Washington State Department of Ecology
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bulkheads and seawalls
slide toppling bulkhead
Bulkheads and seawalls may do little to prevent erosion and sliding of the upper bank

Many landslides in the Puget Sound region occur along shoreline bluffs where erosion by wave and stream action has steepened the slope, thereby decreasing its stability. Property owners often choose bulkheads and seawalls to reduce erosion at the toe of the slope. Bulkheads and seawalls may be constructed of rock, timber, concrete, or other materials.

Toe protection
Seawalls and bulkheads address toe erosion by wave action. Where the stability of the slope is directly related to undercutting at the toe, a bulkhead can reduce erosion and may help stabilize the slope. But rarely is toe erosion the primary trigger of a landslide. A bulkhead may be one element of an overall stabilization plan that also includes drainage improvements and revegetation.

Not always the answer
Seawalls and bulkheads have limited value as retaining structures and are not designed to resist significant lateral forces. Slides are typically triggered by wet conditions and saturated soils on already steep slopes. Perfectly well-built bulkheads can end up buried or destroyed by the very landslides they were built to prevent.

bulkhead broken by a slide

Bulkheads can damage beaches
Bulkheads and seawalls exact an environmental price. Most beaches on Puget Sound are derived from the erosion of coastal bluffs. Bulkheads impede this process -- which can lead to the loss of beaches with impacts to both shoreline ecology and to other properties, where erosion rates may increase.
 
online resources
Sound advice for Sound living

For information on bulkheads, buying property, protecting beach ecology, construction, septic system maintenance, and much more, see Puget Sound Shorelines.
Puget Sound Shorelines
 
links

Bulkheads, Puget Sound Shorelines, Department of Ecology. How bulkheads can increase beach erosion and damage beach ecology.
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