Managed retreat

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Tollesbury Managed Realignment site in Essex, the first large-scale attempt at salt-marsh restoration in the UK Tollesbury bare ground.jpg
Tollesbury Managed Realignment site in Essex, the first large-scale attempt at salt-marsh restoration in the UK

Managed retreat involves the purposeful, coordinated movement of people and buildings away from risks. This may involve the movement of a person, infrastructure (e.g., building or road), or community. It can occur in response to a variety of hazards such as flood, wildfire, or drought. Politicians, insurers, and residents are increasingly paying attention to managed retreat from low-lying coastal areas because of the threat of sea level rise due to climate change. [1] Trends in climate change predict substantial sea level rises worldwide, causing damage to human infrastructure through coastal erosion [2] and putting communities at risk of severe coastal flooding. [3]

Contents

Climate change adaptation strategies to reduce risks from sea level rise for coastal communities: no response; 2 advanced protection; 3 adjustment; 4 advancement; 5 strategic retreat; 6 ecosystem-based adaptation. Responses to Sea Level Rise.svg
Climate change adaptation strategies to reduce risks from sea level rise for coastal communities: ➀ no response; ② advanced protection; ③ adjustment; ④ advancement; ⑤ strategic retreat; ⑥ ecosystem-based adaptation.

The type of managed retreat proposed depends on the location and type of natural hazard, [4] [5] [6] and on local policies and practices for managed retreat. In the United Kingdom, managed realignment through removal of flood defences is often a response to sea-level rise exacerbated by local subsidence. In the United States, managed retreat often occurs through voluntary acquisition and demolition or relocation of at-risk properties by government. [7] [8] In the Global South, relocation may occur through government programs. [9] Some low-lying countries, facing inundation due to sea-level rise, are planning for the relocation of their populations, such as Kiribati planning for "Migration with Dignity". [10]

Managed realignment

In the United Kingdom, the main reason for managed realignment is to improve coastal stability, essentially replacing artificial 'hard' coastal defences with natural 'soft' coastal landforms. [11] According to University of Southampton researchers Matthew M. Linham and Robert J. Nicholls, "one of the biggest drawbacks of managed realignment is that the option requires land to be yielded to the sea." [12] [ unreliable source? ] One of its benefits is that it can help protect land further inland by creating natural spaces that act as buffers to absorb water or dampen the force of waves.

Managed realignment has also been used to mitigate for loss of intertidal habitat. Although land reclamation has been an important factor for salt marsh loss in the UK in the past, [13] the majority of current salt marsh loss in the UK is believed to be due to erosion. [14] This erosion may involve coastal squeeze, where protective sea walls prevent the landward migration of salt marsh in response to sea level rise when sediment supply is limited. [14] [15] Salt marshes are protected under the EU Habitats Directive as well as providing habitat for a number of species protected by the Birds Directive (see Natura 2000). Following this guidance, the UK's biodiversity action plan aims to prevent net losses to the area of salt marsh present in 1992. It is, therefore, a legal requirement that all losses in marsh area must be compensated by replacement habitat with equivalent biological characteristics. [16] This equates to the need to restore approximately 1.4 km2 of salt marsh habitat per year in the UK. One of the major reasons cited for the slow pace of current salt marsh restoration in the UK [14] is the uncertainty associated with the practice (Foresight).

There are no agreed protocols on the monitoring of managed realignment sites [17] and, consequently, very few of the sites are being monitored consistently and effectively. [18] Due to the low levels of monitoring there is little evidence on which to base future managed realignment projects. This has led to the results of managed realignment schemes being extremely unpredictable.

Relocation programs

Managed retreat in the form of relocation has been used in inland and coastal areas in response to severe flooding and hurricanes. In the United States, this often takes the form of "buyout" programs, in which government acquires and relocates or demolishes at-risk properties. [7] [19] In some cases, individual homes are purchased after disasters. [20] In other cases, such as Odanah [21] and Soldiers Grove, Wisconsin, [22] or Valmeyer, Illinois, [23] or Isle de Jean Charles, Louisiana the entire community has relocated.

