AQA Geography - Rivers Content 3.0 / 5 based on 1 rating ? GeographyRivers and fluvial processesASAQA Created by: CatherineCreated on: 29-03-13 13:01 Factors Affecting Discharge. Physical Weather Snow - melt, frozen ground no infiltration Precipitation - heavy rainfall Temperature - evaportranspiration (reduce discharge) Drainage Basin size - rounder quicker Shape - smaller responds more rapidly Slope - steep, water reaches more quickly Vegetation Porus soil type/ permeable rock - slow Impermeable rock - faster 1 of 10 Factors Affecting Discharge. Human Urbanisation - permeable structures, artificial drainage, machinery Land use - dams, argiculture Deforestation 2 of 10 Long Profile & River Processes. Erosion Hydraulic Action - water compresses air making small explosion Abrasion - wearing away of rock by the river Attrition - wearing away of rock from other rocks Corrosion - rocks are dissolved Transportation Traction - large boulders rolles along river bed Saltation - small stones bounce and leapfrog Suspension - sand/silt picked up and carried Solution - minerals transported within the water Deposition Discharge reduced Shallow water Increased size of load (tributary) River floods 3 of 10 Long Profile & River Processes. Vertical Cuts down to base level leaving steep sided valleyes by the processes of abrasion and hydraulic action Lateral Energy used in widening the valley by hydraulic action erosion Capacity Amount of material it can carry Competence Diameter of the largest particle that it can carry for a given velocity 4 of 10 Factors Affecting Load (Material Transported) Climate/seasonal variations Land use - deforestation Precipitation - more water more velocity Vegetation cover Reservoirs Geology - some may be dissolved Runoff Soil properties Topography - relief - height and shape of land Size of basin 5 of 10 Valley Profiles. Channel cross profiles View from side Changes throughout - UP: narror and uneven. MID: meanders. LOW: widen and deepens Upper - large wetted perimeter more friction Higher the hydraulic radius more efficient channel Potential and kinetic energy Determined by volume (discharge) and gradient - increase = increase kinetic Processes depend on this Excess = erosion, insuffient = deposition Graded profile Inputs should balance outputs - changes in system = change in profile Graded river - all energy used so no further erosion Profile of dynamic equilibrium - blance between erosion and deposition Overtime river decrease in gradient - smooth concave shape, adjusted discharge and load 6 of 10 Valley Profiles. Cross profile View of a valley from one side Lower course - very wide, lack erosion, reduced competence Middle course - wider, lateral erosion Upper course - narrow steep sided, vertical erosion Long profile Knick points - rejuventation Change in altitude Steeper upper course - gentle at mouth Irregularities - rapids, waterfalls 7 of 10 Rejuvenation & Knick Points. Rejuventation - increase in energy Cause Isostatic - rise and fall of land Eustastatic - change in sea level Knick points River gains cutting power - vertical erosion Adjustment to new base level Knick points - where old long profile meets new Recedes upstream 8 of 10 Causes Of Flooding. Human Urbanisation Impermeable Natural rivers Smooth surface drainage River strengthened - delivered quickly Deforestation Loss of root soil erosion Reduce interception and evapotranspiration Decrease in channel capacity - increase in sediment Farming Ploughing - soil erosion Planning strategies Over grazing Reduce lage time 9 of 10 Causes Of Flooding. Physical Climatelogical Increased temperature - snow melt - reduced infiltration Coastal Storms Planning control High season tides Nature of Basin Rock types Shape basin - vegetation, relief, runoff 10 of 10
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