Flood prevention schemes will get a £2 billion boost if the Liberal Democrats gain power.
The party wants to target the money at initiatives reducing upstream flooding and the knock-on effects in downstream and coastal areas, as well as providing more defences.
Former energy secretary Sir Ed Davey said: "Flooding is exacerbated by climate change so is hardly the fault of communities up and down the country that have been devastated by flooding.
"In government, it was Liberal Democrats pushing for proper funding for flood defences. The Conservatives have tried to do flood prevention on the cheap, because they simply don't care about the misery it causes."