Sadly, we have a similar situation with photos from my husband's side of the family. In 1963, his parents were dairy farmers on the mid north coast of NSW, when they were flooded ... it was the occasion which prompted Slim Dusty to write his song "When The Rain Tumbled Down In July".
Very very few family photographs survived; - most were washed out into the Pacific, and many of those which remained were badly water-damaged. Up to a point, maybe there's something to be said for storing photos in the roof space?