Effectiveness of Adaptive Coastal Protection in Managing Wave Overtopping and Retaining Beach Views at the Crest of Seabee Seawalls

Seabee armoured seawalls have been constructed at a number of sites globally, the North Cronulla seawall being well known. Seabee armour units have high structural resistance, are cost effective in fabrication and construction but suffer from high wave runup leading to increased wave overtopping or need for higher crest levels.With projected sea level rise of the order of 1 m over the next 100 years, higher extreme water levels and wave heights will impact our coastlines leading to increased wave runup and overtopping of existing structures beyond safe limits. Adaptive methods of coastal protection are required.Within this study, wave deflectors, back beach wave washout zones and the staggering of Seabee seawalls have been physically modelled in wave flume testing at WRL to determine their effectiveness in reducing wave overtopping rates in present and future conditions. Combinations of these adaptive coastal protection measures have been shown to eliminate unsafe levels of wave overtopping that may occur with climate change.In protecting our coastline we must avoid distancing ourselves from it and in so doing diminish the value of beach amenity. As well as holding great economic wealth within the tourism and residential industries, beach views have overwhelming social and emotional importance to the everyday lives of coastal communities and beach users. Within this study various beach user communities at several beaches have been surveyed as to the value of horizon, shoreline and sandy beach views. As well as highlighting strong desires for close beach proximity, survey responses stress the importance of maintaining a strong visual connection with the coastline as opposed to obstructing it through extreme measures of coastal defence. The study emphasises that effective adaptive coastal protection requires an essential compromise between the need for structural integrity and overtopping safety and the communities’ desire for proximity and visual connection with the beach