University of South Florida researchers have found that Tropical Storm Debby swept an estimated 630,900 cubic yards of sand off three barrier islands in Pinellas County in June.
County officials say that restoring the beaches to their previous state could cost more than $25 million.
Officials will want to fix the beaches because they draw tourists and money to the area.
The June storm's three days of strong southerly wind eroded beaches that were already narrow.
The Tampa Bay Times reports that at Pass-A-Grille beach, the sand dune line retreated by nearly 12 feet and the entire area lost about 36,500 cubic yards of sand.
Sunset beach on Treasure Island lost 43,400 cubic yards.