Coastal Setback

Ecosystem services provided by a vegetated coastal ecosystem. Diagram by Gaylard et al., (2020).

Coastal setbacks work in urban or peri-urban areas where buildings are located near hazardous areas related to coastal flooding and erosion. Areas along coasts that receive strong ocean currents and experience erosion and flooding are most suited to this nature-based solution. Coastal vegetated setbacks can be either elevated setbacks or lateral setbacks. They are put in place to dictate a minimum distance between the shoreline and buildings or infrastructure. This creates a safety zone to combat coastal flooding or erosion. This setback is reinforced by vegetation which has many ecological benefits but also improves the stability of the land. See also managed realignment (intertidal).

Name of NbS

Coastal Setback

Type of NbS

Combination

Location

  • Urban
  • Peri-urban
  • Rural.

Case Study

Cyclone Percy Development

Cyclone Percy damage in Tokelau, 2005. Photo by AusAID.

Relationship to Indigenous knowledge

In many Te Moananaui Oceania islands, sea level rise is an obvious problem. Coastal setbacks help protect people’s connection to the land they care for and in return, the land can continue to provide for them.

Climate change benefits
  • Biomass cover loss
  • Coastal erosion
  • Coastal inundation and storm surge
  • Coastal salt-water intrusion
  • Sea level rise

Coastal setbacks serve as vegetative buffers, offering a multitude of advantages such as pollutant filtration, habitat preservation, and erosion mitigation (Desbonnet, 2008). In light of rising sea levels, they emerge as crucial adaptation measures, countering intensified storm surges that trigger coastal flooding and erosion. By relocating human settlements inland, coastal setbacks facilitate natural shoreline restoration while reducing communities’ vulnerability to climate impacts. Employing the “protect, accommodate, retreat” framework (Ferreira, O et al, 2006), these setbacks effectively address coastal erosion and wave attenuation.

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Societal / socio-cultural benefits
  • Disaster risk reduction

Vegetated setbacks play a crucial role in bolstering biomass and delivering societal and ecological benefits, notably enhancing biodiversity and fortifying coastal resilience (Vierros, 2017). Amidst escalating urbanisation pressures, coastal infrastructure is vulnerable to routine and increasingly severe storm surges that threaten property and infrastructure. Embracing nature-based solutions like coastal vegetated setbacks offers a pathway to disaster risk reduction by naturalising and fortifying landscapes through vegetation. 

Research underscores the effectiveness of accommodating and retreating strategies in safeguarding coastlines and inland structures, mitigating the risks of coastal squeeze (Nicholls & Kelin, 2003) and minimising adverse impacts such as exacerbated erosion associated with alternative adaptation methods (Ferreira et al., 2006). 

Introducing vegetated ecosystems along coastlines enriches cultural and spiritual values while serving practical functions like carbon storage, supporting fishing production, providing wildlife habitat, flood mitigation, nutrient cycling, and pollution control.

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Ecological and biodiversity benefits
  • Disturbance prevention
  • Habitat provision

Vegetated coastal setbacks create ecological and biodiversity benefits including a decrease in storm surge impacts and the creation of habitats. Vegetated buffers along the coast allow for wildlife habitat, visual diversity, and recreational opportunities (Desbonnet et al., 1994). 

Using vegetated buffers, like mangrove systems for example, acts not only as a wave attenuation benefit but creates a habitat for benthic invertebrates; including annelids, molluscs & crustaceans (Lundquist et al., 2017). Other ecosystems created through vegetated buffers on coastlines have the same benefits but will cater to different wildlife species.

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Coast watch. Diagram by UNC Sea Grant College Program (1979).

Technical requirements

For vegetated coastal setbacks to be implemented in response to climate change, planning policies need to be put in place. At the local level, coastal setbacks can be implemented within land use planning regulations and building codes. The landscape also needs to be assessed to understand which the best type of coastal setback is, and if it should be a lateral or elevated setback depending on the impacts of the waves on the landscape.

Issues and Barriers

Due to climate change, coastal setbacks will need to becarefully monitored. The establishment of a vegetated coastal setback does not guarantee avoiding all impacts of storm surge and flooding. However, allowing space between the coastline and infrastructure gives more opportunity for vegetated systems to reduce the risk of extreme events.

Opportunities

Opportunities for the implementation of coastal vegetated setbacks include integrating them into existing land use and building regulations. Planning for setbacks will help build the case for managed retreats if needed and prevent new buildings in dangerous places. This ultimately benefits people. When implemented with projects such as sand dune reconstruction or wetland restoration there is an opportunity for connected and resilient ecosystems to develop, supporting biodiversity.

Financial case

The costs associated with implementing coastal setbacks depend on several variables. Factors to be considered are: the distance of the setback required; communication with relevant bodies to be considered as part of the planning process; and enforcement through pre-existing local planning bodies or custom groups. Coastal setbacks are generally described as inexpensive compared with constructed alternatives and the costs of remediating storm, flooding, tsunami, and erosion events.

References
  • Desbonnet, A., Lee, V., Pogue, P., Reis, D., Boyd, J., Willis, J., & Imperial, M. (1995). Development of coastal vegetated buffer programs. Coastal Management23(2), 91-109.
  • Ferreira, O., Garcia, T., Matias, A., Taborda, R., & Dias, J. A. (2006). An integrated method for the determination of set-back lines for coastal erosion hazards on sandy shores. Continental shelf research26(9), 1030-1044.
  • Lundquist, C., Carter, K., Hailes, S. F., & Bulmer, R. (2017). Guidelines for managing mangrove (Mānawa) expansion in New Zealand. NIWA.
  • Nicholls, R.J., & Klein, R. J. (2005). Climate change and coastal management on Europe’s coast. In Managing European Coasts (pp. 199-226). Springer, Berlin, Heidelberg.
  • Vierros, M. (2017). Communities and blue carbon: the role of traditional management systems in providing benefits for carbon storage, biodiversity conservation and livelihoods. Climatic Change140(1), 89-100.

Further resources: