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Providing sufficient structures suitable for vertical evacuation from tsunamis is critically important for a tsunami-prone city like Banda Aceh, the city most severely affected by the 2004 Indian Ocean tsunami. However, lack of sufficient financial capacity along with difficulties to find affordable land to be acquired have prevented some tsunami-prone cities to do so. This research is aimed at investigating potential structures to serve as alternative tsunami vertical evacuation buildings. The research was performed by mapping modified Building Tsunami Vulnerability (BTV) based on numerical simulations and types of the buildings. In 2018, all 79,420 structures in Banda Aceh were surveyed and classified into five building categories. Numerical simulations were performed using the Cornell Multi Grid Coupled Tsunami Model (COMCOT). Five scenarios of earthquake-triggered tsunamis were incorporated in the simulations, namely magnitude 9.2 Mw, 9.0 Mw, 8.8 Mw, 8.6 Mw, and 8.4 Mw events. Results of this research revealed that some 96 to 134 buildings could be used as alternative tsunami vertical evacuation buildings. None of the surveyed buildings could be classified as very low BTV condition. The buildings were schools, hotels, an assembly hall, government offices, and houses. The capacity of the alternatives evacuation buildings to accommodate tsunami evacuees were later calculated. The alternative tsunami evacuation buildings are expected to facilitate about 4 times the present capacity of six official tsunami escape buildings in Banda Aceh, Indonesia. [ABSTRACT FROM AUTHOR]

Ocean currents represent an alternative source of clean energy given their inherent reliability, persistence and sustainability. The general ocean circulation is characterized by large rotating ocean gyres resulting in rapid ocean currents along the western boundaries because of the Coriolis Effect. The Gulf Stream system is formed by the western boundary current of the North Atlantic Ocean flowing along the east coast of the United States, and is of particular interest as a potential energy resource for the United States. This study presents a national database of ocean current kinetic energy resource derived from seven years of numerical model simulations to help advance awareness and market penetration for ocean current energy. A web based GIS interface is provided for dissemination of the national energy resource data: http://www.oceancurrentpower.gatech.edu/ . The website includes GIS layers of computed monthly and yearly mean ocean current speed and associated power density along the coastlines of the United States, as well as joint and marginal probability histograms for current velocities at a variable horizontal resolution of 4–7 km. Various tools are provided for viewing, identifying, filtering and downloading the data from this website. The Gulf Stream system, especially the Florida Current, concentrates the highest kinetic power density ( > 2000 W / m 2 ). The majority of the kinetic power and its variability are only present in relatively shallow water given the strong correlation with the surface wind stress. The kinetic energy flux in the Florida Current is estimated over 30 years to provide temporal variability of the undisturbed kinetic energy with high statistical significance. Available power of approximately 5 GW associated with the undisturbed natural flow condition from the Gulf Stream system is predicted based on hypothetical turbine parameters. Successful development of renewable energy generation requires further studies to account for more precise technical, economic and environmental constraints. [ABSTRACT FROM AUTHOR]

Increasing energy consumption and decreasing reserves of fossil fuels have led to growing interest in renewable energy from the ocean. Ocean currents are an alternative source of clean energy due to their inherent reliability, persistence and sustainability. General ocean circulations exist in the form of large rotating ocean gyres, and feature extremely rapid current flow in the western boundaries due to the Coriolis effect. The Gulf Stream system is formed by the western boundary current of the North Atlantic Ocean that flows along the east coastline of the United States, and therefore is of particular interest as a potential energy resource for the United States. The theoretical energy balance in the Gulf Stream system is examined using the two-dimensional ocean circulation equations based on the assumptions of the Stommel model for subtropical gyres with the quasi-geostrophic balance between pressure gradient, Coriolis force, wind stress and friction driving the circulation. To represent flow dissipation due to turbines a spatially varying turbine drag coefficient is formulated and a finite difference numerical approach is utilized to obtain an implicit solution of the model. The results show that considering extraction over a region representing the entire Florida Current portion of the Gulf Stream system, the average power dissipated ranges between 4 and 6 GW with a mean around 5.1 GW. This corresponds to an average of approximately 45 TWh/yr. However, if the extraction area approximates the entire portion of the Gulf Stream within 200 miles of the US coastline, the average power dissipated becomes 18.6 GW or 163 TWh/yr. The impact of the localized turbine drag on the hydrodynamics is primarily within the turbine region. The extra drag force from turbines slows down the current velocity and leads to redirection of the Gulf Stream flow. It also results in a sea surface drop in the turbine region. Localized turbine drag significantly reduces residual kinetic energy flux in the circulation. However, its influence on the residual volume flux depends on the area of the turbine region. [ABSTRACT FROM AUTHOR]

