Physical/ Human causes of flooding With CASE STUDIES - WATER CYCLE

Question 1

Physical causes of flooding (8)

Answer 1

• Relief/ Topography - Boscastle
• Drainage density - capacity -……
• Natural disasters - tropical storm/ storm surges
• Previous weather conditions - Boscastle
• Snowmelt - northern states of USA
• Rock type - geology
• Vegetation - type - ……
• Amount and type of rain/ prolonged precipitation
• monsoons

Question 2

Human causes of flooding (6)

Answer 2

• Deforestation
• River management - (Channelisation, straighten it to cause faster river flood and affects downstream)
• Change of land use
• Urbanisation - impermeable, water moves faster into river causing flooding)
• Floodplain drainage - Fertile use for agriculture. They are drained for either shouting or farming.

Question 3

How do variations in rainfall patterns cause flooding?

Answer 3

• The UK is associated with prolonged and heavy rainfall during autumn and winter
• South east Asia is sully in monsoon rains between July - Sept.
• Glacial outburst flooding- Jokulhaup in Tagia and Tundra locations such as Scadvania
• Storm surges
• Fluvial convergences ( where a number of rivers meet- during or after periods of heavy rainfall - have higher discharge)
• ITCZ, position of sun in relation to tropics

Question 4

Flooding case studies

Answer 4

1. Sheffield
2. Boscastle
   3.Pakistan

Question 5

Flood prevention case study

Answer 5

1. UK- Cornwall

Question 6

What are key stats for the case study -Sheffield? ( Mainly due to rivers being overwhelmed due to channelisation)

Answer 6

-Occurred in June 2007

Causes:
- 90mm of rain fell in 2 days and drains were overwhelmed which caused flooding
- rainfall fell heavily or 2 weeks
- rivers burst banks and drainage systems could not take more water causing widespread flooding
- ( topography - physical factor as well) several hills surround Sheffield so rainfall class rapidly down as runoff into river systems filling quickly

Impacts:
- 2 people died
- 1,200 homes flooded ( due to location on floodplains of rivers)
- 1,000 business affected
- Affected surrounding areas with floodwater up to 6m high
- business in low lying reads suffered £15 million each in damages
- poor river management and weak building regulations limited ability for rivers to naturally overflow, flood defences not strong enough
- rivers are squeezed into man made channels meaning no space to flow and flood into floodplains instead
- tress fell and blocked ricer channel causing more flooding

Question 7

What are key stats for the case study -Boscastle? (Physical reasons)

Answer 7

• Occured in August 2004

Causes:
- impermeable rock, small/round basin, lack of vegetation
-ground already saturated from previous rainfall and storm downpour
- dominated by stand stone ( check) which encourage surface run off and shortens lag time on hydrograph
- 50mm rainfall fell in 2 hrs

Impacts:
- 1000 residents and tourists affected in total
- people left homeless
- burst of main sewage and damaged buildings made it inaccessible for health and safety reasons
- people trapped in buildings and risk of catching hypothermia
- roads blocked only air access
- damage to many properties with minium quote of £250,000 with business estimated at several million

Responses
- emergency service were available
- response of communication services were quick
- occurred in the afternoon so more ppl were aware

Question 8

What are key stats for the case study -Pakistan? (Deforestation)

Answer 8

• Occurred in August 2010

Causes:
- hit by a five day period of expceptional precipitation and 60 hrs of continuous rainfall which exceed 3 months usual monsoon season
- tsunami like wave of water also tore through mountain valley
- due to deforestation by Taliban and construction of embankments raised river channel leaving areas exposed
- also due to climate change

Impacts:
- 1/5 of Pakistan submerged ( roughly size of England )
- 11,000 villages flooded and 1.2 million houses damaged and estimated 7 million acres of (check) fertile and arable land destroyed
- £1.5 billion worth of agriculture destroyed
- bridges and roads washed away and damage to highway built by Chinese over 20 years which links Islamabad to far west china
- 14 million flood victims ( most were poor)
- 6 million risk of starvation
- conditions were hot and humid with mosquitos
- no reliable supplies, food or water
- some farmers refused to be rescued unless animals were taken with hem representing their only surviving source of income

Responses:
- 30,000 saved in 3 Days by helicopter
- 30,000 soldiers involved delivery food,rebuilding and setting up tents
- Pakistan relief fundraiser £900,000 but accusations of governemet taking money

Question 9

What are key stats for the flood prevention case study -Cornwall?

Answer 9

• scheme put in place to prevent flooding in part of Cornwall in area of bude canal and river neet
• cost - £1.45 million
• will protect 22 homes and 15 commercial properties
• raining and strengthening existing embankments and creating new habitats
• but partial closures or roads and bridges