Tombolo formation will often impede the flow of sand in the down drift direction, resulting in an excess build-up of sand on the up drift side and starving down drift areas of sand. An incorrectly designed breakwater system will result in the formation of a tombolo. While this may seem ideal in creating a beach, the trapping of sand at the project site creates a loss of sand down drift, potentially leading to increased erosion in the affected areas.Ī correctly designed breakwater system will result in the formation of a salient which allows littoral drift to flow down drift between the breakwater and the sand beach.
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If a breakwater is placed too close to shore, or if the series of breakwaters are constructed too close together, an excess of sand may be captured landward of the project. A breakwater can cause millions of dollars in beach erosion in the decades after it is built. Over time, sand will accumulate towards a breakwater. When the longshore current is interrupted, a breakwater will dramatically change the profile of the beach. While sand may naturally build up behind the breakwaters, pre-filling and periodic nourishment is beneficial typically required by regulatory agencies.
When the sediment does not extend completely to the breakwater, the area of sand is referred to as a salient. When the sediment extends from the shore to the breakwater, the area of beach connecting the land and breakwater is referred to as a tombolo. Constructed out of armor stone or precast concrete block placed at a slope, detached breakwaters appear as short, usually shore-parallel structures just offshore of a beach or connected to the land via sediment build-up. These structures also function well in areas where the cross-shore current, or shore-perpendicular transport of materials, is stronger as the structures will provide greater protection of original beach material while capturing new sediment entering the system. Stone or precast concrete modules/blocks are used to build detached breakwater.ĭetached breakwaters are well suited for shallow areas where sand is present in the nearshore. Structures built parallel to shore in the relatively shallow nearshore, often in groupings.
It reduce wave action and assist in beach building. This environment is ideal for the deposition of sediment which in turn aids in retaining and enhancing beach width and thickness. As the waves approach the shore, the breakwaters reduce the energy of the waves, creating a calm environment on the landward side of the structures. Located just offshore, these structures reduce erosion and protect beaches by reducing wave action. Detached breakwaters, also referred to as offshore breakwaters or segmented breakwaters, are shore-parallel structures built in shallow nearshore environments.
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