Evaluation of swimmer-based rip current escape strategies

Rip currents are the primary hazard on surf beaches, and early studies described them as fast, shore-normal flows that extended seaward of the surf zone. Based on this traditional view, commonly promoted safety advice was to escape a rip current by swimming parallel to the beach. However, recent studies have shown dominant rip current re-circulation within the surf zone and have endorsed floating as an appropriate escape strategy. Here, a first quantitative assessment of the efficacy of various rip current escape strategies, with a focus on the underlying physical processes, is presented. A field study was conducted at Shelly Beach, NSW, Australia, measuring three rip currents (two open beaches, one topographic) over 3 days in varying wave conditions. Floating was found to be a longer duration, more variable escape strategy ( $ \overline{t} $  = 3.8 min, σ = 2.4 min), than swimming parallel ( $ \overline{t} $  = 2.2 min, σ = 1.0 min). Neither of the scenarios is 100 % foolproof, and both fail in some scenarios, making simplified safety recommendations difficult. Swim parallel failures are related to swimming against the alongshore current of the rip circulation. Float failures related to surf zone exits, with the highest exit rate occurring in the topographic rip. Float failures also occurred due to multiple re-circulations without the person attaining safe footing on the bar. The variable spatial and temporal behaviour of rip currents suggests that a single escape strategy safety message is inappropriate. Instead, a combined approach and scenario-specific safety advice should be considered by beach safety practitioners to promote to the public.     

On the swimming strategies to escape a rip current: a mathematical approach

Rip currents represent significant hazards to swimmers all around the world. The danger arises when a misinformed swimmer uses an inadequate strategy to escape the rip, such as fighting the current directly. This can lead to fatigue, panic, and in some cases drowning. There exists a range of strategies put forward by experts (both lifeguards and scientists) to escape rip currents. However, these recommendations are based on a limited number of scientific studies and there is still much discrepancy surrounding the best strategy to escape a rip. Thus, here we present a simple, physics-based theoretical model aimed at assessing different escape strategies in terms of their associated ‘energetic cost’ (in work and power) for any given rip current and swimmer’s proficiency level. Many combinations of swimmers and rips are considered, including both idealised and a realistic rip current. Our quantitative results back the common knowledge that swimming against the rip (which is strongly discouraged by lifeguards) is almost universally the worst possible strategy, especially when compared against strategies favoured by experts, such as floating with the current before attempting to swim back to the shore. For a realistic rip, our results suggest that swimming directly against the rip can require several times more power from the swimmer than other strategies advised by lifeguards, thus lending further scientific support to experts’ recommendations. This study may help promote education around the dangers posed by rip currents and how best to address them.

     

Correction to: Rip current hazard assessment on a sandy beach in Liguria,NW Mediterranean

Natural Hazards - The article was published showing the first two author names in the wrong order.     

Non-DRR NGOs strategies for livelihood development in the coastal communities of Bangladesh: a case study

Natural Hazards - This study aimed to assess the effectiveness of non-DRR NGOs’ programs focusing on their contribution to the uplift livelihood of the disaster-affected coastal communities....     

Challenges and strategies for better use of scientific information in the management of coastal estuaries

Numerous studies have concluded that better use of scientific information could improve the quality of coastal and estuarine environmental management. Approaches for effecting such a change include ecosystem-based, integrated, and adaptive management, but such basic re-orientation of estuarine and coastal management has proved difficult to achieve. Even environmental indicators, seemingly straightforward ways of injecting scientific information into decision making, have achieved broad on-the-ground use in relatively few instances—principally the largest estuary management programs. A conceptual framework useful for examining environmental management systems affecting the five PNCERS (Pacific Northwest coastal Ecosystems Regional Study) estuaries conceives of environmental managers, researchers, and interested and affected parties in the public as interacting through the multi-layered institutional arrangements that currently promote the utilization, management, or protection of coastal and estuarine resources. Considerable variation exists in the approach and effectiveness of the region's environmental management organizations. Interaction between science and management in the region appears to be limited to an extent by high transaction costs; a cultural divide between environmental scientists and environmental managers is perceived by members of both groups who work with the PNCERS estuaries as inhibiting communications between them. Mechanisms that both groups identify as useful for improving the flow of information between science and management are little used, perhaps as a result. The two groups have very different patterns of information dissemination and acquisition, and though both chose agency archives and databases as their top methods for disseminating information, neither group relies much on these vehicles for information they seek. Both residents' and practitioners' perceptions of threats to the PNCERS estuaries show patterns of estuary-to-estuary variation. One theme that emerges is that problems associated with poor land management in adjacent uplands are common to most of these estuaries, potentially providing a sense of commonality through which a more regional approach to estuary management could emerge. A common set of estuarine environmental indicators implemented for all estuaries could help instigate such a regional approach, but resource constraints, especially at the local level, will have to be overcome for that to occur. There is currently substantial lack of common vision among coastal practitioners as to the purpose and desirability of indicators, and relatively little experience or knowledge of their use, particularly at the local level. Use of estuarine science in the management of these estuaries appears to be greatest during periods in which the largest programmatic shifts in environmental management approaches occur, an observation consistent with other studies that have concluded that the use of environmental science in environmental management tends to be episodic.     

