Orphan breakwaters – what protection is given when they collapse?

Around the UK, many coastal harbours have reduced in importance and/or lost the original sources of income against which to defray maintenance or refurbishment. Their breakwaters may however still protect harbour-side properties against wave overtopping, and thus flooding. This paper presents results from an exploratory study to identify how blockwork breakwaters common in many smaller UK coastal harbours may collapse due to storm action, and in this paper, how much wave protection is given by collapsed breakwaters. The companion paper by Pearson & Allsop (2017) describes initial work to estimate the failure of blockwork walls, and presents results of wall collapse tests.