Kiawah Island Digest June 2018 - Page 2

2 May 2017 June 2018 5 KICA Core Functions (Continued From Previous Page) the island’s water flow to rivers and marshes. Beachwalker controls 31% of the island, including everything on the ocean side of the parkway from the Main gate to the Vanderhorst gate, as well as the Sea Marsh Drive and Settlement areas Canvasback controls 33%, covering much of Turtle Point and the surrounding neighborhoods on Flyway, Surfsong and Glen Abbey. It is a common misconception that pond levels can be quickly dropped. With 75% of the island’s drainage flowing through two outfalls, it takes days to meaningfully lower water surface elevations. Egret Pond, Pintail Pond and Ocean Park have their own basins, while several smaller systems control the remaining areas. To alleviate a drainage “traffic jam” near Night Heron Park, a new outfall is being designed and engineered this year, with plans for construction to begin in 2019. A very early estimate is in the $400,000 range. The important project can help prevent the inconveniences that area flooding causes. Most of KICA’s 122 retention ponds are interconnected. In 2014, Connor commissioned the first hydrology study of the island, which took two years to complete. KICA needed a computer model to understand and predict the complexities of island drainage. The model was built and is maintained by Stantec, an international engineering design and consulting firm. Today, the team can use the model to assess the storm drainage system in advance, or to analyze what happened during a storm for future storm preparation. It gives KICA a timeline for opening valves at the drainage basins to forestall potential flooding. The program also shows many tide cycles the system needs to drain each basin, and what adjustments need to be made across the basins based on expected rainfall and the tide cycle. The hydrologic model is a significant tool in KICA’s infrastructure arsenal. One improvement Connor and Ellmers are studying is automated outfall technology to remotely open and close flood gates. A fundamental problem with a major outfall structure is that the gates have to be opened and closed manually, by hand turning a 48” diameter wheel, with the tides every six hours. Despite this, KICA simply cannot keep personnel on-island around the clock for as long as a storm might last. Automatic controls, designed and constructed to be operated remotely, would be mounted on the gates, and operated remotely by personnel safely off-island. They can be programed in advance, and have an emergency backup system, allowing the gates