A-level geography [coastal systems and landscapes]

system

an assemblage of interrelated parts that work together by using some driving process

negative feedback

a change in inputs or outputs to restore the balance

positive feedback

when the balance of the system creates a new equilibrium

dynamic equilibrium

maintenance of balance despite constant change in inputs and outputs

how waves are formed

they are caused by wind blowing over the surface of the ocean causing frictional drag to the water surface

factors affecting wave energy

wind strength, wind duration, fetch

fetch

distance travelled by wind or waves across open water

what are features of constructive waves?

long wavelength, lower frequency, low surging waves, strong swash and weak backwash, cause deposition

features of destructive waves

short wavelength, higher frequency, high, plunging waves, weak swash and strong backwash cause erosion

how constructive waves are formed

by weather systems that work in the open ocean, occur on sloped beaches

how are destructive waves formed?

by storm events with strong winds operation closer to the coast, occur on steeply sloped beaches.

wave refraction

changes in wave direction and frequency as they go over different material.

tidal range

the difference between high and low tide.

spring tide

when the sun and moon align causing the highest and lowest tide

neap tide

when the sun and moon are at a right angle giving the smallest tidal range

features of a high energy coastline

large fetch, rocky headlands, cliffs and wave cut notches. erosion \>> deposition

features of a low energy coastline

smaller fetch, sandy beaches and spits, depostion\>> erosion, weak prevailing winds

rip currents

a strong flow of water running from a beach back to the open ocean

riptide

when the ocean tide pulls water through a small area [bay or lagoon]

sediment budget

balance between sediment being added to and removed from a coastal system

sediment cell

a stretch of coastline [usually between two headlands] where movement of sediment is contained.

basis of planning zones

mechanical weathering

the disintegration of a rock due to weather without changing the chemical make up. Eg: wetting and drying/freeze thaw, crystallisation, exfoliation

what is chemical weathering?

the breakdown of rocks through chemical changes. Eg: carbonation and oxidation

biological weathering

the breakdown of rocks by organic activity. Eg: animal burrows or plant roots

mass movement

movement of consolidated material due to gravity [common in high relief coastlines]

rockfall

occurs when rocks or rock fragments fall freely through the air; common on steep slopes

landslide

when a section of the cliff becomes detached and slides down

mudflows

fine particles of mud falling down the cliff face

slumping

ownward intermittent movement of rock debris, usually the consequence of removal of buttressing earth at the foot of a slope of unconsolidated material.

soil creep

slow movement of particles downhill due to gravity

coastal erosion

the wearing away of a coastline

hydraulic action

the sheer force of water as it crashes against the coast

abrasion

the grinding and wearing away of rock surfaces through action of rocks or sand particles

solution

weak acids in seawater can dissolve alkaline rock.

wave quarrying

the action of waves breaking against material [gravel and sands]

transportation

movement of material along the coast

traction

the rolling of coarse sediment along the sea bed that is to heavy to be picked up and carried by the sea

saltation

pebble sized particles are bounced along the seabed by the water force

suspension

small particles are carried along by the water

solution

soluble materials dissolve in the water

what is deposition?

when particles can no longer be carried due to weaker wave energy

why wave energy declines

• energy source altering

• discontinuity in flow

• increased friction

• increased load

steep cliffs

cliffs made of strong, hard rock, occur in high energy landscapes with little to no beach, long fetch and high energy waves

gentle cliffs

cliffs made of soft rocks that erodes easily and gently slope onto the beach, occur in low energy landscapes with a short fetch, large beach (reduces wave energy)

cliff retreat

the moving back of the cliff face [because of erosion]

how a wave cut platform is formed

the base of the cliff is eroded to form a wave cut notch, the top of the cliff is then weathered away, the cliff then weakens and collapses leaving the base of the cliff that was below sea level unaffected as a wave cut platform

beaches

a store of eroded material along the shoreline, they can show the net accumulation or loss

spit

a long narrow beach of sand or shingle extending from shore out to sea. they occur when movement of beach material extends outward

bar

when a spit extends across a bay and rejoins the opposite shore

tombolo

when a spit extends from shore and joins to an offshore island

barrier islands

depositional islands parallel to shore, occur in areas with limited tidal range. long stretch of deposition with erosion in certain sections

where sand dunes develop

in areas with sandy beaches, a large tidal zone, shallow beach gradient, persistent offshore winds

how sand dunes are formed

• sand accumulates against a feature and builds upper beach height

• wind speed drops behind the accumulation leading to more deposition

• halophytes [salt tolerant plants] stabilise the dunes

• these plants reduce the wind speed and Cath and collect sand

stages of a snad dune

embryo dune, foredune, dune, dune slack, dune heath

what environment do salt marshes need to form?

sheltered ares with low wave energy, freshwater and saltwater meet, low tide energy allow deposition

what is eustatic change?

