RIVERS Flashcards
DRAINAGE BASIN DIFFERS FROM A HYDROLOGICAL CYCLE
- drainage basin: open system ( amount of water varies )
- hydrological cycle: closed system ( always same water )
INPUTS DRAINAGE BASIN
- energy from the sun
- precipitation formed from moisture picked up outside the basin
- possibly water from tributary drainage basis
OUTPUTS DRAINAGE BASIN
- the rivers discharge
- the water in its basin from which evaporation and transpiration take place ( this water eventually falls as precipitation in another drainage basin )
STORM HYDROGRAPHS
- record the changing discharge of a river after a rainstorm
- base flow: normal discharge
- storm flow: additional discharge
RIVER REGIMES
- river discharges vary throughout the year
- these variations make up what is termed the river regime
FACTORS AFFECTING RIVER REGIMES
- amount and intensity of the rain
- temperatures affect the form of precipitation
- steep slopes will cause rapid surface run off, so water will reach the river more quickly
- rock type ( permeable or impermeable )
- vegetation and land use
- human intervention
ROCK TYPE
- impermeable rocks will not allow rainwater to sink into it, so will speed up run off
- permeable rocks allow infiltration and percolation of water into the bedrock ( slows delivery of water to the river )
VEGETATION AND LAND USE
- trees and other plants intercept and delay the rain reaching the ground
HUMAN INTERVENTION
- dams and reservoirs are an obvious form of intervention in river regimes
FLUVIAL PROCESSES
( rivers -> shaping landforms )
- erosion
- transport
- deposition
- weathering
- mass movement
EROSION HYDRAULIC ACTION
- water hits the river bed and banks with such force that material is dislodged and carried away ( high discharge )
EROSION ABRASION
- material being carried by a river is rubbed against the sides and floor of the channel
EROSION CORROSION ( SOLUTION )
- minerals in the rocks forming the sides of the river channel are dissolved by the water flowing past them
EROSION ATTRITION
- particles of materials being carried by a river = become rounded and smaller as they collide between
PHYSICAL WEATHERING
- this breaks rocks down into smaller and smaller pieces
CHEMICAL WEATHERING
- this causes rocks to decay and disintegrate ( acidic rain seeping into porous rocks )
BIOLOGICAL WEATHERING
- roots of plants ( especially trees ) growing into cracks in the rocks gradually split the rock apart
TRANSPORT
- traction
- saltation
- suspension
- solution
TRANSPORT TRACTION
- large boulders rolled on the bed
TRANSPORT SALTATION
- small boulders bounced along the bed
TRANSPORT SUSPENSION
- lighter material carried along by the river flow
TRANSPORT SOLUTION
- material dissolved in the water
DEPOSITION
- deposition is the laying down of material transported by the river
- occurs when there is a decrease in:
- energy
- speed
- discharge
… of the river
- likely to happen when a river enters a lake or the sea
FACTORS AFFECTING EROSION, TRANSPORT AND DEPOSITION
- wetter climate
- soften rocks
- gentle slopes
WETTER CLIMATE
- more discharge
- more erosion and transport
SOFTEN ROCKS
- more easily eroded and transported
GENTLE SLOPES
- encourage deposition
CHANNEL CHARACTERISTICS
UPSTREAM DOWNSTREAM
load particle size
-> channel bed roughness
-> slope angle ( gradient )