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Consultants urge a study baseline for Isle of Palms without recommending an immediate policy change
Summary
Consultants presenting the fourth Olsson study told the Isle of Palms committee that the town should adopt a study baseline (distance from development to dune crest) for analysis, but they will not propose an immediate regulatory change; they recommended adding upper-beach metrics to the traditional offshore volume measure.
Consultants from the Olsson team gave an interim briefing to the Isle of Palms Beach Committee on the technical foundations for measuring "healthy beach" and recommended the committee adopt a study baseline for analysis rather than immediate policy change. Chris, the lead presenter, said the study baseline would be "a distance seaward of the development to a dune crest" that the consultants would use to compare alternatives, not a town-adopted regulatory line.
The consultants explained why standard offshore metrics can miss upper-beach conditions. They described the commonly used 380 cubic yards-per-foot metric and the use of a minus-3 reference in cross‑sectional volume calculations, and said a single offshore measure may understate damage to the upper beach and dune. Chris warned that "using one number that 380 minimum may not tell the whole story of really what's going on with the overall beach system" and suggested adding a second metric that tracks upper-beach width or dune elevation.
Committee members pressed on how the study baseline would relate to existing regulatory lines and development limits. The consultant clarified that Hilton Head's 1999 OCRM baseline functions as a regulatory maximum-build line, not a metric of beach health, and told the committee that "the town of Hilton Head has never formally adopted anything other than a line that says we are not allowing development any further than that." The Olsson team said their deliverable will recommend a consistent study baseline for the Isle of Palms study area and explain how it was chosen, leaving formal adoption to the city.
The consultants said the work ahead will refine alternatives—no-action, nourishment-only, and combinations that include structures—produce initial cost estimates, and report back at the July meeting with a detailed alternatives package. The presentation included twice-yearly survey methods, shoreline and volume change metrics, and a proposed approach for monitoring that pairs offshore volume analyses with shoreline/dune-height indicators so the town can better detect changes in the upper beach over time.
The committee generally accepted the approach and directed consultants to return with alternatives and initial cost estimates at the July 2 meeting. The consultants said they will continue regulatory coordination with state agencies while preparing the July deliverable.
