Global-scale analysis of socioeconomic impacts of coastal flooding over the 21st century

Building on a global database of projected extreme coastal flooding over the coming century, an extensive analysis that accounts for both existing levels of coastal defences (structural measures) and two scenarios for future changes in defence levels is undertaken to determine future expected annual people affected (EAPA) and expected annual damage (EAD). A range of plausible future climate change scenarios is considered along with narratives for socioeconomic change. We find that with no further adaptation, global EAPA could increase from 34M people/year in 2015 to 246M people/year by 2100. Global EAD could increase from 0.3% of global GDP today to 2.9% by 2100. If, however, coastal defences are increased at a rate which matches the projected increase in extreme sea level, by 2100, the total EAPA is reduced to 119M people/year and the EAD will be reduced by a factor of almost three to 1.1% of GDP. The impacts of such flooding will disproportionately affect the developing world. By 2100, Asia, West Africa and Egypt will be the regions most impacted. If no adaptation actions are taken, many developing nations will experience EAD greater than 5% of GDP, whilst almost all developed nations will experience EAD less than 3% of GDP

Comparison of Coastal Vulnerability Index applications for Barcelona Province

The Coastal Vulnerability Index (CVI) is one of the simplest and commonly used methods to assess coastal vulnerability to sea-level rise (SLR) driven erosion and/or inundation. In this way, it is a common tool contributing to the decision-making process in long-term coastal planning and management. However, there is not a unique approach to be adopted, and existing ones can supply different information and, thus, promote different decisions. Within this context, the main goal of this paper is to compare and evaluate different methodologies to determine CVI, and to suggest the most appropriate approach that can be generically applied for coastal vulnerability assessment. For doing this, the approaches proposed by Gornitz (1991), Shaw et al. (1998), Thieler and Hammar-Klose (2000), and Lopez et al. (2016) are applied along the 160 km long the Barcelona coastline in the Spanish Mediterranean. Shaw et al.‘s (1998) method appears to be the more realistic approach to assess vulnerability of the Barcelona coast while the overall vulnerability level calculated by the equation proposed by Gornitz (1991) indicate a wide variability, from highly vulnerable to a very low level of vulnerability. This study shows that the ranking tables generated from site-specific databases may not be applicable elsewhere, and indicates that it might be prudent to develop site or region-specific ranking categories to compute the overall CVI in order to provide reliable inputs to local coastal zone management initiatives. Despite the potential bias in the categorization of the overall CVI classes and their expert opinion/judgment approval requirements, CVI tools help decision makers to take the necessary actions to increase the resilience of coastal zones to SLR.Peer ReviewedPostprint (published version

Assessing climate change impacts on the stability of small tidal inlets:Part 1 - Data poor environments

Bar-built or barrier estuaries (here referred to as Small tidal inlets, or STIs), which are commonly found along wave-dominated, microtidal mainland coasts, are highly likely to be affected by climate change (CC). Due to their pre-dominance in tropical and sub-tropical regions of the world, many STIs are located in developing countries, where STI related activities contribute significantly to the national GDPs while community resilience to coastal changes is low, with the corollary that CC impacts on STIs may lead to very serious socio-economic consequences. While assessing CC impacts on tidal inlets is in general difficult due to inherent limitations of contemporary numerical models where long term morphodynamic simulations are concerned, these difficulties are further exacerbated due to the lack of sufficient model input/verification data in often data poor developing country STI environs. As a solution to this problem, Duong et al. (2016) proposed two different process based snap-shot modelling approaches for data poor and data rich environments. This article demonstrates the application of Duong et al.'s (2016) snap-shot modelling approach for data poor environments to 3 case study sites representing the 3 main STI types; Permanently open, locationally stable inlets (Type 1), Permanently open, alongshore migrating inlets (Type 2) and Seasonally/Intermittently open, locationally stable inlets (Type 3). Results show that Type 1 and Type 3 inlets will not change Type even under the most extreme CC driven variations in system forcing considered here. Type 2 inlets may change into Type 1 when CC results in a reduction in annual longshore sediment transport. Apart from Type changes, CC will affect the level of inlet stability and some key behavioural characteristics (e.g. inlet migration distances, inlet closure times). In general, CC driven variations in annual longshore sediment transport rates appear to be more relevant for future changes in inlet stability and behaviour, rather than sea level rise as commonly believed. Based on model results, an inlet classification scheme which, for the first time, links inlet Type with the Bruun inlet stability criteria is presented

Geochemical modeling of magmatic gas scrubbing

The EQ3/6 software package, version 7.2 was successfully used to model scrubbing of magmatic gas by pure water at 0.1 MPa, in the liquid and liquid-plus-gas regions. Some post-calculations were necessary to account for gas separation effects. In these post-calculations, redox potential was considered to be fixed by precipitation of crystalline a-sulfur, a ubiquitous and precocious process. As geochemical modeling is constrained by conservation of enthalpy upon water-gas mixing, the enthalpies of the gas species of interest were reviewed, adopting as reference state the liquid phase at the triple point. Our results confirm that significant emissions of highly acidic gas species (SO2(g), HCl(g), and HF(g)) are prevented by scrubbing, until dry conditions are established, at least locally. Nevertheless important outgassing of HCl(g) can take place from acid, HCl-rich brines. Moreover, these findings support the rule of thumb which is generally used to distinguish SO2-, HCl-, and HF-bearing magmatic gases from SO2-, HCl-, and HF-free hydrothermal gases

How to weigh coastal hazard against economic consequence

It is well recognised that sea level change over the coming century will have an extraordinary economic impact on coastal communities. To overcome the uncertainty that still surrounds the mechanics of shoreline recession and stochastic forcing, land-use planning and management decisions will require a robust and quantitative risk-based approach. A new approach is presented, which has been evaluated using field measurements and assessed in economic terms. The paper discusses a framework for coastal risk analysis which combines four main components 1) the effects of non-stationary climate, including decade scale variability and anthropogenic change; 2) a full probabilistic assessment of incident wave and surge conditions; 3) determination of storm erosion extents; and 4) the economic impact of combined coastal erosion and recession. The framework is illustrated in Figure 1. The operation of this framework has been demonstrated, building upon previous work (Callaghan et al., 2008; Jongejan et al., 2011; Ranasinghe et al., 2011). The first three components relate to physical hazards. Using stochastic simulation, we quantify the 'likelihood' side of risk. That likelihood is typically represented by lines indicating a projected extreme landward shoreline condition and an associated quantitative probability. For the first time, the effects of non-stationary climate (e.g. sea level rise) have been included. This can be extended to include decadal scale climate variation effects such as beach rotation. The fourth component requires the determination of values associated with land threatened by coastal erosion during the time frame being considered. We assign a spatially varying value density relationship. The exceedance probability of erosion is combined with the value density to calculate the expected value of damage at a given point in time. In a non-stationary climate scenario, the exceedance probabilities change with time, and this is also considered. Given a known rate of return on investment, the differentials in the rates of return (between coastal and inland property investments) are subsequently used to determine the efficient position of the setback line. The results are presented within a GIS framework to effectively feed into the coastal land use planning process. We demonstrate the framework by applying it to using real data (both physical and economic) for our subject site, Narrabeen Beach in Sydney