Rivers Case Studies

Rivers Case Studies

1. Rivers

   • River Tees Drainage Basin
     • Source North East england, 893m above sea level, rainfall is around 2000mm+ a year, relife is V shaped valley with steep gradient, river has turbulent flow, clear water sometimes stained by peat.
       • Upper stage- rocky with large irregular shaped boulders, V shaped vallyes, with interlocking spurs, high force water fall largest in the UK
         • Land uses- lack of flat land means settlements and comunication are difficult to develop, sheep farming, and small villages, sparsley populated, few employment oppotunities, tourists attracted to high force, foot paths, pubs and moorland.
           • Narrow steep sides are easy to dam, cow green is an example of a vast water supply
         • Middle stage- river is wide and flows with little turbulance, banks are smooth, and a flood plain had developed, yarm is situated in a meander
           • Human Land Use- attractive market towns, historic sites attract tourists, providing employment. Yarm has developed transport links, is head of river navigation on river tees. larger towns have developed CBD's mixed farming is common due too gradient and fertile soils.
           • Lower Stage- river widens and meanders enlarge as do flood plains, due to meander migration. the mouth is an estuary important habitats on large mud flats, more urbanised, such as Middlesbourgh, docks are important for imports and exports of raw materials.
   • Cumbria 2009 Floods
     • 314mm of rain in 24 hours, 400mm of prolonged rain fall in 72 hours, saturated ground from antecedent rain fall. Cockermouth located at the confluence of two rivers, built on a flood plain of river Derwent. Social Effects: more than 500 people spend the night with friends/family or in emergency shelters; police officer was swept away and killed when a bridge collapsed. A year on 150 people, have still not returned to their properties, 198people in affected areas required psychological help. Economic Effects: 20 roads and bridges and over 200 footbridges were destroyed, floods resulted a £276 million bill, 110 farms were severely affected, transport infrastructure has been heavily damaged
   • Pakistan 2012 Floods
     • 274mm of rain in 24 hours
       • more than half the normal monsoon rainfall fell in a week instead of 3 months
     • River indus carried alot of sediment from the Himalayas, sitlting up the channel becomming prone to flooding
       • Deforestation in the Himalayas increases flood risk more water and sediment reach the river quicker
     • Social Effects
       • 20 million people injured or homeless, death toll reached about 200, up to ten million had to drink unsafe water, increaseing malaria, malnutrition and respiotary infections due to living in tents in cold winters. emergancy shelters to 900,000 households
     • Economic Effects
       • 100s of bridges and 200 healthcare facilities were damaged- $10 billion to inferstructure, $7 billion to the farming sector, there was a shortage of funds for humaitarian response
   • Boscastle 2004 Floods
     • 16th august 2004
       • Flash flood following 50mm of rain in one hour and 125mm in a few hours
     • Very wet august meant ground already saturated, impermiable surfaces increased rate of surface runoff, confluence of rivers Valency and Jordan, as well as high spring tide so it was difficult for water to flow out to sea. sediment built up along bridges, causing a dam effect until the river burst its banks.
       • 50+ cars and caravans were swept out to sea, 6 buildings, boulders swept through the streets showinng the strengh of the flood, no deaths but some with serious injuries
         • 20 accomodations and tourists attractions had to close, insurance premiums rose the sky high levels and high cost of inferstructure repairs
   • Bangladesh 2004 Floods
     • Tectonic uplift in the himalayas means erosion rate of sediment increases due to the rivers having more potential, some parts of the ganges basin recives 500mm of rainfall a day in monsoon season, deforestation of the himalayas reduces interception.
       • the 2004 floods covered 50% of Bangladesh at their peak, 600 deaths and 30million reported homeless, 100,000 in Dahka alone suffered from diarrhoea.
         • the damage to schools and hospitals was estimated at $7 billion, rice crops were devastated as were important cash crops like jute and sugar
           • If sea levels rise Eustatically and Bangladesh sinks Isostatically, the severe problems will occur, 1.5m rise in sea level would affect 17 million in Bangladesh and 22,000km2 of land
     • system of huge embankmments along the coast and rivers and being reinforced by concrete, improved drainage canals to allow water to drain more effectively
   • Three Gorges Dam
     • Largest dam in the world with 18,200 megawatts of energy.
     • the three gorges dam helps improve navigation, prevent flooding, reduce chinas dependancy on coal, HEP
     • 610 ft tall, 1.3 miles from bank to bank, 18,200 megawatts which is equal to 15 to 20 nuclear power stations, reduced burning 50 million tonnes of coal a year.
   • Hebden Bridge 2012
     • 70-80mm in short period of time.
       • A months worth of rainfall in 7 hours.
         • River was at twice the height of its normal, 3ft of flood water.
           • 500 homes/businesses damaged, cumulo nimbus clouds, high relief rainfall.
   • Pickering Soft Engineering
     • The 2007 floods were significant in the pickering area damage was estimated at £2.1billion, climate change may increase the frequency of the floods, resulting in major costs and implications for the regional ecoomy and affected comunities.
       • Improve the effectiveness of current flood defences against climate change but also develop an ecosystem securing a health enviroment.
     • Pickering has a long history of flooding , but their priority is too low due to cost benefit, to town it particularly at risk from summer flash floods due to the steep nature of the catchment
     • Flood prevention schemes, stream side buffer zones- slows runoff and reduces erosion. construction of low level bunds, built on the flood plain create adittional flood water storage, lowering the flood peak by storing water. flood plain woodland form a barrier to flood flows, reducing potential. .
       • creation of debris dams, increases flood storage by raising the water levels, 100 large woood debris dams in pickering beck. lastly drain blocking helps to re wet peats and slow down runoff, 10 drains were blocked to improve water retention and delay flood flows.