Boscastle

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Boscastle

  1. 1. Boscastle floods <ul><li>Where? </li></ul><ul><li>Boscastle is a small village on the north Cornwall coastline. </li></ul>
  2. 5. Boscastle floods <ul><li>When? </li></ul><ul><li>The flood occurred on 17 th August 2004. </li></ul><ul><li>Watch the video and see what effects you can see; </li></ul>HUMAN CAUSES PHYSICAL CAUSES
  3. 6. PHYSICAL CAUSES <ul><li>Three rivers: Valency, Jordan and Paradise, converge on the village. </li></ul><ul><li>Heavy rain caused by extreme frontal activity. 3 million tonnes of water added to a small drainage basin of just 40 square kilometres. </li></ul><ul><li>185mm of rain in just under 5 hours – infiltration excess overland flow </li></ul><ul><li>Soils saturated from rainfall earlier in the week encouraged overland flow </li></ul><ul><li>3 valleys steep and narrow – broader floodplain would have increased hydraulic radius </li></ul><ul><li>Soils thin on steep slopes due to mass movement </li></ul><ul><li>Parent rock is old red sandstone: limited permeability </li></ul><ul><li>Rivers flashy </li></ul><ul><li>Surrounding vegetation agricultural land: limited interception storage </li></ul><ul><li>High tide in the bay – restricted rate of exit of floodwater </li></ul>
  4. 7. <ul><li>Settlement developed on narrow flood plain where rainfall is often high – now over 1000 residents </li></ul><ul><li>Tourist season: population more than doubled – vehicles parked in top car park, and higher levels of stock in the shops </li></ul><ul><li>No flood defences: new ones built in October 2007 </li></ul><ul><li>Narrow bridges – old stone arched design </li></ul><ul><li>Difficult to establish casualty figures due to transience of population – difficult for emergency services </li></ul>HUMAN CAUSES
  5. 8. <ul><li>Use the timeline to look at the effects of the flood </li></ul><ul><li>Here are some to help you to start of with, </li></ul><ul><ul><li>Buildings were demolished, including Harbour Lights and Clovelly Clothing. </li></ul></ul><ul><ul><li>Only 1 casualty (broken thumb) and no deaths </li></ul></ul><ul><ul><li>Empty vehicles and a footbridge were washed out to sea. </li></ul></ul><ul><ul><li>Trees were uprooted. </li></ul></ul><ul><ul><li>4 footbridges on the Valency washed away (debris dams) </li></ul></ul><ul><ul><li>84 cars recovered from harbour, and 32 more ‘lost at sea’… </li></ul></ul>Effects of the flood
  6. 9. Practice question … <ul><li>With reference to a named specific case study describe and explain the causes of the flood. </li></ul><ul><li>You may use a diagram to help you. </li></ul>

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