1,721,058 research outputs found
Estimating the economic cost of sea-level rise
Get PDFTo improve the estimate of economic costs of future sea-level rise associated with global climate change, this report generalizes the sea-level rise cost function originally proposed by Fankhauser, and applies it to a new database on coastal vulnerability developed as part of the Dynamic Interactive Vulnerability Assessment (DIVA) tool.
An analytic expression for the generalized sea-level rise cost function is obtained to explore the effect of various spatial distributions of capital and nonlinear sea-level rise scenarios. With its high spatial resolution, the DIVA database shows that capital is usually highly spatially concentrated along a nation’s
coastline, and that previous studies, which assumed linear marginal capital loss for lack of this information, probably overestimated the fraction of a nation’s coastline to be protected and hence protection cost. In addition, the new function can treat a sea-level rise scenario that is nonlinear in time.
As a nonlinear sea-level rise scenario causes more costs in the future than an equivalent linear sea-level rise scenario, using the new equation with a nonlinear scenario also reduces the estimated damage and protection fraction through discounting of the costs in later periods.
Numerical calculations are performed, applying the cost function to the DIVA database and socioeconomic scenarios from the MIT Emissions Prediction and Policy Analysis (EPPA) model. The effect of capital concentration substantially decreases protection cost and capital loss compared with previous studies, but not wetland loss. The use of a nonlinear sea-level rise scenario further reduces the total cost
because the cost is postponed into the future
Quantifying land and people exposed to sea-level rise with no mitigation and 1.5 and 2.0 °C rise in global temperatures to year 2300
No full textWe use multiple synthetic mitigation sea-level scenarios, together with a non-mitigation sea-level scenario from the Warming Acidification and Sea-level Projector model. We find sea-level rise continues to accelerate post 2100 for all but the most aggressive mitigation scenarios indicative of 1.5°C and 2.0°C. Using the Dynamic Interactive Vulnerability Assessment modelling framework, we project land and population exposed in the 1 in 100 year coastal flood plain under sea-level rise and population change. In 2000, the flood plain is estimated at 540 x103 km2. By 2100, under the mitigation scenarios, it ranges between 610 x103 km2 and 640 x103 km2 [580 x103 km2 and 700 x103 km2 for the 5th and 95th percentiles]. Thus differences between the mitigation scenarios are small in 2100. However, in 2300, flood plains are projected to increase to between 700 x103 km2 and 960 x103 km2 in 2300 [610 x103 km2 and 1,290 x103 km2] for the mitigation scenarios, but 1,630 x103 km2 [1,190 x103 km2 and 2,220 x103 km2] for the non-mitigation scenario. The proportion of global population exposed to sea-level rise in 2300 is projected to be between 1.5% and 5.4% [1.2% to 7.6%] (assuming no population growth after 2100) for the aggressive mitigation and the non-mitigation scenario, respectively. Hence over centennial timescales there are significant benefits to climate change mitigation and temperature stabilization. However, sea-levels will continue to rise albeit at lower rates. Thus potential impacts will keep increasing necessitating adaptation to existing coastal infrastructure and the careful planning of new coastal developments.Plain Language SummaryIf we reduce greenhouse gas emissions and stabilize global temperatures, sea‐level rise (SLR) will continue at a reduced rate for centuries. This is because changes to the ocean and cryosphere (ice) which contribute to SLR take very long timescales to respond to changes in global warming. Early and aggressive climate change mitigation will be most effective to reduce flood risk, particularly after the 21st century. Even with climate change mitigation, the land area exposed to coastal flooding will continue to increase for centuries. Adapting the coast to cope with rising sea levels is inevitably required. The long‐term implications for coastal habitation need to be considered.<br/
Sustainability of complex social-ecological systems: methods, tools, and approaches
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Regionalisation of population growth projections in coastal exposure analysis
