38 



Beach and Nearshore Zone 



Beaches are accumulations of unconsolidated sediment extending shoreward 

 from the mean low tide line to the inland limit of the littoral zone, where 

 vegetation or a change in relief begins to develop (i.e., coastal sand dunes, 

 beach ridges, terraces, or a cliff line) (Komar 1976). Beaches are among the 

 most variable coastal geomorphic features and the most widely distributed of 

 any of the coastal sedimentary environments (Dolan et al. 1972). Extensive 

 beach development occurs on low-lying coasts where great quantities of 

 sediment are available, primarily at barrier coasts, with the remainder occur- 

 ring in pocket beaches, lakes, and rock headlands (Davis 1985). Beach 

 sediments generally range from fine sand to cobbles. Finer materials are 

 present on few ocean beaches, because waves create turbulence which keeps 

 fine materials in suspension. 



Beaches may hug the coastline or show a number of large-scale detached 

 forms. Barrier islands, which are totally disconnected from the mainland 

 shoreline, are typically fronted by beaches (Nummedal 1983), and separated 

 from the mainland by lagoons, wetlands, or tidal marshes. Spits are quasi- 

 linear subaerial landforms caused by longshore deposition in which beaches 

 separate from the main coastline and project into the deeper waters of estuary 

 mouths or bays. If a spit extends across a bay, it is known as a baymouth 

 barrier. Cuspate forelands are seaward-projecting accumulations of materials. 

 Wave refraction around an offshore island may lead to the development of a 

 tombolo, a beach connecting the mainland with the island. 



The beach surface can be divided into two major zones, the 

 backshore, which extends inland from the normal high-tide level, and the fore- 

 shore, which is equated with the intertidal zone (Figure 2). The beach and the 

 nearshore zone, which extends from the low-tide level to the seaward limit of 

 bar-and-trough topography, are closely related but show markedly different 

 forms and processes. 



Generally, most of the backshore consists of one or more berms or beach 

 ridges, which are flat to gently landward-sloping accumulations of wave- 

 deposited sediments. Gravel and cobble beaches may show one or more 

 storm ridges in the backshore. According to Carter (1988), a beach ridge is a 

 berm that has survived erosion, and there is no real morphological or sedi- 

 mentological distinction between them. In this study, two types of beach 

 ridges were distinguished, one which was controlled by runup, and one which 

 was the result of ridge stranding. The seaward limit of the backshore is 

 marked by the berm crest, at which the slope changes along a more steeply 

 inclining beach face. Eroding beaches may show a continuous upper 

 foreshore-to-backshore slope and a slightly concave-upward profile. 



Morphologic features of the foreshore are more variable and numerous 

 than in the backshore. For example, the beach face slope may be inclined 



Chapter 3 Variable Coastal Features 



