Tropical Storm Debby

Post-Debby Beach/Dune

Damage Assessment Report Sarasota Florida

By Weiqi Lin P.E., Ph.D. Coastal Resources/Community Services

June 29, 2012

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BACKGROUND AND SUMMARY Tropical storm Debby formed on June 23, 2012. With maximum sustained wind speed of 45 mph, the storm moved northeast very slowly at 3-4 mph. In Sarasota County, Debby caused major coastal flooding, severe beach/dune erosion and property damage, due to its slow movement, location, long duration of heavy rainfall, and steady winds. The storm surge was estimated to be about 3-5 feet. On June 25 & 26, 2012, Sarasota County Coastal Resources staff conducted beach/dune damage assessment along the countys Gulf shoreline, and found the following:

Major coastal flooding occurred on north Siesta Key. A large portion of Beach

Road was flooded during the storm. Severe beach/dune erosion occurred on south Siesta Key, Casey Key and

Manasota Key. There was 10-20 feet of dune erosion noted at many locations. In some areas, more than 30 feet of dune was lost.

Three residential structures are imminently threatened, at the edge of the newly

eroded bluff on Manasota Key. On Casey Key, one residential structure is threatened by coastal erosion.

Structural damage to decks and dune walkover structures were documented.

Many dune walkover structures were washed out. Heavy loss of sea turtle nests and native dune vegetation was observed. Fallen

palm trees and Australian pine trees were also noted. Significant devastation to the nesting shorebirds was reported by the Sarasota

Audubon Society. Entire colonies were lost from Longboat Key down through Siesta Key, with similar impacts suspected on Manasota Key as well.

A recently constructed sandtube was exposed on Casey Key. A step seawall was

undermined by wave action on Manasota Key. BEACH AND DUNE CONDITIONS Siesta Key Due to its low elevation, Siesta Key is vulnerable to coastal flooding, and has a long history of flooding during storms. North Siesta Key has the lowest elevation of 4 to 5 ft. NGVD and suffered major flooding during Tropical Storm Debby. Several inches to a foot height of water was documented on Beach Road (Figs. 1-3). Most of Siesta Key public beach was covered by waves and white-caps (Fig.4). Severe erosion was observed at the southern most portion of Siesta Key. It is estimated that 20-30 ft. of beach has eroded away at Turtle Beach Public Park. The boat ramp at

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Blind Pass Lagoon was flooded. South of Turtle Beach Public Park, from Fishermans Cove and Fishermans Haven condos down to the Palmer Point Park area, most of the restored beach and restored dune vegetation were washed away (Fig.5). The rock revetment in front of Fishermans Cove and Fishermans Haven was exposed for the first time since the construction of the South Siesta Key beach nourishment project. Several feet of sand was pushed up onto the most southern residential property at 9230 Blind Pass Road (Fig.6). Casey Key Casey Key has a higher elevation of 13-14 ft. NGVD. A small portion of Casey Key Road experienced a flooding problem due to heavy rainfall. Waves over-topped a gulf-front portion of North Casey Key Road. The road was covered with 2-4 feet of sand and not passable during the storm (Fig.7). Debby has caused severe dune/beach erosion. It is estimated about 10-20 feet of dune erosion has occurred throughout Casey Key, due to the combined effects of high wave energy and high tide. The residential structure at 2007 Casey Key Road was threatened by the receding bluff line (Fig.8). A recently constructed sandtube at 2209, 2305, 2309 and 2315 Casey Key Road was exposed (Figs.9-10). More than 30 feet of dune has eroded at that location. Dune vegetation has been washed out, and structural damage to decks and dune walkovers was also observed. Many sea turtle nests have been over-washed. Manasota Key Storm surge and high waves generated by Debby have caused severe erosion on most of Manasota Key. Up to 20 to 30 feet of dune was eroded away throughout most of Manasota Key and North Manasota Key. Numerous sea turtle nests were over-washed and dune vegetation was washed away. Many palm trees were laying on the beach. Big Australian pine trees were also down. Structural damage to decks and dune walkovers was documented. Some dune walkover structures were washed out. The worst erosion occurred from the Sarasota/Charlotte county line north to Blind Pass Park (Middle Beach), and from Blind Pass Park up to just south of the Pearl Motel (7990 Manasota Key Road). At least three residential structures (7160, 7110 Manasota Key Road and 6116 Gnarled Oak Drive) were threatened, at the edge of the newly eroded bluff line (Fig. 11 & 12). The foundation of the residential structure at 7160 Manasota Key Road was undermined and the residence is imminently threatened (Fig.13). More than 30 feet of dune eroded away in front of 7100 Manasota Key Road, and the steps of the dune walk-over structure were washed away (Fig.14). A step seawall at 6110 Manasota Key Road was undermined by wave action (Fig. 15). Two decks at 6210 and 6260 Manasota Key Road were damaged. A portion of Manasota Key Road at the north end of Blind Pass Park was threatened by dune erosion (Fig.16). The bluff has eroded all

