Water on the Land

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  • Created by: Molly6098
  • Created on: 16-11-13 14:05
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  • Water on the Land
    • River Valley
      • Middle Course
        • Medium gradient, gently sloping valley sides, wider, deeper channel
      • Upper Course
        • Steep, V-shaped valley, steep sides, narrow, shallow channel
      • Lower Course
        • Gentle gradient, very wide, almost flat valley, very wide deep channel
      • Profiles
        • Cross Profile: shows what the cross section looks like
        • Long Profile:shows how the gradient changes
      • Erosion
        • Vertical erosion: deepens channel, dominant in upper course
        • Lateral erosion: widens channel, dominant in middle and lower courses
    • Erosion, Transportation, Depositation
      • Transportation
        • Suspension
          • Small particles carried along by water
        • Saltaion
          • Pebble sized particles bounced along river bed by force of water
        • Solution
          • Materials dissolve in water and are carried along
        • Traction
          • Large particles pushed along river bed by force of water
      • Erosion
        • Attrition
          • Eroded rocks smash into each other and break into smaller pieces with rounded edges
        • Abrasion
          • Eroded rocks scrape against channel, wearing it away-most erosion happens like this
        • Solution
          • River dissolves some types of rock
        • Hydraulic action
          • Force of water breaks rock particles away from river channel
      • Deposition
        • Rivers drops material when it slows down
          • Water is shallower
          • Amount of eroded material increases
          • River reaches the mouth
          • Volume of water falls
    • River Landforms
      • Waterfalls and Gorges
        • Form where a river flows over hard rock then soft rock.Soft rock erodes creating a step. Steep drop eventually forms (waterfall). Hard rock becomes undercut and collapses. Collapsed rocks swirled around at bottom and erode rock creating a deep plunge pool.
        • Over time more undercutting makes waterfall move backwards creating a gorge
      • Ox-Bow Lakes
        • Formed by meanders
        • Erosion causes outer bends to get closer, leaving a small bit of land (neck). River breaks through land, river flows along shortest course. Deposition cuts of meander leaving ox-bow lake
      • Flood Plains and Levees
        • Levees
          • Natural embankments along edges of river channel. Created when river floods and heaviest material deposited first.
        • Flood plains
          • Wide valley floor that occasionally gets flooded. when river floods it deposits, building up flood plain. Meanders migrate making it wider. Slip off slopes also build it up.
      • Meanders
        • Middle and lower courses
        • Current is faster on the outside of the bend-river channel is deeper, more erosion takes place causing river cliffs. Current is slower on inside of bend-shallower, eroded material is deposited forming slip-off slopes
    • River Discharge
      • Factors
        • Hot, dry or cold, freezing conditions make ground hard=increases runoff, decreases lag time, increases discharge
        • Urban areas covered in impermeable materials=more runoff, shorter lag time, increased discharge
        • Impermeable rock=more runoff, shorter lag time, more discharge
        • Saturated soil=more runoff, shorter lag time, more discharge
        • Steep slope=shorter lag time, increased discharge
        • More rain and short heavy periods of rainfall=more runoff, shorter lag time, more discharge
      • Words
        • Rising Limb: Increase in river discharge
        • Lag time: delay between peak rainfall and peak discharge
        • Falling limb: decrease in river discharge
      • Hydrographs
        • Flashy
          • Natural river
          • Lack of vegetation
          • High levels of precipitation
          • Intense rainfall
          • Steep valley sides
          • Saturated soils
          • Cold conditions
          • Impermeable rock
          • High drainage density
          • Urban areas
        • Subdued
          • Low valley sides
          • Gentle, steady rainfall
          • Low levels of precipitation
          • Lots of vegetation
          • Hot conditions
          • Permeable surfaces
          • Low drainage density
    • Flooding
      • Case Study
        • Poor
          • Effects
            • Secondary
              • 100,000 people caught water borne diseases
              • Children lost education-4000 schools affected
              • Floods reduced basmati rice yields-prices rose 10%
              • Farmers and factory workers became unemployed
            • Primary
              • Factories closed, livestock killed, rivers polluted
              • 44 schools and 112, 000 houses and 10,000km road destroyed
              • Over 2000 dead, 25 million homeless
          • Causes
            • Melting snow from Himalayas
            • Heavy Rainfall-900 mm in July
            • Peak discharge of both rivers happened at once which increased discharge down stream
          • Responses
            • Secondary
              • Some homes rebuilt on stilts
              • International charities funded rebuilding homes, agriculture and fishing industries
            • Primary
              • Other governments and international charities sent food, water, medical aid and technical equipment
              • No evacuations-blocked transport links slowed any attempts
          • About
            • July and August 2007
            • South Asia (Bangladesh, India
            • Brahmaputra and Ganges
        • Rich
          • Effects
            • Primary
              • 70000 addresses lost power
              • 4 schools flooded, 350 businesses shut
