geography- river discharge and engineering for flooding prevention

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  • Water on the land
    • River Discharge
      • hydrographs
        • rising limb
          • increase in river discharge
        • falling limb
          • decrease in river discharge-return normal level
        • lag time
          • delay between two peaks
        • peak discharge
          • highest river discharge
        • peak rainfall
          • largect volume of rainfall
        • storm flow
          • normal flow
        • maximum river capacity
          • over/above= flood
        • discharge in cumecs
      • factors
        • rainfall
          • lots, short, heavy
            • more runoff
            • decrease lag time
            • increase river discharge
        • temperature
          • hot, dry
            • hard ground
              • increase r. discharge
          • cold, freezing
            • hard ground
              • increase r. discharge
        • previous weather conditions
          • lots of rain=
            • saturated soil=
              • can't infiltrate = increase r.discharge
        • Rock type
          • permeable rock- infiltrate through pore spaces
          • pervious rock- flow along cracks
            • permeable rock- infiltrate through pore spaces
            • not much runoff- less r.discharge
            • impermeable= increase r.dishchage
              • factors
                • rainfall
                  • lots, short, heavy
                    • more runoff
                    • decrease lag time
                    • increase river discharge
                • temperature
                  • hot, dry
                    • cold, freezing
                    • previous weather conditions
                      • lots of rain=
                        • saturated soil=
                          • can't infiltrate = increase r.discharge
                    • Rock type
                      • pervious rock- flow along cracks
                        • not much runoff- less r.discharge
                        • impermeable= increase r.dishchage
                        • land use
                          • urban area=
                            • drainage system
                              • increas r.discharge
                                • impermeable surface
                            • impermeable surface
                        • relief
                          • steep= increase r.disharge
                        • increase runoof, decrease lag time, increase r.disharge
                  • land use
                    • urban area=
                      • drainage system
                        • increas r.discharge
                    • relief
                      • steep= increase r.disharge
                    • increase runoof, decrease lag time, increase r.disharge
                • Enginerring reduce flooding
                  • soft engineering
                    • schemes set up- use knowledge of river and processes to reduce the effects of flooding
                    • examples
                      • flood warnings
                      • preparation
                      • flood plain zoing
                      • do nothing
                  • hard engineering
                    • man-made structures to control the flow of rivers and reduce flooding
                    • examples
                      • dams and resevoirs
                      • channel straightening

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