Cliff recession and behaviour studies, Hunstanton, UK

Abstract

This paper presents the recent case study of cliff recession at Hunstanton, North Norfolk. The cliffs at Hunstanton are composite weak rock cliffs which have retreated by up to 30 m since 1885 in a series of failures of varying size and nature. The paper describes a programme of cliff monitoring and analyses the findings in the context of the available historical data. The geological control over the failure mechanisms, erosion cycle, and hence failure return period is investigated and discussed. Based on observations made, the cliffs have been mapped according to cliff behaviour characteristics, each cliff behaviour unit comprising a recession rate class and a failure type class. In this way the behaviour of the cliffs can be described semi-qualitatively, based on real recession data and the nature and extent of failures. The boundaries between units are seen to traverse the cliffs with time, reflecting the transient nature of the cliffs' response to erosion. The case study demonstrates the importance of high-resolution spatial data in understanding the mechanisms involved in the cliff erosion cycle. The detailed monitoring data collected have enabled a transition from macro-scale predictions of future recession rates for the entire cliff section towards real hazard-related predictions based on failure size and return period at specific localities such as vulnerable structures. The benefits of this approach to coastal managers and planners are illustrated through discussion of remedial options and the anticipated impact of those remedial options on the cliff behaviour.