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Study provides new insights into how shorelines recover after storms

Findings provide input into shoreline management process

A new study into the recovery of shorelines in between destructive storms that move coastal barriers inland has revealed the factors that enable some stretches of coast to recover more quickly and efficiently than others. The study provides important input into the shoreline management planning process, particularly where the use of scarce resources for management needs to be effectively prioritized in order to protect coastal landscapes, ecosystems, human communities and infrastructure.

The researchers led by Birkbeck's Dr Sue Brooks with Cambridge University’s Coastal Research Unit, examined a 15km stretch of the north Norfolk coastline and found dramatic differences in the degree to which the shoreline recovered between storms in different parts of this segment of coast. The three beaches studied were Holkham Bay, Brancaster Bay and Scolt Head Island on the North Norfolk Coast. Using data from wave buoys, tidal gauges, aerial photography, detailed field surveys and archival records of storm occurrences, the researchers discovered that at Holkham Bay shoreline recovery was significantly better than at the other two sites. They determined that this was largely due to the migration of subtidal (below the low-tide line but still shallow) and intertidal (between the low and high tide line) bars of sand which transferred sediment to higher up the beach where, because of the low gradient of the shoreline, it was able to dry out and be picked up by the wind.

Dr Brooks explains: “The features observed at Holkham Bay mean that there is a strong sediment supply which is needed to rebuild the dunes, bringing them closer to the sea and restoring the pre-storm shoreline.”

The researchers found that the key factors providing a strong sediment supply and therefore enabling shoreline recovery were:

  • Broad beaches
  • Low gradients
  • Wind direction
  • Tidal range
  • The presence of subtidal (below the low-tide line but still shallow) and intertidal (between the low and high tide line) bars of sand

The combination of the above factors meant that sand was transported to the upper beach and – crucially – was able to dry sufficiently that it could be moved by the wind to the dunes, which protect vulnerable communities and habitats from flooding and erosion.

Dr Brooks continues: “Sea levels continue to rise and unpredictability in the variability of storminess means that there is an urgent need to understand which stretches of coast are able to recover naturally and may achieve a long-term equilibrium on their own. This will allow coastal planners to efficiently prioritize deployment of man-made interventions to prevent coastal erosion.”

The study ‘Storm Impacts and Shoreline Recovery: Mechanisms and controls in the southern North Sea' has been published today  in the journal Geomorphology.  

[Image: Brancaster Bay]

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