Managed retreat can be very controversial. [24] A lawsuit in Del Mar California brought on by residents was initiated to stop a managed retreat program based on worries that home values, insurance costs and restricted home expansion have been effects of the policy. [25] Some areas included in managed retreat are above sea level and are recommended based primarily on estimated engineering costs and by studies financed by the California Coastal Commission itself. [26] [27] [28]

Despite the controversy, as the costs of climate change adaptation increase, more communities are beginning to consider managed retreat. [29] One such community is Marina, California, adjacent to Monterey Bay. Marina's general acceptance of managed retreat became the subject of a Los Angeles Times feature article, published in 2020. [30]

Realignment examples

Freiston Shore Managed Realignment site, Lincolnshire Freiston Shore low tide.jpg
Freiston Shore Managed Realignment site, Lincolnshire

In the UK, the first managed retreat site was an area of 8,000 square metres (86,000 sq ft) at Northey Island in Essex flooded in 1991, followed by larger sites at Tollesbury and Orplands (1995), Freiston Shore (2001) and Abbott's Hall Farm, at Great Wigborough in the Blackwater Estuary, it is one of the largest managed retreat schemes in Europe. It covers nearly 280 hectares (690 acres) of land on the north side of the estuary (2002) and a number of others. The programme was started by the Essex Wildlife Trust (EWT) who own Abbott's Hall Farm. They made five breaches in the original old sea wall to allow the held-back sea to flood through to create salt marshland. The marshland over time reverted to its original state before cultivation, providing excellent bird habitat and breeding grounds. [31] [32]

Forced retreat under climate change

Since 2010, the New Zealand Coastal Policy Statement, a policy under the Resource Management Act of 1991, has required the government to conduct managed retreats. [33]

As a result of two climate change related landslides in New Zealand in 2005, the Whakatane District Council began to plan for climate-related migration to the Matata township over the next decade. The vast majority of residents accepted the need to relocate and did so with council assistance and compensation but as of October 2021, one resident has rejected both the process and the need to move and is now the neighbourhood's sole remaining occupant. NIWA coastal hazards expert Rob Bell says the issue of retreat is primarily socio-political rather than technocratic. [34]

See also

Related Research Articles

<span class="mw-page-title-main">Holkham National Nature Reserve</span> Nature reserve in the United Kingdom

Holkham National Nature Reserve is England's largest national nature reserve (NNR). It is on the Norfolk coast between Burnham Overy Staithe and Blakeney, and is managed by Natural England with the cooperation of the Holkham Estate. Its 3,900 hectares comprise a wide range of habitats, including grazing marsh, woodland, salt marsh, sand dunes and foreshore. The reserve is part of the North Norfolk Coast Site of Special Scientific Interest, and the larger area is additionally protected through Natura 2000, Special Protection Area (SPA) and Ramsar listings, and is part of both an Area of Outstanding Natural Beauty (AONB) and a World Biosphere Reserve. Holkham NNR is important for its wintering wildfowl, especially pink-footed geese, Eurasian wigeon and brant geese, but it also has breeding waders, and attracts many migrating birds in autumn. Many scarce invertebrates and plants can be found in the dunes, and the reserve is one of the only two sites in the UK to have an antlion colony.

<span class="mw-page-title-main">Salt marsh</span> Coastal ecosystem between land and open saltwater that is regularly flooded

A salt marsh, saltmarsh or salting, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. It is dominated by dense stands of salt-tolerant plants such as herbs, grasses, or low shrubs. These plants are terrestrial in origin and are essential to the stability of the salt marsh in trapping and binding sediments. Salt marshes play a large role in the aquatic food web and the delivery of nutrients to coastal waters. They also support terrestrial animals and provide coastal protection.

<span class="mw-page-title-main">Tantramar Marshes</span>

The Tantramar Marshes, also known as the Tintamarre National Wildlife Area, is a tidal saltmarsh around the Bay of Fundy on the Isthmus of Chignecto. The area borders between Route 940, Route 16 and Route 2 near Sackville, New Brunswick. The government of Canada proposed the boundaries of the Tantramar Marshes in 1966 and was declared a National Wildlife Area in 1978.

<span class="mw-page-title-main">Tidal marsh</span> Marsh subject to tidal change in water

A tidal marsh is a marsh found along rivers, coasts and estuaries which floods and drains by the tidal movement of the adjacent estuary, sea or ocean. Tidal marshes experience many overlapping persistent cycles, including diurnal and semi-diurnal tides, day-night temperature fluctuations, spring-neap tides, seasonal vegetation growth and decay, upland runoff, decadal climate variations, and centennial to millennial trends in sea level and climate.

