The investment will help to build 2,000 new flood and coastal defence schemes and better protect 336,000 properties in England over the next six years.
Mr Sunak said communities in Britain have been “hit hard” by severe flooding this winter, saying it is “right that we invest to protect towns, families, and homes across the UK”.
The funding - which doubles the £2.6bn spent on flood defences between 2015 and 2021 - is expected to be targeted in every region, and will be available from next April.
More money was expected as the Conservative manifesto in last year’s General Election promised £4bn in “new” funding for schemes across the country.
It is understood that despite being described as “new” money during the election and “additional funding” by Environment Secretary George Eustice last month - leading to the belief it would be added to previous levels of funding - the £4bn figure was meant as a baseline figure, as a new capital spending period meant the previous sum promised was not carried over.
Luke Pollard, Labour’s Shadow Environment Secretary, said: “Communities hit by floods are in no shortage of government press releases and promises.
“The proof will be whether this funding reaches the frontline without the strings that have been attached to previous money.”
But Mr Sunak said: “This Budget will be about delivering on our promises to the British people, and levelling up all parts of the UK is a big part of that.
“Communities up and down Britain have been hit hard by the floods this winter - so it is right that we invest to protect towns, families, and homes across the UK.”
The UK has been battered by a string of storms over recent months, leading to severe flooding across the UK - particularly in Wales, south Yorkshire and the Midlands.
Prime Minister Boris Johnson made his first trip to a flood-hit community yesterday, and was greeted by hecklers in Bewdley in Worcestershire.
Mr Johnson has been criticised for not visiting those affected sooner, and some called him a “traitor” as he viewed flood barriers - one person told him to “do your f***ing job” as he posed with teenagers for a selfie on a bridge in the town.
But others greeted him warmly and the PM said it was “too easy” for a PM to “come to a place in a middle of an emergency”, but that it was “not so easy, frankly, for the emergency services”.
Mr Johnson said he would “get Bewdley done” as he spoke to residents affected by the floods.
He said he was “so sorry to hear it” when he heard homes had been overwhelmed by as much as two feet of water.
He was later mobbed by members of the public as he continued his walk.
A number of people tried to shake his hand and to take photos as he made his way along the river.
He has also met members of the emergency services who responded when the water levels rose.
The Prime Minister joined them for a cup of tea and biscuits as he told them that the defence structures in the town were “pretty amazing”. He told reporters the flooding had “badly affected quite a lot of residents here”.
He thanked the Environment Agency and emergency services, before adding he would also “look at what we can do to make sure this doesn’t happen again”.
“We’re doubling the budgets we’ve set aside for investment in flood protection across the country from £2.6bn to £5.2bn,” he said.
The Chancellor is also set to announce a £120m winter defence repair fund to fix assets damaged in the recent storms as quickly as possible when he delivers his first Budget on Wednesday.
But in Calderdale, one of the areas hit hardest by the impact of Storm Ciara, council leader Tim Swift said: “One-off capital funding is not enough.”
He said: “Although community efforts to recover and build resilience are always incredible, we are simply unable to keep responding at the level required.
“The Council’s budget has reduced by £100m since 2010 and we have 250 fewer staff since the last major floods on Boxing Day 2015.
“We urge Government to grant us Tier 1 status to recognise this distinct and sustained level of threat and to unlock ongoing resources.
“We are pushing hard for a level of funding in the UK Budget on March 11 which recognises our challenge, equivalent to the support we received after the 2015 floods.
“Local people are telling us that they’re angry and they feel like the Calder Valley has been forgotten by the Government. One-off capital funding is not enough.
“With recurrent revenue funds of £3m a year, we could provide support and response teams in risk areas, and help sustain and develop more natural flood management initiatives – all key to our future resilience.”