The Bridge End Inn next to the river Usk in Crickhowell has had to close "for the foreseeable future" after the river burst its banks during the night.
Elaine Baker, who along with her husband Howard owns the pub, said her first thought was "oh no, here we go again" after waking up on Saturday morning to find more than 2ft of water in the downstairs bar area.
Elaine said that the pub rarely flooded despite its riverside location and the last time she could remember it happening to this extent was in 2003.
She said: "The cellar floods from time to time, which we expect. But to come downstairs and find the ground floor bar areas under water and furniture floating around was very upsetting.
"I must admit I shed a tear because there’s nothing we can do and it means we’ve got a lot of hard work ahead of us."
She said fire crews were at the scene and desperately trying to pump out the water. But she said they would be fighting a "losing battle" until the rain stops and the water levels start to subside.
"I think the rain’s starting to ease now, but it’s going to be a long time before we can pump all the water out. The cellar, with all our beer and cider kegs, bottles of wine and fruit juices, is completely submerged but we’re had that before and can deal with it. There’s about 2ft of water in the downstairs bar. Fortunately our living area upstairs - where I live with my husband and our big dog - is unaffected but it’s still very depressing to see all your hard work ruined. Hopefully we’ll be able to put in an insurance claim but that’s a long process and you’re never sure if they’ll pay enough to cover all the damage.
"You see people having their homes flooded on television, so I guess it’s worse for them but it’s very upsetting."
Mrs Baker said she only realised her pub had flooded when she tried to go downstairs. She said after the fire crews had arrived she then had to ring her staff to stop them coming into work. "Our chef’s in Cardiff so there’s not much point in him travelling in. We’ve got about a dozen people helping out here as well as the fire crews. Our poor dog hasn’t had his walk yet either!"The road from Crickhowell to Llangattock is impassable in places and the A40 is reported to have been closed at Glangrwyney by the flooding.