Erosion observed on Siesta, Casey and Manasota keys as a result of Hurricane Idalia’s ‘onshore winds and rough surf,’ county staff reports

Numerous Manasota Key homes ‘further imperiled’

County Commission Chair Ron Cutsinger surveys part of the damage to Manasota Key Road. Last week, he and Commissioners Mark Smith and Joe Neunder toured areas affected by Hurricane Idalia, accompanied by county staff members, staff reported on Facebook. Image courtesy Sarasota County via Facebook

Because of “onshore winds and rough surf,” the beaches on Siesta, Casey and Manasota keys all experienced erosion as a result of Hurricane Idalia’s passage through the Gulf of Mexico on Aug. 29 and 30, Sarasota County Environmental Protection Division staff has reported.

Manasota Key appears to have taken the brunt of the storm, the document indicates, with homes that sustained damage from Hurricanes Ian and Nicole last year “further imperiled by Hurricane Idalia.” The report adds, “Other properties on Manasota [Key] experienced significant new erosion that resulted in damage to previously undamaged structures.”

Further, as The Sarasota News Leader has noted, the segment of Manasota Key Road north of the public parking lot for Blind Pass Beach Park collapsed. Additionally, the report says, “A historic rock revetment and a water utility pipe that run along the seaward side of Manasota Key [Road] were exposed by the erosion, and sand covered the road near the northern extent of the public beach. Very little dune vegetation remains along the norther section of Blind Pass Public Beach.”
That damage occurred in the area where the county paid for beach renourishment that took place in 2020, the report points out.

Conversely, the report adds, “The public beach experienced only minor erosion of the sandy beach and very minor impacts to dune vegetation.”

In regard to the county shoreline in general, the report notes, “Hurricane Idalia did not appear to have caused widespread wind-related damage to structures. The event resulted in localized flooding and a wide range of dynamic erosional changes to our coastline. Storm surge and wave action, which were exacerbated by the blue moon high tides, pushed sand landward into backyards, onto decks, and into the ground-levels of several structures on Manasota Key,” the report says.

The report was prepared by Howard Berna, manager of the county’s Environmental Permitting Division, and Staci Tippins, an environmental specialist in that division.

Siesta Key

This Aug. 31 photo shows erosion at Turtle Beach Park. Photo courtesy Sarasota County

During the staff members’ visit to Turtle Beach on Siesta Key, they observed “some leveling and recontouring” in the area of the South Siesta Key Beach Repair Project, which was completed in June to mitigate damage that Hurricane Hermine inflicted on that part of the island’s shoreline in 2016, just months after the county had finished its second renourishment of the area. (See the related article in this issue.)

The post- Idalia report adds, “The beach appears to have narrowed, but sand lost due to [Idalia] appears to remain within the system. Large areas of dune vegetation planted as part of the beach restoration project remained in place.”

During a visit to the property located at 7816 Sanderling Road, which marked the northern end of the Beach Repair Project limits, staff found that the area “experienced substantial sand accretion with the rock revetment being nearly completely covered by deposited sand.”

These are pre- and post-Idalia photos of the property located at 7816 Sanderling Road. Photos courtesy Sarasota County

Staff also visited the property located at 9230 Blind Pass Road, which — the report notes — “is located at the very southern end of Siesta Key adjacent to Palmer Point Park.” The report continues, “This site regularly experiences impacts from storm events.” Sand placed on the seaward side of a wall on the property during the beach repair project late this spring was lost, the report says. “As a result, the structure continues to be in direct contact with the Gulf of Mexico and remains vulnerable to damage.”

The report also points out that the swimming pool on the site “was partially filled with sand.”

On the northern part of the island, Beach Access 1, on North Shell Road, “was inundated” when staff visited the site. Moreover, the report continues, “Private fencing was damaged and sand loss was observed, which caused additional concrete rubble to be visible …” The concrete slab at the handicapped parking space was undermined, as well, the report notes.

Beach Access 2, the report points out, “exhibits regular bouts of erosion and accretion. Hurricane Idalia removed sand from this segment of beach, as evidenced by … pre- and post-storm photos.”

