Physically-based Assessment of Hurricane Surge Threat under Climate Change

Storm surges are responsible for much of the damage and loss of life associated with landfalling hurricanes. Understanding how global warming will affect hurricane surges thus holds great interest. As general circulation models (GCMs) cannot simulate hurricane surges directly, we couple a GCM-driven hurricane model with hydrodynamic models to simulate large numbers of synthetic surge events under projected climates and assess surge threat, as an example, for New York City (NYC). Struck by many intense hurricanes in recorded history and prehistory, NYC is highly vulnerable to storm surges. We show that the change of storm climatology will probably increase the surge risk for NYC; results based on two GCMs show the distribution of surge levels shifting to higher values by a magnitude comparable to the projected sea-level rise (SLR). The combined effects of storm climatology change and a 1 m SLR may cause the present NYC 100-yr surge flooding to occur every 3–20 yr and the present 500-yr flooding to occur every 25–240 yr by the end of the century.United States. National Oceanic and Atmospheric Administration (Postdoctoral Fellowship Program)National Science Foundation (U.S.

Dynamics of Wind Setdown at Suez and the Eastern Nile Delta

BACKGROUND: Wind setdown is the drop in water level caused by wind stress acting on the surface of a body of water for an extended period of time. As the wind blows, water recedes from the upwind shore and exposes terrain that was formerly underwater. Previous researchers have suggested wind setdown as a possible hydrodynamic explanation for Moses crossing the Red Sea, as described in Exodus 14. METHODOLOGY/PRINCIPAL FINDINGS: This study analyzes the hydrodynamic mechanism proposed by earlier studies, focusing on the time needed to reach a steady-state solution. In addition, the authors investigate a site in the eastern Nile delta, where the ancient Pelusiac branch of the Nile once flowed into a coastal lagoon then known as the Lake of Tanis. We conduct a satellite and modeling survey to analyze this location, using geological evidence of the ancient bathymetry and a historical description of a strong wind event in 1882. A suite of model experiments are performed to demonstrate a new hydrodynamic mechanism that can cause an angular body of water to divide under wind stress, and to test the behavior of our study location and reconstructed topography. CONCLUSIONS/SIGNIFICANCE: Under a uniform 28 m/s easterly wind forcing in the reconstructed model basin, the ocean model produces an area of exposed mud flats where the river mouth opens into the lake. This land bridge is 3-4 km long and 5 km wide, and it remains open for 4 hours. Model results indicate that navigation in shallow-water harbors can be significantly curtailed by wind setdown when strong winds blow offshore

A framework for the probabilistic analysis of meteotsunamis

This paper is not subject to U.S. copyright. The definitive version was published in Natural Hazards 74 (2014): 123-142, doi:10.1007/s11069-014-1294-1.A probabilistic technique is developed to assess the hazard from meteotsunamis. Meteotsunamis are unusual sea-level events, generated when the speed of an atmospheric pressure or wind disturbance is comparable to the phase speed of long waves in the ocean. A general aggregation equation is proposed for the probabilistic analysis, based on previous frameworks established for both tsunamis and storm surges, incorporating different sources and source parameters of meteotsunamis. Parameterization of atmospheric disturbances and numerical modeling is performed for the computation of maximum meteotsunami wave amplitudes near the coast. A historical record of pressure disturbances is used to establish a continuous analytic distribution of each parameter as well as the overall Poisson rate of occurrence. A demonstration study is presented for the northeast U.S. in which only isolated atmospheric pressure disturbances from squall lines and derechos are considered. For this study, Automated Surface Observing System stations are used to determine the historical parameters of squall lines from 2000 to 2013. The probabilistic equations are implemented using a Monte Carlo scheme, where a synthetic catalog of squall lines is compiled by sampling the parameter distributions. For each entry in the catalog, ocean wave amplitudes are computed using a numerical hydrodynamic model. Aggregation of the results from the Monte Carlo scheme results in a meteotsunami hazard curve that plots the annualized rate of exceedance with respect to maximum event amplitude for a particular location along the coast. Results from using multiple synthetic catalogs, resampled from the parent parameter distributions, yield mean and quantile hazard curves. Further refinements and improvements for probabilistic analysis of meteotsunamis are discussed

