coasts and rivers Flashcards
abrasion
a form of erosion where loose material and sediment ‘sandpapers’ the walls and floors of the river
attrition
rocks bang each other chipping away to make small and smoother rocks
hydraulic action
is the sheer force of water crashing against the coastline causing material to be dislodged and carried away by the sea
constructive waves characteristics
have stronger swashes than backwashes
backwashes are not strong enough to remove the sediment
low energy
begins to build up the coastline
far apart
destructive wave characteristics
weak swash
strong backwash
the strong waves removes sediment from the beach
steep
close together
sea walls disadvantages
can protect one area of the coasts but can increase erosion further down the coastline by disturbing the natural sediment movement
they can be visually intrusive which can spoil the natural beauty of the coastline
expensive to build and maintain-as sea levels rise, sea walls may need to rebuilt higher or more frequently making it more expensive
rock wall (rock armour) disadvantages
can interfere with natural processes like longshore drift leading to increased erosion in unprotected areas down the coast
often look out of place
makes access to the beach difficult as people might have to clamber on rocks or take a detour to get onto the beach
strong waves can cause the boulders to move causing them to have to be replaced
gabions disadvantages
they are weak than other management strategies which means they need regular maintenance
labour intensive
bulky and space-consuming
what are gabions?
are costal defences that consist of rocks and boulders encased in wired material
types of mass movement
rock falls
mudslide
landslide
slumping
beach nourishment
sediment can be put onto beaches
lorries dump thousands of tonnes of sand and shingle
widens the beach
does not stop erosion but slows it down but it is only a short term solution
relatively cheap
attractive
attracts tourists and local people as it provides a wider beach
concerned that the environment will get damaged
does not protect the whole beach
involves heavy machinery which can disrupt local tourism and businesses
beach reprofiling
change the shape of the coastline so it can absorb more wave energy
existing methods redistributed
relatively cheap
sustainable and natural looking
quick to implement
short term effectiveness
ongoing costs
disruption during work
limited protection
dune regeneration
is the artificial creation of new sand dunes or the restoration of existing sand dunes
act as a physical barrier
natural by most people
attractive amenity to the local people and tourists
may also increase biodiversity
easily damaged by storms
time consuming to plant the grass
doesn’t maintain the area
what is managed retreat?
it is a coastal management strategy that allows the shoreline to move inward instead of attempting to hold the line with structural engineering
formation of a headland and bay
most likely to form on a discordant coastline where bands of alternating layers of hard and soft run perpendicular to the coastline
the sea erodes these rocks at different rates. Softer rock, like clay, erode more quickly, while harder rocks such as a chalk and limestone, erode more slowly
the soft rock is eroded inwards, forming an bay
where are waterfalls normally located?
the upper course
how do geological structure and rock affect the coastline
Hard resistant rock will erode more slowly than less resistant rock leaving a resultant headland which sticks out
the less resistant rock will be eroded to form a bay causing indentations in the coast
A coast where the structure of the land is parallel to the coast will result in a very straight coast. Where the land is perpendicular to the coast this will lead to an irregular coastline leading to headlands and bays
types of weathering in coastal areas
1.freeze-thaw
2.biological
3.chemical
how to tell a coast is being eroded?
there are caves
there are headlands
there are stumps
there are stacks
what does porous rocks mean?
contains holes
process of freeze-thaw weathering
1.water enters small cracks in rocks
2.water freezes widening the crack
3.ice melts the water going to deeper in in the rock
4.process repeats until the rocks splits
process of biological weathering:
1.plant roots can get into cracks in the rocks
2.as the roots grow the cracks widen
3.this causes small pieces of rock to break away
chemical weathering
-rainwater and salt water can act as weak acid
-if the coastline is made up of limestone or chalk over time they can become dissolved by the acid in the rocks
4 types of erosion:
1.abrasion
2.attrition
3. solution
4.hydraulic action
what is solution?
this is when sea water dissolves certain types of rocks. in the Uk chalk and limestone cliffs are prone to this type of erosion
4 types of transportation
1.saltation
2.suspension
3. traction
4.solution
characteristics of an estuary
an estuary is when a river meets the sea
a lot of mudflats
how can physical factors affect flood risk?
heavy rainfall can saturate the ground leading to increased surface runoff and flooding
water flows more rapidly downhill on steeper slopes leading to quicker runoff and a higher risk of flash floods
flat or gentle sloping areas may have a greater risk of flooding as water can spread out easily and take longer to drain way
