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How Sand Dunes Protect Us

How Sand Dunes Protect Us

Sand dunes provide natural protection from coastal flooding and winds during storms. They also provide a natural buffer that can absorb the impact of erosion, protecting areas and communities behind them.

Over the next few decades, the effects of climate change, including sea level rise, will have a considerable impact on coastal communities. With rising sea levels there will be more frequent and more serious flooding of low-lying coastal areas by extreme tides, storm surge and wave effects. There is also potential in many coastal areas for considerable erosion.

Our dunes can play an important role to lessen the impacts of these coastal hazards by protecting low lying coastal areas from flooding. They can also act as a buffer against erosion,  forming a reserve of sand, replenished when beach levels are high and released to nourish the foreshore during storm erosion.  

Coastal Flooding

Sand dunes can provide significant protection from coastal flooding associated with storm surge and wave effects. The height and width of the dune can mitigation and often prevent wave flooding further inland.

Coastal Erosion

The dunes will not stop coastal erosion but they can provide a natural buffer enabling communities to live with natural shoreline movement. The wider and higher the dunes between development and the sea the greater the level of natural protection provided. 

During major storms the beach and dunes can be eroded with sediments often deposited on offshore bar systems. These sand deposits can sometimes protect the beach during these storms by breaking waves offshore and dissipating excess wave energy. Depending on the severity of the erosion the dune face may collapse.

In calmer weather the eroded sand is gradually moved back onshore. The binding vegetation will gradually extend down the eroded face of the dune, slowly trapping windblown sand and rebuilding the dune. 

Sand Reserve

The concept of a coastal cell suggests that there are stretches of shoreline in which sediment is circulated by waves and currents with relatively little input from, or output to, adjacent sections of coast.

One important management implication of this is that if sand is lost to the cell, fresh supplies will not come in from outside to replace the lost sediment. Wind erosion damage associated with disruption of stabilising dune vegetation by a variety of human activities can lead to sands being blown out of the coastal cell. This loss of sand will reduce the overall mass of the beach and sand dune system which acts as a buffer to the sea. 

Sand dunes are also a sand reserve that will be required to maintain beaches in the event of a shoreline retreat, as may occur in response to projected sea level risk and other climate change impacts. The vegetation on the dunes is an essential feature in capturing windblown sand, maintaining the stability and building up that reserve.