An Investigation into Sediment Transport along a Beach and The Ways in Which Coastal Processes Such as Transport are Managed.

These graphs show that the pebble shapes are very different between the sites. At site 1 the pebbles were mostly angular with no very rounded pebbles, but site 2 had over 30% very rounded and over 50% of them rounded.

The differences between the sites is because of coastal erosion which happens along every coast all over the world.

The four types of erosion are:

Hydraulic power - the sheer force of the waves crashing against cliffs ? air and water trapped in cracks is compressed ? pressure increases ? rock fractures explosively.

Corrasion/Abrasion - stones and pebbles are thrown against cliffs by breaking waves ? cliffs are worn and undercut by the sandblasting effect.

Corrosion - seawater slowly dissolves calcium carbonate in chalk and limestone.

Attrition - stones and pebbles carried by waves smash into each other, braking into smaller and rounder pieces ? eventually becoming sand.

Looking at the different types of erosion here I think that the most likely one to be taking place here is attrition.

Erosion only happens when the pebbles are in water and for the pebbles to be in the sea must mean that they are being transported and beach material is transported along the beach in four ways:

Traction - boulders and cobbles are rolled along by powerful waves.

Saltation - pebbles are bounced along by waves.

Suspension - sand and silt are carried in suspension.

Solution - calcium carbonate and salts are dissolved in the seawater.

I think the most likely form of transportation on this beach is Saltation because as the pebbles bounce any rough edges will get knocked off making the pebbles smother and smaller.

So along this beach there is Saltation and attrition taking place. The pebbles will also be moving along the beach between sites 1 and 2; this process is called longshore drift or LSD for short.

Analyses Two

How and why is The Transport of Sediment along This Beach Managed?

This beach has groynes to slow down LSD along the beach.

A groyne is a protruding set of logs from the edge of the beach towards the sea. The purpose of the groynes is to slow down the effects of longshore drift. Longshore drift is how the pebbles travel from one end of the beach to the other along the waves.

Longshore drift is when pebbles are picked from the beach and dragged to sea at 90o. They are dragged out by the backwash, the pebbles are pushed up the beach at 45o by the swash and the pebbles move along the coast in a zigzag fashion.

LSD can totally strip a beach of all its materials. In tourist areas it is important to keep the beach so groynes are made at right angles to the sea trapping beach material.

Analyses Three

What Other Methods Are Employed To Manage Coastal Processes?

There are many more types of coastal defence used to protect our coastlines. Some are to prevent erosion, and some are to prevent transportation of beach materials, like the groynes.

Some of the types of coastal management used around the UK's shoreline are as follows:

Rip-Rap/Rock Armour

This is a collection of large interlocking boulders sometimes fixed into position to protect the coast by disrupting the waves. It costs £ 3,000 per metre.

Revetment

This is a gently sloping concrete wall, which allows the waves to run up it, thereby dissipating their energy. It costs £ 2.000 per metre. A cheaper, but less longstanding revetment is a sloping wooden frame (baffle) on to which planks are evenly spaced. It decreases wave energy and allows water and sediment to build up under the planks. It costs £ 500 per metre, but this ignores repair costs.

Stone Gabions

This is a strong steel cages filled with rocks and some surface sand on which salt tolerant grasses can become established. It costs £ 200 per metre, but gabions have the big disadvantage of being ugly constructions

Sea Wall

This is made with stone or concrete. It usually has a curved top to reflect wave energy back on to the next advancing wave. A concrete promenade can be built on top of the wall. It costs £ 5,000 per metre.

Embankments

These are high walls that are situated where a beach meets the land or cliff. They are usually made of concrete or stone and bounce back storm waves.

Beach Rebuilding

The sand that is lost through longshore drift is replaced every year, but this is very expensive and a long task.

These are all useful and effective methods of coastal defence and they are all worth while investing into, the only problem with them is that they are all expensive. None of these are permanent so they have to be replaced every few years.