The photos show the old groin on a parcel that Siesta resident Mike Cosentino owns. After Idalia, as the report points out, the structure is more exposed “and interfacing with wave action …”

As for Siesta Public Beach: The report says, “The low elevation of the wide [beach] allowed Gulf waters to travel into and beyond the vegetation line. Localized flooding of pedestrian sand paths and pockets of standing water on the beach were observed.”

Casey Key

These photos show pre- and post-Idalia conditions on Casey Key. Photos courtesy Sarasota County

On Casey Key, staff noted that the step revetment areas on the northern end of that barrier island experienced wave energy that was “still quite active” during staff’s visit on Aug. 31. The waves were producing “oversplash across the road,” the report says, adding that road “damage also was observed at each step-revetment area, with large portions of delaminated asphalt creating displaced ‘mats’ on the road surface.”

A ”couple of small areas of eroded roadway” were observed in the vicinity of 712 N. Casey Key Road, the report continues, “but the road was passable. Guardrail damage was also noted at the step-revetment in the 712 N. Casey Key road area.” Further, the report says, “Several of the rocks along the top of the step revetment near 316 N. Casey Key Road” were missing; a county crew was in the process of replacing them.

The report also discusses the area between the parcels located at 2207 and 2120 Casey Key Road, which have a seawall on the Gulf. Because of wave action and “changes observed along the seawall,” the report explains, “it appears that 18 to 24 inches of sand was removed from the area at the wall.”

Moving on to the segment of the island located between 2110 and 2100 Casey Key Road, staff found that the county-installed sandbags south of the bend in the road “sustained damage but remained intact to provide protection to Casey Key Road and existing cabana structures.” However, Hurricane Idalia lowered the beach elevation, “exposing the bottom row of TrapBags,” which are an oversize type of sandbag. Further, the report says, “Staff observed sandbars immediately offshore in this area, so it is likely that the sand that was removed from the beach remains in the system but was transported offshore.”

That portion of the report also notes, “The County is actively developing plans and pursuing permits for stabilizing this area with a more permanent structure.”

Additionally, staff visited the area of the island between 2100 and 2016 Casey Key Road, the report says. “Several privately installed TrapBag systems are located south of the County’s TrapBag structure,” the report explains. “These structures exhibited signs of damage but continued to provide a level of shoreline protection for these properties.”

The owners of the residences standing from 2016 Casey Key Road through 2100 Casey Key Road recently won “Coastal Setback Variance authorization for construction of a seawall,” the report adds. The owners are “going through the state permitting process for the proposed seawall.”

At 2007 Casey Key Road, where a seawall recently was constructed, the beach lost about 2 feet of elevation seaward of that wall, the report says. Wave run-up was at the wall during staff’s visit. Additionally, “wave refraction at the wall caused more severe erosion at the north and south ends of the wall, with the bluff nearly reaching the landward edge …”

These are pre- and post-Idalia conditions at the property located at 2007 Casey Key Road. Photos courtesy Sarasota County

More details about Manasota Key

Among other examples of the damage to Manasota Key, staff noted that Idalia “eroded all of the dune vegetation that was landward of the home” standing at 6780 Manasota Key Road “and undermined the home by about 10 feet. A portion of the slab-on-grade foundation failed” and was lying on the beach.

At 6810 Manasota Key Road, which was the “second to last northern property that received sand [during the recent renourishment project] … [a]ll of the dune vegetation was washed away, and the home was undermined by 12 feet on the north side.”

These are pre- and post-Idalia photos of the property located at 6780 Manasota Key Road. Photos courtesy Sarasota County

Between 7090 and 7270 Manasota Key Road, the report says, a seawall was completed earlier this year after the owners of the parcels obtained a Coastal Setback Variance for that construction. “Hundreds of cubic yards of beach compatible sand were added on the landward side of the wall to bury the wall tie-backs,” the report points out. “This area experienced erosion on the seaward and landward sides of the new wall during Hurricane Idalia. Sand elevations on the landward side of the wall were lowered” by 1.8 feet to 3 feet, while sand on the seaward side was scoured, with elevations reduced by 3 feet to 6 feet. “Residential structures did not appear to have sustained damage in this area,” the report adds, “but staff noted minor damage to accessory structures such as decks and detached sheds.”

Further, a septic tank located on the southern side of the home at 7270 Manasota Key Road “was exposed by erosion.”