Beach nourishment, a process in which sand or sediments lost by longshore drifts or erosion are replaced on a certain area of a beach. It involves the transportation of sand or other materials from other areas to the affected area. This process is usually cheap. This is part of a coastal defense scheme. However, the downside of this is that the beach must be constantly nourished as the seas will continue to erode it.
Primary functions:
- to provide temporary protection to backshore property
- to temporarily increase the recreational space along the shore
- Replicates natural coastal processes by augmenting coastal sand budgets
- Sediment texture (grain size and sorting) is critical for success. Sand fill needs to be as coarse grained and clean as native beach sand.
Environmental issues:
- dredging may cause direct mortality to sessile organisms, modifies seafloor habitats and sedimentary character
- burial of plants and organisms (SAV, shellfish)
- blockage of light in water (coral reefs, SAV)
- toxicity of sediments
- dredging too close to shore can cause erosion
Beach nourishment projects
Beach nourishment projects are usually constructed along shorelines where an erosional trend is present that could be either natural or a result of human activities. In those cases where this trend is due to human activities, the project will perform much better if the cause of the erosional trend can be minimized or eliminated in conjunction with construction of the beach nourishment project. The setting of a beach nourishment project is key to design and potential performance. Possible settings include a long straight beach , a project adjacent to an inlet that may be either a natural or modified inlet and a pocket beach. Projects constructed on rocky or seawalled shorelines, that otherwise have no sediment, present unique problems.
Response alternatives on an eroding beach
- Structural -The structural approach is simply to prevent upland loss and can be in the form of: revetments, seawalls, detached breakwaters, or groins, etc. If well designed, armoring in the form of shore parallel structures (seawalls or revetments) is emplaced on an eroding shoreline, it will satisfy its intended function of preventing erosion of the upland; however, with continuing erosion, the beach will narrow and eventually the beach will no longer be present. Groins trap sand from the littoral stream and may impact adjacent shorelines. Recognizing that there are cycles of shoreline advancement and recession superimposed on the long-term shoreline change, the armoring will tend to occur during periods of erosional cycles. The time required before no fronting beach is present may be decades.
- Retreat - A second option is retreat as the shoreline erodes. This option has been exercised very infrequently along the United States shoreline; however, a number of examples exist. Retreat would appear to be the most appropriate option in areas of high erosion and in the presence of small economic revenue base. Many, but not all areas of high erosion are due to human activities. These activities interfere with the natural sediment flows either through dam construction (thereby reducing riverine sediment sources) or construction of littoral barriers such as jetties, or by deepening of inlets; thus preventing longshore transport of sediment across these channels.
- Beach Nourishment - A third option for responding to an eroding shoreline is beach nourishment. This process usually consists of the placement of large quantities of good quality sediment along the water’s edge to advance the shoreline seaward. Beach nourishment is the only alternative that addresses the sand deficit directly through the placement of additional sediment. Beach nourishment is usually but not always carried out on an eroding shoreline and is favored by a substantial upland investment and a relatively mild erosion rate. Beach nourishment has a finite lifetime and renourishment is almost always required.
Benefits of a beach nourishment project
Storm protection
It has been demonstrated from both field studies and theory that a wide beach provides significant benefits in the form of storm damage reduction. During storms with elevated water levels and high waves, a wide beach performs as an effective energy absorber with the wave energy dissipated across the surf zone and wide beach rather than impacting on the upland structures. The storm damage reduction benefits of beach nourishment projects have been well established.
Recreational benefits
In many coastal areas, the recreational benefits of a wide beach can be substantial. An excellent example of this is the ten mile long Miami Beach, FL, USA project that was constructed over the period 1976 and 1981, cost approximately $64,000,000 and has revitalized the economy of this area. Prior to nourishment of the Miami Beach project, it was quite difficult to walk along many portions of this beach, especially during periods of high tide.
Potential environmental benefits
There are potential environmental benefits associated with beach nourishment projects. These include increased habitat for sea animal nesting, nesting and foraging areas for sea birds, and habitat for beach flora.
Possible settings for beach nourishment projects
There are a number of possible settings for beach nourishment projects.
- Long straight beach
- Beach nourishment adjacent to inlets
- Pocket beaches
- Seawalled beach
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