Topic 4 Flashcards
Why are there increasing risks of coastal flooding?
Climate change leads to rising sea levels and increased chances of storms/flooding occurring
How does human activity influence coastal landscapes?
Coastal management - hard engineering stops erosion in one place but increases it down the coast
Settlements - 20 million live near coast zones. 29 villages lost in 1000yrs due to coastal erosion
Construction - dredging (also removed sand and gravel) in 1897 from sea bed to Plymouth docks caused immediate rapid erosion and storms destroyed nearby village
Agriculture - sea level rise affects farm land and fishing industry
Infrastructure - large industries are along the coastline (eg. Roads, chemical plants) could be affected by sea levels rising
How have physical and human processes affected Swanage Bay
Natural - coastal erosion and deposition (South of Bay) , some erosion of hard limestone cliffs (north)
Human - south is well defended but north is unprotected.
This South is far more built up and residential meaning there is more defence in that part of the bay causing rapid erosion in north of Swanage bay.
What parts of England are most at risk?
South East and East Midlands
How has rising sea levels affected the coast?
Cliffs being undercut and collapsing will retreat quicker.
Wave cut platforms will change height and positions.
Soft rock coastlines will erode more.
How will rising sea levels effect deposition and what will that bring?
Beaches, spits, and bars will be at more risk of erosion and submergence
On Studland Peninsula in Dorset the tourist attracting beach is being eroded 2-3 metres a year. Buildings and infrastructure are under threat which could cause local economic damage
What is a storm surge?
Large scale increase in sea level due to a storm. Onshore gale force winds drive water up coastline where air pressure allows sea to rise. Can last for hours to days
How effective are groynes?
Prevent long shore drift and build up the beach - larger beach dissipates wave energy. Can increase erosion downdrift. £2000 per metre. Hard
How effective is coastal engineering?
Sea wall - effective but considered ugly. Hard
Beach nourishment - adds sediment to beach - looks natural and cheap although replacement of sediment is often - soft
Slope stabilisation - vegetation is planted to keep cliffs in place but very expensive. Soft
What is a soil creep?
Individual particles of soil move slowly down the slope under the force of gravity. They collect at the bottom of the valley sides. the river may then erode this material.
What is slumping
Happens when the bottom of the valley side is eroded by the river. The slope becomes steeper and the material above slides downwards rotating it as it does so
Key terms to sum up erosion processes for hydraulic action, abrasion, solution, attrition
Hydraulic action: trapper air, cracks, pressure, wears, breaks
Abrasion: rocks, wear down, river bed and banks
Solution: soluble particles, dissolved into river
Attrition: rocks, carried, smash together, smaller particles
What is long profile?
Showing the gradient of the river and how this changes with distance from source
Channel cross profile
Shape of the river channel (width/depth/shape)
Valley cross profile
Shape of land surrounding river (height/gradient)
Factors affecting river velocity
Gradient of river
Roughness of the channel
Cross section shape of the channel
Formation of v-shaped valley
Low discharge means vertical erosion. Valley sides are slowly broken through weathering (bio, chem, phy). Soil creep occurs on valley sides, transporting sediment into river. Occurs until v-shaped. This is in upper course
How does a meander form
In middle course, river erodes laterally forming large bends. The river erodes the outside of the bends where the current is strongest. River cliff forms on outside of bend. Slip off slope on inside. Erosion and deposition occur.
How does an oxbow lake form?
Hydraulic action and abrasion cause the outside of the bends closer together until only small bit of land is left (neck). River breaks through neck until river flows along shortest course. Deposition cuts off meander forming an oxbow lake.
Physical factors affecting storm hydrography
Steep relief increases discharge
Saturated soil means less infiltration flooding more likely, increase discharge
Impermeable rock increased surface run off, low infiltration, increased discharge.
How do human activities affect storm hydrograph
Deforestation: interception is less, soil becomes saturated, less infiltration, surface run off discharge increases.
Urbanisation: less interception, increased surface run off, increased discharge, drainage system carries precipitation quickly
Land use change (farming): increased interception, decrease in surface run off, lower discharge
Land use change (cattle grazing): cattle eat grass less infiltration decrease in surface run-off
Human factors affecting Sheffield flooding
Urbanisation
Lack of flood defences
Physical factors affecting the Sheffield flooding
Depression at the time
Location - more rainfall
Antecedent - recent rainfall
What are the factors affecting increasing flood risk
Air temperature - hot air holds more moisture and water particles
Global warming makes storms more common
El Niño has affected the jet stream - delivering more storms
engineering methods to manage flood risks
Hard - flood walls (increases river capacity) , levees (increases river capacity) , flood barrier (steel movable gate which controls river flow)
Soft - flood plain retention (floodplain lowered and vegetation increases), river channel adaptation (meanders rebuilt, slowing erosion)
