| Abstract: | Studies of sediment dynamics in the nearshore zone cover a broad spectrum of disciplines and it is difficult to determine what particular trend is emerging in current research because many problems, particularly those confronting coastal engineers, are practical rather than academic and consequently demand rapid solution. Restrictive physical factors, such as heavy swell and wave turbulence in the breaker area, have undoubtedly limited in situ measurements and may partly account for the apparent poor correlation between field data and laboratory results and theoretical prediction. The development of sophisticated field instrumentation is an attempt to resolve this problem and this Review draws attention to some of the more recent techniques that have been reported in the extensive literature during the last decade or so.For the purpose of this paper, the nearshore zone is sub-divided into swash, surf/breaker and offshore zones. A summary is given of littoral transport rates, particularly with regard to the value of tracer experiments and models, and the difficulty of measuring surge-swash velocities and bottom profiles is assessed. Brief mention is made of swash percolation and groundwater flow and, bearing in mind the engineering problem of arresting the loss of beach sand to the backshore and dune system of some coastlines, the shear stress of sea breeze has also been evaluated. The problems of predicting changes in the plan shape of beaches and in the rate of mobility of shingle under wave action are discussed. Methods for measuring suspended sediment and bulk density are also described. Variations in wave refraction and wave energy relative to theoretical computation are appraised and reference is made to the use of radar in hydrodynamic surveying.Other sections of the review refer to the relationship that appears to exist between edge waves and crescentic bars; and the use of photography in studying coastal processes. |
