Longshore drift has been drilled into school children by geography teachers for decades. If advancing waves arrive at a beach from a slight angle, then the up-beach wash, sometimes known as Swash, throws some pebbles, or sand particles, up the beach in the direction of the angled breaking wave. Some of the wave water percolates into the beach, but some flows back down the beach by gravity, dragging pebbles and sand with it. This is known as Backwash and it can assist some sediment to move towards the nearshore zone. After one wave cycle some pebbles have moved laterally, longshore, by centimetres or metres. Quantities moved are related to the size and direction of the waves.

Over the past 20 years the University of Plymouth have conducted intensive surveys of beaches in Start Bay to record beach levels. That data has been integrated to calculate volume of sediments. Multiple surveys at different times of the year have been compared with changing climate patterns. Results show how beach volumes have been moved both North and South. Reversals are common over time scales of less than one year to several years. Recently beach volumes, and their corresponding levels, have caused a build up of shingle at the Strete Gate (Northerly) end, and reduced volumes at the Torcross (Southerly) end.