From The Blog
Record-Breaking Tidal Flooding: A Storm Recap and Damage Assessment
Yesterday, Kiawah Island experienced the impacts of a Nor’easter, combined with tropical moisture, which traveled up the eastern coastline. KICA has received several inquiries about this storm and our drainage systems. We wanted to share with you both details of the storm and its impacts.
On Thursday and Friday, Kiawah was forecasted for 2-4” of rainfall and minimal coastal flooding. KICA’s ponds were at or below normal stage levels. It was decided that the ponds had the capacity to handle this rainfall event. However, KICA closed all drainage gates, to reserve capacity in the ponds for the upcoming rainfall. On Saturday, KICA continued to monitor forecasts, including speaking with a local forecaster about Kiawah specifically. Forecasts had increased to 3-5” of rain and moderate flooding in Charleston Harbor. KICA continued to believe that it was prepared to handle what was expected to be mostly a rainfall event, with some nuisance flooding in expected low areas. Sunday morning, National Weather Service Charleston issued a revised forecast with 4-7” of rainfall, with the greatest rainfall occurring in the afternoon & evening, and major flooding in Charleston Harbor with the morning high tide.
On Sunday, Kiawah received approximately 3.3” of rainfall, which was within the 2-4” of rainfall forecast on Friday. However, unlike the forecast, the highest rainfall fell in our area during the morning hours, leading into a high tide at 11:30 a.m. Again, the ponds had capacity to handle the rainfall event. The 11:30 a.m. high tide was originally forecasted at 6.2 feet. However, by 11:30 a.m., the high tide was over 9 feet, rising to 9.96 feet at 12:00 p.m., according to the tide gauge at the Kiawah River Bridge. According to the Post & Courier, this was the highest non-tropical tide in Charleston’s history and the 4th highest tide if tropical events are included.
As we saw in this storm, some of a storm’s most potent impacts can be from storm inundation, especially if storm inundation coincides with a high tide. During a storm inundation, winds from a storm push water up onto the island on the ocean side, but also from the Kiawah River and surrounding marshland. Unlike a rainfall event, this type of flow can’t be addressed by the drainage system. Simply put, the island’s pond network is overwhelmed by the waters from a storm inundation. At this tide level, KICA drainage outfalls are also overtopped from the marsh, with marsh water accessing the pond systems. While proactive planning may create additional capacity for heavy rainfall, storm inundation is an insurmountable amount of water.
Impacts of the Storm
Once tidal flood water receded Sunday late afternoon, there were still areas of localized flooding. Electronic drainage gates were opened on Sunday late afternoon to begin the release of water from the Beachwalker & Canvasback drainage systems, which handles 70% of the island’s water. Our KICA team worked overnight to pump down Governors Drive between 1st Flyway & Yellowthroat Lane. Today, the Lakes team is working to release water from all drainage systems, in order to normalize pond levels. KICA also has a drainage contractor on island clearing drainage lines of debris on Kiawah Island Parkway, Governors Drive, and roads that experienced heavy tidal flooding.
Most roads were undamaged. However, Sea Marsh Drive, near Marsh Hawk Lane, received road damage from storm inundation. This area is being addressed by KICA’s contractors this week, so that it is able to be opened prior to the Christmas holiday. However, additional repairs will still need to be done in January. KICA has several other wash-out areas from the storm inundation, to include areas on Virginia Rail Road, Blue Heron Pond Road and along the leisure trail by Egret Pond.
Flood project 2, where the new outfall was built along Kiawah Island Parkway, had an associated berm which kept higher tides from Kiawah Island Parkway. This berm was overtopped, damaged and will require repairs.
Rhett’s Bluff dock had some missing boards, which have already been replaced today. Cinder Creek and Eagle Point appear to be fine. KICA staff are continuing to inspect crab docks, towers and leisure trails.
The beach experienced erosion from the storm. There is currently debris littering the beach. KICA does have 9 boardwalks with some damage, and they are currently closed. These include boardwalks 0 (Timbers), 1 (Duneside) and 8A (Sandcastle), as well as boardwalks 9, 10, 12, 13 & 15 (Eugenia Avenue) and 39 (Flyway). A structural engineer is currently assessing the KICA boardwalks. KICA will keep the membership updated on repairs to these boardwalks. Please continue to exercise caution on the beach.
KICA’s landscape crews, assisted by an emergency contractor, are cleaning up road debris. Roads on the front of the island and the major roads on the back of the island have been initially cleared. Tomorrow, KICA will continue to work on neighborhood roads on the back of the island. Main leisure trails from the main gate to 2nd Flyway have been initially cleared. Leisure trail work will continue tomorrow, as well.
We thank you for your patience as we continue to recover the island.