FOUR of the Sunshine Coast's seven major dams were overflowing this morning, well ahead of the worst of the downpours expected from Cyclone Marcia.

Borumba, Ewen Maddock, Lake McDonald and Wappa dams had exceeded capacity, the over-spill adding to downstream flooding.

SEQWater reported that all of the flood storage capacity of Somerset and Wivenhoe dams behind Brisbane was still available.

Wivenhoe had 100% of its 1,967,000 megalitre flood storage available and Somerset 99% of its 721,000ML.

On the Sunshine Coast, Baroon Pocket Dam in the Blackall Ranges was holding 41,310 megalitres or 67.7% of capacity, Borumba 46,240ML (100.6%), Cooloolabin, in the north, 7526 ML (54.4%), Landsborough's Ewen Maddock 18,983ML (114.4%), Noosa's Lake Macdonald 8534ML (106.4%), Poona 615ML (94%) and Wappa Dam 5353ML (114%).