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Beaches Beaches

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An AS level presentation on features of a beach.

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Page 1: Beaches AS

BeachesBeaches

Page 2: Beaches AS

Depositional Landforms - Depositional Landforms - BeachesBeaches

Source of beach

material

My Guess (%)

Actual (%)

Cliff erosion

Offshore

Rivers

Page 3: Beaches AS

Depositional Landforms - Depositional Landforms - BeachesBeaches

Source of beach

material

My Guess (%)

Actual (%)

Cliff erosion 5

Offshore 5

Rivers 95

Page 4: Beaches AS

BeachesBeaches

Depositional landforms are produced on Depositional landforms are produced on coastlines where sand and shingle accumulate coastlines where sand and shingle accumulate faster than they are removed.faster than they are removed.

This normally occurs in areas of coastline This normally occurs in areas of coastline dominated by constructive waves of low energy.dominated by constructive waves of low energy.

Beaches are the most common landform of Beaches are the most common landform of deposition and represent the accumulation of deposition and represent the accumulation of material deposited between the positions of the material deposited between the positions of the lowest tides and highest storm waves.lowest tides and highest storm waves.

Beach material in the form of sand, shingle, Beach material in the form of sand, shingle, pebbles and cobbles comes from three sources; pebbles and cobbles comes from three sources; cliff erosion, offshore and rivers.cliff erosion, offshore and rivers.

Page 5: Beaches AS

BeachesBeaches

Sand produces beaches with a gentle gradient; Sand produces beaches with a gentle gradient; usually less than 5usually less than 5º. º.

This is because its small particle size means that This is because its small particle size means that it becomes compact when wet, allowing little it becomes compact when wet, allowing little percolation during backwash.percolation during backwash.

Shingle produces steeper beaches; often 10-20º. Shingle produces steeper beaches; often 10-20º. Shingle may make the upper part of the beach, Shingle may make the upper part of the beach,

where rapid percolation due to larger air spaces where rapid percolation due to larger air spaces means that little backwash occurs and so means that little backwash occurs and so material is left at the top.material is left at the top.

Page 6: Beaches AS

Factors Affecting the Beach ProfileFactors Affecting the Beach Profile

1.1. Wave Energy.Wave Energy. High energy waves tend to High energy waves tend to produce shingle beaches. Sandy beaches are produce shingle beaches. Sandy beaches are found in low energy areas.found in low energy areas.

2.2. Wave Type.Wave Type. Destructive waves = stronger Destructive waves = stronger backwash = more material moving back down backwash = more material moving back down the beach = shallower profile. Constructive the beach = shallower profile. Constructive waves = strong swash = more material moved waves = strong swash = more material moved up the beach = steeper beach profile.up the beach = steeper beach profile.

3.3. Longshore Drift. Longshore Drift. 4.4. Sediment Calibre.Sediment Calibre. Shingle beaches are

generally steeper as backwash percolates easily through the shingle reducing its energy and ability to comb material back down the beach.

Page 7: Beaches AS

BermsBerms

Smaller ridges that develop at the position of the mean high tide mark resulting from deposition at the top of the swash.

Berms are generally created by smaller waves which have less energy so the material is smaller.

Page 8: Beaches AS

Storm BeachStorm Beach

At the back of the beach, very strong swash during storm conditions may deposit larger material, forming a storm beach or ridge.

Page 9: Beaches AS

Ridges and RunnelsRidges and Runnels

The spreading out of the waves’ energy/work across a wide area of beach tends to produce ridges and intervening depressions called runnels.

They are particularly common on shallow, sandy beaches.

Page 10: Beaches AS

Beach CuspsBeach Cusps

Cusps are semi-circular Cusps are semi-circular depressions; they are smaller depressions; they are smaller and more temporary features and more temporary features formed by a collection of waves formed by a collection of waves reaching the same point.reaching the same point.

The sides of the cusp channel The sides of the cusp channel the incoming swash into the the incoming swash into the centre of the depression and centre of the depression and this produces a stronger this produces a stronger backwash which drags material backwash which drags material down the beach from the centre down the beach from the centre of the cusp.of the cusp.