Get PDFLarge-area coastal exposure and impact analysis has focussed on using sea-level rise (SLR) scenarios and has placed little emphasis on ocioeconomic scenarios, while neglecting spatial variations of population dynamics. We use the Dynamic Interactive Vulnerability Assessment (DIVA) Framework to assess the population exposed to 1 in 100-year coastal flood events under different population scenarios, that are onsistent with the shared socioeconomic pathways (SSPs); and different SLR scenarios, derived from the representative concentration pathways (RCPs); and analyse the effect of accounting for regionalised population dynamics on population exposure until 2100. In a reference approach, we use homogeneous population growth on national level. In the regionalisation approaches, we test existing spatially explicit projections that also account for urbanisation, coastal migration and urban sprawl. Our results show that projected global exposure in 2100 ranges from 100 million to 260 million, depending on the combination of SLR and population scenarios and method used for regionalising the population projections. The assessed exposure based on the regionalised approaches is higher than that derived from the reference approach by up to 60 million people (39%). Accounting for urbanisation and coastal migration leads to an increase in exposure, whereas considering urban sprawl leads to lower exposure. Differences between the reference and the regionalised approaches increase with higher SLR. The regionalised approaches show highest exposure under SSP5 over most of the twenty-first century, although total population in SP5 is the second lowest overall. All methods project the largest absolute growth in exposure for Asia and relative growth for Africa
Benefits of climate change mitigation for reducing the impacts of sea-level rise in G-20 countries
No full textThis paper assesses the potential benefits of climate change mitigation in reducing the impacts of sea-level rise over the 21st century in G-20 countries (excluding the European Union as a whole), using the Dynamic Interactive Vulnerability Assessment model. Impacts of the expected number of people flooded annually and wetland losses were assessed. To assess the benefits of mitigation, it was assumed that defences were not upgraded during the study. Globally, with a sea-level rise of 0.68m by the 2080s (with respect to 1980-1999), representing a potential future with limited climate change mitigation, and with the SRES A1 socio-economic scenario, 123 million additional people could be flooded annually and 39% of present global wetland stock could be lost. For a 0.19m rise in sea-level, associated with a substantial reduction in emissions, the number of people flooded could reduce to 13 million per year, with 21% of global wetland stock loss, unless new wetlands emerge. Collectively, non-Annex 1 G-20 countries experience a disproportionate higher number of people flooded in their nations compared with the proportion of population flooded globally. The greatest wetland losses for G-20 countries are projected for Australia, Indonesia and the USA. Thus, G-20 nations with the highest emissions or gross domestic product, frequently do not experience the greatest impacts, despite some of these nations being potentially more able to pay for adaptation. <br/
Non-linear interaction modulates global extreme sea levels, coastal flood exposure, and impacts
Get PDFWe introduce a novel approach to statistically assess the non-linear interaction of tide and non-tidal residual in order to quantify its contribution to extreme sea levels and hence its role in modulating coastal protection levels, globally. We demonstrate that extreme sea levels are up to 30% (or 70 cm) higher if non-linear interactions are not accounted for (e.g., by independently adding astronomical and non-astronomical components, as is often done in impact case studies). These overestimates are similar to recent sea-level rise projections to 2100 at some locations. Furthermore, we further find evidence for changes in this non-linear interaction over time, which has the potential for counteracting the increasing flood risk associated with sea-level rise and tidal and/or meteorological changes alone. Finally, we show how accounting for non-linearity in coastal impact assessment modulates coastal exposure, reducing recent estimates of global coastal flood costs by ~16%, and population affected by ~8%
Analysis of trends and variability of water levels
Get PDFKnowledge about the magnitude and frequency of extreme water levels is essential for assessing the risk of coastal flooding, which is the major coastal hazard worldwide. In the last years, significant effort has been directed to analyzing extreme water levels and their potential future changes under climate change. This thesis aims to contribute to this field by analyzing the historical variability of water levels and their components (i.e. tides and surges) at different temporal and spatial scales, and the potential effects of sea-level rise on the short-term variability of storm surges. Knowledge of both long and short term variability of water levels is required for reducing the uncertainties associated with the estimation of the likelihood of extreme water levels for flood impact assessments. Specifically, this thesis investigates long-term trends and inter-annual variability of water levels, tides and surges at two of the longest tide-gauge records of the southern hemisphere: Buenos Aires and Mar del Plata (Argentina). Over the last century, both water level series show an increasing trend caused by the rise of the mean sea-level, but also a decrease of the tidal amplitude. In the case of Buenos Aires, the changes in the tides are likely to be caused by the long-term changes in river discharge, as indicated