Old Dunedin Pass (Big Pass)

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Old Dunedin Pass (Big Pass) - An old pass, capped-off due to significant shoaling from longshore current compounded by several tropical storms.

Old Dunedin Pass once separated Caladesi Island and Hog Island (Clearwater Beach). The original opening was located further south, closer to Clearwater Beach, when the orientation of all entrance channels in the area were northeast to southwest. Construction of what is now Memorial Causeway/SR 60, the channelization of St. Joseph Sound and Clearwater Harbor, the dredging and filling of land masses, have mostly contributed to the geological instability of the pass. The opening of Clearwater Pass (Little Pass) in 1848, and Hurricane Pass in 1921 have contributed to the instability of Dunedin Pass (Big Pass) by altering the currents entering and leaving Clearwater Harbor.

Each pass between barrier islands has a "tidal prism", or an area of backwaters, in the shape of a quadralateral which is flushed through the pass. When adjacent passes open or close, they alter the tidal prism of the original pass. In this case, the tidal prisms of the new Hurricane Pass to the North, and mechanically dredged Clearwater (Little) Pass to the South had encroached on that of Dunedin Pass. The channel had realigned, shoaling had occured, and the "river of sand" guided by breaking waves and the longshore current had capped-off the pass and created a backwater lagoon.

A combination of natural and human-induced changes, therefore, have led to the closing of Old Dunedin Pass.