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the way to the edge of that portion of the road (about 200-300 ft long). There is approximately 40 feet of dune estimated to have eroded away at this location. SUMMARY In Sarasota County, Tropical Storm Debby caused major coastal flooding, severe beach/dune erosion and coastal property damage. The storm produced significant impacts on our coastal communities, coastal environments and coastal systems. In terms of flooding and beach/dune erosion, Debbys effects were equivalent to those of a much higher category storm. ATTACHED PHOTOS

Figure 1. Waves over-topped the most northern portion of Beach Road, causing major coastal flooding in this area.

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Figure 2. Flooding at Public Beach Access#3. More than a foot of water and two feet of sand covered this portion of Beach Road.

Figure 3. Flooded Beach Road at the exit of Siesta Key Public Beach main parking lot.

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Figure 4. Most of Siesta Public Beach was covered by waves and white-caps.

Figure 5. Restored beach, dune and native dune vegetation were washed out in front of Fishermans Cove and Fishmans Haven condos.

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Figure 6. Several feet of sand was washed on shore at 9230 Blind Pass Road.

Figure 7. Waves washed sand on top of a Gulf-front portion of North Casey Key Road. The road was impassable during the storm.

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Figure 8. The residential structure at 2007 Casey Key Road is threatened by the eroded bluff. The wooden deck suffered structural damage and collapsed.

Figure 9. This photo shows the beach/dune conditions in front of 2209, 2305 and 2309 Casey Key Road on May 1, 2012. It was taken by staff during a pre-storm beach/dune condition inspection for comparison with post-storm beach/dune inspections.

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Figure 10. This June 26, 2012 photo was provided by Mote Maine Lab showing more than 20 feet of dune eroded away by Tropical Storm Debby. The sand tube was exposed just two years after construction.

Figure 11. The residential structure at 7110 Manasota Key Road was threatened by beach/dune erosion. The wooden deck collapsed and the dune-walkover was washed out. The adjacent neighbor at 7160 Manasota Key suffered similar damage.

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Figure 12. The receding bluff line also threatened this residential structure at 6116 Gnarled Oak Drive. The wooden deck collapsed and the dune-walkover washed away.

Figure 13. The foundation of the residence at 7160 Manasota Key Road was exposed after the sand under the deck washed out. The residential structure is imminently threatened.

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Figure 14. More than 30 feet of dune eroded in front of the residence at 7100 Manasota Key Road. The dune walkover structure is damaged and the steps washed away.

Figure 15. A step seawall at 6210 Manasota key Road was undermined by wave action. A big hole was created landward of the seawall and the deck was structurally damaged.

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Figure 16. The bluff eroded all the way to the edge of a gulf-front portion of Manasota Key Road (about 200-300 ft ) and approximately 40 feet of dune was estimated to be eroded away at this location.

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By Weiqi Lin P.E., Ph.D.Coastal Resources/Community ServicesBACKGROUND AND SUMMARY