Flood losses in coastal cities will rise due to increasing populations and assets. Research now quantifies average losses in the 136 largest coastal cities. Estimated at approximately US$6 billion in 2005, average annual losses could increase to US$52 billion by 2050 on the basis of projected socio-economic change alone. If climate change and subsidence are also considered, current protection will need to be upgraded to avoid unacceptable losses. Flood exposure is increasing in coastal cities1,2 owing to growing populations and assets, the changing climate3, and subsidence4,5,6. Here we provide a quantification of present and future flood losses in the 136 largest coastal cities. Using a new database of urban protection and different assumptions on adaptation, we account for existing and future flood defences. Average global flood losses in 2005 are estimated to be approximately US$6 billion per year, increasing to US$52 billion by 2050 with projected socio-economic change alone. With climate change and subsidence, present protection will need to be upgraded to avoid unacceptable losses of US$1 trillion or more per year. Even if adaptation investments maintain constant flood probability, subsidence and sea-level rise will increase global flood losses to US$60–63 billion per year in 2050. To maintain present flood risk, adaptation will need to reduce flood probabilities below present values. In this case, the magnitude of losses when floods do occur would increase, often by more than 50%, making it critical to also prepare for larger disasters than we experience today. The analysis identifies the cities that seem most vulnerable to these trends, that is, where the largest increase in losses can be expected.

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Future flood losses in major coastal cities

Recent research has strengthened the understanding of the links between climate and tropical cyclones (TCs) on various timescales Geological records of past climates have shown century-long variations in TC numbers While no significant trends have been identified in the Atlantic since the late 19th century, significant observed trends in TC numbers and intensities have occurred in this basin over the past few decades, and trends in other basins are increasingly being identified However, understanding of the causes of these trends is incomplete, and confidence in these trends continues to be hampered by a lack of consistent observations in some basins A theoretical basis for maximum TC intensity appears now to be well established, but a climate theory of TC formation remains elusive Climate models mostly continue to predict future decreases in global TC numbers, projected increases in the intensities of the strongest storms and increased rainfall rates Sea level rise will likely contribute toward increased storm surge risk Against the background of global climate change and sea level rise, it is important to carry out quantitative assessments on the potential risk of TC-induced storm surge and flooding to densely populated cities and river deltas Several climate models are now able to generate a good distribution of both TC numbers and intensities in the current climate Inconsistent TC projection results emerge from modeling studies due to different downscaling methodologies and warming scenarios, inconsistencies in projected changes of large-scale conditions, and differences in model physics and tracking algorithms WIREs Clim Change 2016, 7:65–89 doi: 101002/wcc371

For further resources related to this article, please visit the WIREs website

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Tropical cyclones and climate change

This review assesses the degree of resilience of mangrove forests to large, infrequent disturbance (tsunamis) and their role in coastal protection, and to chronic disturbance events (climate change) and the future of mangroves in the face of global change. From a geological perspective, mangroves come and go at considerable speed with the current distribution of forests a legacy of the Holocene, having undergone almost chronic disturbance as a result of fluctuations in sea-level. Mangroves have demonstrated considerable resilience over timescales commensurate with shoreline evolution. This notion is supported by evidence that soil accretion rates in mangrove forests are currently keeping pace with mean sea-level rise. Further support for their resilience comes from patterns of recovery from natural disturbances (storms, hurricanes) which coupled with key life history traits, suggest pioneer-phase characteristics. Stand composition and forest structure are the result of a complex interplay of physiological tolerances and competitive interactions leading to a mosaic of interrupted or arrested succession sequences, in response to physical/chemical gradients and landform changes. The extent to which some or all of these factors come into play depends on the frequency, intensity, size, and duration of the disturbance. Mangroves may in certain circumstances offer limited protection from tsunamis; some models using realistic forest variables suggest significant reduction in tsunami wave flow pressure for forests at least 100 m in width. The magnitude of energy absorption strongly depends on tree density, stem and root diameter, shore slope, bathymetry, spectral characteristics of incident waves, and tidal stage upon entering the forest. The ultimate disturbance, climate change, may lead to a maximum global loss of 10–15% of mangrove forest, but must be considered of secondary importance compared with current average annual rates of 1–2% deforestation. A large reservoir of below-ground nutrients, rapid rates of nutrient flux and microbial decomposition, complex and highly efficient biotic controls, self-design and redundancy of keystone species, and numerous feedbacks, all contribute to mangrove resilience to various types of disturbance.