When the sea level itself rises or falls

isostatic change

When the land rises or falls relative to the sea [local sea level change]

isostatic subsidence

when land sinks due to the weight of the ice

isostatic readjustment

when the land rises back up after the ice melts

how landforms are changed by a change in sea level

changes in sea level effect the shape of the coastline and the formation of new landforms, a fall in sea level exposes land previously covered by the sea, creating an emergent coastline, a rise in sea level floods the coastline and creates a submerging coastline

how tectonic activity can cause eustatic change

it increases and decreases the size of ocean basins

submergent coastline

Where the ocean has overtaken previously low lying areas

submergent coastal landforms

rias, fjords, dalmation coasts

ria

a drowned river valley that cause floodplains to vanish, fed by rivers and sea though branching tributaries

Fjord

a long, steep-sided glacial valley now filled by seawater

Dalmatian coastline

submergent coastlines that form in landscapes of ridges and valleys [dalmation coast Croatia]

Steady-state equilibrium

The condition that occurs in a system when the rates of input and output are equal and the amounts of energy and stored matter are nearly constant around a stable average.

Meta-stable equilibrium

abrupt shifts in the steady state to a new equilibrium

potential impacts of rising sea level

• loss of coastal habitats

• environmental refugees

• loss of productive coastline, delta and river floodplain agriculture

• higher rates of insurance

• increased measures in plac

hard engineering techniques to reduce coastal erosion

reventments, gabion's, groins, concrete tetrapods, offshore reefs

hard engineering techniques to reduce coastal flood risk

flood barrage, closure dams, sea wall

soft engineering techniques

beach nourishment, dune regeneration, living shoreline barners

coastal realignment

allowing flooding on low value land to absorb water and protect low lying areas

reasons for coastal realignment

danger after erosion

prevention of flooding or erosion

protection of valuable land

management of coastline flooding

why we don’t protect all coastlines

uneconomic

bad for the environment

coast is a system so may protect itself

the environment agency's criteria for coastal protection

how many (deprived) households at risk?

impact on farming and agriculture \n impact on environment, wildlife and habitats \n is erosion affecting transport and infrastructure? \n cost (construction, management and maintenance)

Equilibrium budget

state of balance between energy + sediment in terms of erosion, removal, transport, storage and deposition

source

contributes sediment

store

sediment deposition that can be added to or taken away from

sink

a site of sediment deposition that is beyond future potential access

point source / store

A specific coastal location where sediment is removed from (source) or deposited (store)

line source / store

an extended zone of coast where sediment is removed from (source) or deposited (store)

components responsible for the degree of change

energy levels

intensity

sediment supply

consistency of geology

changes of sea level

processes in operation

aims of ICZMs in general

establish sustainable levels of economic and social activity resolve social, economic and environmental challenges and conflicts

and protect the coastal environment

flambrough head characteristics

mostly chalk rock and primarily erosional landforms

bridlington bay to spurn head characteristics

large amounts of erosion and sediment transfer due to rapid cliff retreat

spurn head characteristics

a spit formed at the estuary of the river humber

till cliffs

cliffs made out of soft glacial till.

till is weak and easily eroded. water can also easily seep in and weaken the rock further.

inputs and outputs in holderness

inputs - weak and unconsolidated till cliffs

output - smaller and weaker sediment is washed offshore. some of the larger and courser sediment is moved southward within longshore drift.

flamborough head

a large headland made up of chalk rock. the sea is eroding the base of the cliffs leading to rockfall, overtime this forms wave cut platforms and stacks.

waves have low energy by the time they get to the bay as they are bent / refracted. this leads to a deposited beach in the bay meaning that they exposed headstands take on more of the face of the waves.

bridlington bay to spurn head

this stretch of the coastline has retreated by up to 5km since the roman times. this is a result of rates of erosion varying from 1m to 10m in varying parts of the coastline.

lots of sediment is part of a negative feedback loop and is transferred to the south to create beaches through longshore drift.

spurn head is fed by this sediment and protects the river humber from waves and flooding.

why bridlington bay to spurn head has the most rapid rates of erosion in Europe

• long fetch and powerful waves

• weak, unconsolidated till cliffs

• excessive mass movement (lots of slumping due to undercutting and clay saturation)

• narrow beach making the cliffs vulnerable

• lack of coastal defenced away from the populated areas.

spurn head

a temporary sediment store/sink.

a majority of the material that forms the spit is transferred to the spit comes form longshore drift from the rest of the coastline.

ICZM

integrated coastal zone management

opportunities in Odisha

* wide variety of marine/ coastal flora and fauna (mangroves, salt marshes, sand dunes, estuaries and lagoons)


* large fish / animal stocks
* huge potential for offshore wind and tidal power
* clay and limestone resources
* offshore oil and gas opportunities
* local people are employed in aquaculture and coastal fishing
* culture and architecture draw in tourists
* Chilika lake bird sanctuary boosts bird species

risks in Odisha

rates of erosion have increased (both human and physical causes)

majority of people live in the coastal plain making governments worry about the vulnerability of coastal communities.

cyclone risk in Odisha

Odisha is at risk of cyclones and storm surges, scientists believe that this risk could increase over time as a result of climate change and sea level rising.

in the past a cyclone in the local area caused damage to lives, homes and crops. overall this cyclone caused $700000 worth of damage.

management in Odisha

localised management is proving to be doing more harm than good as they are offsetting the natural systems balance

Odisha ICZM aims

establishing sustainable levels of economic and social activity

resolve social, environmental and economic conflict and challenges

protect the coastal environment

Odisha steak holders

world bank, government, local community, ministry of conservation