Wave Energy as an ecological function
What is wave energy?
A wave, measured by its length, period, and height, is energy moving through water. Shorter waves, generated by local winds and vessel wakes, influence the water elevation that already varies with tide and season. Wave energy moves across the water and is ultimately expended on the shoreline, working to erode, transport, and deposit beach sediment. Compared with other locations in the U.S., Puget Sound is considered to be a moderate wave-energy environment.
Under natural conditions, wave energy is primarily generated by localized wind patterns and can be greatly increased during storm events. In addition, waves may be generated by geologic sources (i.e., large-scale bluff collapse, seismic forces).
Wave energy is relevant in marine and lake shoreline types. Some rivers within King County experience significant boat traffic, but these areas are not in King County's jurisdiction.
Why is wave energy important?
Wave energy transfers from the water to the shoreline, helping with the sediment process. In lakes, turn over of thermal stratification also occurs as an interaction between cooling temperatures and wave energy.
What affects wave energy?
Wave energy can be affected by:
- high boat traffic
- shoreline armoring,
- bulkheads and revetments,
- jetties and breakwaters,
- and overwater structures such as docks and piers.
The amount of wave energy or frequency of waves reaching the shoreline can be increased through boat traffic and can increase sediment erosion.
The natural transfer of energy onto the shoreline is altered by shoreline armoring, especially when it is below the ordinary high-water mark. The type and the tidal elevation of shoreline armoring play a strong role in the effect of the alteration.
Hardened armoring approaches, such as bulkheads and revetments, represent the types of shoreline modifications most likely to affect wave-energy regimes. Encroachment of the structure into the intertidal zone also may increase wave energy.
Jetties and breakwaters are designed specifically to decrease wave energy through intervention before it reaches the shorelines. While not generally designed to affect wave energy, docks and piers can also have a similar effect.
References: Williams et al 2003; U.S. Army Corps of Engineers 2002; Terich 1987; McDonald and Witek 1994; and Anchor Environmental 2000.