Beach ridges are the beaches believed to have been built during high storms. Although storms are destructive, this characteristic loads the storm waters with eroded beach material which is deposited at the upper end of the shore as a ridge.
Each ridge is believed to correspond to a particular storm. These are generally normal or transverse to the dominant waves. The storm waves depend upon the direction of storm winds and fetch. Though storms may reach a shore from any direction probably, the longest fetch will determine the direction of storm waves on which will depend the beach ridge direction. In between the ridges are depressions parallel with them. These depresses are called swales while the ridges are called berms or fulls Sometimes there may be 60 ridges parallel to the shore. If the material is coarse, there may be only a few beach ridges. Thus, there are half a dozen beach ridges in shingle on Dorset coast in south England.
The essential constituents of a beach are: (i) The upper beach of coarser material in the backshore zone; (ii) the lower beach of the foreshore there is a marked change in the size of sediments, and slope at the junction of the upper and lower beach.
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The upper beach may take the form of berms or beach ridges whose height decreases as one move towards the sea. Beach slope is related to the size of beach material. According to Shepard, the following relationship is generally found:
(i) Boulder cobble and gravel beach (256 mm to 64 mm) 24-degree slope
(ii) Pebbles and granules (64 mm – 62 mm) 11-17 degree slope
(iii) Very coarse and coarse sand (2 mm – 5 mm) 7-9 degree slope
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(iv) Coarse to medium sand (.5 mm – .25 mm) 5-7 degree slope
(v) Medium to fine sand (.25 mm – .12 mm) 3-5 degree slope
(vi) Fine sand (.25 mm- .12 mm) 1 degree slope.
According to Guilcher, however, shingle beach has a slope of 30 degree. Three types of beach profiles are recognized by Shepaid. One type has only a foreshore section with seaward slope. A second type of beach occupies both the foreshore and backshore zones. The backshore section consists of a more or less horizontal beach terrace or berm while the foreshore section slopes seaward like the first type. The third has a low-tide terrace in the foreshore zone and it may or may not have a backshore section.