Ian Stephens, of Cumbria Tourism, said there was a need to "reassure" travel firms and "get the message out businesses are operating as usual".
He said the reopening of the A591 was a "massive priority" after a four-mile section between Keswick and Grasmere was closed by a landslide.
Some areas were hit by flooding three times in as many weeks in December.
Mr Stephens said the impact on visitor numbers was "still unfolding".
"We've seen a collapse in forward bookings, which is a very worrying trend," he said.
"Accommodation held up reasonably well over the Christmas period.
"As you'd expect there were fewer day trippers around and fewer people in the towns and villages, which has an economic impact, and there's an urgent need to get a positive campaign on the road."
Storm Desmond saw a record amount of rainfall in the county over the weekend of 5 and 6 December, followed by more in the rest of the month.
Carlisle, Keswick, Appleby and Glenridding were badly affected, with water deluging homes and shops.
Cumbria Tourism launched a social media campaign before Christmas and is continuing to work with Visit Britain and Visit England.
"It's a big job to do," Mr Stephens said. "We're talking to coach and travel operators so they don't change their itineraries.
"There's a big danger of them saying, 'We'll wait and go somewhere else in the UK until things are better in Cumbria,' and we then lose a huge number of bookings across the year."
Keswick Tourism boss Linda Furniss, said last week that local businesses had "suffered".
Flooding in Cumbria has led to a "collapse" in bookings in the county, a tourism chief has said.