Household response to cyclone and induced surge in coastal Bangladesh: coping strategies and explanatory variables

The purpose of this research is to explore indigenous coping strategies and identify underlying demographic, socio-economic and other relevant variables that influence the adoption of coping strategies in three distinct cyclone-prone coastal villages of Bangladesh. The study finds that cyclones and induced surges are a recurrent phenomenon in coastal Bangladesh; hence people are used to adjusting their lifestyle and adopting their own coping strategies intelligently. Adoption of a particular set of coping strategies depends not only on the magnitude, intensity and potential impacts of the cyclone and induced surge, but also age, gender, social class, dissemination of early warning information, locational exposure, external assistance, social protection and informal risk sharing mechanisms within the community. Indigenous cyclone disaster prevention and mitigation strategies significantly minimize the vulnerability of the people. Under extreme situations, when such disasters surpass the shock-bearing capacity of the victims, informal risk sharing mechanisms through social bonding and social safety-nets become vital for short-term survival and long-term livelihood security. Therefore, proper monitoring and understanding of local indigenous coping strategies are essential in order to target the most vulnerable groups exposed to disasters. Additionally, proper dissemination of early warning and government and non-government partnerships for relief and rehabilitation activities should be prioritized to ensure pro-poor disaster management activities. The study also recommends effective monitoring of the impact of aid to ensure corrective measures to avoid the development of relief dependency by disaster victims.     

Rip current-related fatalities in India: a new predictive risk scale for forecasting rip currents

This study analyzes fatalities caused by rip currents in important locations along east and west coasts of India for the period 2000–2010. Results include the frequency of fatalities from rip currents, their cause, and their spatial distributions. Rip current fatalities are most common in the southeastern India, with a non-uniform spatial distribution. August and October are identified as most favorable for rip current generation. In India, rip current-related drowning is estimated as 39 per year during the last decade. East coast of India averaged 30–40 drownings, and west coast of India averaged 5–10 drownings per year. In coastal Andhra Pradesh, more than 350 people had been drowned due to rip currents and only 10 people were rescued. Visakhapatnam recorded highest drowning (293); R. K. beach is the most vulnerable potential rip current zones. From 2007 onward, rip current deaths increased at an alarming rate. The frequency of rip current drownings increased markedly during shore-normal wave incidence and mid-low tidal stages. A new empirical forecasting technique has been developed for prediction of rip current risk in India for the first time. FORTRAN-based software was developed to generate automatic rip current forecast report for any given location. The scale’s performance was tested with field data and by using different statistical methods. The new predictive scale is predicting rip current occurrences reasonably well.     

Co-contamination of water with chlorinated hydrocarbons and heavy metals: challenges and current bioremediation strategies

Chlorinated hydrocarbons can cause serious environmental and human health problems as a result of their bioaccumulation, persistence and toxicity. Improper disposal practices or accidental spills of these compounds have made them common contaminants of soil and groundwater. Bioremediation is a promising technology for remediation of sites contaminated with chlorinated hydrocarbons. However, sites co-contaminated with heavy metal pollutants can be a problem since heavy metals can adversely affect potentially important biodegradation processes of the microorganisms. These effects include extended acclimation periods, reduced biodegradation rates, and failure of target compound biodegradation. Remediation of sites co-contaminated with chlorinated organic compounds and toxic metals is challenging, as the two components often must be treated differently. Recent approaches to increasing biodegradation of organic compounds in the presence of heavy metals include the use of dual bioaugmentation; involving the utilization of heavy metal-resistant bacteria in conjunction with an organic-degrading bacterium. The use of zero-valent irons as a novel reductant, cyclodextrin as a complexing agent, renewable agricultural biosorbents as adsorbents, biosurfactants that act as chelators of the co-contaminants and phytoremediation approaches that utilize plants for the remediation of organic and inorganic compounds have also been reported. This review provides an overview of the problems associated with co-contamination of sites with chlorinated organics and heavy metals, the current strategies being employed to remediate such sites and the challenges involved.     

