County and city staff assessments conducted after the storm’s passage by the coast earlier this month
The recently renourished south Siesta Key Beach and Casey Key appeared to have suffered more erosion than other areas of the county as a result of Tropical Storm and eventual Hurricane Hermine, staff of the Sarasota County Environmental Protection Division reported after assessments on Sept. 1, 2 and 6.
As for the city of Sarasota: City Engineer Alexandrea DavisShaw told The Sarasota News Leader via email this week that sand loss on Lido Key associated with the storm was estimated at 50,000 cubic yards. The city and the U.S. Army Corps of Engineers have been awaiting a decision by staff of the Florida Department of Environmental Protection regarding their application for a Lido renourishment project. (See the related story in this issue.
Regarding the $21.5-million south Siesta Beach initiative — which was completed in late April — county staff reported that an area at Turtle Beach showed signs of beach erosion and approximately 5 to 10 feet of dune erosion, including a limited loss of some of the recently planted dune vegetation at the south end of the project area.
Additionally, staff observed that high tide, storm surge and wave energy in the Gulf of Mexico during Hermine resulted in approximately 1 to 5 feet of dune erosion on Casey Key, Manasota Key and North Manasota Key. The storm also produced widespread coastal flooding on Siesta Key, especially in the area of North Beach Road and Avenida Messina near Siesta Village, the report notes.
Sand was deposited on beaches both from dunes and offshore sand bars in several areas, the report says.
Hermine also caused limited property damage to dune walkovers and stairs, the county report notes. Many sea turtle nest markers were observed washed out, the report adds, and some nests were buried by deposited sand.
As of Sept. 10, Mote Marine reported that a total of 4,447 loggerhead nests and eight green turtle nests had been reported in the county, with Casey Key continuing to account for the largest number: 2,053 — including all the green turtle nests. During the 2015 nesting season, Mote records show that a total of 2,410 nests were logged, with Casey Key again leading the way. It had 958 loggerhead nests and 29 green turtle nests last year.
Nesting season runs from May 1 through Oct. 31.
Waves over-topped a portion of North Casey Key Road, depositing limited sand on the roadway, and damaged the wooden guardrail along the road, the county report continues. However, “the step revetment at that location continues to protect the roadway from erosion,” the report notes.
A geotextile sand container system located at 2209, 2305 and 2309 Casey Key Road has been exposed again, the report continues. Staff had documented that this area was experiencing exposure prior to effects of Tropical Storm Colin
In June, the report explains. The owners had covered the container system after Colin, as required by permits, the report adds.
Dune erosion at 2120 Casey Key Road has further exposed a wall, the report says, and the eroded bluff is approximately 2 feet seaward of the edge of pavement of Casey Key Road.
The house at 2007 Casey Key Road “experienced further exposure of foundation and underpinnings due to dune erosion,” the report continues. “Most of the recently placed sand underneath the wooden deck has been washed away,” the report adds. “Several of the previously installed sand bags have shifted location, but many of the remaining bags continue to provide protection to the foundation.”
Sand deposition also was observed along the seawall at 2411 Casey Key Road, the report says.
Staff provided other details about dunes on county beaches, staff observed:
- Sand deposition at Caspersen Beach.
- Minor loss of dune vegetation.
- Dune erosion further exposed the pile foundation at 6810 Manasota Key Road, a site “that experienced severe dune erosion” during Tropical Storm Colin earlier this year. However, evidence of sand deposition also was observed in this area.
- Minor dune vegetation loss was observed at Manasota Public Beach.