Uniendo ingeniería y ecología: la protección costera basada en ecosistemas

En un contexto de crecientes impactos y riesgos socio-económicos en las costas del planeta, la protección costera basada en ecosistemas surge como un nuevo paradigma que une los principios de protección, sostenibilidad y resiliencia, a la vez que proporciona múltiples beneficios. Este artículo ofrece una perspectiva sobre qué son y cómo se pueden utilizar las defensas naturales en el diseño, planificación y gestión de costas. La política pública muestra un creciente interés por su implementación general y el cuerpo de conocimiento y experiencia alrededor de la también denominada infraestructura ?verde? es creciente, pero aún existen importantes barreras que salvar. Una de ellas es estandarizar su diseño en términos ingenieriles, así como reconocer los aspectos que los diferencian respecto a enfoques tradicionales. La adaptación climática y la reducción de riesgos son áreas en las que su utilización puede ser más significativa, debido a la variedad de servicios que ofrecen. Tanto desde el punto de vista técnico como económico, existen argumentos sólidos para evitar la degradación de los ecosistemas, avanzando su restauración y conservación, como también desde la perspectiva de la defensa de las costas.In a context of increasing socio-economic impacts and risks in the coastal areas of the planet, coastal protection based on ecosystem features becomes a new paradigm that combines the principles of conservation, sustainability and resilience, while providing multiple benefits. This paper provides a perspective on what these are and how they can be used in the design, planning and management of the coastal zones. Policy-makers are calling for further uptake and implementation across the board and the body of knowledge and experience around the socalled ?green? infrastructure is growing, but there are still major barriers for a widespread uptake. One of them is to standardize designs in engineering terms, recognizing the different characteristics compared to traditional engineering solutions. Climate adaptation and risk reduction are areas where its use may be more significant, for the variety of services they offer. Both technically and economically, there are strong arguments to prevent degradation of ecosystems and to advance in their restoration and conservation, as well as from a coastal defense perspective

Coastal flooding by tropical cyclones and sea-level rise

The future impacts of climate change on landfalling tropical cyclones are unclear. Regardless of this uncertainty, flooding by tropical cyclones will increase as a result of accelerated sea-level rise. Under similar rates of rapid sea-level rise during the early Holocene epoch most low-lying sedimentary coastlines were generally much less resilient to storm impacts. Society must learn to live with a rapidly evolving shoreline that is increasingly prone to flooding from tropical cyclones. These impacts can be mitigated partly with adaptive strategies, which include careful stewardship of sediments and reductions in human-induced land subsidence

Hurricanes and Typhoons

Tropical cyclones represent one of nature’s most destructive forces and the effects of climate variability and continued coastal development are likely to exacerbate these impacts. Disasters and disaster recovery will depend heavily on improved predictions over short time intervals for evacuation decision-making and over many years for community planning and development of resilient coastal areas for natural and urban landscapes (Brantley et al., 2014; Sealza and Sealza, 2014). These storms are fundamentally a heat engine taking energy from the sea via the latent heat of evaporation and depositing the energy at mid-tropospheric levels via condensation. This engine converts the heat energy directly into mechanical energy (winds, waves and currents). Potential positive feedbacks, related to the dependence of evaporation rates on wind speed and storm intensity and mid-tropospheric heating rates, exist in this system. Therefore, tropical cyclones will continued to strengthen in ocean areas with high water temperatures, minimal vertical shear, and moist air aloft until the mechanical and heat energy losses equal the heat sources

Bay of Bengal cyclone extreme water level estimate uncertainty

Accurate estimates of storm surge magnitude and frequency are essential to coastal flood risk studies. Much research has focused on tide–surge interaction and joint probability techniques to combine multiple cyclone characteristics. In the Bay of Bengal, extreme water levels are derived from numerical storm surge models based on an idealised cyclone event; however, uncertainty within such calculations for this region is poorly understood, especially when propagated through to the flood hazard. We use the IBTrACs data set to estimate natural variability in four key parameters used to describe an idealised cyclone and create a set of idealised but equally likely “1 in 50 year” recurrence interval cyclone events. Each idealised cyclone is then used to force a storm surge model to give predicted peak water levels along the northern Bay of Bengal coast. Finally, extreme water level uncertainty is propagated through an inundation model to predict flood extent and depth over inland coastal floodplains. The descriptive parameters of 18 cyclone events (between 1990 and 2008) appear to show no statistically significant variation (at the 5 % level) due to landfall location, which allows us to pool characteristics for the entire Bay of Bengal. We find that the natural variability of cyclone parameters translates into large uncertainty both for storm surge height (of the order of metres) and for coastal inundation (hundreds of km2). Using the variability estimates for a 1-in-50-year cyclone event making landfall at the 2007 Sidr location, cyclone central pressure drop uncertainty had the greatest effect upon simulated storm surge magnitude. However, uncertainty within cyclone track characteristics (track speed, landfall and genesis location) has greater influence on subsequent inundation extent. Storm surge hazard uncertainty due to cyclone parameter variability was found to be comparable to the inundation difference simulated when the peak surge coincided with either a mean spring high or low water. Our research indicates the importance of improving extreme water level estimates along the Bay of Bengal coastline for robust flood hazard management decisions in the Bay of Bengal