How does beach erosion occur

Grassy turf extends out over a wave-cut notch. Taken on June 20, , the photo on the right shows what often follows such undercutting: chunks of coastline tumbling into the sea. In the past, protecting the coast often meant "hardening" the shoreline with structures such as seawalls, groins, rip-rap, and levees. As understanding of natural shoreline function improves, there is a growing acceptance that structural solutions may cause more problems than they solve.

Additional reasons to avoid structural protective measures include the high costs to install and maintain them, state or local prohibitions against them, their propensity to cause erosion to adjacent beaches and dunes, and the unintended diversion of stormwater and waves onto other properties.

Many states have shifted toward non-structural shoreline stabilization techniques. Unlike structural projects, nature-based or "green infrastructure" protection measures enhance the natural ability of shorelines to absorb and dissipate storm energy without interfering with natural coastal processes. One common strategy for dealing with coastal erosion is beach nourishment—placing additional sand on a beach to serve as a buffer against erosion or to enhance the recreational value of the beach.

However, beach nourishment has also become a controversial shore protection measure, in part because it has the potential to adversely impact a variety of natural resources. Consequently, these projects must comply with a wide range of complex laws and regulations. Beach nourishment is also expensive: check the Beach Nourishment Viewer to explore details about sand placement efforts for more than 2, beach nourishment projects since Adding sand to a beach does not guarantee that it will stay there.

Some communities bring in huge volumes of sand repeatedly, only to see it wash out to sea in the next season's storms. When completed in , the beach was 60 feet wide and sloped up to 5 feet above mean low water.

Nonetheless, many communities still practice beach nourishment. Army Corps of Engineers USACE is authorized to carry out beach nourishment for shoreline protection: their Beach Nourishment site describes the benefits of adding sand to beaches. Recently, the U. Army Corps of Engineers has re-emphasized the need to consider a whole range of solutions to coastal erosion, not only structural solutions.

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Coastal erosion is a natural process which occurs whenever the transport of material away from the shoreline is not balanced by new material being deposited onto the shoreline. Many coastal landforms naturally undergo quasi-periodic cycles of erosion and accretion on time-scales of days to years.

This is especially evident on sandy landforms such as beaches, dunes, and intermittently closed and open lagoon entrances.

However, human activities can also strongly influence the propensity of landforms to erode. For example, the construction of coastal structures such as breakwaters, groynes and seawalls can lead to changes in coastal sediment transport pathways, resulting in erosion in some areas and accretion in others. The removal of sediments from the coastal system e. At larger scales, natural and human-induced climate change can modulate the likelihood and rate of coastal erosion.

Coastal erosion becomes a hazard when society does not adapt to its effects on people, the built environment and infrastructure.

The most vulnerable coasts are those made up of unconsolidated sediments, such as beaches, dunes and sand cliffs, on open coasts that experience net longshore drift of sediment and on the shores of coastal lakes and lagoons. DEA Coastlines is a free, publicly available dataset that identifies annual shorelines and rates of coastal change along the entire Australian coastline from to the present.

The tool enables historic trends of coastal erosion and progradation growth to be seen at both a local and continental scale.

The Smartline national dataset maps record the location of those coastal substrates and landforms that have greater or lesser sensitivity to potential coastal impacts of climate change and sea-level rise IPCC , such as accelerated erosion and shoreline recession, increased slumping or rock fall hazards, changing dune mobility, and other hazards.

Qin, G.