Climate Change and Major floods.

Does climate change cause damaging floods is the wrong question, as Kevin Trenberth pointed out,  Every weather event contains an element of climate change because the atmosphere is 1C warmer and is holding 7% more moisture.  These may not look like very large or significant figures but the weather is very sensitive to change and very volatile.
Most of our rain comes from low pressure systems and we are familiar with those on our TV weather reports.This is a typical one approaching the UK.

---

The centre of the swirl is typically caused by warm water in the ocean and as the heat rises it goes into a swirl, anti-clockwise in the northern hemisphere and the opposite in the South. As it rises it causes a small vacuum or low pressure area, hence its name, and then we get to the important part. 

---

In another quote from Kevin Trenberth “Typical storms reach out a distance of about three to five times the radius of the rain dimension, and gather in the water vapour, to produce precipitation.”
The extra moisture in the atmosphere gets drawn towards the centre and concentrated where the rain falls and this gives an amount of water that would not otherwise be there.
There has been an increase in heavier rain events all round the world but not many go over the top and cause substantial floods and damage but as we head towards a 2C temperature rise and 14% more moisture in the atmosphere we should get used to the idea that one day a major flood will come to where you live.