Coastal Erosion

What is beach erosion?

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Beach Erosion” by versageek licensed under CC by 2.0

Beach erosion occurs when waves and currents remove sand from the beach. The loss of sand causes the beaches to become narrow and lower in elevation. Storm waves carry the sand offshore, depositing and storing the sediment in large sand bars.

Dune Erosion

16011876170_c590dec35b_o.jpgWindy” by Susanne Nilsson licensed under CC by 2.0

Dune erosion occurs when a storm surge creates waves higher than the beach. This allows them to attack and erode the coastal dunes. When sand is removed from the dune the front of the dune becomes steep. The volume and elevation of the dune is reduced due to the erosion process. In return this makes the dune more vulnerable to future storms and the potential for over wash. Then the eroded sediment is carried off shore and stored in large sandbars. The sand dune can recover over a period of years, gaining in elevation and volume via wind-blown sand.

Over wash

Over washing is when storm induced waves exceed the height of the sand dunes, sand is transported over the top of the dune and deposited inland. Over washing can cause a significant change in the landscape of the island.  During this process dunes are often completely eroded away and the sand is deposited inland in large layers called over wash fans. These fans can bury the first floors of homes, cover roads, fill ponds, and cover vegetation. In some cases these fans, depending on the severity of the storms can cover the entire width of the island. When the sand is transported from seaward to the landward side of the island, the island migrates landward in a process known as barrier island rollover.

Marsh Erosion

Marsh erosion occurs along wetlands that are exposed to the open ocean and wide bays. Waves induced by storms and currents erode the muddy wetlands soil, causing the fragile coastlines to erode significantly, often it transforms a land area into open water. One recent example of marsh erosion is the loss of over hundreds of square miles of land during hurricanes Katrina and Rita in 2005 (Barras and Johnson, 2006). want to learn more about this? Click here!

 

When does this become an issue?

Coastal erosion becomes a problem when there is no room to accommodate the changes that are occurring. Highly urbanized coastal zones will certainly face difficulties with coastal erosion. European coasts for example, are facing increasing urbanization. The demand for the shoreline defenses and erosion control also increases. This could lead to self reinforcing effect as additional property and economic activities require further and often more robust defenses. These developments will all lead to reduced coastal resilience since the coastline has nowhere to move. It is a questionable if this type of development is sustainable in the long term, especially with climate change.

 

Climate change and coastal erosion

Climate change will lead to an increase in coastal erosion. The rising sea level is the most important contributor. A rising sea level implies an increase in sediment demand, which results in coastal retreat. Higher sea levels will rise the water level, this allows waves to break closer to the shore line and transmit more wave energy to the shoreline. This will promote erosion and coastal retreat at locations that lack sediment. There are other drivers to this issue these include increased storms, higher waves, and change in wind direction. The conditions and performances of existing coastal defenses structures may also deteriorate through interactions with rising sea levels, higher waves, and more storms.

If you wan to learn more about sea levels rising, check out Marisa’s blog!

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“Sea-level-rise scheme” by Wikimedia Commons licensed under CC by 3.0

What can help with erosion?

There are a few different ways that we may be able to manage coastal erosion….

Port-a-bag barrier walls these bags are self-erecting and are an excellent way to create a stable barrier for coastal restoration. They are a sustainable leave in place, or as a temporary solution. They can protect dunes, rebuilding coastal shorelines or preserving beaches. They proved a solid defense against incoming tides and wave action.  Breakwater tubes are more commonly used for long, demanding, or extended shoreline support. This tubes acts as a first layer of defense against waves as the break along the shore. This allows the beach to naturally retain sand and helps limits the deterioration of the shoreline. The coconut fiber log is also another mechanism to use. There are natural fiber logs that are designed to help with erosion control along the beaches. Logs can be put in sand dunes or vegetative areas that help establish roots. Geotextiles are also a product that can be sued. They are paired with retaining walls to increase stabilization and strength.  Erosion control mats are sometimes used as an option as well. They are mats that are typically designed to further the growth of vegetation by stabilizing an area long enough for plants, trees, and roots to establish them.

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2 thoughts on “Coastal Erosion”

  1. Nice post! I loved how this topic was much different the other ones I have read. My one piece of advice would be to add an intro about what erosion is before you start talking about the different kinds.

    Liked by 1 person

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