river case studies Flashcards
1
Q
physical causes of the floods in Boscastle
A
- heavy rainfall from what was left of hurricane Alex produced large quantities of surface run-off which reached the channel of the river Valency more quickly than the channel could cope with
- 1400 L of water in two hours
- The ground was already saturated due to a wetter than average summer this rain could not infiltrate into the soil
- Little interception because there are few trees on the moors so all rain reaches the ground quickly
- steep slopes rainfall doesn’t have time to infiltrate so goes down the slope to channel very quickly
- River Jordan joins the river Valency just above Boscastle which bought even more water to the village; two channels became one
2
Q
human causes of the floods in Boscastle
A
- Low bridges across the narrow river trapped debris being carried by the floodwater this created dams that held back the water
- river had been narrowed as it went through Boscastle so reduced the amount of water the channel could hold
- breakwaters at the mouth of the river stopped the river water escaping into the sea quickly so it piled up behind
3
Q
environmental impacts of the flood in Boscastle
A
- flood water gushed into houses shops and pubs; the church was filled with 6 feet of mud and water
- cars, walls and even bridges washed away, 50 cars ended up in the harbour
- trees were up rooted and swept into peoples gardens
- The weight of water eroded riverbanks damaged gardens and pavements
- damage to local wildlife habitats
- coastal pollution caused as debris and fuel from cars flowed out to sea
4
Q
economic impacts of the flood in Boscastle
A
- cost of the rescue seven helicopters airlifted 100 people to safety 29 of Cornwall County Fire Brigade stations were involved
- loss of business/income shops like, ‘Cloverley Clothing’ and ‘Things’ had to be demolished
- happened during the tourist season tourists were put off plus attractions had to close e.g. the witchcraft Museum, the visitors centre had to be demolished
- damage to buildings and services cost the council up to £2 million
5
Q
social impacts of the flood in Boscastle
A
- around 1000 residents and visitors affected
- no one died only one minor injury
- stress and anxiety of people traumatised by the incident
6
Q
management strategies after the flood in Boscastle
A
- £4.6 million flood defence scheme was completed in 2008
- The river was widened and increased its depth so that I can hold more water- this cost a lot and dredging will need to be done regularly to maintain width and depth, also riverside hotel lost some of its patio
- flood defence walls were built so the river has to rise further to flood- it cost a lot to build and maintain, reduces access to the river and isn’t aesthetically pleasing
- removed the low bridges and replaced with wider span bridges debris can no longer be caught and create a damn- lasts a long time
- widen river channel upstream of the village- river will flow more slowly here and deposit sediment and debris- creates an area where the river can flood without causing damage
- encouraged land owners to plant trees on the Valley side- increases interception and more infiltration and less surface run off- creates animal habitats- long-term solution
7
Q
River flooding in an MEDC
A
Flash flooding on the river valency, boscastle in Cornwall UK, 2004
8
Q
river flooding in an LEDC
A
river flooding in Bangladesh Dhaka July and August 2004
9
Q
physical causes of flooding in Bangladesh
A
- Bangladesh is mainly made up of a delta from three massive rivers, this means the land is very flat and very low 70% of the land is below 1 m sealevel
- three massive rivers all join together in the Delta bringing water from a huge area increases flood risk
- every summer melting snow from the Himalayas adds to the amount of water in the three Rivers
- Bangladesh has a monsoon climate and get heavy rainfall during the summer wet season June to September; in 2004 the monsoon rains came in early
- over a seven day period 300 mm of rain fell
10
Q
human causes for the flooding in Bangladesh
A
- deforestation in the Himalayas has reduced interception increasing surface run off causing rainwater to reach the rivers more quickly
- A dam nearby burst and added water to the river
- The increased surface run-off and lack of vegetation roots has caused soil erosion. soil is washed into the three rivers and carried downstream where is deposited raising the river beds and clogging up the channels so water does not flow away as easily
- unplanned growth of urban areas has produced more impermeable surfaces and therefore more surface run off
11
Q
environmental impacts of the flood in Bangladesh
A
- approximately 38% of the total land area was flooded including 800,000 ha of agricultural land
- over50% of Dhaka was flooded
- water contamination ; Dhaka was swimming with sewage
- damage to infrastructure-roads, bridges, embankments, railway lines
12
Q
economic impacts of the flooding in Bangladesh
A
- damage to irrigation system is impacted on crop out put in the future
- all domestic and internal flights had to be suspended and Road and rail links into Dhaka were severely affected- loss of business
- value of damage was assessed as being in the region of $2.2 billion
13
Q
social impacts of the flood in Bangladesh
A
- isolation of areas due to damage to transport network- difficult to get aid in
- 36 million people were made homeless
- 1.5 million in danger of malnutrition within eight weeks
- death toll of 800-result of disease because of no clean water
14
Q
short-term management strategies for the flooding in Bangladesh
A
- The government working with none governmental organisations provided emergency relief: rice, clothing, medicines, blankets, water and towels
- United Nations activated a disaster management team to coordinate the activities of the various United Nations agencies, they supplied critical emergency supplies and conducted a damage and needs assessment in affected areas
- bilateral aid (aid directly to Bangladesh from individual countries) was directed to the united nations team
15
Q
long-term management strategies for the flooding in Bangladesh
A
- $100 million government project
- earth embankments-alongside the main channel to hold back water after the flood these actually stopped the water getting back into the river channels prolonging the flood
- sluice gates which can be closed when water levels rise and opened to allow water back into river
- slope protection-slope covered in concrete blocks to reduce erosion
- storm drains-to take water back into the river channels
- pumping stations-to remove water from the city
- Financial aid granted for a period of five years this was mainly in the form of a loan from the World Bank to pay for repairs to infrastructure water resource management and education
