Longterm Erosion Rates
Long term erosion rates are determined by analyzing historical shoreline positions and calculating annual erosion rates based on beach profile data. Each year, DHEC monitors over 400 survey monuments on state beaches and analysis is conducted in conjunction with professional shoreline experts.
Baseline - Within a standard erosion zone the baseline is established at the location of
the crest of the primary oceanfront sand dune in that zone. In a standard erosion zone in which the shoreline
has been altered naturally or artificially by the construction of erosion control devices, groins, or other
man-made alterations, the baselines must be established by the Department using the best scientific and
historical data, as where the crest of the primary ocean front sand dune for that zone would be located if
the shoreline had not been altered.
Within an unstabilized inlet zone the baseline must be determined by the Department as the most landward point of erosion at anytime during the past forty years, unless the best available scientific and historical data of the inlet and adjacent beaches indicate that the shoreline is unlikely to return to its former position. In collecting and utilizing the best scientific and historical data available for the implementation of the retreat policy, the Department as part of the State Comprehensive Beach Management Plan provided for in this chapter, among other factors, must consider: historical inlet migration, inlet stability, channel and ebb tidal delta changes, the effects of sediment bypassing on shorelines adjacent to the inlets, and the effects of nearby beach restoration project on inlet sediment budgets.
Within a stabilized inlet zone the baseline location must be determined in the same manner as provided for in a standard erosion zone. However the actual location of the crest of the primary oceanfront sand dune of that erosion zone is the baseline of that zone, not the location if the inlet had remained unstabilized.
Setback line - The line landward of the baseline that is established at a distance which is forty times the average annual erosion rate as determined by historical and other scientific means and adopted by the Department in the State Comprehensive Beach Management Plan. However, all setback lines shall be established no less than twenty feet landward of the baseline, even in cases where the shoreline has been stable or has experienced net accretion over the past forty years. Note: Subsequent to S.C. Code of Laws 48-39-290, a setback line is not present on Folly Beach.
Standard Zones - a segment of shoreline which is subject to essentially the same set of coastal
processes, has a fairly constant range of profiles and sediment characteristics, and is not directly influenced by
tidal inlets or associated inlet shoals.
Unstabilized Inlet Zones - inlets that have not been stabilized by jetties, terminal groins, or other structures.
Stabilized Inlet Zones - inlets which are stabilized by jetties, terminal groins, or other structures.