Maitland Conservation)

Bluff erosion

According to the Maitland Valley Conservation Authority, there are three factors that influence the rate of erosion. [12]

Climate change is expected to affect all three erosion factors. Erosion at the base of the bluff is affected by lake water levels and wave activity. When lake levels are relatively low (as they were from 2000-2014), waves break further from the shore. This erodes the bed of the lake, which deepens the waters approaching the shore.

Then, when the lake levels are higher, incoming waves are larger and break closer to the shore, which increases the erosion rate at the base of a bluff. More extreme water level changes are predicted for the Great Lakes, which will likely accelerate this process.

Maitland Conservation also found that without historical ice cover from 1980-2020, wave energy reaching the shore would have been 32% higher. [14] Lake Huron’s ice cover is anticipated to continue to decline as the temperature increases, likely speeding up the erosion processes.

Shorter winters and more frequent thawing events, an increase in total annual precipitation, and more frequent and intense weather events such as storms will increase both the surface water and groundwater seepage. What’s more, increased temperatures could impact the survival rate of trees planted in shoreline environments. [15]

Trees and plants play an important role in bluff stability. [16] Their roots bind the sedimentary soil together, much like reinforcing steel in concrete structures, and make it more resistant to erosion.

Their foliage protects the bluff from the direct impact of rain and other precipitation. Decomposing leaves and twigs can also hold water like a sponge, allowing it to release more slowly into the ground over time.

Plants also need water to live: their root systems draw up water to transport to their stems and leaves, removing it from the soil.

Go hug a tree!

Water: Dunes

Dunes

Beach there, dune that.

Lake Huron is renowned for its beautiful sandy beaches, which make up only 2-3% of the lake’s total shoreline. The flat part of the beach where you lay a towel down is only one part of a larger system, which includes the grassy sand dunes behind the beach and the lakebed and sandbars in the water. These parts all work together to keep the beach in place as the water levels in the lake rise and fall.

When lake levels are low, more sand is exposed to the air. As wind blows across the beach, it picks up sand and deposits the grains into the dunes behind the beach. The dunes then become a sort of “sand battery” that recharges the beach when water levels rise again. During high lake levels, the sand stored in the dunes is eroded and dragged back into the lake, reinforcing the sand on the beach and building up sand bars under water. [17]

Dune and beach ecosystems are already rare and fragile; a changing climate has the potential to threaten them even more. Increased air and water temperatures are likely to lead to higher wind speeds off the lake, which increases the threat of dune erosion.

Less winter ice cover could also leave beaches more exposed to winter storms. Conditions may also become more favourable to invasive species, such as the European Common Reed, which can displace native plant species and have negative impacts on the dune ecosystems. [18]

To help avert the risk to people and property due to flooding and erosion, Maitland Valley Conservation Authority (MVCA) has recently updated their jurisdiction’s existing shoreline hazard mapping to consider climate change.

Using LiDaR (Light Detection and Ranging, a remote sensing method that can make high-resolution measurements and maps) in combination with an understanding of the bluff and rock composition as well as predicted changes in Lake Huron water levels and wave activity, MVCA predicted how shorelines might erode or flood over the next 100 years.

Now you see it...

...soon you might not!

dune erosion

View the interactive map here