<span class="mw-page-title-main">Coastal management</span> Preventing flooding and erosion of shorelines

Coastal management is defence against flooding and erosion, and techniques that stop erosion to claim lands. Protection against rising sea levels in the 21st century is crucial, as sea level rise accelerates due to climate change. Changes in sea level damage beaches and coastal systems are expected to rise at an increasing rate, causing coastal sediments to be disturbed by tidal energy.

<span class="mw-page-title-main">Climate change adaptation</span> Process of adjusting to effects of climate change

Climate change adaptation is the process of adjusting to the effects of climate change. These can be both current or expected impacts. Adaptation aims to moderate or avoid harm for people, and is usually done alongside climate change mitigation. It also aims to exploit opportunities. Humans may also intervene to help adjust for natural systems. There are many adaptation strategies or options. For instance, building hospitals that can withstand natural disasters, roads that don't get washed away in the face of rains and floods. They can help manage impacts and risks to people and nature. The four types of adaptation actions are infrastructural, institutional, behavioural and nature-based options. Some examples of these are building seawalls or inland flood defenses, providing new insurance schemes, changing crop planting times or varieties, and installing green roofs or green spaces. Adaptation can be reactive or proactive.

<span class="mw-page-title-main">Marine ecosystem</span> Ecosystem in saltwater environment

Marine ecosystems are the largest of Earth's aquatic ecosystems and exist in waters that have a high salt content. These systems contrast with freshwater ecosystems, which have a lower salt content. Marine waters cover more than 70% of the surface of the Earth and account for more than 97% of Earth's water supply and 90% of habitable space on Earth. Seawater has an average salinity of 35 parts per thousand of water. Actual salinity varies among different marine ecosystems. Marine ecosystems can be divided into many zones depending upon water depth and shoreline features. The oceanic zone is the vast open part of the ocean where animals such as whales, sharks, and tuna live. The benthic zone consists of substrates below water where many invertebrates live. The intertidal zone is the area between high and low tides. Other near-shore (neritic) zones can include mudflats, seagrass meadows, mangroves, rocky intertidal systems, salt marshes, coral reefs, lagoons. In the deep water, hydrothermal vents may occur where chemosynthetic sulfur bacteria form the base of the food web.

<span class="mw-page-title-main">Flood management</span> Methods for reducing detrimental effects of flood waters

Flood management describes methods used to reduce or prevent the detrimental effects of flood waters. Flooding can be caused by a mix of both natural processes, such as extreme weather upstream, and human changes to waterbodies and runoff. Flood management methods can be either of the structural type and of the non-structural type. Structural methods hold back floodwaters physically, while non-structural methods do not. Building hard infrastructure to prevent flooding, such as flood walls, is effective at managing flooding. However, it is best practice within landscape engineering to rely more on soft infrastructure and natural systems, such as marshes and flood plains, for handling the increase in water.

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Low marsh is a tidal marsh zone located below the Mean Highwater Mark (MHM). Based on elevation, frequency of submersion, soil characteristics, vegetation, microbial community, and other metrics, salt marshes can be divided to into three distinct areas: low marsh, middle marsh/high marsh, and the upland zone. Low marsh is characterized as being flooded daily with each high tide, while remaining exposed during low tides.

