- Shingle beaches typically have a steep gradient (over 10˚) because the waves easily flow through the coarse, porous surface of the beach, decreasing the effect of backwash erosion and increasing the formation of sediment into a steep sloping back.
- Sandy beaches are typically flatter (>5˚) and wider as the smaller particles are evenly distributed and water takes longer to percolate down into the sand so more sand is removed with the backwash.
Beach Profile Features
Ridges & Runnels
Parallel “hills and valleys” of sand found at the low water mark. These are formed due to the interaction of tides, currents and shallow beach topography and so are often formed as breakpoint bars.
A ridge of boulders and shingle found at the back of the beach which have been thrown up to the back of the beach by the largest waves at high tides.
Semicircular depressions formed by waves breaking directly on the beach with a strong swash and backwash.
Develop on sandy beaches as a result of wave and tidal movements.
Beach Plans & Longshore Drift
A beach plan is formed as a product of the angle at which waves approach a beach.
- Drift aligned beaches are produced where waves break at an angle to the coast. The swash therefore occurs at an angle but the backwash runs perpendicular to the beach. As a result, material is transported along the beach via longshore drift.
- Some beaches show oblique alignments to the dominant wave fronts. This usually occurs where the beach gradient is steep and the wavelength is short. This is because the waves break at different points on the beach.
- Swash aligned beaches (e.g. Hell’s Mouth) are produced where the waves break in line (parallel) with the coast. Swash & backwash movements move material up and down the beach producing the aforementioned beach profile features. Swash aligned beaches are smoothy curved, concave beaches. The beach face is orientated parallel to the fronts of the dominant waves. Beaches which face the waves are termed swash aligned.