I work for the Environment Agency in flood risk management and am still heavily involved in the recovery works from last winter's floods in Yorkshire.
My instinct would be not to buy the house, but people have many reasons for wanting to live somewhere. If you still want to go ahead with the house, really, really check out the insurance side of things. I don't work in the team that advises insurers anymore, but in the past there have been restrictions on insuring new owners (ie: current policies extended but not transferred to new ownership), insuring houses built after 2004/5 (when the EA flood maps were introduced), although this has been reviewed recently with Flood Re. If this is OK, then check the existence of any flood defences, but beware that the EA has very few legal duties (a great many powers, but v few duties) to maintain flood defences - they just have to not make flooding worse than it would be in the natural state.
Presumably the property would be covered by the EA flood warning system? Worth checking
If the property runs up to a river you are likely to have "riparian responsibilities" regarding the maintenance of the river bank, private defences and conveyance of the river alongside your property.
Even if you resolve all these issues, flooding is heartbreaking. It's sudden (even with flood warnings, if can be very very fast), destructive (flood water is not clean river water, it's mixed up with sewage and sewers invariably overflow too) and can have you out of your home for months. I think there were people living in temp accommodation for nearly 3 years after the Carlisle floods of 2005.
If you PM me the name of the village/property postcode, I'll let you know which EA office to write to if you want further info on the flood history of the area. The sudden onset of deep flooding in a steep upland valley is very different to a few cm that dribble in slowly with 24 hrs notice. I'd avoid the first (some properties in Hebden Bridge flooded into the first floor level on Boxing Day, the weather changed so quickly we didn't foresee those floods until late in Christmas Day), but with the right kind of ground floor flooring, plaster, electrics etc I may consider the second for an amazing house.
Might also want to look at Living on The Edge and EA flood map and National Flood Forum.