by the high correlation observed between these two variables. In addition, river discharge is also highly correlated to the inter-annual variability of the extremes. Therefore, climate change induced changes in river discharge can in turn result in changes in the tides and storm surges at the Rio de la Plata estuary. Regarding the short-term variability of extreme water levels, two aspects are investigated in this thesis: namely the variability of the water level curve and the tide-surge interaction. The latter causes a dependency between the tide and the surge component, complicating their separation and posterior combination and thus the assessment of the water level curve evolution. To overcome this issue of tide-surge interaction, the skew surge parameter has been defined and shown to be independent on the high tidal level in semidiurnal regimes. Mixed semidiurnal regimes are characterized by a higher variability of high tidal levels, which can cause a dependency between the tide and the skew surge. This is statistically investigated for 15 sites worldwide, finding that half of these sites show a dependency between high tidal levels and extreme skew surges, and thus not any extreme skew surge can occur at any high tidal level. The skew surge does not contain information of the temporal evolution of the storm surge (water level curve), which is required as input of flood models. The uncertainties related to not accounting for the variability of the water curve when assessing coastal flooding is investigated for a coastal stretch of the German Bight. The high variability found at times around the water level peaks, when overflow/overtopping is more likely, can lead to a threefold increase of the total overflow volumes between events. Sea-level rise produces an increase of the water levels at times around the water level peaks, and this increase is relatively larger for low to moderate sea-level rise scenarios. Therefore, neglecting the variability of the water level curve can introduce large uncertainties in flood assessments and thus using the skew surge parameter might not be recommended when assessing coastal flooding. The results presented here provide important information about the long and short term variability of tides and storm surges that can be used for reducing uncertainties when estimating future extreme water levels and their associated coastal flood risk
Eine Plattform zur Vorhersage der Brandgefahr auf Sardinien: Entwicklung eines web-basierten Feuergefahr-Vorhersagesystems für Landschaften im Mittelmeerraum unter Verwendung von Open Source Software und durch Crowdsourcing bereitgestellte Wetterdaten - exemplarisch durchgeführt für die Insel Sardinien
Get PDFThis thesis covers the preparation and realisation of setting up a fire danger forecasting platform for the Isle of Sardinia. The system created uses, firstly, crowd sourced weather data as input for calculation of fire danger predictions and, secondly, only free and open source software for the actual implementation. The platform is meant to provide regional, daily fire danger forecasting maps. Its configuration is based on a ten-year study of fire occurrence on Sardinia and Crete. The Fire Weather Index (FWI) with threshold values adapted to Sardinia is used for the forecasts.Diese Arbeit beschäftigt sich mit der Konzeption und Umsetzung einer Feuergefahr-Vorhersageplattform für die Insel Sardinien. Das erstellte System verwendet, zum Ersten, durch Crowdsourcing bereitgestellte Wetterdaten als Eingabewerte für die Berechnung der Feuergefahr und, zum Zweiten, ausschließlich freie und quelloffene Software für die eigentliche Implementierung. Ziel der Plattform ist die Bereitstellung von regionalen, täglichen Feuergefahr-Vorhersagekarten. Die Konfiguration des Systems basiert auf einer Studie zum Auftreten von Feuern über einen Zeitraum von 10 Jahren auf Sardinien und Kreta. Für die Vorhersagen wird der Fire Weather Index (FWI) mit auf Sardinien abgestimmten Schwellenwerten verwendet
Medium-term morphodynamics of the Mittelplate area, German North Sea coast
Get PDFIn view of climate change and sea level rise the prediction of the morphological evolution of coastal areas in medium-term and long-term has become a matter of increasing concern in the field of coastal management. Process-based modelling has recently emerged as an effective tool for studying coastal morphodynamics and for predictive estimation of the coastal development. The main focus of the thesis is to study, analyse and assess the medium-term morphodynamics of a complex network of tidal channels, flats and shoals in the Mittelplate area, Dithmarschen Bight, German North Sea coast. In this framework numerical techniques for accelerating morphodynamic simulations are also critically evaluated. Taking full advantage of recent available high-resolution bathymetric surveys over a period of six years, the natural morphodynamics was thoroughly investigated. Essential reasons for the morphological changes are provided on the base of a structural analysis. The medium-term morphological changes were studied by means of numerical modelling. Process-based models