Impact of hydrological and marine extreme events on coastal ecosystems and infrastructures. Adaptation strategies and community resilience

Session lead: Dr. Damià Gomis (IMEDEA), Dr.Sathaporn Monprapussorn (Srinakharinwirot University)

Climate change will affect hydrological and marine extreme events. Eventual changes in the intensity, frequency, duration, or path of the storms can have an impact on floods and draughts, as well as on sea level and wave extremes. These changes will add to the changes in the main regimes of these key parameters, among which sea level is a paradigmatic example: mean sea level rise will add to the heights of sea level extremes, regardless of any changes in the storm-related component, accentuating the threat of coastal inundation.

As discussed in the IPCC AR5, statistical analyses of tide-gauge observations have shown that the increase in sea level extremes observed worldwide has been caused primarily by increase in mean sea level. Dominant modes of climate variability, particularly ENSO and NAO, also have a measureable influence on sea level extremes in many regions. Recent projection studies indicate that the same will hold for the 21st century. Changes in ocean wave conditions are determined by changes in the major wind systems, especially in the main areas affected by tropical and extra-tropical storms. Although at present the confidence in projections of future storm conditions and hence in projections of ocean waves is still low, there has been continued progress in translating climate model outputs into wind–wave projections. Changes in storminess may also affect hydrological extremes such as floods and draughts but the limited geographical coverage of studies and uncertainties associated with storminess changes prevent up to date a general assessment on either observed changes or future projections.

Changes in hydrological and marine extreme events will affect coastal ecosystems, having a potentially damaging impact on habitats and biodiversity. They will also constrain coastal activities such as marine transportation, fisheries, tourism or aquaculture, which are essential components of many national economies and also provide substantial benefits to local communities. It is therefore crucial that all relevant stakeholders prepare comprehensive adaptation strategies to ensure the resilience of nation and local economy. Up to date, coastal developments have largely been driven by rapid economy growth, especially in coastal megacities, and paying no attention to long-term changes derived from climate change. The cost of protecting coastal ecosystems and infrastructures is very high, and therefore needs of thorough cost-benefit assessments to increase resilience of coastal areas and community settlement to climate change. Although different studies have already been carried out (e.g. on the exposure of the world’s large port cities in the 2070s) and many countries have already launched adaptation strategies, there is still a lot to do in this field.

With this session we intend to put in contact scientists working in the field of hydrological and marine extreme events with stakeholders responsible for coastal ecosystems and infrastructures (e.g. harbours). The stakeholders should contribute by stating which are the key parameters constraining the safety and operability of the systems; some of the parameters are surely common to all them (e.g. sea level), while others may be particular to specific locations (e.g. flooding/draught risk or water temperature). Stakeholders should also provide information on socioeconomic issues such as future change in land use and population dynamics, which are nowadays being considered by climate scientist as significant drivers of climate change impacts. Scientists should contribute with the existing projections of key parameters and, most important, with the uncertainties limiting those projections. The ultimate aim would be to assess what are at present the main limitations to carry out accurate cost-benefit assessments for natural systems and coastal infrastructures, as well as to delimitate the expected progress in the near future.