river landscapes

NATURAL RIVER FEATURES
1. RIVER BASINS
  1. SOURCE: the start of the river
    1. TRIBUTARY: a small stream that joins a larger stream/ river
      1. CONFLUENCE: where 2 rivers meet
        MOUTH/ ESTUARY: where the river meets the sea
  2. DRAINAGE BASIN: the area drained by a river and its tributaries
    1. WATER SHED: the boundary between 2 drainage basin, generally hills
2. CHARACTERISTICS OF A RIVER AKA. THE RIVERS PROFILE
3. RIVER FLOODING
  1. NATURAL CAUSES
    1. RAINFALL INTENSITY
      1. GEOLOGY
        SNOW MELT
        DRAINAGE BASIN
        STEEP SIDED VALLEYS/ LOTS OF TRIBUTARIES MEANS WATER ENTERS THE RIVER QUICKER
        WARMER TEMPERATURES IN SPRING CAUSE THE SNOW TO MELT, CREATING MORE WATER
        HARD ROCKS AKA. GRANITE ARE IMPERMEABLE, SO WATER CAN'T PERCOLATE FROM THE SOIL BELOW
      2. LOTS OF RAINFALL OVER A SHORT PERIOD OF TIME = NO SOIL INFILTRATION
        EXCESS WATER FLOWS TOWARDS THE RIVER AS SURFACE RUN OFF OR GROUND WATER
        WATER REACHES THE CHANNEL FASTER, FORCING THE RIVER LEVEL TO RISE ABOVE THE BANK, RESULTING IN FLOODING
  2. HUMAN CAUSES
    1. DEFORESTATION
      1. CLIMATE CHANGE
        URBANISATION
        RAIN IS FORCED TO QUICKLY FLOW INTO SEWERS AND DRAINS RATHER THAN IMPERMEABLE TARMAC
        MELTING GLACIERS AND ICE SHEETS RESULT IN MORE WATER
      2. LESS WATER IS INTERCEPTED BY PLANTS AND TREES, INTENSIVE FARMING LEADS TO MORE SURFACE RUN OFF
        EXCESS WATER FLOWS TOWARDS THE RIVER AS SURFACE RUN OFF OR GROUND WATER
        WATER REACHES THE CHANNEL FASTER FORCING HE RIVER LEVEL TO RISE ABOVE THE BANK, RESULTING IN FLOODING
  3. REDUCING THE IMPACTS
    1. PLANNING
      1. AREAS AT RISK ARE USED FOR PARK LAND RATHER THAN HOUSING, TO REDUCE THE IMPACT OF FLOODING: this is called LAND USE ZONING.
    2. PREVENTION
      1. THE EA OFFERS ADVICE ON HOW TO REDUCE FLOOD DAMAGE , aka. use ceramic tiles not carpet, raise electrics up the walls, use synthetic materials for windows and doors, install heating systems on upper floors.
        eg. in LIC's homes are built on stilts to prevent flood damage.
    3. EDUCATION
      1. THE EA KEEPS PEOPLE UP TO DATE ON FLOODING BY: RELEASING LEAFLETS, ADVERTISING, POSTING INFORMATION AND FLOOD WARNINGS ONLINE, PROVIDING PHONE HELPLINES AND ORGANISING FLOOD DRILLS
        flood drills are common in schools along the missouri river (nebraska) and green river (washington) in the USA
    4. PREDICTION
      1. THE EA AND FEMA MONITOR RIVERS. THEY USE THIS INFO TO: help forecast potential floods and give advanced/ early warnings of flooding
        after the Boscastle flood in 2004, the EA built new overflow channels to carry excess water.
4. STAGES OF A RIVER
  1. THE UPPER COURSE: STEEP SLOPES, DOWNWARD EROSION, SMALL DISCHARGE, SLOW FLO, SHALLOW, NARROW, STEEP V SHAPED VALLEYS
    1. THE MIDDLE COURSE: LARGE RIVER, ERODING LATERALLY, STARTING TO MEANDER AND BEND, A MUCH WIDER, FLATTER VALLEY
      1. THE LOWER COURSE: WIDE, DEEP, FAST FLOWING RIVER, CARRYING A LARGE AMOUNT OF MATERIAL (LOAD), THE BED LOAD IS VERY SMALL, VALLEY IS FLAT AND VERY WIDE, MOSTLY FLOOD PLAIN.
        FLOOD PLAINS
        in the lower course, the river is nearing the sea and is carrying lots of sediment (alluvium)
        when the river floods,excess water spills into the surrounding area, depositing sediment which forms the flood plain.
        the flood plain is shaped by lateral erosion and meanders as they slowly migrate downstream and deposit material on their inner bends.
        LEVEES
        when flooding occurs the river bursts its banks. the heavier sediment is deposited close to the banks due to the rivers decrease in energy, resulting in natural embankments.
        the smaller sediment, alluvium, is deposited further from the river on the flood plain, enriching the soil. the levees build up over time.
