Abiy S. Kebede

Impacts of Climate Change and Sea-Level Rise: A Preliminary Case Study of Mombasa, Kenya

Abstract Mombasa is the second largest city in Kenya and the largest international seaport in East Africa, with over 650,000 inhabitants. The city has a history of natural disasters associated with extreme climatic events, most recently, the severe rain-induced flooding in October 2006, which affected about 60,000 people and caused damage to important infrastructure. Because the city is expected to continue to experience rapid growth, the future impacts of such events can only increase. Changes in sea level and storm surges are components of climate change that have the potential to further increase the threats of flooding within the city. This geographic information system–based study provides a first quantitative estimate, both now and through the twenty-first century, of the number of people and associated economic assets potentially exposed to coastal flooding due to sea-level rise and storm surges in Mombasa. The current exposure to a 1 ∶ 100 y extreme water level for the Mombasa district is estimated at 190,000 people and US

Sea-level rise impacts and responses: a global perspective

470 million in assets. About 60% of this exposure is concentrated in the Mombasa Island division of the city, where about 117,000 people (2005 estimate) live below 10 m elevation. By 2080, exposure could grow to over 380,000 people and US

Indirect impacts of coastal climate change and sea-level rise: the UK example

15 billion in assets, assuming the well-known A1B sea-level and socioeconomic scenario. Future exposure is more sensitive to socioeconomic than climate scenarios. However, there is significant scope within the city limits to steer future development to areas that are not threatened by sea-level rise. Hence, forward planning to focus population and asset growth in less vulnerable areas could be an important part of a strategic response to sea-level rise. The methods used here could be applied more widely to other coastal cities in Africa and elsewhere to better understand present and future exposure and worst-case risks due to climate change and rising sea levels.

Direct and indirect impacts of climate and socio-economic change in Europe: a sensitivity analysis for key land- and water-based sectors

Coastal hazards have long been present and are evolving due to a variety of different drivers: the long-term threat of climate change, including sea-level rise, adds a new dimension to these problems which is explored here. Globally, sea levels could rise in excess of 1 m this century, but the local rate of relative sea-level rise could be much greater than this because of subsidence or other factors which lower the land surface. This is important as the population of these subsiding areas is significant. Relative sea-level rise will result in inundation, flooding, erosion, wetland loss, saltwater intrusion and impeded drainage. This chapter has investigated the impacts of sea-level rise at a global scale on: (1) Sandy environments; (2) Wetlands and low-lying coasts; (3) Built environments; and (4) Energy and transport systems. Results indicate that without appropriate adaptation, environments could be significantly impacted, and those remote or financially less well off could become increasingly vulnerable. Further research and action is required into integrated impact assessments (including non-climatic drivers of change) to help those at risk and develop appropriate adaptation polices over short, medium and long timescales.

Applying the global RCP–SSP–SPA scenario framework at sub-national scale: A multi-scale and participatory scenario approach

Owing to globalization, the potential impacts of climate change/sea-level rise in one country/region are likely to affect and be felt elsewhere. Such indirect impacts could be significant but have received a limited analysis. This deficiency is addressed here using the indirect impacts on coastal infrastructure for the UK as an example. National opportunities and threats are identified. Potential indirect national threats include disruption of supply chains, security threats due to forced migration, a decline in national prestige, and impacts on the finance and insurance industries. Potential opportunities include export of world-leading coastal hazard and management expertise, and benefits to national prestige conferred by a strong response to climate change. Such opportunities and threats depend on several distinct dimensions of change, especially the magnitude of climate and socio-economic change, and the success/failure of appropriate responses. Promoting adaptation and climate mitigation is important to exploit the opportunities and address the threats. Adaptation should deal with more than the effects of climate change and link to the wider development agenda. These lessons are transferable to other developed countries and, indeed, many of the actions will be strengthened by collective action. Policy relevance National-level measures to address these indirect impacts will make a positive contribution to the global effort in addressing climate change (e.g. supporting emissions reductions). Countries should include the indirect effects of climate change in national assessments so that the national context and useful responses can be identified. Cooperation between nations is also important; countries must act together to more effectively address the direct and indirect effects of climate change (e.g. promoting a widespread adaptation response). International initiatives (such as the Belmont Forum initiative on Coastal Vulnerability) should be promoted and global environmental change research shared (e.g. within multilateral institutions).

A framework for identifying and selecting long term adaptation policy directions for deltas

Integrated cross-sectoral impact assessments facilitate a comprehensive understanding of interdependencies and potential synergies, conflicts, and trade-offs between sectors under changing conditions. This paper presents a sensitivity analysis of a European integrated assessment model, the CLIMSAVE integrated assessment platform (IAP). The IAP incorporates important cross-sectoral linkages between six key European land- and water-based sectors: agriculture, biodiversity, flooding, forests, urban, and water. Using the IAP, we investigate the direct and indirect implications of a wide range of climatic and socio-economic drivers to identify: (1) those sectors and regions most sensitive to future changes, (2) the mechanisms and directions of sensitivity (direct/indirect and positive/negative), (3) the form and magnitudes of sensitivity (linear/non-linear and strong/weak/insignificant), and (4) the relative importance of the key drivers across sectors and regions. The results are complex. Most sectors are either directly or indirectly sensitive to a large number of drivers (more than 18 out of 24 drivers considered). Over twelve of these drivers have indirect impacts on biodiversity, forests, land use diversity, and water, while only four drivers have indirect effects on flooding. In contrast, for the urban sector all the drivers are direct. Moreover, most of the driver–indicator relationships are non-linear, and hence there is the potential for ‘surprises’. This highlights the importance of considering cross-sectoral interactions in future impact assessments. Such systematic analysis provides improved information for decision-makers to formulate appropriate adaptation policies to maximise benefits and minimise unintended consequences.