Mangrove forests: Resilience, protection from tsunamis, and responses to global climate change

Floods, wildfires, heatwaves and droughts often result from a combination of interacting physical processes across multiple spatial and temporal scales. The combination of processes (climate drivers and hazards) leading to a significant impact is referred to as a ‘compound event’. Traditional risk assessment methods typically only consider one driver and/or hazard at a time, potentially leading to underestimation of risk, as the processes that cause extreme events often interact and are spatially and/or temporally dependent. Here we show how a better understanding of compound events may improve projections of potential high-impact events, and can provide a bridge between climate scientists, engineers, social scientists, impact modellers and decision-makers, who need to work closely together to understand these complex events.

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Future climate risk from compound events

Climate phenomena and their relevance for future regional climate change

Assessments of tropical cyclone risk trends are typically based on reported losses, which are biased by improvements in information access. Now research based on thousands of physically observed events and contextual factors shows that, despite projected reductions in tropical cyclone frequency, projected increases in demographic pressure and tropical cyclone intensity can be expected to exacerbate disaster risk.

https://ssec.wisc.edu/~kossin/articles/nclimate1410.pdf

Global trends in tropical cyclone risk

Revealing Risk, Redefining Development, Global Assessment Report on Disaster Risk Reduction

This paper presents estimates of the geographical and technical potentials for solar electricity generation in rural areas of West Africa (ECOWAS region). The study is performed by application of Geographic Information Systems (GIS) and Multi-Criteria Decision Making (MCDM) methods. We study both opportunities for large-scale grid-connected solar systems (photovoltaic, and concentrated solar power technologies), and for off-grid solar systems (photovoltaic). Locations are evaluated according to their suitability for solar systems’ deployment according to topographical, legal, and social constraints, as well as factors that could facilitate or impede solar generation development. The study is conducted on a regional scale. The results can be used for identification of potential areas of interest for solar generation deployment, and as a support for integration between electricity grid expansion and off-grid electrification policies.

GIS-based assessment of photovoltaic (PV) and concentrated solar power (CSP) generation potential in West Africa

Pressures on natural resources are increasing and a number of challenges need to be overcome to meet the needs of a growing population in a period of environmental variability. Some of these environmental issues can be monitored using remotely sensed Earth Observations (EO) data that are increasingly available from a number of freely and openly accessible repositories. However, the full information potential of EO data has not been yet realized. They remain still underutilized mainly because of their complexity, increasing volume, and the lack of efficient processing capabilities. EO Data Cubes (DC) are a new paradigm aiming to realize the full potential of EO data by lowering the barriers caused by these Big data challenges and providing access to large spatio-temporal data in an analysis ready form. Systematic and regular provision of Analysis Ready Data (ARD) will significantly reduce the burden on EO data users. Nevertheless, ARD are not commonly produced by data providers and therefore gettin...

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Building an Earth Observations Data Cube: lessons learned from the Swiss Data Cube (SDC) on generating Analysis Ready Data (ARD)

The tsunami that deeply impacted the North Indian Ocean shores on 26 December 2004, called for urgent rehabilitation of coastal infrastructures to restore the livelihood of local populations. A spatial and statistical analysis was performed to identify what geomorphological and biological configurations (mangroves forests, coral and other coastal vegetation) are susceptible to decrease or increase coastal vulnerability to tsunami. The results indicate that the width of flooded land strip was, in vast majority, influenced by the distance to fault lines as well as inclination and length of proximal slope. Areas covered by seagrass beds were less impacted, whereas areas behind coral reefs were more affected. The mangroves forests identified in the study were all located in sheltered areas, thus preventing to address the potential protecting role of mangroves forests.

http://portal.nceas.ucsb.edu/working_group/valuation-of-coastal-habitats/relevant-papers/Chatenoux%20and%20Peduzzi%2C%202007.pdf/attachment_download/file

Bruno Chatenoux

Papers

Global trends in tropical cyclone risk

Revealing Risk, Redefining Development, Global Assessment Report on Disaster Risk Reduction

GIS-based assessment of photovoltaic (PV) and concentrated solar power (CSP) generation potential in West Africa

Building an Earth Observations Data Cube: lessons learned from the Swiss Data Cube (SDC) on generating Analysis Ready Data (ARD)

Impacts from the 2004 Indian Ocean Tsunami: analysing the potential protecting role of environmental features