Rivers

Rivers

1. The water cycle and drainage basin

   • evaporation
     • condensation
       • precipitation
         • infiltration
           • when water filter though the ground and the tiny pores in the soil
         • transpiration
           • water evaporated from leaves
         • throughflow
           • rainfall/water flow through soil
         • percolation
           • water moves downwards through soil into saturated rocks
         • surface storage
           • precipitation retained on the ground surface
         • groundwater flow
           • deep movement of water through underlying rock
         • soil moisture
           • water is stored in soil

2. river processes

   • erosion
     • the wearing away of the river bed and banks or the loads
     • HYDRAULIC ACTION
       • high velocity water pushes air into cracks on the banks
     • ATTRITION
       • loads bumping into each other and breaks
     • ABRATION
       • loads that are thrown against bed and banks causing them to be worn away
     • SOLUTION
       • acid and alkali dissolve the bed & banks
   • transportation
     • SUSPENSION
       • particles supended in the river carried by its flow
     • SALTATION
       • pebbles are bounced along the river bed
     • SOLUTION
       • dissolved materials
     • TRACTION
       • big boulders bouncing along the bed
     • the movement of the load down the river
   • deposition
     • the laying down of a river's loads as its velocity decreases
     • factors
       • less water
       • increasing amount of loads
       • shallow
       • recah its mouth
     • drop its biggest load first

3. river landscapes

   • drainage basin
     • source
       • the start of a river
     • tributary
       • a small stream that joins a large river
     • confluence
       • where a tributary joins a large river
     • an area of land drained by a river and its tributaries
     • watershed
       • the edge of a river basin
     • mouth
       • the end where a river joins the sea
   • long profile
     • UPPER COURSE
       • v-shape valley
       • narrow
       • shallow
       • waterfall/gorges
         • river flows over the hard resistant rock
           • erodes the less resistant soft rock quickly
           • abration and hydraulic action undercuts the hard rock leaving an overhung and a plunge pool
             • overhang collapses
             • repeated collapsing
               • steep sided gorge
       • interlocking spurs
         • the river wind around the spurs because it's near its source and is not powerful enough to cut through the spurs so it has to flow around them
     • MIDDLE COURSE
       • gentle sloping valley
       • wider/deeper
       • meanders
         • faster flow on the outside bend, slower flow on the inside bend
           • faster flow : more energy and erosion, forming a river cliff
           • slower flow : less energy and deposition forming slipp-off slopes
           • over time erosion on the outside and deposition on the inside makes the neck becomes narrower
             • swan's neck meander
             • swan's neck part of the meander becomes filled with sediments, creates a straight path for the river
               • ox-bow lake
       • river cliff
       • slip off slope
     • LOWER COURSE
       • floodplain
         • migrating meanders erode the sides of the valley
           • wide
         • migrating meanders leaves deposite of sand and clay
           • flat
       • levees
         • river breaks its banks
           • deposit biggest loads firstalong the side of the river channel creating a levee
       • estuary
         • where river meets the sea
           • salt and fresh water mixes
         • high tide
           • incoming water stops the river flow
           • deposites fine silts + sand that were in suspension
             • making mud flats

4. flooding

   • PHYSICAL FACTORS
     • precipitation
     • geology
     • steep slopes
   • HUMAN FACTORS
     • urbanisation
     • deforestation
     • agriculture
   • HYDROGRAPHS
     • peak rainfall
       • highest amount of rainfall
     • rising limb
       • how quickly discharge rises
     • peak discharge
       • highest recorded discharge
     • lag time
       • time difference between peak rainfall & discharge
     • falling limb
       • reduced discharge once run-off has passed
     • base flow
       • normal flow of a river
     • bankfull discharge
       • horizontal line : level of dischargeabove which flooding will occur
   • BANBURY FLOODS
     • impact of 1998 flood
       • closure of railway station
       • 12,500,000 pound worth of damage
       • closure of shops and businesses, homes damaged
     • FLOW CONTROL STRUCTURE
       • low flow
         • the weir control the flow
       • medium flow
         • upstream baffle controls the flow
       • high flow
         • downstream baffle controls the flow
     • EARTH EMBANKMENT
       • the borrow area
         • resevoir
         • hardwick & huscote
         • embankment
           • storage area
   • FLOOD MANAGEMENTS
     • FLOOD RELIEF CHANNEL
       • man made river channel
     • FLOOD WARNINGS
     • FLOODPLAIN ZONING
       • land use restrictions on the floodplain