Understanding lake fetch

What is lake fetch? Fetch is an important understanding of your lake formation and the direction and speed of winds to create waves.

Diagram of a lake showing wind direction of fetch. Photo credit: Beth Clawson, MSU
Diagram of a lake showing wind direction of fetch. Photo credit: Beth Clawson, MSU

In its simplest term lake fetch is the maximum length of open water wind can travel. Waves are formed by wind. Therefore, the highest energy waves are going to form where there is a long expanse of unobstructed water and sustained high winds. In other words, the longer that wind blows over a greater expanse of water, the more energy builds up creating bigger, high-energy waves.

This spells bad news to the beaches on the receiving end of the wave where the wind and wave energy can cause serious erosion damage. This is especially true in areas that were de-vegetated for development to improve access to the water with docks and beaches.

Longer distances have some big waves like what we see on the oceans that have very long unobstructed distances. Conversely, shorter distances or areas that have obstructions will experience reduced wave action and reduced erosion. Natural outcroppings and lake shapes can contribute to reducing wave action. Natural areas with water plants, reeds and rushes also help reduce wave action before it can reach the shore. Leaving these in place or restoring them can protect shorelines from erosion. You can estimate the risk of erosion on lake shorelines by knowing average wind direction and speed in correlation to your location.

Regardless of energy level, maintaining plant communities along shorelines can help reduce waves and control erosion on lake shorelines. Some native aquatic plants that serve this purpose are emergent such as: grasses, rushes and reeds, cattails, Pontederia and Sagittaria; shoreline shrubs and trees; and a wide variety of other native plants and ferns.

For more information about the natural shoreline restoration, contact Beth Clawson, Michigan State University Extension educator. To learn more about invasive organisms and invasive aquatic plants contact MSU Extension Natural Resources educators who are working across Michigan to provide aquatic invasive species educational programming and assistance. You can contact an educator through MSU Extension’s “Find an Expert” search tool using the keywords “Natural Resources Water Quality.”

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