              • Roads and bridges damaged
              • 3 dead, 3000 homeless
              • Rivers polluted
            • Secondary
              • Stress related illnesses increased
              • Children lost education
              • 3000 jobs at risk
          • Causes
            • Large urban area-increased run-off
            • 200 mm of rain in 36 hours-saturated soil, increased run-off
            • Caused discharge to reach 1520 Cumecs (usually 52)
          • Responses
            • Secondary
              • Flood defence scheme set up
              • Community groups set up to provide support
            • Primary
              • Centres provided food and drink
              • People evacuated
              • Temporary accommodation set up
          • About
            • 8th January, 2005
            • Carlisle, England
            • River Eden
      • Causes
        • Physical (climatic)
          • Low evapotranspiration
          • Coastal storms
        • Human Factors
          • Dam bursting-sudden rush of water
          • Poor artificial levee construction-Give way=big rush of water
          • Government corruption-cheap labour
          • Farming-Soil compaction=less porous
          • Global warming-creates more extreme weather
          • Channelisation-Artificially straightened
        • Physical (drainage basin)
          • Impermeable rock
          • Small river basin-flash floods
          • Little vegetation cover
          • Saturated soils
    • Hard and soft engineering
      • Soft Engineering
        • Flood Plain Zoning
          • Benefits: risk of flooding reduced-impermeable surfaces aren't created, Impact of flooding reduced
          • Restrictions prevent building on parts of flood plain likely to be affected
          • Disadvantages: expansion of an urban area is limited, no help to areas already built on.
        • Preparation
          • Benefits: Impacts of flooding reduced. People less likely to worry
          • Buildings modified to reduce damage flood could cause. People make plans in case of flooding
          • Disadvantages: doesn't guarantee safety from a flood, gives false sense of security, expensive to modify buildings
        • Do nothing
          • Benefits: When river floods in deposits eroded material making farmland more fertile
          • No money spent on preventing floods or preparing for them-flooding is a natural process
          • Disadvantages: risks and impacts of flooding aren't reduced, flood will probably cause a lot of damage
        • Flood Warnings
          • Benefits: Impacts reduced-people more prepared
          • Environment Agency warns people of floods through media
          • Disadvantageds: Doesn't stop floods. Living in a place with lots of warnings makes it difficult to get insurance. People may not hear warnings
      • Hard Engineering
        • Channel Straightening
          • Benefits: Water moves out of the area more quickly
          • River's course is straightened by cutting off meanders
          • Disadvantages: More chance of flooding and erosion down stream
        • Dams and Resevoirs
          • Benefits: Reservoirs store water which reduces risk of flooding. Stored water can be used as drinking water and for HEP
          • Dams built across rivers, resevoirs form behind them
          • Disadvantages: Expensive to build. Can flood existing settlements. Eroded material deposited in reservoir not on rivers natural course so farms down stream are less fertile
      • Cas Studies
        • Hard engineering
          • Defences
            • Many levees built along river
            • 3 Gorges Dam-101m high, reservoir holds 22km of water, largest HEP station in the world
          • About
            • 5 major floods in  last century
            • Seasonal flooding common
            • 1947-covered 193,000 km, killed 33, 169, 18 million moved
            • Yangtze, China-6380km long
            • 1998-killed 3000, 14 million homeless
          • Effects
            • Negative
              • Could destroy habitats and endanger species
              • Dam traps sediment which could cause dam to burst resulting in catastrophic floods
              • Dam causes water levels  to rise and increases flooding on tributaries
              • Farmland, 657 factories and 1300 sites of cultural and historical interest submerged
              • Many levees broke adding to devastating floods in 1998
              • 1.3-2 million will have to relocate-13 cities and 1352 villages submerged
            • Positive
              • Turbines produce enough electricity for 3% of China
              • Reduced major flooding
              • Made it much easier to navigate up the Yangtze
        • Soft engineering
          • Defences
            • Flood wardens communicate advice and warnings
            • Improvements made to riparian buffers
            • Detailed advice on internet about reducing flood damage
            • Planning restrictions on new builds
            • Restrictions on land use
            • Low-value land allowed to flood
            • Local flood warning plan and 24 hour floodline
            • Gravel soakways along A34
            • Tesco revised extension plans
          • About
            • 1500 properties have 1% chance of flooding a year
            • Abingdon, England on flood plains of Thames and Ock
            • Regular floods over the years
          • Effects
            • Several flood warnings used
            • Difficult to measure success
            • Recent floods did less damage
  • Form where a river flows over hard rock then soft rock.Soft rock erodes creating a step. Steep drop eventually forms (waterfall). Hard rock becomes undercut and collapses. Collapsed rocks swirled around at bottom and erode rock creating a deep plunge pool.

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