Data for coastal GIS: issues and implications for management

Geographic information systems can provide easy access to large quantities of geographically-referenced data for monitoring, planning and environmental decision support for coastal applications. The dynamic and variable nature of the coastal ocean environment gives rise to data issues different than those associated with land-based GIS. This paper investigates, in particular, the use of different data, including those produced by numerical simulations or ocean models, for coastal management and is illustrated with examples from a Baltic Sea GIS implementation. Implications for the use of these data in environmental management are discussed.     

Communicating uncertainty: lessons learned and suggestions for climate change assessment

Assessments of climate change face the task of making information about uncertainty accessible and useful to decision-makers. The literature in behavior economics provides many examples of how people make decisions under conditions of uncertainty relying on inappropriate heuristics, leading to inconsistent and counterproductive choices. Modern risk communication practices recommend a number of methods to overcome these hurdles, which have been recommended for the Intergovernmental Panel on Climate Change (IPCC) assessment reports. This paper evaluates the success of the most recent IPCC approach to uncertainty communication, based on a controlled survey of climate change experts. Evaluating the results from the survey, and from a similar survey recently conducted among university students, the paper suggests that the most recent IPCC approach leaves open the possibility for biased and inconsistent responses to the information. The paper concludes by suggesting ways to improve the approach for future IPCC assessment reports. To cite this article: A. Patt, S. Dessai, C. R. Geoscience 337 (2005).     

Leveraging the diaspora for development: lessons from Ethiopia

This paper uses investment data for the period 1994–2008 and information from in-depth interviews with key informants in Ethiopian government agencies and 15 entrepreneurs who returned to Ethiopia to start business ventures, to assess the success of the Ethiopian government in attracting diaspora investment. The study found that diaspora investment was highly concentrated geographically and sectorally. Among the significant issues facing diasporan investors were access to land, access to finance, lack of reliable information, poor contract enforcement and frequent changes in government policies and sectoral priorities. The authors recommend the development of frameworks for the enforcement of laws and standards to make investing in Ethiopia more attractive. They also propose that the government consider the long-term sustainability of policies before they are implemented, foster diversification and the better use of the country’s natural resource clusters, and establish policies that facilitate the circulation of knowledge and skills through input from expatriate professionals and experts.     

Pollution and paradigms: lessons from Icelandic volcanism for continental flood basalt studies

This paper is based on the premise that research into the environmental impact of continental flood basalt (CFB) volcanism has paid insufficient attention to the potential ecosystem damage that would result from the direct deposition of hundreds of megatons (Tg) of sulphur and other volatiles. The environmental impacts of the 1783 Laki Fissure eruption are reviewed in outline. It is shown that in a relatively brief period of volcanic activity, volatiles emitted by the eruption damaged and destroyed vegetation from the Arctic Ocean to the Mediterranean. Air pollution was so intense that human health was affected and the national death rate increased dramatically in both England and France.

It is proposed that the events of 1783 may be used as a paradigm for the environmental impacts of a CFB lava flow, and the emissions of 1783 are scaled up to illustrate this point. Thus, if a Laki style event were to erupt for a year it would approach the physical scale of a single episode of the Roza flow in the Columbia River CFB and potentially yield 576 Tg of sulphur gases which could have been oxidised into approximately 945 Tg of aerosol. This could generate a tropospheric aerosol mass of approximately 708 Tg H₂SO₄.

The ecosystem impact of the deposition of acids on this scale would be profound and, as with the actual Laki event, be continental in scale. All parts of the plant life cycle would be disrupted, including photosynthesis and fruiting. Inevitably, with the disruption of food webs animals would also be affected. Poorly buffered inland waters would be acidified, as would Boreal soils, reducing their biodiversity.

In our already polluted and interdependent world, any future event on this scale would have serious consequences for human health and trade.     

