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Frage | Antworten |
processes of erosion | hydraulic action: force of water breaks rock particles away corrasion: rocks scrape against river channel wearing it away attrition: rocks smash into each other corrosion: water dissolves some rock e.g chalk/limestone |
processes of transportation: the movement of eroded material | traction: large particles pushed along river bed by water saltation: pebble-sized particles bounce along riverbed suspension: small particles (silt) carried along by water solution: soluble materials dissolve in water |
course of the river | upper - steep - narrow/shallow middle - medium - wider/deep lower - gentle - very wide/deep |
features of a drainage basin | tributary: smaller river joins main river source: where river starts in upland area e.g mountains confluence: point where two rivers join mouth: river flows into sea or lake |
causes of flooding | prolonged rainfall heavy rainfall snowmelt |
flood managements | dams and reservoirs channel straightening man-made levees flood warnings preparation flood plain zoning |
the hydrological cycle | shows how water moves around |
infiltration | water soaks into the soil |
percolation | water moves vertically down through soil and rock |
throughflow | water in the soil flows downhill |
groundwater flow | water in rock flows downhill |
surface runoff | water flows overground |
channel flow | the flow of water in a river |
channel storage | water is held in a river |
groundwater storage | water is stored underground in soil and rock |
interception storage | water lands on things like leaves and doesn't hit the ground |
surface storage | water is held in things like lakes, reservoirs and puddles |
permeable rocks | rocks that absorb water: chalk |
impermeable rocks | rocks that don't absorb water: granite |
drainage basin | the area of land drained by a river |
drainage basins are separated by a boundary called a watershed - ridges of high land |
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a drainage basin |
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tributary | smaller river that joins a main river |
source | where the river starts, usually in an upland area |
confluence | the point where two rivers join |
mouth | where a river flows into the sea or a lake |
weathering in a drainage basin | the breakdown of rocks where they are (material doesn't get taken away) |
mechanical weathering | the breakdown of rock without changing its chemical composition - freeze-thaw |
chemical weathering | the breakdown of rock by changing its chemical composition - carbonation weathering |
biological weathering | the breakdown of rocks by living - plant roots grow into cracks on the surface, pushing them apart |
hydraulic action | the force of water breaks rock particles away from the river channel |
corrasion | eroded rocks scrape against river channel wearing it away |
attrition | rocks smash into each other breaking them into smaller fragments |
corrosion | water dissolves some rock e.g chalk/limestone |
traction | large particles are pushed along the river bed by the force of the water |
saltation | pebble-sized particles are bounced along the river bed by the force of the water |
suspension | small particles like silt and clay are carried along by the water |
solution | soluble materials dissolve in the water and are carried along |
deposition | when a river drops eroded material - happens when a river loses velocity (slows down) |
waterfalls and gorges are found in the upper course of a river |
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interlocking spurs |
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meanders: large bends in a river |
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ox-bow lakes: formed from meanders |
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flood plain | the wide valley floor on either side of a river which occasionally gets flooded |
levees: natural embankments along the edges of a river channel |
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deltas: low lying areas where a river meets the sea or a lake | rivers slow down when they meet the sea/lake and deposit material - it builds up, the channel is blocked and splits up into smaller rivers: distributaries |
types of delta |
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river discharge | the volume of water that flows in a river per second - measured in cumecs |
storm hydrograph |
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peak discharge | the highest discharge in the period of time |
lag time | the delay between peak rainfall and peak discharge |
rising limb | the increase in river discharge as rainwater flows into the river |
falling limb | the decrease in river discharge as the river returns to its normal level |
factors that increase discharge and make the hydrograph steeper | high rainfall intense rainfall impermeable rock previously wet conditions - saturated soil steep slopes less vegetation |
factors that decrease discharge and make the hydrograph gentler | low rainfall light rainfall permeable rock previously dry conditions gentle slopes more vegetation |
urban areas have drainage systems and are covered with impermeable materials increasing discharge so hydrographs are steep | rural areas have more vegetation and reservoirs decreasing discharge so hydrographs are gentle |
human causes of flooding | deforestation - more water reaches river channel urbanisation - buildings are impermeable increasing surface runoff |
hard engineering to reduce flooding | dams and reservoirs channel straightening man-made levees |
soft engineering to reduce flooding | flood warnings preparation flood plain zoning |
hard engineering | man made structures built to control the flow of rivers and reduce flooding |
soft engineering | schemes set up using knowledge of a river and its processes to reduce the effects of flooding |
flood in MEDC: River Eden, Carlisle, 8.1.2005 heavy rainfall | 3 deaths 3000 homeless 4 schools flooded some roads were damaged |
flood in LEDC: River Ganges, India, July 2007 heavy rainfall | 2000 deaths 25 million homeless 44 schools destroyed 10,000km road destroyed |
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