Coastal erosion on an OS map

Some coastal erosion features will not appear on an OS map. Features like blowholes are often too small to be easily identified at this scale.

Here are some examples of erosional features easily identified from a map.

An ordnance survey map of Thurlestone.Map 1 - Ordnance Survey Coastal Features © Crown copyright and database rights 2013 Ordnance Survey

Name evidence

The term ‘point’ (meaning headland) appears at Warren Point, 667421 (Map 1).‘Cove’, indicates where erosion has produced a small bay - Butter Cove at 661432 (Map 2) and Soar Mill Cove at 697376 (Map 3). ‘Cliff’ is another place name indicating erosion - West Cliff, 688383 (Map 3).

Shape

The shape of the coast is a good indicator.

The large headland at Burgh Island, 646438 (Map 2) stand outs, suggesting a much more resistant rock type than the coast on either side.

Smaller headlands like Warren Point and Thurlestone Rock, 675414 (Map 1) enclose sandy bays like the ones depicted at 676416 (also Map 1).

An ordnance survey map of Burgh Island.Map 2 - Ordnance Survey Coastal Features © Crown copyright and database rights 2013 Ordnance Survey

There are small islands off Thurlstone Rock 673417 (Map 1) and Cathole Cliff, 693376 (Map 3). These will be former parts of headland now worn down to be stacks or stumps. Burgh Island was separated from the mainland by erosion.

Over time the sand shown building up between Burgh Island and the mainland may become permanent and form a tombolo linking the island to the mainland.

Symbol evidence

Symbol evidence is also important and Map 3 shows the symbols for cliffs at 688383 and steep slopes at 682387.

Around here, contour lines appear to run into the sea, indicating the height of the cliffs at that point.

The flat rock symbol on the seaward side of the coastline indicates a wave-cut platform at 669421 (Map 1).

An ordnance survey map of Bolberry Down.Map 3 - Ordnance Survey Coastal Features © Crown copyright and database rights 2013 Ordnance Survey

Coastal transportation and deposition

Transportation of particles along a coastline is influenced by the strength of waves and the angle at which the waves strike the shoreline.

This is determined by the direction from which the prevailing wind blows.

Longshore drift

As can be seen in the diagram below, a pebble or sand particle moves from point A to B, carried by the swash up the beach, the angle determined by the wave and wind direction.

It is then pulled down the beach from B to C, carried by gravity and the wave's backwash.

Waves approaching the beach at an angle with arrows showing the movement of a pebble in line with the direction the waves are moving.

This process is repeated over and over again and the particle moves along the shoreline - this is called longshore drift.

When large numbers of sand particles or pebbles are moved along a coastline in this way, a depositional feature called a spit may form.