Setback area

Definition of Setback area: A strip along the coastal zone where certain development activities are prohibited or significantly restricted in order to limit exposure to coastal flooding and erosion and to facilitate adaptation to sea-level rise. This is the common definition for Setback area, other definitions can be discussed in the article

Table 1. Setback lines in different countries as reported by Simpson et al. (2012) and Rochette and Billé (2010.)

The setback area is delimited by setback lines, defining the distance from the shoreline within which certain types of development or construction are prohibited or restricted. The shoreline along the open coast is generally defined as the high-water line, but in some cases it is defined as the dunefoot or first vegetation line. The shoreline of estuaries and tidal rivers generally corresponds to existing embankments or levees.

Many countries have defined setback lines that are laid down in coastal regulations, see Table 1. However, in many countries their use as coastal zone planning instruments and their enforcement are challenged by urban and industrial development pressures (Fig. 1). The definition of a setback area should be underpinned by an analysis weighing the costs of development restrictions against the reduction in flood and erosion risk, where risk is determined from the probability of hazardous events and the resulting damage. The absence of setback lines can lead to dramatic situations, as illustrated in Fig. 2. See also the article Coastal cities and sea level rise.

There is no generally appropriate method for defining a setback area. Its delineation can depend on many site-specific factors: coastal morphology, erosion trends, extreme-event erosion, flood levels, topography, existing development, land use, coastal protection, planning objectives and the time horizon considered. A few examples of setback regulations in different countries are given below.

In the Netherlands, there is no fixed setback distance from the coastline. Building is strongly restricted within coastal defense zones that include the beach, sea dike or frontal dune, while additional restrictions on development in the coastal dune area follow from spatial-planning and nature-conservation regulations.

In the US, several coastal states have defined setback areas based on estimates of local long-term coastline erosion. The setback distance corresponds to 30–60 times the mean annual shoreline-retreat rate, measured from a baseline such as the high-water mark, first vegetation line or crest of the first dune row. See for example South Carolina Beachfront Permitting. Other instruments that can complement setback regulations include conservation covenants, rolling easements and transferable development rights (TDR); these are discussed in Climate adaptation measures for the coastal zone.

In France, the width [math]L[/math] of the coastal risk zone is defined as [math]L = 100 R + L_{max}[/math], corresponding to the expected long-term retreat over 100 years plus the maximum retreat caused by an extreme event. Here [math]R[/math] is the average annual retreat rate and [math]L_{max}[/math] the value of the maximum retreat following an extreme event.

In the UK, local planning authorities are encouraged to embed local shoreline management in their spatial plans by identifying coastal change management areas (CCMAs) where rates of shoreline change are significant over the next 100 years, taking account of climate change. Coastal change management areas should make provision for any vulnerable properties and infrastructure that may need to be relocated at a future point.

The Mediterranean ICZM Protocol prescribes a coastal setback for all contracting Mediterranean countries. This zone may not be less than 100 meters in width from the highest winter waterline, subject to specified exceptions.

Due to coastal erosion and sea-level rise, fixed setback areas can provide an adequate separation from coastal hazards for only a certain period. This period should not be shorter than the average lifespan of coastal development.

Figure 1. Urbanization of setback area in Kerala (India).

Figure 2. Destruction of fishermen's houses on the beach of Saint-Louis (Senegal) by swell waves at high springtide (March 2015).

References

The main author of this article is Job Dronkers Please note that others may also have edited the contents of this article. Citation: Job Dronkers (2026): Setback area. Available from http://www.coastalwiki.org/wiki/Setback_area [accessed on 27-09-2026] For other articles by this author see Category:Articles by Job Dronkers For an overview of contributions by this author see Special:Contributions/Dronkers J