[coasts] coastal landforms & management

[ BBC Bitesize 'Coastal Management ⇢ Coast' page 1 ] [ BBC Bitesize 'Costal Management ⇢ Coastal Landscapes' page 2 ] + geography school book

Coast

The part of the land adjoining or near the sea

Erosional Landforms:

• headland

• bay

• cave

• arch

• stack

• stump

Headland

A high area of land that extends out into the sea, near a bay.

Bay

A low-lying inlet of land on the coast by a headland.

Formation of a Bay and Headland:

1. bands of soft rock (clay and sand) by a coast erode quickly, forming bays

2. hard rock (chalk) resists erosion, creating headlands

Caves

Recess in a cliff where waves have enlarged a crack in the rock face.

Arches

A natural rock formation often created by two sea caves eroding backwards towards each other until the back walls disappear.

Stack

A pillar of rock left standing in the sea when the top of an arch has collapsed.

Stump

The remains of a stack which the sea has eroded away.

Explain how the geology of the Holderness Coast affects the erosional landform.

• average annual rate of erosion = 2m per year

• soft rock (clay) eroded to form a bay (Bridlington Bay)

• hard rock (chalk) resists erosion, forming a headland (Flamborough Head)

Explain how the climate will affect the geomorphic processes that take place at Holderness Coast.

• strong prevailing wind from the south to the west

• this transports and deposits sediment along the coast (longshore drift)

• more erosion and weathering

1st Stage of Forming a Stump

Cracks are formed in the headland through the erosional processes of hydraulic action and abrasion.

2nd Stage of Forming a Stump

As the waves continue to grind away at the crack, it begins to open up to form a cave.

3rd Stage of Forming a Stump

The cave becomes larger and eventually breaks through the headland to form an arch.

4th Stage of Forming a Stump

The base of the arch continually becomes wider through further erosion, until its roof becomes too heavy and collapses into the sea, leaving a stack.

5th Stage of Forming a Stump

The stack is undercut at the base until it collapses to form a stump.

Depositional Landforms:

• beaches

• spits

Beach

Gently sloping land by a shore, which is formed from eroded material transported and deposited by the sea. For this to occur, waves must have limited energy, so beaches often form in sheltered areas like bays.

Types of Beaches:

• sandy beaches → located in shallow bays with low-energy waves; tend to be gentle-sloping

• pebble/shingle beaches → form near eroding cliffs with high-energy waves; tend to be steeper

Transportation

The movement of eroded material from one place to another.

Spit

A stretch of beach at one end of a coastline caused by waves depositing material.

Formation of Spits:

1. when the coastline ends and the process of longshore drift continues, sediment is deposited off the coastline

2. a long thin ridge of material is deposited; this is the spit

3. a hooked end can form if there is a change in wind direction

4. waves cannot get past a spit, therefore the water behind a spit is very sheltered; silts are deposited here to form salt marshes or mud flats

Conditions Affecting the Formation of a Spit:

• speed of longshore drift

• amount of sediment available

Berm

Ridges on the beach left as a mark of the tide.

Deposition

When material is dropped due to a decrease of energy.

Solution

Type of Erosion - chemicals in the water dissolves soluble material from the rocks.

Abrasion

Type of Erosion - rocks and other loose materials chisel the cliff, acting like sandpaper and causing the cliff/surface to crack further.

Attrition

Type of Erosion - rocks smashing together causing them to break into smaller pieces of rock.

Hydraulic Action

Air getting trapped in the cracks of cliffs, weakening and breaking down the cliff.

Mitigate

To make something less severe or serious

Hard Engineering

Involves building artificial structures which try to control natural processes, usually expensive infrastructure.

Soft Engineering

Involves a more sustainable and normal approach to managing the coast.

Sea Walls (Hard Engineering)

Structures separating land and water areas - protecting the land on the coast from the crashing waves.

Disadvantages of Sea Walls

• very expensive

• can look ugly

Groynes (Hard Engineering)

A wooden barrier built at right angles to the beach, preventing longshore drift.

Disadvantages of Groynes

• may create problems elsewhere because they starve other beaches of sediment

• need to be maintained

Longshore Drift

Movement of material along beaches by waves (backwash + swash).

Swash

When a wave reaches the shore, the water that rushes up the beach.

Backwash

The water that flows back towards the sea.

Rip Rap/Rock Armour (Hard Engineering)

Large boulders piled up on the beach, absorbing the energy of the waves that crash upon it.

Disadvantages of Rip Rap/Rock Armour

• large/powerful waves can move or undermine the boulders

• can look ugly.

Beach Replenishment (Soft Engineering)

Unwanted, extra sediment (dredged from the sea) is dumped onto the beach to widen and increase the depth of the beach, meaning waves won't have enough energy to erode the cliffs.

Disadvantages of Beach Replenishment

• doesn't last very long

• can alter ecosystems

• time-consuming

Revetments (Hard Engineering)

A wooden or concrete, slopping structure placed at the foot of the cliff to reflect and damage the impact of the waves.

Disadvantages of Revetments

• expensive to build

• big visual impact

• need to be maintained

Gabions (Hard Engineering)

Wire, cages filled with small rocks and stone/pebbles placed at the bottom of the cliffs.

Disadvantages of Gabions

• unattractive

• cages rust within 5-10 years.

Breakwaters (Hard Engineering)

Offshore structures built from stone parallel to the coastline; help absorb the energy of breaking waves.

Disadvantages of Breakwaters

• disrupts the natural flow of sediments along the coast