The components of a beach profile are illustrated below in figure 1. The locations of most of these zones and their features may vary with tidal stage and beach state (erosional or accretional), they are not permanent either temporally or spatially, but migrate both shoreward and seaward. The profile below illustrates a mesotidal beach more typical of the North Shore of Massachusetts. Multiple berms are displayed around neap tide and destroyed during spring tide. Most textbook illustrations of beach profiles show a single berm, a well defined step, and little to no low tide terrace. Such profiles are more common in microtidal settings, and for introductory students are often difficult to reconcile with the beach morphology observed locally.

Figure 1. Zones and features of the shoreface. Stb=storm berm, Sptb=spring tide berm, MHW=mean high water, MLW=mean low water.

The shore zone to refer to the region of mobile sediment that is available to waves and currents for building of the beach. It contains the body of sediment that forms the slope extending from the foredune ridge or a bluff to the shelf. The seaward limit is defined by a change in slope where the sediment wedge meets the shelf and the depth of closure, the depth below which waves are incapable of moving sediment. As would be expected the shore zone may undergo radical changes as wave climate varies. The components of the shore zone are as follows.

Shore and Beach: The strip of land in direct contact with the water between high and low water. The term beach applies if the region is composed of unconsolidated sediment. The width of the shore is determined by tidal range and slope.

Backshore: The region of a beach  extending from the berm crest landward to a foredune ridge, vegetation line, seawall or some other physiographic break. Under typical conditions the berm area includes the supratidal area of a beach.

• The backshore is typically beyond the reach of ordinary waves and tides but is influenced by aeolian processes. Swash processes are important along the berm crest. The backshore becomes wider during the Summer and narrower during the Winter.
• In some instances along engineered coasts the backshore may be missing.  For example, waves reflecting from a seawall at high tide create turbulence and scouring that eventually remove the sand along its base.

Foreshore: The sloping portion of the beach between the limits of high tide and low tide swash.

• This is the intertidal zone that includes the beach face and low tide terrace--the region affected by swash and backwash. Along macrotidal shores the beach face is commonly separated by a plunge step, a small trough filled with coarse sand or shells from by the breaking of small plunging waves at the base of the beach face. On gravel (shingle) beaches there may be an abrupt transition from gravel (beach face) to sand (low tide terrace).

Shoreface/inshore: The area seaward of the foreshore extending to a point outside the breaker zone. The inshore is subtidal and below mean low water. Sediment motion here is dominated by wave activity and not by swash and backwash. Slope is the principal factor controlling the width of the shoreface.  However, breaker location will fluctuate daily and seasonally depending on variables wave height, tidal stage, and beach state.

Offshore: The extending from the breaker zone to the the edge of the continental shelf

Note: Sometime the term shoreface is loosely used to include the entire shore zone

berm

The dry, upper flat portion of the beach generally located at or above MHW (supratidal) is the berm. This is the area that you set your towels when you don't want to move them again when the tide rises. The berm is periodically overtopped during storms or extreme high tides.

• On sandy and shingle beaches berms build seaward through the multiple accretion of bars to the beach face. (See fig. 3 below) Vertical accretion to the berm is accomplished by swash (fig. 2), which is influenced by wave height. The berm height approximates 1.3 x the significant Ho. Therefore, all other factors being equal (e.g. grain size), berms on beaches facing the open ocean are higher than those on beaches in sheltered coves.
• A beach may have more than one berm or none at all (e.g. an eroded beach backed by a seawall).
• Some beaches, particularly mesotidal gravel beaches, may exhibit multiple berms (e.g. LHT berm, HHT berm, summer berm, winter berm, storm berm, etc). High-water berms are formed during storm surges or spring tides (HHT berm). The most ephemeral berm would be the low berm formed during neap tide (LHT berm).

• The berm crest, formed along the upper limit of wave swash, is the linear break in slope marking the seaward limit of the flat berm and shoreward limit of the sloping beach face. The berm crest migrates seaward during periods of accretion and landward during periods of erosion.

Figure 2. Singing Beach, Manchester by the Sea, MA. (late October 99). During high tide, waves breaking on the beach face over-top the berm. Vertical accretion occurs when water percolating down through porous sand leaves behind its load. The shallow uprush of water that carries the sediment is termed swash. The limit of swash during a tidal cycle is marked by a band of debris pushed shoreward by the leading edge of the swash.

Figure 3. Goldthwaite/Devereau Beach, Marblehead, MA (July 03). This steep shingle beach typically contains multiple berms formed by the welding of gravel bars during various monthly levels of high tide. The highest ridge on the beach is formed during northeasters when large amounts of gravel are thrown on the beach. Also, gravel tossed onto residential lawns is bulldozed back to the beach ridge.

beach face

• The sloping portion of the beach dominated by wave swash and backwash.

• An offshore bar is an inshore(below mlw) linear deposit of sediment that forms a ridge that typically runs parallel to shore. The trough is the swale shoreward of the bar. Breakers will form in response to the shoaling caused by offshore bar, therefore the location of an offshore bar can be identified by noting breaker zones.
  • Offshore bars are generally composed of sand eroded from the beach face during storms
  • breaker zone: zone of convergent between onshore and offshore currents
  • In tidal regions there may be two sets of bars formed and high and low tide
  • Offshore bars act as filters, allowing only waves of a certain height to pass

• A ridge and shoreward trough formed by the landward migration of an offshore bar
  • A breach in the ridge formed by water rushing seaward from the runnel is called the runnel outlet
  • generally absent from gravel beaches

• The flat lower portion of the beach exposed during low tide.
  • On microtidal beaches the low tide terrace is very narrow or lacking.
  • On mesotidal and macrotidal beaches the low tide terrace is very broad and is composed of finer sediment than that on the beach face. Typically the dominant region during low tide.
  • The low tide terrace is compose largely of fine grain material (sand, silt or clay) even on gravel beaches.

• The beach step is the final breaking point of waves before they rush up as swash on to the beach face. Because this is a high energy environment sediment along the beach step is typically coarse grained. The beach step is best developed microtidal beaches.

• A scarp formed along the foreshore by beach erosion. During periods of erosion the berm crest is replaced by a landward migrating beach scarp. The berm become progressively narrower which the low tide terrace widens.

• A series of embayments separated by horns of coarser sediment located in the foreshore region. Horn spacing ranges from 1 to 60m. Cusps are thought to be formed by edgewaves, which move parallel to the shore.

• The outermost portion and a dune backing a sandy beach. With the exception of erosional bluffs and artificial structures the foredune ridge marks the backshore limit of most sandy beaches.

Figure 4 (below). Singing Beach, Manchester by the Sea (Fall 93) taken close to low tide. The beach zones on this photo are quite clear. Before moving the cursor over the figure try to identify the berm, beach face, low tide terrace and the fitted riprap revetment that terminates the backshore.

Note: On the low tide terrace lies a bar (ridge) cut by numerous runnel outlets. Sand eroded during a storm is now migrating onshore. The dry sand on the berm is lighter in color that the wet sand along the beach face and low tide terrace. Shoreward of the bar lies light band between the low tide terrace and the beach face. This highly reflective band is water ponded in the trough (runnel), located along the step.

nearshore zone

• The entire area affected by wave bores, swash and backwash. It includes the foreshore and inshore.
  • swash zone: The area of wave swash (uprush of water) and backwash (back rush of water)--foreshore
  • surf zone: The zone landward of the breaking wave where there is the forward translation of water called wave bores
  • Breaker zone: The zone of breaking waves

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