The Environment Agency (EA) is warning planners to think carefully before allowing shops demolished in the Boscastle floods to be rebuilt.
Floodwaters ripped through Boscastle on 16 August
North Cornwall Council's planning committee has deferred two applications to rebuild shops in the harbour area, which the EA says are in a flood plain.
The floods on Monday 16 August caused
millions of pounds of damage.
A 3m (10ft) wall of water crashed through the village when 77mm (3in) of rain fell in just a couple of hours.
Mike Robins, the EA's planning and corporate services manager, said: "We are giving planners an idea of the potential risk of new and redeveloped buildings.
"It has to be a material planning consideration. It's not the only planning consideration and the committee has a very difficult job in considering all the other factors that must be considered in terms of regeneration there."
But the owner of the Museum of Witchcraft at Boscastle, Graham King, says he would rather see the authorities finding alternative routes for flood water than not have the harbour redeveloped.
He said: "I don't think there's any reason the river couldn't be made a metre or so wider.
"We have constrictions like the little bridge by the museum. It would be a crying shame to lose it, but if we have to at least the water would go out to sea instead of going on the road."
Debbie Beszant, owner of a shop demolished after the floods in Boscastle, said she was angry that she might not be able to rebuild it.
The EA said her gift shop Things was in the flood plain and the planning committee deferred an application to rebuild the shop on the same site.
Ms Beszant, who attended the meeting, said: "The delay is frustrating."