Top Gard official Thierry Dousset told BFM-TV that about 750 people were evacuated from five campsites.
The Gard government also said four German children were hospitalised for hypothermia in Bagnols-sur-Ceze.
BFM-TV reported that the missing person was a 70-year-old German.
Jean-Yves Chapelet, mayor of Bagnols, said many Dutch tourists were among the 350 campers evacuated there.
Authorities also said 119 children in nearby Saint-Julien-de-Peyrolas have been sent to an emergency shelter.
The rescue was carried out by hundreds of firefighters who were backed by four helicopter in the evacuation.
More to follow…