      2. MEANDERS
        (cross section)
      3. OXBOW LAKE- FORMED BY LOOPING MEANDERS WHICH ARE EVENTUALLY BYPASSED BY THE RIVER. THE FINAL OXBOW MAY FILL IN.
    2. INTERLOCKING SPURS
      1. AS THE STREAM ISN'T STRONG ENOUGH TO ERODE RESISTANT ROCK, IT BENDS AROUND THE SPURS, WHICH EVENTUALLY INTERLOCK.
    3. WATERFALLS
      1. COMMON FEATURE IN UPPER COURSE, FORM IN GORGES DUE TO VERTICAL EROSION.
RIVER MANAGEMENT
1. SOFT ENGINEERING
  1. AFFORESTATION: REPLANTING TREES IN THE DRAINAGE BASIN
    1. PROS: vegetation intercepts ground water. woodlands provide habitats and reduces visual pollution
    2. CONS: land can't be used for other things
  2. LAND USE ZONING: PREVENTING HOUSING DEVELOPMENT ON FLOOD PLAINS
    1. PROS: residential projects can be built built in low risk areas, and non vital recreational spaces can be put in high risk areas
    2. CONS: access for the public can be made difficult, it can cause planning problems in other areas
  3. WASHLANDS: AREAS ON THE FLOODPLAIN WHICH ARE ALLOWED TO FLOOD
    1. PROS: a relatively cheap way to solve the issue of excess flood water, less visual pollution
    2. CONS: use of the floodplain for agriculture or residential areas is restricted
2. HARD ENGINEERING
  1. FLOOD RELIEF CHANNELING: extra channels to to carry surplus water
    1. PROS: water is channeled from the river, preventing flooding nearby
    2. CONS: visually unattractive, only needed during periods of flooding, expensive to build and maintain.
  2. EMBANKMENTS: LEVEES BUILT ON OR NEAR RIVER BANKS
    1. CONS: flood water can spill over into protected areas. The levees can burst under pressure, causing widespread damage
    2. PROS: uses natural materials, prevents water moving into areas at risk
  3. CHANNELISATION: deepening and widening the river
    1. PROS: allows water to flow away more quickly from areas at risk from flooding
    2. CONS: visually unattractive, increases the flood risks to settlements downstream
  4. DAMS: USED TO TRAP AND STORE WATER, CAN BE USED TO CREATE HYDROELECTRICITY. (eg. the aswan dam)
    1. CONS: ugly, expensive to build and maintain, can reduce soil quality the valleys below (think nile flooding)
    2. PROS: create large areas for irrigation, fishing and water sports
  5. FLOOD WALLS: USED TO PROTECT SETTLEMENTS FROM FLOODING
    1. PROS: very effective
    2. CONS: ugly and expensive to build and maintain
  6. STORAGE AREAS: EXCESS WATER CAN BE PUMPED FROM THE RIVER TO TEMPORARY STORAGE AREAS IN ORDER TO REDUCE FLOODING eg. the mississippi diverts into lake pontchartrain
    1. PROS: effective, looks natural
    2. CONS: uses lots of space, can be expensive to pump so much water
CASE STUDIES
1. RIVER NENE, NORTHAMPTON 1998
  1. CAUSES
    1. TORRENTIAL RAINFALL AND STORMS ON APRIL 8TH & 9TH, 3 X THE NORMAL AMOUNT. THE GROUND WAS SATURATED COMPLETELY. THERE WAS NO EFFECTIVE WARNING SYSTEM
  2. IMPACTS
    1. SOCIAL: 2 PEOPLE DIED, 1500 WERE EVACUATED. SEWAGE IN NORTHHAMPTON CAUSED SERIOUS HEALTH RISKS
    2. ECONOMIC: 2500 PROPERTIES WERE AFFECTED, 5000 CARS WERE WRITTEN OFF, £350, 000, 000 WORTH OF DAMAGE WAS CAUSED.
  3. MANAGEMENT STRATEGIES
    1. HARD ENGINEERING
      1. FLOOD RETENTION RESEVOIR AT BILLINGDON AQUADOME, to hold extra water
      2. EARTHEN LEVEES ALONG THE RIVER BANKS, replanted with trees to give more structure and make it visually attractive
      3. 4M HIGH FLOOD WALLS NEAR THE TRAIN STATION, in order to prevent flooding on the tracks
    2. SOFT ENGINEERING
      1. 4 WARNING SIRENS AND A 2 HOUR WARNING PERIOD were installed by the EA.
      2. THE UPTOWN HOUSING ESTATE WAS BUILT ABOVE THE FLOODPLAIN, to reduce damage to the residential area
      3. A WASHLAND AT FAR COTTON AND ST JAMES is being created. major roads are being RAISED ON EMBANKMENTS. SPECIAL FLOOD GATES are being built, and 2 METRE HIGH CONCRETE WALLS to protect the roads.
2. MISSISSIPPI, USA 2011
  1. CAUSES
    1. HUMAN: increased development and intensive farming on impermeable floodplains
    2. PHYSICAL: heavy rain and snow fall in kentucky, 4 x the normal amount. high proportion of tornadoes
  2. IMPACTS
    1. SOCIAL: outbreaks of tetanus and E. coli, loss of life
    2. ECONOMIC: homes flooded, cost of insurance, food and fuel increases
    3. ENVIRONMENTAL: crops and farmlands were destroyed, fertilisers washed away, habitats destroyed
  3. MANAGEMENT STRATEGIES
    1. SOFT ENGINEERING
      1. SUBSIDISED INSURANCE SCHEME to regulate land use on the floodplain
      2. AGRICULTURAL LAND that has been flooded is used to store excess water
      3. RESTORATION OF WETLANDS UPRIVER- these act as sponges during heavy rain fall
      4. GOVERNMENT FUNDING FOR FARMERS who convert land into wildlife reserves and water storage areas.
    2. HARD ENGINEERING
      1. FLOODWAYS & CUT OFFS divert water in times of flood
      2. LEVEES built in the 18th century
      3. RIVER STRAIGHTENING

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	Criado por meg watts mais de 8 anos atrás