Guidance for coastal management and risk planning

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Coastal Risk

Guidance for Coastal Management and Risk Planning


This section is design to provide guidance on the approach to climate change adaptation to people working within the Coastal Management and Risk Planning sector.

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Key Considerations

a. Sea level rise

Global sea level rise is caused by thermal expansion (ocean water expanding as it heats up), and ice melting, as a response to increasing concentrations of greenhouse gases in the atmosphere, changing the climate. Relative sea level rise occurs where there is a local increase in the level of the ocean relative to the land, which might be due to ocean rise and/or land level subsidence. Rates of sea level rise are increasing, and having negative impacts on communities and ecosystems around the planet. Local sea level rise varies to the global rate: some Pacific island countries are currently experiencing four times greater sea-level rise than the global average of 3.2 mm sea level rise per year.

Image by Carbon Brief, created using data in Table 13.5 – Chapter 13 of the IPCC’s Fifth Assessment Report.
https://www.carbonbrief.org/what-the-new-ipcc-report-says-about-sea-level-rise 
Image by Carbon Brief, created using data in Table 13.5 – Chapter 13 of the IPCC’s Fifth Assessment Report.
Malé, capital of the Indian Ocean archipelago Maldives, shows the vulnerability of densely built-up, low-lying islands to rising seas.
Malé, capital of the Indian Ocean archipelago Maldives, shows the vulnerability of densely built-up, low-lying islands to rising seas.
Photograph by Wolfgang Kaehler, LightRocket via Getty Images

b. Impact of climate change on coastal hazards erosion and inundation

Sea level rise contributes to coastal erosion and inundation of low-lying coastal regions, especially during extreme storms, tides, inland precipitation and runoff. Impacts vary based on the geophysical setting: increased storm damage to coastal development, rapid coastal erosion, shoreline change (including loss of protective natural barriers), changes in tidal prism, saltwater intrusion into freshwater systems; impacts on coastal ecosystems, human settlements and activities, and water resources (including clean freshwater and sanitation).

c. Impacts on coastal ecosystems (coral reefs and mangroves)

Higher sea levels can flood terrestrial habitats, creating new areas of inundation; greater tidal levels can change the salinity regime of estuaries and coastal freshwaters; redistribution of shallow marine and intertidal habitats due to landward migration of coastal habitats (erosion); increased depth in marine environments can affect light availability to seagrass ecosystems; greater depth over reef ecosystems can reduce the storm protection of dissipating wave energy effectiveness. Mangroves can suffer alteration, losing their protective function towards inundation and erosion. Coastal ecosystems loss would have impacts on carbon sequestration, loss of organisms and species, loss of interception of nutrients, pollutants, stabilisation of soils during storm events.

d. Current usage of the coastal zone and trends

Coastal zones are used for human settlement, agriculture, trade, industry, amenity, maritime activities, responding to needs for economic growth.

Some Pacific communities have already been relocated, including 3 villages in Fiji and 2 villages in the Solomon Islands. Low-lying Pacific islands are exposed to the physical impacts of sea level rise, these communities have a high dependency on coastal resources and infrastructure for supporting sustainable livelihoods (housing, water, food, health services) and for generating income (fisheries, agriculture and tourism), all highly vulnerable.

