Rivers 1

Mind Map by booe4221, updated more than 1 year ago
Created by booe4221 over 6 years ago



Resource summary

Rivers 1
  1. River Fluctuation
    1. The discharge of a river is the volume of water passing down a river. It can fluctuate a lot in a matter of hours in response to periods of rain.
      1. Storm Hydrography: used to show how a river responds to a period of rainfall. Rivers that respond rapidly to rainfall have a high peak and short lag time and are referred to as flashy. A lower peace and long lag time shows a delayed hydrography
        1. Precipitation: any source of moisture reaching the ground
          1. Interception: water being prevented from reaching the surface by trees/grass
            1. Surface Storage: water held on the ground surface
              1. Soil Moisture: water held in the soil layer
                1. Percolation: water seeping deeper below the surface
                  1. Groundwater: water stored in the rock
                    1. Transpiration: water lost through pores in vegetation
                      1. Evaporation: water lost from ground/vegetation surface
              2. Infiltration: water sinking into soil/rock from the ground surface
          2. River DIshcharge
            1. Influenced by rainfall, temperature, previous weather conditions, relief, rock type and human land use
              1. Lot of rain falling causes high river levels, while less rainfall results in lower river levels.
                1. High amounts of rain saturate the soil and underlying rock. Drizzle: time for water to infiltrate the soil and underlying roc, freeing up more space for rain
                  1. Temperature affects the loss of water from the drainage basin and therefore the level of discharge. When temperatures are higher, there is greater water loss via evaporation and transpiration, so river levels go down.
                    1. Previous weather conditions also have an impact on river discharge. If its dry, it will take longer for the water to reach the river and the amount will be less if there had been a number of wet days
                      1. Deforestation: if trees are removed, water reaches the surface faster and the trees do not extract water from the ground. Urbanisation: expanding towns create an impermeable surface.
                      2. Steep slopes encourage fast run-off as the water spills rapidly downwards due to gravity
                        1. Rock type determines how much water infiltrates and how much stays on the surface. Areas with impermeable rocks, have more surface rivers than permeable rocks, which are porous, or pervious.
                    2. Floods
                      1. Floods occur when a river bursts its banks. It is an extreme situation due to high levels of flow. Building on floodplains results in property being damaged and lives being lost in what becomes a hazard.
                        1. Rivers flood due to prolonged rainfall, heavy rain, snowmelt and steep relief. People often unintentionally increase the likelihood and severity of flooding. Mainly due to deforestation and construction work
                          1. Floods appear to be an increasingly frequent event
                            1. The effects of flooding vary according to their size and location. The impact tends to be more severe in LEDCs. responses are generally more immediate in countries at further stages of development and the attempts made to reduce the effects come from within the affected area or country. In LEDCs attempts made to reduce the effects may be delayed and require international effort.
                        2. Case Studies
                          1. LEDC: Bangladesh 1998
                            1. Effects: The water in Dhaka, was 2 metres deep and covered three-quarters of the city. Electricity was cut off for several weeks and there was no safe drinking water. 7 million homes were destroyed and over 25 million were homeless. The death toll was over 1300. There were shortages of food and medicines. 2 million tonnes of rice was destroyed. Thousands of kilometres of roads, a third of the railways and Dhaka's airport were all flooded
                              1. Responses: Emergency supplies for food, water tents and medicines. Aid from other countries. Reduce Deforestation in Nepal and the Himalayas. Construction of dams, and boats to rescue people. Repair and Rebuild houses. Assistance from the UN and other charities. International food aid programmes. Fodder for livestock, Farmers provide with free seeds and water purification tablets:
                            2. MEDC: Boscastle, UK 2004
                              1. Effects: Destroyed homes, stress and anxiety for local people,. Cars belonging to more than 1,000 people were washed away. 25 business properties were destroyed. Bridges and roads were damaged. 4 footbridges washed away. Area relies on tourism for 90% income, most of which earned in summer months.. Insurance companies paid out £20 million to repair.
                                1. Responses: Major incident declared at 5pm. RAF search and rescue services were alerted to rescue trapped people. Non-one died cut to the rapid response of the emergency services. Trees near river removed. Rescue boats to rescue trapped people. Radio and television coverage
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