river landscapes

river landscapes

1. NATURAL RIVER FEATURES

   • RIVER BASINS
     • SOURCE: the start of the river
       • TRIBUTARY: a small stream that joins a larger stream/ river
         • CONFLUENCE: where 2 rivers meet
           • MOUTH/ ESTUARY: where the river meets the sea
     • DRAINAGE BASIN: the area drained by a river and its tributaries
       • WATER SHED: the boundary between 2 drainage basin, generally hills
   • CHARACTERISTICS OF A RIVER AKA. THE RIVERS PROFILE
   • RIVER FLOODING
     • NATURAL CAUSES
       • RAINFALL INTENSITY
         • 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
         • 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
     • HUMAN CAUSES
       • DEFORESTATION
         • 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
         • 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
     • REDUCING THE IMPACTS
       • PLANNING
         • AREAS AT RISK ARE USED FOR PARK LAND RATHER THAN HOUSING, TO REDUCE THE IMPACT OF FLOODING: this is called LAND USE ZONING.
       • PREVENTION
         • 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.
       • EDUCATION
         • 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
       • PREDICTION
         • 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.
   • STAGES OF A RIVER
     • THE UPPER COURSE: STEEP SLOPES, DOWNWARD EROSION, SMALL DISCHARGE, SLOW FLO, SHALLOW, NARROW, STEEP V SHAPED VALLEYS
       • THE MIDDLE COURSE: LARGE RIVER, ERODING LATERALLY, STARTING TO MEANDER AND BEND, A MUCH WIDER, FLATTER VALLEY
         • 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.
         • MEANDERS
           • (cross section)
         • OXBOW LAKE- FORMED BY LOOPING MEANDERS WHICH ARE EVENTUALLY BYPASSED BY THE RIVER. THE FINAL OXBOW MAY FILL IN.
       • INTERLOCKING SPURS
         • AS THE STREAM ISN'T STRONG ENOUGH TO ERODE RESISTANT ROCK, IT BENDS AROUND THE SPURS, WHICH EVENTUALLY INTERLOCK.
       • WATERFALLS
         • COMMON FEATURE IN UPPER COURSE, FORM IN GORGES DUE TO VERTICAL EROSION.

2. RIVER MANAGEMENT

   • SOFT ENGINEERING
     • AFFORESTATION: REPLANTING TREES IN THE DRAINAGE BASIN
       • PROS: vegetation intercepts ground water. woodlands provide habitats and reduces visual pollution
       • CONS: land can't be used for other things
     • LAND USE ZONING: PREVENTING HOUSING DEVELOPMENT ON FLOOD PLAINS
       • PROS: residential projects can be built built in low risk areas, and non vital recreational spaces can be put in high risk areas
       • CONS: access for the public can be made difficult, it can cause planning problems in other areas
     • WASHLANDS: AREAS ON THE FLOODPLAIN WHICH ARE ALLOWED TO FLOOD
       • PROS: a relatively cheap way to solve the issue of excess flood water, less visual pollution
       • CONS: use of the floodplain for agriculture or residential areas is restricted
   • HARD ENGINEERING
     • FLOOD RELIEF CHANNELING: extra channels to to carry surplus water
       • PROS: water is channeled from the river, preventing flooding nearby
       • CONS: visually unattractive, only needed during periods of flooding, expensive to build and maintain.
     • EMBANKMENTS: LEVEES BUILT ON OR NEAR RIVER BANKS
       • CONS: flood water can spill over into protected areas. The levees can burst under pressure, causing widespread damage
       • PROS: uses natural materials, prevents water moving into areas at risk
     • CHANNELISATION: deepening and widening the river
       • PROS: allows water to flow away more quickly from areas at risk from flooding
       • CONS: visually unattractive, increases the flood risks to settlements downstream
     • DAMS: USED TO TRAP AND STORE WATER, CAN BE USED TO CREATE HYDROELECTRICITY. (eg. the aswan dam)
       • CONS: ugly, expensive to build and maintain, can reduce soil quality the valleys below (think nile flooding)
       • PROS: create large areas for irrigation, fishing and water sports
     • FLOOD WALLS: USED TO PROTECT SETTLEMENTS FROM FLOODING
       • PROS: very effective
       • CONS: ugly and expensive to build and maintain
     • 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
       • PROS: effective, looks natural
       • CONS: uses lots of space, can be expensive to pump so much water

3. CASE STUDIES

   • RIVER NENE, NORTHAMPTON 1998
     • CAUSES
       • TORRENTIAL RAINFALL AND STORMS ON APRIL 8TH & 9TH, 3 X THE NORMAL AMOUNT. THE GROUND WAS SATURATED COMPLETELY. THERE WAS NO EFFECTIVE WARNING SYSTEM
     • IMPACTS
       • SOCIAL: 2 PEOPLE DIED, 1500 WERE EVACUATED. SEWAGE IN NORTHHAMPTON CAUSED SERIOUS HEALTH RISKS
       • ECONOMIC: 2500 PROPERTIES WERE AFFECTED, 5000 CARS WERE WRITTEN OFF, £350, 000, 000 WORTH OF DAMAGE WAS CAUSED.
     • MANAGEMENT STRATEGIES
       • HARD ENGINEERING
         • FLOOD RETENTION RESEVOIR AT BILLINGDON AQUADOME, to hold extra water
         • EARTHEN LEVEES ALONG THE RIVER BANKS, replanted with trees to give more structure and make it visually attractive
         • 4M HIGH FLOOD WALLS NEAR THE TRAIN STATION, in order to prevent flooding on the tracks
       • SOFT ENGINEERING
         • 4 WARNING SIRENS AND A 2 HOUR WARNING PERIOD were installed by the EA.
         • THE UPTOWN HOUSING ESTATE WAS BUILT ABOVE THE FLOODPLAIN, to reduce damage to the residential area
         • 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.
   • MISSISSIPPI, USA 2011
     • CAUSES
       • HUMAN: increased development and intensive farming on impermeable floodplains
       • PHYSICAL: heavy rain and snow fall in kentucky, 4 x the normal amount. high proportion of tornadoes
     • IMPACTS
       • SOCIAL: outbreaks of tetanus and E. coli, loss of life
       • ECONOMIC: homes flooded, cost of insurance, food and fuel increases
       • ENVIRONMENTAL: crops and farmlands were destroyed, fertilisers washed away, habitats destroyed
     • MANAGEMENT STRATEGIES
       • SOFT ENGINEERING
         • SUBSIDISED INSURANCE SCHEME to regulate land use on the floodplain
         • AGRICULTURAL LAND that has been flooded is used to store excess water
         • RESTORATION OF WETLANDS UPRIVER- these act as sponges during heavy rain fall
         • GOVERNMENT FUNDING FOR FARMERS who convert land into wildlife reserves and water storage areas.
       • HARD ENGINEERING
         • FLOODWAYS & CUT OFFS divert water in times of flood
         • LEVEES built in the 18th century
         • RIVER STRAIGHTENING

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