Flashcards
geog key terms phys rivers
Cards in this deck (39)
- 1Dischargethe volume of water in a channel passing a particular point in a particular time, usually cubic metres per second or cumecs. Calculated by multiplying cross-sectional area of the river by its velocity.
- 2Interceptionthe capture of precipitation by the plant canopy and its subsequent return to the atmosphere through evaporation or sublimation. The amount of precipitation intercepted by plants varies with leaf type, canopy architecture, wind speed, available radiation, temperature, and the humidity of the atmosphere.
- 3Infilltrationmovement of water from the surface into the soil
- 4Evapotranspirationtotal moisture lost through evaporation and transpiration.
- 5Transpirationthe loss of water from plants through the stomata in the leaves.
- 6PercolationThe vertical movement of water from the soil into underlying rock
- 7PermeabilityThe rate at which a liquid flows through rock.
- 8PorosityThe percentage pore space in a rock.
- 9Throughflowthe lateral movement of water through soil to a river channel.
- 10Groundwaterthe flow of water through the rock underground.
- 11Storm hydrographa graph which combines a bar chart of precipitation in a particular event with a line graph of discharge for a particular river channel in the catchment area of that event and thus the reaction of the channel to the precipitation.
- 12Drainage densityIs the measure of the length of stream channel per unit area of drainage basin. Mathematically its is expressed as: Drainage Density (Dd) = Stream Length / Basin Area
- 13Abrasion/CorrasionCorrasion occurs when the river picks up material and rubs it along its bed and banks, wearing them away by abrasion, rather like sandpaper. This process is most effective during times of flood and is the major method by which the river erodes both vertically and horizontally.
- 14Hydraulic Actiondue to the action of water. In geography, a process of erosion whereby flowing water moves unconsolidated material due to forces of drag.
- 15Solution/CorrosionThis occurs continuously and is independent of river discharge or velocity. It is related to the chemical composition of the water, e.g. the concentration of carbonic and humic acid.
- 16AttritionAS the bedload is moved downstream, boulders collide with other material and the impact may break the rock into smaller pieces. In time, angular rocks become increasingly rounded in appearance.
- 17Depositionthe placing down of material being transported by an agent of erosion due to a loss of energy.
- 18BraidingWhen a stream consisting of multiple small, shallow channels that divide and recombine numerous times forms a pattern resembling the strands of a braid. Braided streams form where the sediment load is so heavy that some of the sediments are deposited as shifting islands or bars between the channels.
- 19Hjulstrom curvea graph showing critical stream velocities for the erosion, transport and deposition of different sizes of load.
- 20Tractionthe rolling of bedload along the bed of a river channel
- 21Suspensionthe transport of load in the body of the water in a river i.e being carried along in the flow.
- 22Saltationthe transport of the dissolved load in the body of water in a river.
- 23Waterfalla sudden vertical or near vertical fall of water where a river course is interrupted by a drop away in the land over which it is flowing.
- 24Meanderan exaggerated, looping, bend in a river. Once formed, meanders grow in such a way that they will eventually cut themselves off from the river and cease to exist.
- 25ThalwegIn hydrological and fluvial landforms, the thalweg is a line drawn to join the lowest points along the entire length of a stream bed or valley in its downward slope, defining its deepest channel. The thalweg thus marks the natural direction (the profile) of a watercourse. Almost always the line of fastest flow in any river.
- 26Pools and RifflesIn a flowing stream, a riffle-pool sequence develops as a stream's hydrological flow structure alternates from areas of relatively shallow to deeper water. Only in streams carrying gravel coarser sediments. Riffles are formed in shallow areas by coarser materials such as gravel deposits over which water flows.
- 27(POOLS)Pools are deeper and calmer areas whose bed load is made up of finer material such as silt.
- 28ox-bow lakesa crescent-shaped lake formed when the main bend of a meander is cut off and becomes isolated from the main river channel.
- 29Floodplainsthe part of the valley floor occasionally flooded by the river. Over time sediment or alluvium builds the elevation of the plain
- 30Leveesthe naturally raised bank of a river. When flooding occurs, the water immediately begins to lose energy and deposits the larger load. With distance from the channel the deposited load is increasingly smaller. This leaves the banks higher than the rest of the floodplain.
- 31Arcuate deltaCurved or bowed delta with its convex outer margin facing the sea or lake eg.Nile
- 32Birds foot deltaA delta with long, projecting distributary channels that branch outward like the toes or claws of a bird. Eg. Mississippi
- 33Factors affecting transfers and stores of matter in a Drainage Basin 1. VegetationThick vegetation - more interception and evaporation
- 342. Soil typeSome soils are porous and this allows water to infiltrate quickly.
Other soils are less porous and cannot infiltrate making overland flow the main transfer - 353. SeasonsThe warmer temps of summer = more evapotranspiration, which lowers discharge levels. If the soil becomes hard baked it will not allow infiltration. Autumn- less interception when leaves fall. Winter- frozen ground=no infiltration
- 364.GeologyIf underlying rock soil is porous, then there is more percolation and groundwater flow. This reduces the soil store and the amount of water transferred by overland flow
- 375.Urban areasLess vegetation so there is less interception and less infiltration due to impermeable surfaces. Water channelled through drains directly into rivers
- 386.ReliefSteeper- less infiltration therefore more surface run-off, less water in soil store
Lowland areas- more infiltration, water remains in soil store for longer - 397.How heavy the rain isDuring heavy rainstorms, rain falls at faster rate than the soil can accommodate infiltration, if this occurs, overland flow is likely to happen
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- Flashcards on geog key terms phys rivers, created by Emily Adams on 18/11/2016.
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- Emily Adams
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