Policy lessons from practice: Australian bush products for commercial markets

Bush products provide one of few prospects for new or expanded natural resource-based enterprise activity by indigenous people of remote regions of arid central and tropical northern Australia. Realizing this potential requires development of effective certification or branding, functioning producer associations and joint ventures if returns to Aboriginal people are to improve. Nine steps are suggested as part of a strategy to address the challenges facing viable bush product enterprises.     

Enhancing preparedness for managing debris from earthquakes: lessons from Italy

Natural Hazards - Earthquakes can generate large volumes of debris which may threaten public health, hinder reconstruction and impact the environment. The present paper aims at investigating how...     

Review: Simulation-optimization models for the management and monitoring of coastal aquifers

The literature on the application of simulation-optimization approaches for management and monitoring of coastal aquifers is reviewed. Both sharp- and dispersive-interface modeling approaches have been applied in conjunction with optimization algorithms in the past to develop management solutions for saltwater intrusion. Simulation-optimization models based on sharp-interface approximation are often based on the Ghyben-Herzberg relationship and provide an efficient framework for preliminary designs of saltwater-intrusion management schemes. Models based on dispersive-interface numerical models have wider applicability but are challenged by the computational burden involved when applied in the simulation-optimization framework. The use of surrogate models to substitute the physically based model during optimization has been found to be successful in many cases. Scalability is still a challenge for the surrogate modeling approach as the computational advantage accrued is traded-off with the training time required for the surrogate models as the problem size increases. Few studies have attempted to solve stochastic coastal-aquifer management problems considering model prediction uncertainty. Approaches that have been reported in the wider groundwater management literature need to be extended and adapted to address the challenges posed by the stochastic coastal-aquifer management problem. Similarly, while abundant literature is available on simulation-optimization methods for the optimal design of groundwater monitoring networks, applications targeting coastal aquifer systems are rare. Methods to optimize compliance monitoring strategies for coastal aquifers need to be developed considering the importance of monitoring feedback information in improving the management strategies.     

Lithogeochemical exploration for komatiite-associated Ni-sulfide deposits: strategies and limitations

Summary Lithogeochemistry of komatiites can be useful in exploration for nickel sulfides in two distinct ways: indirectly, through identification of favourable volcanic environments, and more directly, through identification of signatures of crustal contamination and sulfide liquid segregation. However, the discrimination between mineralised and unmineralised sequences is not straightforward.Komatiite chemistry is influenced by a variety of primary magmatic variables, overprinted to various degrees for various elements by the effects of metasomatic alteration. Once highly metasomatised samples have been filtered, primary magmatic signatures are largely retained for the elements Mg, Fe, Si, Al, Ti and Cr, even in cases of extensive CO₂ metasomatism and talc-carbonate alteration. Incompatible trace elements such as Zr and REE are modified to some degree by alteration, particularly in cumulate rocks, but there is evidence for some retention of primary signatures.Favourable volcanic environments, i.e. those containing large-volume lava pathways, can be identified on the basis of their distribution and ratios of whole rock Mg, Fe, Ni, Cr and Ti. Nickel depletion can be recognised in some cases of large mineralised systems where large volumes of sulfide formed at low silicate:sulfide (R) ratios, but is not effective in finding small high-grade ore shoots. PGE in low-S rocks do not appear to be an effective discriminant, owing to the local scale of S-saturation.Crustal contamination is indicated in some mineralised suites on the basis of enriched ratios of strongly to weakly incompatible lithophile elements in fractionated lavas, but the effects of alteration are significant and may be misleading. On the whole, mineralised sequences tend to have more enriched signatures than unmineralised ones, but there may be many false positives and negatives, and if the most CO₂-metasomatised suites are discounted the contrast largely disappears. Overall, the presence of Ni-enriched sulfides is by far the best lithogeochemical indicator there is, and it may be the only really effective one.     

自然灾害应急救灾的若干经验和建议

自然灾害应急救灾是社会危机管理的重要内容, 也是对一个国家综合国力、政府危机管理水平和社会精神文明建设成果的直接检验. 近几十年来, 我国应急救灾管理体制在应对数次大规模突发性自然灾害的实践中得到不断完善与发展. 通过多年参与应急救灾一线工作实践, 总结归纳了几点有助于救灾管理体制向着法制化、科学化、规范化和有序性方向发展的体会和建议, 以期能对灾害危机管理人员和受灾群众的自救互救工作有所启示.