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References

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  2. ↑ Leatherman, S. P., Zhang, K., & Douglas, B. C. (2000). Sea level rise shown to drive coastal erosion. Eos, Transactions American Geophysical Union, 81(6), 55-57.
  3. ↑ Vitousek, S., Barnard, P. L., Fletcher, C. H., Frazer, N., Erikson, L., & Storlazzi, C. D. (2017). Doubling of coastal flooding frequency within decades due to sea-level rise. Scientific reports, 7(1), 1-9.
  4. ↑ Greiving, Stefan; Du, Juan; Puntub, Wiriya (7 November 2018). "Managed Retreat — A Strategy for the Mitigation of Disaster Risks with International and Comparative Perspectives". Journal of Extreme Events. 05 (2n03): 1850011. doi: 10.1142/S2345737618500112 . S2CID   169804224.
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  9. ↑ Ajibade, Idowu (2 September 2019). "Planned retreat in Global South megacities: disentangling policy, practice, and environmental justice". Climatic Change. 157 (2): 299–317. Bibcode:2019ClCh..157..299A. doi:10.1007/s10584-019-02535-1. S2CID   201716223.
  10. ↑ McNamara, Karen E (May 2015). "Cross-border migration with dignity in Kiribati". Forced Migration Review. The 'migration with dignity' policy is part of Kiribati's long-term nation-wide relocation strategy.
  11. ↑ Pethick, J. (2002). Estuarine and tidal wetland restoration in the United Kingdom: policy versus practice. Restoration Ecology, 10(3), 431-437.
  12. ↑ Linham, Matthew M.; Nicholls, Robert J. "Managed Realignment". ClimateTechWiki. Archived from the original on 17 October 2011. Retrieved 29 August 2018.
  13. ↑ Allen, J. R. L., & Pye, K. (1992). Coastal saltmarshes: their nature and importance. Saltmarshes: Morphodynamics, conservation and engineering significance, 1-18.
  14. 1 2 3 Morris, R. K. A.; Reach, I. S.; Duffy, M. J.; Collins, T. S.; Leafe, R. N. (2004). "On the Loss of Saltmarshes in South-East England and the Relationship with Nereis diversicolor". Journal of Applied Ecology. 41 (4): 787–791. doi: 10.1111/j.0021-8901.2004.00932.x . JSTOR   3505709.
  15. ↑ Hulme, Philip E. (28 September 2005). "Adapting to climate change: is there scope for ecological management in the face of a global threat?". Journal of Applied Ecology. 42 (5): 784–794. doi: 10.1111/j.1365-2664.2005.01082.x .
  16. ↑ Crooks et al. 2001[ full citation needed ]
  17. ↑ Atkinson, Philip W.; Crooks, Steve; Drewitt, Allan; Grant, Alastair; Rehfisch, Mark M.; Sharpe, John; Tyas, Christopher J. (2004-09-23). "Managed realignment in the UK–the first 5 years of colonization by birds". Ibis. 146 (146): 101–110. doi: 10.1111/j.1474-919X.2004.00334.x .
  18. ↑ Wolters, Mineke; Garbutt, Angus; Bakker, Jan P. (May 2005). "Salt-marsh restoration: evaluating the success of de-embankments in north-west Europe". Biological Conservation. 123 (2): 249–268. doi:10.1016/j.biocon.2004.11.013.
  19. ↑ Freudenberg, Robert (2016). Buy-in for buyouts: The case for managed retreat from flood zones. Cambridge, MA: Lincoln Institute for Land Policy. ISBN   978-1-55844-354-9. OCLC   1078995484.[ page needed ]
  20. ↑ Binder, Sherri Brokopp; Greer, Alex (28 December 2016). "The Devil Is in the Details: Linking Home Buyout Policy, Practice, and Experience After Hurricane Sandy". Politics and Governance. 4 (4): 97. doi: 10.17645/pag.v4i4.738 .
  21. ↑ Hersher, Rebecca (August 15, 2018). "Wisconsin Reservation Offers A Climate Success Story And A Warning". NPR.
  22. ↑ FEMA, Village Locals Reflect Moving Was Best Flood Protection
  23. ↑ Elam, Stephanie. "A flood forced this town to move. It could be a model for others hit by the climate crisis". CNN.
  24. ↑ Koslov, Liz (2 May 2016). "The Case for Retreat". Public Culture. 28 (2 79): 359–387. doi: 10.1215/08992363-3427487 .
  25. ↑ "Del Mar stands firm against 'planned retreat'". San Diego Union-Tribune. 22 May 2018.
  26. ↑ Local Assistance Grant Program, California Coastal Commission
  27. ↑ San Diego Union Tribune Article "Del Mar stands firm against 'Planned Retreat'"
  28. ↑ "ESA Cost Benefit Presentation "Cost Benefit Analysis Methodology Overview" slide 24". Archived from the original on 2018-08-29. Retrieved 2018-08-29.
  29. ↑ Gopal, Prashant (September 20, 2019). "America's Great Climate Exodus Is Starting in the Florida Keys". Bloomberg.
  30. ↑ Xia, Rosanna (24 February 2020). "Most California cities refuse to retreat from rising seas. One town wants to show how it's done" . Los Angeles Times. Archived from the original on 1 March 2020.
  31. ↑ Information on Abbott's Hall from Essex Wildlife Trust
  32. ↑ Pictures of the Tollesbury and Orplands managed retreat sites
  33. ↑ "New Zealand Coastal Policy Statement 2010". New Zealand Department of Conservation website. 2010.{{cite web}}: Missing or empty |url= (help)
  34. ↑ McClure, Tess (29 October 2021). "Forced retreat: one New Zealand town's fate highlights coming fight over climate adaptation". The Guardian. London, United Kingdom. ISSN   0261-3077 . Retrieved 2021-10-30.
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