Chalk Shore platform erosion in the vicinity of sea defence structures and the impact of construction methods

Dornbusch, Uwe, Robinson, David A, Williams, Rendel B G and Moses, Cherith A (2007) Chalk Shore platform erosion in the vicinity of sea defence structures and the impact of construction methods. Coastal Engineering, 54 (11). pp. 801-810. ISSN 0378-3839

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Abstract

Erosion of the intertidal chalk platform in the vicinity of groynes and seawalls is evident to the naked eye along many stretches of the engineered coastline of southeast England, leading to undermining and eventually failure of these structures. However, quantification of the magnitude and spatial extent of the erosion has been difficult to date because of a lack of data about the past elevation of the platform. The application of softcopy photogrammetry makes it possible to recreate past platform elevations from historic air photographs and to compare these with elevations from modern air photographs. Coastal sea defence structures have been installed along the chalk coast east of Brighton at various dates over the past 70 years. During this period, the construction methods have changed from predominantly manual labour to a reliance on heavy machines. The analysis of erosion patterns around structures built since the 1970s using heavy machinery show that surface lowering is 4 to 25 times greater in the vicinity of these structures than across the platform as a whole. In contrast, there is no similar pattern of increased erosion around structures built using predominantly manual labour in the 1930s. A four fold increase in average surface lowering is found also along a vehicle trackway that crosses the mid platform. Depressions developed by enhanced lowering in the front of seawalls generate their own dynamic of increased erosion by trapping pebbles and cobbles that enhance the abrasion of the chalk through bedload transport under standing waves in front of the walls.

Item Type: Article
Additional Information: Output from EU-funded Beaches at Risk (BAR) Project. Robinson senior authour, Dornbusch Post-Doc. employed on the project. Paper quantifies for the first time the impact of engineering construction methods on rates and patterns of shore platform erosion.
Schools and Departments: School of Global Studies > Geography
Depositing User: David Robinson
Date Deposited: 06 Feb 2012 15:14
Last Modified: 04 Apr 2012 13:27
URI: http://sro.sussex.ac.uk/id/eprint/11220
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