RECESSION OF PREDOMINANTLY SANDY BLUFFS

Climate change and sea level rise are anticipated to accelerate coastal erosion, a major societal issue during the past half-century (Hapke, et al., 2009). While important progress has been made in predicting sandy beach responses to various ocean climates, a similar progress has not been made for coastal bluffs. Coastal bluff recession is a natural process that can become a hazard when it endangers buildings and developed properties. Despite some early works on cohesive shoreline erosion mechanisms (Dalrymple, et al., 1986; Sunamura, 1985), prediction of bluff recession still remains one of the main questions in coastal zone management. Several experiment studies were conducted in wave flumes to investigate the effective parameter. Earlier experiments focused mainly on hard cliff and cohesive bluffs erosion in the 1970s, under normally incident waves and have been reported by Sanders (1968), Horikawa and Sunamura (1970), and Sunamura (1983). During the 1980s–1990s a number of studies were conducted to understand erosion of cohesive coastal profiles with or without an overlying veneer of sand (Nairn, 1986, and Skafel and Bishop, 1994). These works used artificial or prototype clays for the cliff and focused primarily on the erosion process of the clay at beach or foreshore. A recent study by Caplain et al. (2011) investigates the effect of wave climate on the rate of sandy cliff recession in a wave flume. They reported observations of sand movements, sand bars dynamics and cliff recession rate.