physical landscapes in the uk - rivers

drainage basin

* area of land drained by a river and its tributaries
* watershed - edge of a river basin

rivers long profile

* source and steep gradient
* gentle gradient
* very gentle gradient and mouth

rivers cross profile

* v shaped valley and steep sided, narrow shallow turbulent river
* floodplain, wider flat floor, wider and deeper valley
* levees, very wide and flat valley, wide deep river

river processes of erosion

* hydraulic action - force of water hitting river bed and banks
* abrasion - load hits bed or banks
* attrition - stones carried by river knock against each other
* solution

river processes of transportation

* solution
* suspension
* traction
* saltation

river erosion landform - interlocking spurs

* upper course
* vertical erosion
* winds around areas of resistant rock creating interlocking spurs

river erosion landform - waterfalls

* steps in rivers long profile
* hard rock overhang eventually collapses and waterfall retreats
* undercutting of softer rock by hydraulic action and abrasion
* plunge pool - very turbulent water
* retreats and forms a gorge

river erosion landform - gorges

* narrow, steepsided valley found downstream of a retreating waterfall

river erosion and deposition landforms - meanders

* bends in river
* thalweg swings from side to side causing erosion on outside bend and deposition on inside
* inner bend - slip off slope
* outer bend - river cliff

river erosion and deposition landforms - ox-bow lakes

* the neck of the meander is gradually eroded
* water now takes shortest route
* deposition seals of the old meander
* the meander neck is cut through completely - leaving oxbow lake

river deposition landforms - floodplains

* wide flat areas on either side of a river
* created by migrating meanders and floods depositing layers of silt to form alluvium

river deposition landforms - levees

* form when in low flow deposition raises river bed so the channel cant carry as much water
* during flooding water flows over the sides of the channel
* as velocity decreases coarser sediment is deposited first on the banks - then finer sand and mud, raising the height of the levees

river deposition landforms - estuaries

* where the river meets the sea
* affected by tides, wave action, and river processes

physical factors increasing flood risk

* precipitation
* geology
* relief

human factors increasing flood risk

* urbanisation
* deforestation
* agriculture

hard engineering - dams and reservoirs

* widely used to regulate river flow and reduce risk of flooding
* often multi-purpose eg HEP
* can be effective om regulating water flow
* expensive and reservoirs often flood large areas of land

hard engineering - channel straightening

* cutting through meanders creating a straight channel speeding up water flow
* can increase flood risk downstream
* may be lined with concrete which is unattractive and damage wildlife

hard engineering - flood relief channels

* at times of high flow sluice gates allow excess water to flow into the flood relief channel, reducing threat of flooding

soft engineering - afforestation

* trees obstruct water flow
* water taken up by trees and evaporated from leaves and branches
* cheap with environmental benefits

soft engineering - river restoration

* uses natural processes and features of a river eg meanders and wetlands to slow down flow and reduce the likelihood of flooding downstream

preparing for floods

* flood watch - flooding of low lying lands
* flood warning - threat to homes and businesses
* severe flood warning - extreme danger to life and property
* the environment agency