Changing Landscapes Of The Uk - Rivers Flashcards
Mass movement
The movement of rocks and soil downslope due to gravity
Soil creep
Individual particles of soil move slowly down a slope
Sliding
Material moving rapidly down a slope in one go e.g landslide
Flows
Masses of rocks moving downslope as they mix with water and flow like a liquid
Deposition
When a river no longer has enough energy to carry its load (material) so drops the material the process of material being dropped by the river
Transportation
A river picks up and carries material as it flows downstream
Hydraulic action
Air is forced into cracks in rocks in the river,forcing rocks apart
Attrition
Rocks and pebbles in the river crash into each other, causing the rocks to become smoother and smaller
Abrasion
Rocks in the river crash into river banks and are dragged along the river bed causing erosion like sand paper
Solution
Acidity in the river dissolves soft rock
Weathering
The breakdown of rocks at or near the surface by natural processes (usually on the river valley sides)
Biological weathering
Living things, such as the roots of trees,breaking soil and rocks apart
Chemical weathering
Rainfall is slightly acidic therefore it dissolves softer rocks
Mechanical weathering (Freeze-thaw)
Water that’s has seeped into the cracks of rocks as it freezes it expands in volume by 9% in volume cracking and forcing the rock apart it is repeated until the rock splits in two
Saltation
Small rocks are bounced along the river bed
Suspension
Small sediments are carried in the river (held up) downstream
Solution (transportation)
Small grains of sediment are dissolved and carried down the river downstream
Traction
Large boulders being rolled along the river bed downstream
point bars
Point bars are made up of the deposited material that accumulates on the inside bend of a river meander.
They are crescent-shaped, are very gently sloping and found below the slip-off slope.
They are made of alluvium.
levees
Levees are piles of sediment that form at the side of river channels after repeated flooding.
mouth
the end point of a river where it meets the sea or ocean
levee
a raised bank of sediment along the side of a river
waterfall
a flow of water falling from a height into a plunge pool
source
the starting point of a river
confluence
the point where two rivers meet
gorge
a steep narrow valley with rocky sides
meander
a bend in a river caused by erosion and depostition
tributary
a small stream or river that joins a larger one
drainage basin
A drainage basin is the area of land around the river that is drained by the river and its tributaries.
oxbow lake
A horse-shoe shaped lake left after the necks of meanders meet
floodplain
the flat fertile land in a valley next to a river that often floods
watershed
the boundary between the drainage basins
interlocking spurs
Pieces of land that over lap , they are hills that a river meander around in a V shaped valley. When viewed from downstream these spurs appear to be locked together
How are meander formed and oxbow lakes
Outside of a river flows at high velocity, causing lateral erosion, inside slower so material deposits forming a point par. Literalersonion eveuntially becomes curved process continues creating a meander
Oxbow lake
During flooding the river takes a straight past From neck of mender this eroded material eventually. Creating a slight line . This forms an oxbow lake
How are waterfalls formed?
Band of Gand rock positioned above exposed soft rock, less resistant rock is eroded creating and over a hand. After more erosion over hang falls forming a plunge pool
A steep suedes gauge is formed at side and a waterfall where it originally was
River dee and its long profile
Located in snow Donna wales flows east into England its mouth is located in Chester
Upper - steepest - waterfalls etc
Middle - widens, menders
Lower- flood plains , levee
How is the river Dee important
Import t water source for newly 3 million people
Provides habitats for. Range of animals
Flows through areas f natural bath
Physical changes to river Dee-
Drought
Climate through the yer is variable in UK, and rainfall influences river flows. During drought, river flows are low, however , when rainfall is high , river flows r high. This causes erosion to church
Causes and effects of flooding
Flooding first of all is when a river bank bursts and overflows onto the nearby land
What causes flooding
Heavy rainfall
Narrow shallow rivers
Blocked drain
Building houses on Floodplains
Roads impeable water rushes Ito river
Physical Causes
Duration of rainfall
Intense rainfall
Rocks- imprarmable
Relief- water reaches river channel much faster where stopes are steeper as water travels faster
Snow melt- in high altitude areas, snow falls during inter. When temp rise in summer, this snow melts and causes rivers to flood
Human
Deforestation- trees and plant intercept water
Urbanisation- more concrete Tamra
Climate change- extreme weather more common. So more storms and rainfall
Impacts- Cumbria flood in Workington
Social
1 death- PC Bill Barker
50 people had to be rescued from their homes
25 bridges destroyed or loses due to damage
1300 homes flooded in Cocker-mouth and Workington
Economic-
Cockermouth high street was completely flooded, forcing businesses to close
3057 businesses were affected in some way
Total cost was over £270 million
Environmental- river derwents course was changed by erosion
Flood Defences
Soft Enineering
Washlands- areas on flood plain that are allowed to flood
Pros
Give safe place fo floodwater to go
Improves rivers natural sedimentation processes
Cons
Allowing land to flood limits usage of the land
River restoration
Restoring the rivers original course
Pros
Slows river down
Natural rivers are more attractive
Cons
Some flood banks are often still needed
Floodplain zoning
Locating more areas of land to different uses, according to their level of old risk
Pros
Flood risk management aims to recent homes and businesses and high risk zone.
Such as open space for leisure
Cons
May not be best places of activities in terms of public access Italy
Flood plains are attractive places to build on
Hard engineering
Embankments(levees)- high banks built on river banks
Pros
St pater from spreading into areas where it could cause problems- such as housing
They can be earth and gras banks which blend in with the environment
Cons
Flood may still go over to- water can be trapped behind them
Can burst under pressure, possibly causing even greater damage
River Channelisation
Deepening or strengthening the river
Pros
This allows more water to floe
Cons -
Water taken ownstream may put ther places at risk
Does not look natural
Flood relief channels- extra channels built next to the river-
Can accommodate high flow of water
Cons
May not be needed often
May be unsightly
Dams and reservoirs
Long lasting ad can also be used to produce hep
Cons expensive and can cause displacement of people
What is river discharge
the volume of water flowing through a river channel; measured at any given point in cubic metres per second.
