Hydrology + F : Case Studies

Question 1

Causes of flooding in Carlisle

Answer 1

• Carlisle lies on a floodplain of the river Eden
• average annual precipitation of 2,800mm in the upper course Eden + 760mm in Carlisle
• upper Eden is moorland over 600m high
• from Thursday 6th Jan to Saturday 8th —> 15% annual rainfall fell in 36 hours
• winds up to 120 mph —> blowing down trees —> widespread road + river blockages
• discharge in Eden reached max of 1,500 cumecs
• defences were not built to withstand a 1 in 170 year event —> flood levels in some areas ended up 1m higher than defences

Question 2

Immediate effects (Carlisle)

Answer 2

• 1,600 homes flooded, estimated cost 100 mil
• 6,000 people had to be rehoused
• 1,150 trees fell
• roads + bridges closed for 2 days
• fire station flooded
• RAF + coastguard rescue teams evacuated people by boats + helicopter
• 2 schools seriously flood damaged —> estimated cost over 4 million

Question 3

Medium term effects (Carlisle)

Answer 3

• emergency repairs to flood defences
• 50 buses brought in from northern region + new fleet purchased
• shortage of second hand cars
• builders + flood restoration firms drafted into city —> boosts B+B trade in surrounding areas

Question 4

Longer term effects (Carlisle)

Answer 4

• reassessment of flood defence needs for city - works expected to last 3 years + cost £20 million
• plans to rebuild police station on a new site
• plans to significantly alter city centre
• many small family firms closed down
• increases in household and car insurance premiums throughout the city

Question 5

Describe the Kissimmee River?

Answer 5

• 165 km long river, floodplain up to 5km wide
• low lying, wetlands - sustains large population of wading birds

Question 6

Flood control

Answer 6

• canal reduced length of river from 165 km to 90 km
• channelised - concrete channel, 10m deep
• wetland drained - 14,000 ha, reduced to 2000 - caused a 92% reduction in wading birds
• during floods water stays in the basin for 1 day instead of 11 (average)

Question 7

Problems of flood control

Answer 7

• by 1971, loss of water soaking into aquifers reduced available water
• this allowed salt water encroachment from the sea
• threatening Orlando water supplies

Question 8

Flood restorations

Answer 8

• 11,000 ha of wetland created
• de-channelisation + filling in to create meanders that were removed in 1962
• cost of initial channelisation =$20 million, cost of de-channelisation = $400 million
• therefore the cost to get something that looked exactly the same as before was $420 million