Risk-based benefit assessment of coastal cliff protection

Abstract

Cliff protection schemes are designed to reduce the risk of damage or permanent loss of cliff-top assets as a result of coastal cliff recession and landsliding. To identify the most efficient scheme in economic terms requires an assessment of the beneficial risk reduction that each of the scheme options will achieve. This paper introduces a risk-based approach to evaluating the economic benefits of coastal cliff protection. The approach is applicable to economic appraisal of schemes for currently protected and unprotected coastal sites. Example appraisals of sites prone to progressive cliff recession, large catastrophic landslides and minor recurrent ground movement are included. Methods for including and structuring expert judgements of failure probabilities are explored. A risk-based approach is preferable to current practice, which is essentially deterministic, because it reflects the uncertainty that is inherent in recession predictions. Current deterministic methods can underestimate the economic risk associated with cliff recession.