Approximately two-thirds of coastal and Great Lakes states have some type of construction setback or construction control line requiring development be a certain distance from the water's edge. Of those that do not have state-mandated setback regulations, most have delegated authority for local governments or Local Coastal Programs to establish setbacks.
The type of setback used, including how and from where it is established can vary widely. Setback lines are often measured from a specific shoreline feature such as the high-tide line, extreme high water mark, or dune vegetation line.
Some states have arbitrary setback lines. An arbitrary setback line, while the simplest to establish, does not reflect the true erosion threat to shorefront structures. For example, an arbitrary 100 foot setback may not be adequate in a highly erosive area but may be too restrictive in a very stable environment. Therefore, many coastal states, such as North Carolina and Florida, have developed setbacks based on annual erosion rates for beach-front lots. Although erosion along estuarine shores can also be problematic, setbacks based on erosion rate data are rarely used in these environments, to date. Few estuarine shorelines have sufficient annual erosion rate data to be able to calculate setbacks based on erosion rate for these shorelines.
While more realistic, establishing setbacks based on the erosion rate can be more difficult because it requires a significant amount of data on past shoreline change—something that may not be available for the entire shoreline or is costly to obtain. Erosion rates can change over time, therefore, the setback lines must also be reassessed routinely. For example, South Carolina updates their setback lines and erosion rate data every 8-10 years.
To overcome gaps in its erosion rate data, Minnesota adopted a hybrid approach to their setback lines along the North Shore of Lake Superior. Minnesota's North Shore Management Plan establishes a setback of 50 times the annual erosion rate plus 25 feet in areas where erosion data is available and reverts to a standard 125-foot setback elsewhere.
Frequently, setback lines based on erosion rates are set 30 or 50 times the annual erosion rate. The assumption being that the structure should last long enough to pay off a 30-year mortgage. However, even a setback line set to the 30-year annual erosion rate may not be adequate. Setback lines do not factor is catastrophic storm events, such as Hurricane Katrina that hit the Gulf Coast in 2005.
Establishing new setback lines can be very controversial if the setback renders some properties unbuildable. This can result in "takings" claims, requiring the state or local government to compensate the property owner for their loss. The same can be true if the setback line is placed landward of an existing structure. While the structure can exist as is, typically, if it is significantly damaged or destroyed by a storm, it must be rebuilt to comply with the new setback line. If there is not enough space on the lot to move the structure behind the setback line, a "taking" could also result.
Setback regulations should clearly stipulate when (or if) it would be allowable for a building damaged or destroyed by a storm or chronic erosion to be rebuilt. For example, in Maine, if repairs will cost more than 50 percent of the structure's value, the existing structure must comply with the setback requirements. One way to avoid "takings" claims is to ensure waterfront lots are sufficiently deep to allow for relocation as the shore retreats. Rolling easements, discussed in more detail under the erosion control easement section, are another way to minimize or prevent "takings" claims.
In addition to creating clear policies on when a structure can be repaired or rebuilt, states or local governments also need to establish clear policies stating how setback lines can move as the beach naturally or artificially accretes. For example, New Jersey's Coastal Zone Management Rules do not allow a waiver from the setback if the beach accretes. A permit application for development within a setback area of an accreting beach would be denied. However, if an Administrative Hearing request was filed, the applicant could petition for a permit if they can show the accreted beach offers sufficient increased protection from erosion.
Benefits: Reduces the need for costly and/or unsightly shoreline erosion control structures and minimizes property damage due to erosion. Maintains natural shoreline dynamics. Helps to maintain lateral beach/shorefront access.
Drawbacks: Requires good scientific data to establish effective setback lines. Can be viewed as a "taking" if the setback causes property to be unbuildable or significantly restricts the size of the building. Only prolongs the life of the building, eventually another shoreline policy will be needed such as retreat or stabilization if the shore continues to advance.
Kauai County's Shoreline Setback and Coastal Protection Ordinance was passed in 2008 (and amended in 2009) to reduce the impact of coastal hazards to property, life, and coastal resources, establishing the most progressive setback standards in Hawaii. While state law requires setbacks of not less than 20 feet and not more than 40 feet, Kauai’s ordinance requires that structures in Kauai be setback a minimum of 40 feet from the certified shoreline.
Specifically, the ordinance establishes two standards for setback determination based on average lot depths, building footprints, and annual erosion rates:
The latter standard, which can also be applied to shallow lots if an applicant so chooses, incorporates current science-based erosion data into land use planning. It helps to ensure that, even with average shoreline erosion, when buildings will still be approximately 40 feet away from the water when they reach the end of their design life (70-100 years).
In August 2009, new setback rules took effect in North Carolina. North Carolina's Administrative Code for Ocean Hazard Areas (15A NCAC 7H .0306) now bases setbacks solely on size and does away with an exemption in the previous rules that treated single-family homes larger than 5,000 square feet differently than other similarly sized structures. The new minimum setback remains 30 times the long-term average annual erosion rate, as measured from the first line of stable and natural vegetation, for all structures less than 5,000 square feet. The setback for ALL structures between 5,000 and 9,999 square feet is 60 times the erosion rate. For structures 10,000 square feet and larger, the setback increases incrementally with structure size, reaching a maximum setback of 90 times the erosion rate for structures 100,000 square feet and larger.