Published on March 6, 2014
Rivers, floods and management Rivers, floods and management
Rivers, floods and management The drainage basin hydrological cycle
Rivers, floods and management River discharge The storm hydrograph
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
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
Rivers, floods and management The long profile
Rivers, floods and management The Hjülstrom curve
Rivers, floods and management Amanda Barker An upper course channel
Rivers, floods and management Amanda Barker A middle course channel
Rivers, floods and management Amanda Barker A lowland channel in flood
Rivers, floods and management High Force waterfall • vertical erosion (by hydraulic action and corrasion) below the waterfall deepens the plunge pool the resistant Whin Sill and results in headward erosion John Pallister • undercutting of the softer rock leads to eventual collapse of
Rivers, floods and management The development of an oxbow lake
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
Rivers, floods and management Features related to rejuvenation • knick points, rapids and waterfalls • river terraces The city of Durham is built inside an entrenched meander Aerofilms • incised meanders, both entrenched and ingrown
Rivers, floods and management Flooding Physical causes of flooding • excessive precipitation over a long period of time • the nature of the drainage basin • intensive precipitation over a short period of time • relief • snowmelt • natural vegetation • climatic hazards such as hurricanes • rock and soil type
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.
Rivers, floods and management Flooding Areas of high flood risk in England and Wales
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, food • disaster planning for the future • armed services for evacuation and building emergency defences • flood management programmes
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
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
Transcript of Mississippi river presentation. Animals who live in and along side of the river Animals who live in the river Animals that live along side of the
Title: River 1 River Lower Course River Channel Down Stream Portion of River Work of River River Valley Flood Plains and Levees Deltas Landforms. Arcuate Delta
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