A Simulation Model of a Complex Recurved Spit

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A simulation model of a particular coastal spit is presented to illustrate the value of such models in studying the processes that lead to spit formation. Hurst Castle spit in Hampshire was chosen for the model as it has a distinctive form due to the operation of several easily identified wave types. The processes forming the spit have been discussed by W. V. Lewis. The main ridge, which is composed of shingle, is prolonged by westerly waves, while storm waves build it up. The recurves are formed of material drifted round the end of the main ridge by waves from a southerly point. Waves from the northeast, coming down the Solent, build the lateral recurves. These become longer and more numerous toward the distal end of the spit. The computer program simulates the operation of waves from the west, storm waves, southeasterly waves, and waves from the northeast. In addition, a depth factor simulates the increasing depth of water offshore. This accounts for the increase in number of recurves toward the distal end. A refraction factor allows the curvature of the main ridge to be simulated. The proportion of random numbers allocated to these variables can be adjusted in the data input to elucidate the part they play in the formation of the spit. The close fit of the standard spit to the real spit suggests that the controlling variables are being correctly simulated.