A cost-benefit appraisal of coastal managed realignment policy

Abstract

European coasts are coming under increasing threat as a result of climate change from erosion and flooding. While coastal defences such as sea walls have been constructed since Roman times to protect human settlements from the sea, it is now increasingly recognised that these defences are unsustainable. The security provided by 'hard' engineered defences has encouraged development on the coast, and the defences themselves have led to the loss of intertidal habitat and the natural protection it provides. An alternative to maintaining 'hard' defences (hold-the-line) to protect land from increasing sea levels is managed realignment, where the engineered defences are deliberately breached. By allowing the coastline to recede to a new line of defence further inland, intertidal habitat is created providing natural protection from flooding and erosion. The study evaluates the economic efficiency - using cost-benefit analysis - of various managed realignment scenarios compared to a strategy of holding-the-line within the Humber estuary in North-east England. The results of this analysis show that managed realignment can be more economically efficient than holding-the-line over a sufficiently long time period - generally greater than 25 years. Sensitivity analysis demonstrates that results are more sensitive to the amount and value of intertidal habitat generated than they are to the amount and value of carbon stored by this habitat. Cost-benefit analysis is viewed as one component of a wider policy appraisal process within integrated coastal management.