Bluff erosion and stability

As a bluff erodes, the top edge moves landward. This is a natural process that becomes a hazard when it threatens buildings or other developed property. Bluff erosion rates will vary from year to year, much like the weather. Even a steep bluff may remain unchanged for many years, or slump a large amount of sediment once every few years. Fine silt and clay eroded from bluffs may end up on mud flats or salt marshes at the base of the bluff, helping to reduce wave energy and slow the overall rate of bluff erosion. Eroded sand and gravel become part of the beach at the base of the bluff, helping to stabilize the shoreline.

A Highly Unstable Bluff is near vertical or very steep with little vegetation and lots of exposed, loose sediment. Fallen trees and displaced chunks of sediment are common on the bluff face and at the base of the bluff.
An Unstable Bluff is steep to gently sloping and mostly covered by shrubs with a few bare spots. Bent and tilting trees may be present.
A Stable Bluff has a gentle slope with continuous cover of grass, shrubs or mature trees, and a wide zone of ledge or sediment at its base. Over time, stable bluffs can become unstable due to natural changes or human activities.