HUMAN INFLUENCE ON THE EBB TIDAL DELTA, BIG SARASOTA PASS, FLORIDA

Big Sarasota Pass is located between Lido Key on the north and Siesta Key, a drumstick barrier along the central Gulf Coast of the Florida peninsula. This inlet has been the site of a well-developed, asymmetrical ebb-tidal delta at least throughout recorded history.

Net longshore transport along this coastal reach is north to south with rates typically up to 50,000 m3/yr. There has been a tendency for the inlet to migrate to the south as is typical with an inlet and the adjacent updrift end of a drumstick barrier island. As development of Siesta Key took place beginning primarily in the 1920s, there was concern about this slow, southerly migration of Big Sarasota Pass. In the early 1960s a series of non-integrated protective structures was constructed along the south side of Big Sarasota Pass in order to stabilize the channel and prevent erosion. The Lido Key side of the inlet channel was not stabilized so that there was continued bypassing of substantial volumes of sand across the ebb delta which provided sediment bypassing to nourish the prograding north end of Siesta Key

The result of these circumstances coupled with a diminishing tidal prism in the inlet due to dredge-and-fill construction in Big Sarasota Bay and beach nourishment on the updrift Lido Key, caused the ebb delta to enlarge and to migrate further to the south. Now this bypassed sand is moving onshore at Siesta Key several hundred meters further south than it did a century ago. The consequence is that the northernmost end of Siesta Key is now eroding due to an absence of sediment supply. That sediment supply is being transferred to a more southerly location where the beach is prograding rapidly.