Assessing Flood Impacts, Wetland Changes and Climate Adaptation in Europe: The CLIMSAVE Approach

To better anticipate potential impacts of climate change, diverse information about the future is required, including climate, society and economy, and adaptation and mitigation. To address this need, a global RCP (Representative Concentration Pathways), SSP (Shared Socio-economic Pathways), and SPA (Shared climate Policy Assumptions) (RCP-SSP-SPA) scenario framework has been developed by the Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC-AR5). Application of this full global framework at sub-national scales introduces two key challenges: added complexity in capturing the multiple dimensions of change, and issues of scale. Perhaps for this reason, there are few such applications of this new framework. Here, we present an integrated multi-scale hybrid scenario approach that combines both expert-based and participatory methods. The framework has been developed and applied within the DECCMA1 project with the purpose of exploring migration and adaptation in three deltas across West Africa and South Asia: (i) the Volta delta (Ghana), (ii) the Mahanadi delta (India), and (iii) the Ganges-Brahmaputra-Meghna (GBM) delta (Bangladesh/India). Using a climate scenario that encompasses a wide range of impacts (RCP8.5) combined with three SSP-based socio-economic scenarios (SSP2, SSP3, SSP5), we generate highly divergent and challenging scenario contexts across multiple scales against which robustness of the human and natural systems within the deltas are tested. In addition, we consider four distinct adaptation policy trajectories: Minimum intervention, Economic capacity expansion, System efficiency enhancement, and System restructuring, which describe alternative future bundles of adaptation actions/measures under different socio-economic trajectories. The paper highlights the importance of multi-scale (combined top-down and bottom-up) and participatory (joint expert-stakeholder) scenario methods for addressing uncertainty in adaptation decision-making. The framework facilitates improved integrated assessments of the potential impacts and plausible adaptation policy choices (including migration) under uncertain future changing conditions. The concept, methods, and processes presented are transferable to other sub-national socio-ecological settings with multi-scale challenges.

Sea-level rise impacts on Africa and the effects of mitigation and adaptation: an application of DIVA

Deltas are precarious environments experiencing significant biophysical, and socio-economic changes with the ebb and flow of seasons (including with floods and drought), with infrastructural developments (such as dikes and polders), with the movement of people, and as a result of climate and environmental variability and change. Decisions are being taken about the future of deltas and about the provision of adaptation investment to enable people and the environment to respond to the changing climate and related changes. The paper presents a framework to identify options for, and trade-offs between, long term adaptation strategies in deltas. Using a three step process, we: (1) identify current policy-led adaptations actions in deltas by conducting literature searches on current observable adaptations, potential transformational adaptations and government policy; (2) develop narratives of future adaptation policy directions that take into account investment cost of adaptation and the extent to which significant policy change/political effort is required; and (3) explore trade-offs that occur within each policy direction using a subjective weighting process developed during a collaborative expert workshop. We conclude that the process of developing policy directions for adaptation can assist policy makers in scoping the spectrum of options that exist, while enabling them to consider their own willingness to make significant policy changes within the delta and to initiate transformative change.

Cross-sectoral impacts of climate change and socio-economic change for multiple, European land- and water-based sectors

This chapter presents the Coastal Fluvial Flood (CFFlood) meta-model that has been developed and integrated into a participatory integrated assessment tool to facilitate a two-way interactive process. The goal of the model is to allow users to explore flood impacts and adaptation options under a range of climate and socio-economic change scenarios in Europe. The tool enables users to understand the socio-economic flood impacts and wetland change/loss due to changes in model parameters within ranges that are designed to reflect future uncertainty. Changes in flood frequency due to changes in river flows and relative sea-level rise are used to determine the flood extent and depth, which are combined with information on urban land use, population density, and Gross Domestic Product (GDP) to estimate impacts. Wetland changes and losses in the floodplain are assessed considering three influencing factors of accommodation: space, sediment supply, and rate of relative sea-level rise. The benefits of a number of adaptation measures including flood protection upgrades, realignment of flood defenses, resilience measures, and mixed responses for reducing flood risks are assessed. Flood impact simulations show that future climate and socio-economic conditions significantly influence socio-economic impacts, especially when coastal flooding is increased due to sea-level rise. In contrast, impacts caused by fluvial flooding may decrease in Southern Europe and parts of Western Europe due to the decrease in precipitation. Incremental losses of coastal wetland habitats (i.e., saltmarsh and intertidal flats) are simulated with the increase of sea-level rise. Under high-end scenarios, impacts increase substantially unless there are corresponding adaptation efforts.