for simulating flow, waves and sediment transport were developed, calibrated and validated against collected field data. According to internationally accepted quality criteria the developed models proved to represent well the hydrodynamics and sediment dynamics in the area of concern. By means of coupling of the process models a morphodynamic model was set-up. Benchmark simulation using the full time series of forcing of tide, wind and waves was conducted for a two-year period and the model proved good ability in reproducing the observed morphological changes. The single effects of the driving forces tide, wind and waves on the morphological development were analyzed and assessed. Main mechanisms driving the morphological evolution of the area were identified. An input reduction method, the so-called "representative period method" applied to time series of wind in conjunction with "morphological factor approach", was used to analyse effectiveness of numerically accelerated simulations for the prediction of morphodynamics. The results show that the method was restrictively applicable for reproducing the medium-term morphodynamics because (i) it disregards associated classes of wind speed and wind direction in time series when shortening the long-term wind data to much shorter "representative period" data; (ii) the interaction of tide, wind and waves from long-term is changed or widely lost in the "representative period". Recommendations for the improvement of the applied input reduction method and the model performance are provided.Im Angesicht von Klimawandel und Meeresspiegelanstieg ist die Vorhersage der mittel- und langfristigen morphologischen Entwicklung von Küstengebieten von steigendem Interesse im Küstenmanagement. Hier sind prozessbasierte numerische Modelle zu effizienten Werkzeugen für Studien zur Morphodynamik und für vorausblickende Abschätzungen der Küstenentwicklung geworden. Hauptziel der Arbeit ist die Untersuchung, Analyse und Einschätzung der mittelfristigen Morphodynamik in einem komplexen System aus Gezeitenrinnen, Wattflächen und Wattrücken im Mittelplate-Gebiet der Dithmarscher Bucht, Deutsche Nordseeküste. Dabei werden auch numerische Techniken zur Beschleunigung morphodynamischer Simulationen kritisch beleuchtet. Unter Verwendung vorliegender hochauflösender topografischer Vermessungen über einen Zeitraum von 6 Jahren wird zunächst die natürliche Morphodynamik betrachtet. Über Strukturanalysen werden wesentliche Gründe für morphologische Veränderungen offengelegt. Mit Hilfe numerischer Modellierungen werden dann die mittelfristigen morphologischen Veränderungen eingehender untersucht. Dazu wurden prozessbasierte Modelle zur Simulation von Strömung, Seegang und Sedimenttransport entwickelt, kalibriert und verifiziert. Gemäß internationalen Prüfverfahren sind die Modelle befähigt, Hydro- und Schwebstoffdynamik im Zielgebiet in guter Qualität zu reproduzieren. Durch Kopplung der prozessbasierten Modelle wurde ein Morphodynamikmodell aufgebaut. Eine „Benchmark“-Simulation mit vollständiger Zeitreihe der Antriebsgrößen Tide, Wind und Seegang wurde für einen Zeitraum von 2 Jahren durchgeführt. Eine Gegenüberstellung mit Topografiedaten unterstrich die Fähigkeit dieses Modells, die beobachtete Morphologieentwicklung gut zu reproduzieren. Mit dem Modell wurden die Einzeleffekte der Antriebsgrößen auf die morphologische Entwicklung analysiert, bewertet und die Hauptantriebsmechanismen identifiziert. Das Eingabereduktionsverfahren „Repräsentative Periode Methode“, wurde für Windzeitreihen angewandt und mit dem Ansatz „Morphologischer Faktor“ kombiniert, um die Effizienz numerisch beschleunigter Simulationen zur Vorhersage der Morphodynamik zu analysieren. Es wird gezeigt, dass diese Verfahren zur Reproduktion der mittelfristigen Morphodynamik eher eingeschränkt anzuwenden sind, weil a) sie eine Zusammengehörigkeit von Gruppen von Windgeschwindigkeit und Windrichtung bei der numerischen Zerschneidung der Langzeitreihen zu weit kürzeren „repräsentativen Perioden“ außer Acht lassen, und weil b) die Interaktion von Zeitreihengruppen aus Tide, Wind und Seegang durch Verkürzung zu „repräsentativen Perioden“ geändert werden oder verloren gehen. Es werden Empfehlungen zur Verbesserung der angewandten Reduktionstechnik und der Modellleistung gegeben
Processes and factors controlling and affecting the retreat of mangrove shorelines in South Vietnam
Get PDFMangrove coasts are under eroding in some areas. The processes that control the erosion have not been studied yet. This study was carried-out at two mangrove cliff shorelines in South Vietnam to answer this question.
At both sites, the erosion is affected by both the duration of tidal inundation and wave energy input. The most dominant factor is the duration of tidal inundation, which usually lasts longer during neap tide. Especially, the erosion is higher during neap tide. As well, tidal current, in particular strong asymmetry and speed, can influence the erosion. Higher shear strength of the cliff soil can reduce the erosion rate. Without mangroves, the erosion will accelerate
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