The northwest of England has suffered once-in-a-century floods for the second time in 10 years

* Claims could be up to 250 million pounds

* More than 5,000 properties affected

* Floods in northwest could rewrite record book

By Carolyn Cohn and Noor Zainab Hussain

LONDON, Dec 7 (Reuters) - British insurers could have to pay out up to 250 million pounds ($375 million) in claims to owners of homes and businesses, industry specialists said on Monday, after the northwest of England suffered once-in-a-century floods for the second time in 10 years.

As world leaders meet in Paris to seek a deal on global warming, insurers in Britain have been adjusting their forecasting models to cope with more frequent floods.

More than 5,200 properties have been affected by the weekend flooding, according to an official from the Environment Agency. The flood-hit area includes the towns of Carlisle, Keswick and Lancaster, and the Lake District National Park, which attracts millions of tourists.

More rain was expected on Monday and the number of properties hit by flooding would inevitably go up, the official added.

"Based on what we can see so far, insurance costs could be between 150 and 250 million pounds," said Mohammad Khan, head of general insurance at consultants PwC.

"A typical flood claim is about 30,000 pounds, but it would not be exceptional to have a 130,000 pound claim," said Jill Boulton, director of catastrophe risk modellers JBA Risk Management, adding that while floods hit a similar area of the country in 2005, the current floods looked "that bit deeper".

"IT'S A REAL MESS"

"Looking down the main street where I am now I can't tell where the river starts and where it ends. It's a real mess," Mark Walker, a teacher, told Reuters from Carlisle at the weekend.

He said the water had reached waist high at points along the road and had flooded local businesses including a car dealership and a convenience store. Emergency services had been evacuating homes by boat and helicopter.

Five of the six wettest years on record have happened since 2000, according to the Association of British Insurers, which said flooding in the Carlisle area cost insurers 272 million pounds in 2005.

Neil Hancox, senior property insurance adviser at Direct Line, said the company had set up mobile offices in the area to deal with claims, mainly to help those left without electricity. The UK arm of Allianz reported a 300 percent increase in the number of household claims calls, and a 100 percent rise in commercial calls.

Aviva said it would pay for alternative accommodation where needed, including for pets.

This second set of floods in the same area "will lead insurers to question whether they will provide cover in the affected areas", said Robert Powell, technical officer for UK retail at insurance broker Arthur J Gallagher.

After an earlier outbreak of flooding, the government and insurers agreed to develop a scheme to make insurance accessible for property-owners in areas of high flood risk. However, the scheme, known as Flood Re, is not scheduled to launch until April next year.

Boulton said JBA Risk Management's models could cope with the greater frequency of floods, though she added:

"It's possible this one is going to rewrite the record books." ($1 = 0.6639 pounds) (Additional reporting by Simon Jessop; editing by Sinead Cruise and Giles Elgood)

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