Water (rivers)

Water (rivers)

1. Processes that are associated with rivers

   • Erosion
     • Abrasion
       • Rocks Act like sand paper against the banks and cliffs
     • Hydraulic action
       • The pure power of the water pushes into cracks
     • Corrosion (solution)
       • Acidic water dissolves rock/mineral
     • Attrition
       • Rocks that are being carried bang into each other making themselves smaller rocks
   • Transportation
     • Traction
       • Large rocks and boulders rolled along the river bed
     • Saltation
       • Pebbles bounce along the river bed
     • Suspension
       • Sand and clay sized particles are carried,suspended in the water
     • Solution
       • Dissolved particles carried in the water
     • The movement of material carried by the river
   • Deposition
     • When the river loses energy it drops the material it is carrying. it drops the heaviest material first and the lighter material last

2. Rivers

   • Upper coarse
     • V-shaped valleys, interlocking spurs, waterfalls, gorges
   • Middle coarse
     • Meanders and OX bow lakes
   • Lower course
     • Floodplains and levees
   • Formations
     • This is how a waterfall forms
     • eanders and OX bow lakes
   • Drainage basin
     • An area of land drained by a river and all of its tributaries
     • Factor that can increase or decrease flooding
       • Increase
         • Steep slopes(means that water travels faster towards the river increase the likelyhood of flooding
         • Lack of vegetation/deforestation( there is less trees to intercept the rainfall meaning more of the water enters the river)
         • Impermeable bedrock( water can'nt infiltrate into the ground and so more flows over the surface)
         • Building on the floodplain
           • More impermeable concrete surfaces
         • Saturated ground
         • Size of a drainage basin
       • Drainage basin
         • Watershed ( the area of high land forming the boundary and edge of a river basin
         • Source( where a river begins)
         • Mouth (where a river meets the sea)
         • Confluence( the point at which two rivers meet)
         • Tributary ( a small river or stream that joins a larger river)
         • Channel ( this is where the river flows)
         • Drainage basin ( this is the area of land drained by a river and its tributaries
   • storm hydrograph
     • Shows a rivers response to a particular rainfall event, it shows how quickly the water gets into the river. the quicker the water reaches the river the more likely there is to be a flood event

3. CASE STUDY

   • Niagara falls
     • People have utilised the waterfall to make a profit from tourism i.e. Hotels,Restaurants,Museums,information centres,Boat rides and Helicopter rides which take full advantage of the tourism)
       • ADVAN(creates jobs and improves the economy)
       • DISADVAN( are that the falls become overcrowded, the tourist attractions can make it look like a theme park and the tourists can have an environmental impact though erosion,pollution and litter)
   • Boscastle
     • Contributers to the flooding in boscastle
       • Human factors
         • Village developed on flat land of floodplain
         • Natural channel of river has been walled preventing it from adjusting to variations in discharge
       • Natural factors
         • Narrow valley with interlocking spurs
         • 185mm of rainfall in 5 hours
         • Steep valley sides that encourage rapid runoff
         • The village as it is at the confluence of 2 rivers
     • Monday 16th August 2004
     • 60mm of rainfall fell in 2 hours
     • The ground was saturated due to weeks of above average rainfall
     • Effects
       • Short term
         • People are homeless and have no access to money within a week of the flood
         • Damage caused by river to cars and people other belongings, also includes their homes
       • long term
         • The pain and anguish of the flood in 2004 may still effect people who lost their homes or treasured percessions
         • Fear of more freak floods
         • Financial difficulties, as it will take a long time for the insurance companies to pay for the damage caused
         • Tourism actually increased in the long term

4. Hard and soft engineering

   • Hard
     • Artificially trying to alter and control the course of a river
     • Usually more expensive
     • Not always environmentally friendly
     • Less aesthetic
     • Can be very effective
     • Can cause unforeseen problems further down stream
     • Building a DAM to control and regulate water flow
     • Building LEVEES to provide protection against flooding
     • STRAIGHTENING the river channel to avoid settlement or speed up the flow of water through an area
     • WIDENING AND DEEPENING the river channel to increase the amount of water the river can hold
   • Soft
     • using the natural features of a river to try and control flooding
     • Usually cheaper
     • More environmentally friendly
     • Can be less effective
     • AFFORESTATION planting trees to increase the amount of interception and reduce the amount of water entering the river
     • PLANNING LAWS the local authority can introduce policies to stop developments being built on the floodplain
     • MANAGED FLOODING the river is allowed to flood naturally in some places to prevent it flooding in populated areas
     • EARLY WARNING SYSTEMS floodline and flood plans have been set up by the environment agency to prepare residents in flood prone areas

5. Future foolding in the uk

   • No. people at high risk of flooding will rise from 1.5 million to 3.5 million
   • Cost of flood damage will rise from £1billion a year to £27 billion a year
   • Climate change is one of the main cause of the extra flood risk
   • 10% of UK homes are on floodplains as new homes need to be built this could increase
   • What should be done to reduce this
     • Householders encouraged not to pave over gardens, this creates more permeable surfaces in towns and cities
     • Block drainage in upland mountain areas and develop more peat bogs to store water. this stores water in the mountains meaning less reaches the river
     • Make homes more flood proff by putting plug sockets higher up walls etc
     • Restrict building on floodplains
     • Invest in flood defence schemes but be weary of hard engineering that can cause further problems downstream

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