This document discusses rivers, floods, and flood management. It describes the hydrological cycle and factors that influence river discharge patterns. It also examines river landforms and processes such as waterfalls, meanders, and deltas. The document then discusses flooding, including causes, areas at high risk, and short-term and long-term responses. It provides examples of both hard and soft engineering techniques used for flood management.

1. Rivers, floods and management
Rivers, floods
and management

2. Rivers, floods and management
The drainage basin hydrological cycle

3. Rivers, floods and management
River discharge
The storm hydrograph

4. Rivers, floods and management
River discharge
What factors might result in a ‘flashy’ hydrograph?
• short-lived but intense rainfall
• impermeable underlying rock such
as granite
• steep relief
• urban area, where water is
channelled through drains to the
stream
• small round drainage basin

5. Rivers, floods and management
River discharge
What factors might create a hydrograph like this?
• dense woodland vegetation
• high infiltration capacity of soil
• permeable underlying rock, such as
limestone
• elongated drainage basin

6. Rivers, floods and management
The long profile

7. Rivers, floods and management
The Hjülstrom curve

8. Rivers, floods and management
An upper course channel
Amanda Barker

9. Rivers, floods and management
A middle course channel
Amanda Barker

10. Rivers, floods and management
A lowland channel in flood
Amanda Barker

11. Rivers, floods and management
High Force waterfall
• vertical erosion
(by hydraulic action
and corrasion)
below the waterfall
deepens the plunge
pool
• undercutting of the
softer rock leads to
eventual collapse of
the resistant Whin
John Pallister
Sill and results in
headward erosion

12. Rivers, floods and management
The development of an oxbow lake

13. Rivers, floods and management
Reasons for formation of a delta
• the sediment load carried by the river is substantial
• the river has a large drainage basin
• the mouth of the river is located on a coastline where ocean currents and
tides are weak so the rate of deposition exceeds the rate of sediment
removal

14. Rivers, floods and management
Features related to rejuvenation
• knick points, rapids and
waterfalls
• river terraces
• incised meanders, both
entrenched and ingrown
Aerofilms
The city of Durham is built inside
an entrenched meander

15. Rivers, floods and management
Flooding
Physical causes of flooding
• excessive precipitation over • the nature of the drainage
a long period of time basin
• intensive precipitation over • relief
a short period of time • rock and soil type
• snowmelt • natural vegetation
• climatic hazards such as
hurricanes

16. Rivers, floods and management
Flooding
Influence of human activities on flooding
• Urbanisation creates impermeable surfaces so reducing infiltration.
Surface water is therefore transported more rapidly through drains to
the river.
• Deforestation reduces interception and increases runoff.
• Some methods of river management, such as channelisation, increase
flood risk downstream.
• Global warming leads to more extreme rainfall events.

17. Rivers, floods and management
Flooding
Areas of high flood risk in England and Wales

18. Rivers, floods and management
Flooding
Responses to flooding
Short-term responses: Long-term responses:
• media broadcasts of information • government and/or foreign aid
• emergency relief, rescue, shelter, • disaster planning for the future
food • flood management programmes
• armed services for evacuation and
building emergency defences

19. Rivers, floods and management
Flooding
Examples of hard engineering
• channelisation, to raise, straighten or strengthen banks
• dams and weirs
• diversion channels
• dredging
• retention basins and balancing lakes
• artificially raising the height of the floodplain

20. Rivers, floods and management
Flooding
Examples of soft engineering
• afforestation
• floodplain zoning
• land-use management, e.g. contour ploughing
• wetland and riverbank conservation
• river restoration
• improved forecasting and warning