rivers Flashcards
what is evapotranspiration?
-veg intercepts and takes up water through roots
overland flow?
-upland streams flow down-hill and join at confluences
to form slow-moving wide rivers
drainage basin?
-drains all water which lands on earths surface
features of a drainage basin?
-watershed
-source
-confluence
-tributary
-mouth
drainage density?
-number of tributaries in draininage basin
what is traction?
-large rocks roll along river bed
what is saltation?
-smaller materials bounce along the river bed
what is suspension?
-lighter materials are carried within river flow
what is solution?
-materials are dissolved in water
what is the wetted perimeter?
-length of wet part of channel cross-section
cross-section area?
-area of flowing water
what is river discharge?
-the amount of water flowing in a channel
what is hydrualic action?
-air is forced into headland cracks, removing material
what is abrasion?
-material in water rubs against banks
what is attrition?
-material carried by river hit each other and become smaller and rounder
what is corrosion?
-rocks dissolve by acidic water
what is the long profile of a river?
-shows the changes in river gradient from source to mouth
what is the cross profile?
-sections from 1 bank to another
formation of a waterfall…
-soft rock erodes quicker, undercutting the hard rock and creating a plunge pool
-this leads to the development of an overhand of hard rock which overtime collapses
-overhand falls into the plunge pool, increasing abrasion and making plunge pool deeper
-process repeats and waterfall retreats upstream.
formation of a v-shaped valley…
-vertical erosion is dominant in the upper course of a river
-this cuts down into the river bed and deepens the river channel
-weathering and mass movement leads to material from valley sides collapsing into river
-forming a v shaped valley
formation of a meander…
-fastest flow on the outside of river bend (leads to erosion)
-erosion undercuts riverbank
-riverbank collapses and the edge of the meander moves further out
-slowest flow on inside of river bend, leads to deposition forming slip-of slope
-erosion on one side and deposition on the other leads to meandering migrating across the valley.
formation of an oxbow lake…
-as erosion continues, the neck of the meander is worn away and gets narrower and narrower
-during flooding, the river cuts straight across the neck
-loop of meander gets sealed off and turns into an oxbow lake
-lake gets covered with weeds in time
what is vertical erosion?
-dominant in upper course of river
-inc depth of river and valley
what is lateral erosion?
-dominant in the middle and lower course
-inc width of river as it erodes sideways
why is lateral erosion more effective than vertical erosion in lower reaches of river?
-vertical erosion makes channel deeper but lateral widens river, better so more deposition can flow into mouth
how are leeves formed?
-as water spills out from flood the heaviest particles are deposited 1st
-every time a flood occurs more particles are added to these deposits
-build-up and form levees
what is a flood plain?
-flat area of land found on either side of river in lower course
whats an estuary?
-meeting point between river and sea
whats a delta?
-depositional feature made from material dropped by river
-formed when river lacks energy
oppotunities from rivers…
-leisure
-tourism
-source of water
-fishing
-transportation
-generating electricity
causes of flooding…
-heavy rainfall
-landslides
-ice melt
damage caused by flooding…
-death
-water disease spread
-transport routes damaged
-loss of farm land
factors which can inc flood risk?
-deforestation
-urbanisation
-agriculture
-climate change
factors affecting flood RISK
-relief
-rock type
-soil
-weather
protection from floods…
-dams/reservoirs
-flood relief channels
-straightened channels
-flood plain zoning
-afforestation
