Treasure Island / Long Key Summary & Conclusions

• Erosion of both (Long Key and Treasure Island) fill areas has occurred since completion of the fill placement.  Total losses from within the fill areas only at the time of the August 1999 survey were -169,913 cubic yards at Long Key, and -59,516 cubic yards at Treasure Island.
• Approximately 123,022 cubic yards of material had accreted south of the fill area on Long Key during the 3-year monitoring study.  This equates to 67% of the material eroded from the fill area during the 3-year monitoring period, or 49% of total fill placement.  This indicates a strong trend of southerly transport of material along Long Key.  This southward transport of material out of the fill area has been observed during the monitoring of previous beach fill placements on northern Long Key, and emphasizes the importance of continuing renourishment of the Upham Beach Park area, since this area acts as a feeder beach providing a souce of nourishment for the remaining 3.5 miles of Long Key's beaches to the south.
• The net volumetric changes adjacent to the fill area on Treasure Island were an accretion of 38,847 cubic yards along the 3,000-foot reach of shoreline to the immediate north of the fill area, and a net erosion of -2,823 cubic yards along the 3,000-foot reach of shoreline south of the fill area.  During the third year of project monitoring the erosive trend observed in the first two years reversed, as 20,507 cubic yards of material accreted south of the fill area.  The data suggests that material is being dispersed out of the fill area in both directions, but primarily to the north.

• In contrast to the expected trend, net accretion of both (Long Key and Treasure Island) fills occurred during the first year of project monitoring.  A total accretion of +24,485 cubic yards was measured along the Long Key survey area and +7,260 cubic yards of accretion was measured along the Treasure Island survey area.  In both cases some spreading of the project fill into the adjacent coastal areas was noted.  Infilling of the two borrow areas also occurred during the first year of project monitoring, with Blind Pass gaining 1,049 cubic yards and Johns Pass gaining 58,237 cubic yards of material.