River Mole Case Study (water And Carbon)

Question 1

Gatwick flood defences

Answer 1

-£8 million invested
-Working closely with environment agency to reduce flood risk: Gatwick stream Flood attenuation scheme
-Porous asphalt to help increase infiltration
-Detention pond with iron flood gates built designed to store over 180,000 cumecs of water from Gatwick stream only during high flood periods should ‘double level of protection Gatwick has’
-Gatwick also investing £4m into upper mole flood alleviation scheme

Question 2

Source and mouth location and basin size and permeability

Answer 2

Source: Rusper, Horsham, West Sussex
Mouth: River Thames
Basin size: 512 km sq (20% catchment is urban) 60% low permeability

Question 3

2013 floods Christmas Eve

Answer 3

-24th December 2013, wettest day for 35 years. Over 71mm in parts of catchment. Equivalent to 260 million buckets of water falling on river mole drainage basin
-Precipitation events such as these are likely to increase due to climate change

Question 4

Upper mole flood alleviation scheme

Answer 4

-£15 million environment agency project designed to reduce flooding along river mole.
-In particular the urban areas in the upper reaches prone to flooding such as Crawley, Horley and Gatwick airport.
-Various schemes are being built to attenuate the flood peak in the upper reaches including upgrading of the flood retention reservoir at clay lake and construction of a higher dam wall at Tilgate lake.

Question 5

2013 Christmas Eve floods impact on Gatwick

Answer 5

-Gatwick airport: power failure from flooding causing delays with luggage handling on Christmas Eve; 100 flights delayed or cancelled; thousands of travellers were left stranded and rail connections disrupted.

Question 6

2013 Christmas Eve floods power cuts

Answer 6

-Power cuts across the country; 100 homes in Mestham left without power for 3 days
-Uk power networks raised compensation for customers without power.

Question 7

Factors contributing to increased flood risk of river mole

Answer 7

-Blocked drains caused much of flooding in Horely
-Mole basin has expanding land uses such as golf courses, industrial parks, airport car parks, Chelsea FC in cobham
-Growth of towns like Crawley, Horsham, Horely and Gatwick; airport car parks have increased runoff. 20% basin urbanised; increased lag time. Urbanisation reduced interception and water abstracted by trees.

Question 8

Holistic/sustainable approaches to flood management

Answer 8

-Upper mole catchment includes Grattons park, Nutfield marshes; wetlands and flood plains lead to reduced risk of floods
-Moors project owned by Surrey Wildlife trust