It's not like the flash floods which hit Boscastle in Cornwall, or those of Lynton and Lynmouth in North Devon where people, boulders, and cars were washed into the harbour and out to sea without any warning - these folks in Cumbria had advance environmental agency and meteorological office advice of the flooding.
Not belittling their situation, but if you choose to live bang on the fringes of a major river then you're always aware you can be flooded. They face a weekend of further rain and gales, and the drainage of that rain off the high ground could take another ten days to percolate down into the river.
One person is suspected to have probably lost their life, some policeman who was standing on a bridge which was swept away by the surge of the water.
Other reports of missing people are majorly due to roads and communications being down, it's by no means a disaster - but there will be a big mopping up operation to follow in the months to come.
The met' office are speaking in terms of the rainfall being the highest ever recorded in Cumbria, something like fourteen inches of rain is estimated to have fallen over the last few days.