River Landscapes Case Studies and Examples

Boscastle Floods (2004)
1. Causes
  1. Human
    1. Bridge
      1. This constricted the flow of the water through the village, forcing the river to burst its banks.
    2. Impermeable Urban Surfaces
      1. Tarmac and concrete had been put in place by people living in the village. This means that the water cannot soak through the ground, resulting in more surface runoff reaching the river at one time, increasing the flood risk. Also, the drains take water very quickly to the river.
  2. Physical
    1. Heavy Rainfall
      1. Heavy rainfall is less likely to infiltrate into the soil and will reach the river quickly. This will result in a rapid increase in river discharge. It can also saturate the soil so it cannot hold any more water and so more water reaches the river at a time. This also increases the flood risk.
      2. Over 60mm of rainfall fell in two hours (a month's rainfall)
      3. 2 million tonnes of water surged through the village.
    2. Impermeable Ground
      1. There are clay-rich soils. Rainwater cannot soak through this and so goes straight to the river as surface runoff, increasing the amount of discharge and so the flood risk.
      2. The first two layers of rock below the clay rich soils are impermeable: slate and shale. This meant that any rainfall that penetrated the soil was unable to get past the rock.
    3. Confluence of Two Rivers
      1. Boscastle stands where two valleys meet, formed by the rivers Valency and Jordan. This increases the amount of discharge and so increases the flood risk.
    4. Topography of the Surrounding Area
      1. Boscastle is in a valley, with high ground either side of it. The slopes of the valley are very steep and so rain water rushes to the river quickly, increasing the flood risk.
2. Effects
  1. People
    1. Damage to and Loss of Property
      1. Homes, Businesses and cars belonging to more than 1000 people were swept away. Around 75 cars and six buildings were washed into the sea. This is an impact on people as homes were lost and money had to be spent on repairing and replacing property.
      2. 32 of the 75 cars that were swept away were never recovered.
      3. Several boats were lost.
    2. Loss of Income
      1. Income from tourism was lost as people were unlikely to visit the area. This had an impact on livelihoods as people lost their jobs or their businesses lost money. This has a negative impact on the local economy.
    3. Insurance Claims
      1. Vast numbers of insurance claims were made by people and businesses to cover the costs of the damage.
    4. No Lives Were Lost
      1. This is partly due to the rapid response of the emergency services, which is often the case in HICs such as the UK (due to well trained emergency services and weather forecasting to give warning).
      2. The worst injury that anyone experienced was a broken thumb.
  2. Environment
    1. Hundreds of Trees Were Uprooted and Wildlife Habitats Were Flooded
      1. This caused damage to the environment.
River Management: River Nene, Northampton
1. Overview
  1. Heavy rain on 9th April 1998 caused the River Nene in Northampton to overflow, flooding the town and causing two deaths. As a result it was decided that the River Nene needed to be managed in order to protect the city from future flooding.
2. Hard Engineering
  1. Building an Embankment in 2002 (Cost £2 Million)
    1. The level of the land at Weedon was raised by 10m by building a clay embankment across the river valley of a tributary of the River Nene. Water would be stored behind the embankment in times of flood. This would result in less water entering the River Nene, and so reducing the flood risk at Northampton. The embankment has been landscaped to minimise the visual impact and to create habitats for local wildlfie..
  2. Floodwalls
    1. At Foot Meadow, 4m high floodwalls have been built to stop water from spreading out from the channel in order to protect housing, industry, the railway and the Castle Inn.
3. Soft Engineering
  1. Creation of a Washland
    1. A washland was created in the Upton area where 1.2 million cubic metres of water could be stored during times of flood. This means that less water will reach the River Nene at Northampton, and so reducing the flood risk to the city.
  2. Improvements to the Flood Warning System (2003)
    1. Residents in the Far Cotton area would be given 2 hours notice of a flood occurring. This would give time for people to protect their properties and valuables, and evacuate if needed. This, therefore reduces the cost and impact of the flood.

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	Criado por Alex Collins mais de 9 anos atrás