Common Approaches

a. Generic adaptation strategies – defend, retreat, accommodate

  • Accommodate: adapt an existing development to be more resilient to the risks of changing conditions, reducing the consequences of the hazard (structure maintenance, elevated buildings, early warning systems, disaster risk reduction, ecosystem-based approaches). Pros: lower capital costs, lower impacts on ecosystems, minimal social disruption. Cons: may not be suitable in long term, risk may be reduced but not eliminated.
  • Retreat or avoidance action: relocating existing structures to avoid impacts, or avoid through planning restrictions, eliminating the risk.  Pros: long-term security, reduction of risks to ecosystems, no risk of failure, minimum maintenance requirements and costs, potential increase of better use of amenity areas in public space (beaches). Cons: perceived loss of use of land, unavailability of land for relocation or high cost, services required and potentially not economically viable or compensation needed.
  • Defend: protect assets with physical constructions to withstand the impacts. Options can be “hard” (rock wall) or “soft” (beach nourishment). Pros: immediate benefit for purpose, effective if adequately designed and built, suitable for short and mid term, could improve amenity. Cons: high ongoing maintenance and replacement costs, can impact the environment and ecosystems, can impact amenity, high regrets if failure. Should be used in combination with retreat action or accommodate action.

b. Coastal hazard studies

Costing the effect of damage on the community and ecosystems, through a professional technical assessment of the possible threats of climate change, extreme weather and sea level rise, to assist in better understanding and planning for the risks associated. 

c. Coastal process modelling

Coastal process modelling visualises the future trends of erosion and inundation, is beneficial to identify risks  in short and long term, including what would happen with each possible action adopted,  enabling the decision making process towards what strategies should be adopted.

“Hard” adaptation measures need to be designed based on the understandings from coastal and flood risk modelling, as well as climate and sea level projections.

d. Three pass assessment framework

Understanding the potential for physical coastal impacts on a shoreline by three logical 'passes' of assessment: the susceptibility of a shoreline to coastal hazards with geomorphic and topographic mapping; followed by a 'regional' assessment, identifying the physical processes acting, showing severity of risks and indicative time frames under different scenarios, and making initial assessment of protection and adaptation options; followed by a specific assessment that will highlight areas that may require further investigation and action.

e. Land use planning – strategic and development controls

Land use planning strategies are important to respond as a mechanism for controlling land use and development, reducing risks to the community.  Identifying development at risk, designing for risk and avoiding high risk areas. It is part of  retreat/avoidance action, mentioned on point a.

Examples / Case Studies

a. Planning mechanism – planned retreat Choiseul - Solomon Islands

Choiseul Bay is a provincial capital with around 1000 people on Taro Island, which is less than 2 metres above sea level. The Integrated Climate Risk Assessment and Adaptation Plan for the township assessed current and future coastal and climate risks, and produced an adaptation plan with disaster prevention measures in the short term but also build a new town in safer mainland, moving the population in stages.

b. Coastal hazard study – Port Vila – Vanuatu

Port Vila was identified by the Natural Hazards Risk Atlas (a global risk analysis study) as the world´s most exposed city to natural disasters, amongst 1,300 cities. This analysis considered the combined risk posed by cyclones, tsunamis, earthquakes, floods, coastal hazards, landslides and fires.

As part of the Mainstreaming Disaster Risk Reduction Project, a coastal hazard study was undertaken to identify the hazards and the risk areas for short and long term, as well as developing an urban risk assessment to assess how prepared was the community to the risks. Providing data of which areas had the highest hazard and risk, and what areas had lower levels of hazard and therefore could be potentially developed.

This information was beneficial for decision makers and planners, as well as understanding the readiness of the community to hazards, promoting solutions to minimise the risk such as land use plans, development controls and standards, evacuation maps for community response, recommendations for tools to reduce risk.

c. SAMOA, COMMUNITY-BASED INTEGRATED COASTAL PROTECTION

Implementation of a community-based integrated coastal protection model, increasing the resilience of the coastal infrastructure and communities and reducing the vulnerability, with activities including re-vegetation of coastal areas, building protection structures and raising awareness. Prior to this, a climate analysis was done, followed by a vulnerability and adaptation assessment was undertaken. Analysing vulnerabilities, adaptive capacity and adaptation opportunities, as well as socio-economic assessment and cost-benefit analysis to select the most appropriate tools and solutions.

Including the community, stakeholders and decision makers in the process through engagement and participation, to raise awareness of climate change, and measures available to reduce vulnerability, encouraging their support and ownership.