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Why can raising a lake’s water level increase shoreline erosion?

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lake Lake Ann in North Cascades National Park, Washington, U.S., viewed from the park's Maple Loop Trail. The North Cascades National Park is a large wilderness area that preserves majestic mountain scenery, snowfields, glaciers, and other unique natural features.

Raising a lake’s water level can increase shoreline erosion because it exposes previously stable or higher-elevation land to direct wave and current action.

In a lake’s natural state, the shore tends toward an equilibrium where the coastline form balances the energy of the water. When the water level rises, waves—which derive their energy from wind speed, duration, and fetch—begin to strike areas of the bank that were not previously subjected to constant hydraulic force.12

This process often leads to significant bank cutting, as the water energy is now directed against materials that may be more vulnerable to erosion than the original, established shoreline. Furthermore, human-made changes to lake levels or the construction of structures like jetties can alter natural circulation, concentrating flow and wave energy against previously stable sections of the shore, thereby accelerating the erosional process.3