Storm impacts and shoreline recovery: mechanisms and controls in the southern North Sea

Brooks, Susan and Spencer, T. and Christie, E.K. (2017) Storm impacts and shoreline recovery: mechanisms and controls in the southern North Sea. Geomorphology 283 , pp. 48-60. ISSN 0169-555X.

Abstract

Storm impacts play a significant role in shoreline dynamics on barrier coastlines. Furthermore, inter-storm recovery is a key parameter determining long-term coastal resilience to climate change, storminess variability and sea level rise. Over the last decade, four extreme storms, with strong energetic waves and high still water levels resulting from high spring tides and large skew surge residuals, have impacted the shoreline of the southern North Sea. The 5th December 2013 storm, with the highest run-up levels recorded in the last 60 years, resulted in large sections of the frontline of the North Norfolk coast being translated inland by over 10 m. Storms in March and November 2007 also generated barrier scarping and shoreline retreat, although not on the scale of 2013. Between 2008 and 2013, a calm period, recovery dominated barrier position and elevation but was spatially differentiated alongshore. For one study area, Scolt Head Island, no recovery was seen; this section of the coast is being reset episodically landwards during storms. By contrast, the study area at Holkham Bay showed considerable recovery between 2008 and 2013, with barrier sections developing seaward through foredune recovery. The third study area, Brancaster Bay, showed partial recovery in barrier location and elevation. Results suggest that recovery is promoted by high sediment supply and onshore intertidal bar migration, at rates of 40 m a− 1. These processes bring sand to elevations where substrate drying enables aeolian processes to entrain and transport sand from upper foreshores to foredunes. We identify three potential sediment transport pathways that create a region of positive diffusivity at Holkham Bay. During calm periods, a general westward movement of sediment from the drift divide at Sheringham sources the intertidal bar and foredune development at Holkham Bay. However, during and following storms the drift switches to eastward, not only on the beach itself but also below the − 7 m isobath. Sediment from the eroding barrier at Brancaster Bay, and especially Scolt Head Island, also sources the sediment sink of Holkham Bay. Knowledge of foredune growth and barrier recovery in natural systems are vital aspects of future coastal management planning with accelerated sea-level rise and storminess variability.

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