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North Captiva Island Erosion Control Project (1998-2010)

Dredging of Redfish Pass ebb tidal shoal as a sand source for beach restoration on Captiva Island in 1981 and 1989 resulted in impacts to adjacent beaches.  Humiston & Moore Engineers (H&M) was selected by the property owners on the north side of the inlet to design an erosion control project.  The project design consisted of three low profile T-groins, designed specifically to balance beach stability with continued littoral transport in order to avoid downdrift impacts.  This innovative design was developed by H&M engineers, and was the first of its kind constructed in Florida when it was completed in 1998 at a cost of approximately $500,000.  The unique structure design employed sheetpile for precise elevation control that allows sand bypass to occur without the downdrift impacts often associated with conventional groins, and a rock apron to stabilize the sheetpile and minimize wave reflection. 

This project stabilized approximately 800 feet of shoreline adjacent to the north side of the inlet that had been eroding at a rate of over 60 feet per year.  There was no beach fill placed in conjunction with the structures, no maintenance nourishment has been needed, and there have not been any downdrift impacts.  H&M was also appointed by DEP as a member of a Technical Advisory Committee to complete an Inlet Management Plan for Redfish Pass. 

Long term impacts to adjacent shorelines from the dredging in the 1980s have continued, both on Captiva Island south of Redfish Pass, and north of the inlet on North Captiva Island updrift of the T-groin project.  In 2004, Hurricane Charley cut a new inlet through the narrowest part of North Captiva, approximately 6,000 feet north of the inlet.  This new inlet, known as Charley’s Cut, compounded erosion problems by trapping sand.  Although the original T-groin project continues to perform well in stabilizing the south tip of the island, homes between the T-groin project and Charley’s cut were threatened by erosion.  Since that time, the cut has closed and the collapsed ebb shoal has moved south providing protection to the property owners and adding fill to the T-groin field. 

After 12 years of being exposed to strong tidal currents, waves, and a major hurricane, the structures required maintenance to restore the rock apron.  In 2010, the T-heads were maintained through the placement of additional rock and the structure continues to function as designed.

H&M Staff that worked on this project:

  • Ken Humiston, P.E., Project Manager/Project Engineer

  • Brett D. Moore, P.E., Assistant  Project Manager

  • Mohamed Dabees, Ph.D., P.E., Regional & local coastal process modeling, nearshore and inlet morphology modeling.

  • Steve Foge, Monitoring & Analysis

Project Tasks Included

  • Hydrographic mapping

  • Analysis of erosion control alternatives

  • Hydrodynamic modeling 

  • Innovative T-groin design

  • Construction Observation

Scope Included

  • Alternatives Analysis

  • Design and Permitting

  • Contract Documents & Specifications

  • Construction Observation

  • Project Monitoring

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