Delray Beach Summary & Conclusions

• In the 12 months since construction 122,000 cubic yards of sediment has eroded from the total Delray Beach study area.  This loss is comparable to previous first year losses after the renourishments at Delray Beach.
• The shoreline since the 1992 construction has retreated an average of 35.2 feet.  The rapid shoreline loss is expected post-construction as the construction beach develops toward the natural equilibrium shoreline.  Based on previous projects, it is expected that this loss will slow down over the next year.

• In the 24 month period following the completion of the project the MHW shoreline retreated an average of 65.2 feet.  The high erosion and shoreline loss seen in the first and second years post-construction is similar to losses seen following the 1973, 1978 and 1984 projects.  The high losses may also be related to Tropical Storm/Hurricane Gordon which impacted the coastline of Delray Beach November 15 through 19, 1994, three weeks prior to the survey.

• The shoreline since the 1992 construction has retreated an average of 52.7 feet.  As occurred in previous Delray Beach projects, the shoreline acreted (+12.6 feet) between two year and three year surveys.  This appears to be the result of the shoreline and profile reaching equilibrium and as a result becoming somewhat more stable.

• The project area mean high water shoreline is an average of 62 feet wider than the pre-construction shoreline position.   The shoreline has reached an equilibrium condition relative to the construction profile and has become somewhat more stable.

• The project area mean high water shoreline is an average of 33 feet wider than the 1992 pre-construction shoreline position.  Between January 1999 and February 2000, the shoreline in the project area receded an average of 25 feet.  This recession rate is an acceleration compared to the trend of recent years, and is likely the result of a high wave climate during the year, dominated by Hurricanes Dennis, Floyd, and Irene.

• Since 1973, the City of Delray Beach has conducted five beach restoration projects using sand from offshore of the City.  Approximately 6 million cubic yards of sand has been placed as a result of the City's beach preservation efforts.  A volume of 3.8 million cubic yards, or 63% of the total volume placed since 1973 remains within the City limits.  Since the initial nourishment of 1973, the City has maintained the beach through beach renourishment on four occasions, including 1978, 1984, 1992 and 2002.
• The fourth periodic beach renourishment project constructed by the City of Delray Beach was built in February and March of 2002.
• The one year post-construction survey (March 2003) indicated that the expected adjustment to natural equilibrium slope had progressed.  During the two year post-construction period, sand is expected to continue to move offshore until the system reaches a natural equilibrium slope. Shoreline measurements taken in March 2003 have documented an average advance of 190 feet over the project area, compared to the pre-construction condition.

• Of the 1,230,000 cubic yards placed in 2002, the May 2004 survey indicated that 915,760 cubic yards (or 74%) of the original fill remains within the project area.  In the center of the project area between DEP monuments R-181 to R-187 approximately 56% of the original fill remains.