Factors controlling the mobility of shingle beaches, with particular reference to the north Kent coast
Despite their scarcity on a global scale, shingle beaches are a common feature of the coastline ofthe UK, in particular southern England. Shingle beaches have the ability to dissipate large amounts of wave energy over short distances. As a result of this ability, shingle beaches have become a popular 'soft' engineering option for providing protection to coastal regions from the effects of sea flooding and erosion. Shingle beaches are mobile features and, as a result, are subjected to transport under the action of waves and currents. Whilst this mobility allows shingle beaches to respond rapidly to changing environmental conditions, it often also results in localised erosion. This leads to the lowering ofbeach levels and a subsequent reduction in the level of protection afforded to the shoreline. Numerical modelling techniques have been used in conjunction with archived wind, water level, wave and beach profile data to assess the factors which influence the mobility and stability of the shingle beaches on the coastline of north Kent in the southeast of England. Shingle beaches which become eroded are commonly replenished using offshore gravel deposits. Frequently, it has been found that the replenishment material contains a higher percentage of fine-grained material than occurred on the natural shingle beach. These replenished beaches are more reflective than their natural counterparts; this has important implications for the estimated life expectancy of replenishment schemes and for the performance of replenished beaches under storm conditions.