Abstract: A geodatabase of tidal constituents is developed to present the regional assessment of tidal stream power resource in the USA. Tidal currents are numerically modeled with the Regional Ocean Modeling System (ROMS) and calibrated with the available measurements of tidal current speeds and water level surfaces. The performance of the numerical model in predicting the tidal currents and water levels is assessed by an independent validation. The geodatabase is published on a public domain via a spatial database engine with interactive tools to select, query and download the data. Regions with the maximum average kinetic power density exceeding 500W/m2 (corresponding to a current speed of ∼1m/s), total surface area larger than 0.5km2 and depth greater than 5m are defined as hotspots and documented. The regional assessment indicates that the state of Alaska (AK) has the largest number of locations with considerably high kinetic power density, followed by, Maine (ME), Washington (WA), Oregon (OR), California (CA), New Hampshire (NH), Massachusetts (MA), New York (NY), New Jersey (NJ), North and South Carolina (NC, SC), Georgia (GA), and Florida (FL). [Copyright &y& Elsevier]

Abstract: The tidal stream power potential along the coast of the state of Georgia is evaluated based on numerical modeling and validated with the available data. The Georgia coast consists of a complex network of tidal rivers and inlets between barrier islands that funnel and locally amplify the strength of the ambient tidal currents in the region. The number of existing tidal current prediction locations is not sufficient to resolve the temporal and spatial changes in the current speeds and patterns. Therefore, the currents are modeled with the Regional Ocean Modeling System (ROMS) to determine the locations with high tidal stream power potential and the results are validated against measurements. The wetlands and the topographical features are integrated in the computational model with wetting and drying of computational cells. The locations with the largest mean tidal stream power density are identified and their characteristics are provided. The effect of power extraction on estuarine hydrodynamics is simulated by implementing an additional retarding force in the governing momentum equations in ROMS. Two different power extraction schemes are simulated at the Canoochee River. The first scheme involves extracting 20% of the original kinetic power across the entire cross-section of the river, and is found to have substantially lower impact on the original flow than the second scheme with 45% extraction. The summation of removed and residual kinetic powers is found to be larger than the original kinetic power in the cross-section, which is attributed to the recovery in the flow momentum through reorganization of stream flow energy. In both of the cases the major impact on the currents is limited to a partial reach of the river. The change in the maximum and minimum water levels is observed to be on the order of centimeters. [Copyright &y& Elsevier]

Abstract: A multi-criteria assessment methodology that accounts for the physical, environmental and socioeconomic constraints is proposed to assist in the selection of the most suitable locations for tidal stream power conversion projects. For this purpose, the tidal stream power resource data are incorporated into a Geographical Information System (GIS) database together with datasets that are related to different aspects of the site selection methodology. The proposed method is applied to the Georgia coast to find and rank the best locations for power conversion. The suitable areas are narrowed down to a subset of the high power density areas that satisfy the constraints of a tidal stream power conversion scheme. A demonstrative ranking procedure with equal weighting factors for all criteria shows that the Savannah, Ogeeche, Canoochee and Medway Rivers and the Cumberland Sound have the best locations for tidal power conversion on the coast of Georgia. This methodology is also applicable to other sites where sufficient geospatial data are available. [Copyright &y& Elsevier]

Abstract: The wave power potential along the southeast Atlantic coast of the United States of America bounded by latitudes 27° N and 38° N and longitudes 82° W and 72° W (i.e. North Carolina, South Carolina, Georgia, and northern Florida) is investigated. The available data from National Data Buoy Center wave stations in the given area are examined. Temporal trends of the wave heights, wave periods and the wave power are analyzed for a time scale of weeks. The time series from the wave stations are downsampled with a 15-day moving average filter with near 50% overlapping to study the seasonal trends. Power calculated from hourly significant wave heights and average wave periods is compared to power calculated using spectral wave density. It is found that a factor of 0.61 needs to be applied to the wave power calculated from hourly significant wave heights and average periods in order to get the same results with the power calculated from spectral wave density. The mean power within 50km of the shore is determined to be ∼9kW/m, whereas higher power (∼15kW/m) is available further offshore. [Copyright &y& Elsevier]

On September 16, 2015, a M w 8.3 earthquake struck the north-central Chile coast, triggering a tsunami observed along 500 km of coastline, between Huasco (28.5°S) and San Antonio (33.5°S). This tsunami provided a unique opportunity to examine the nature of tsunami deposits in a semi-arid, siliciclastic environment where stratigraphic and sedimentological records of past tsunamis are difficult to distinguish. To improve our ability to identify such evidence, we targeted one of the few low-energy, organic-rich depositional environments in north-central Chile: Pachingo marsh in Tongoy Bay (30.3°S). We found sedimentary evidence of the 2015 and one previous tsunami as tabular sand sheets. Both deposits are composed of poorly to moderately sorted, gray-brown, fine-to medium-grained sand and are distinct from underlying and overlying organic-rich silt. Both sand beds thin (from ∼20 cm to <1 cm) and fine landward, and show normal grading. The older sand bed is thicker and extends over 125 m further inland than the 2015 tsunami deposit. To model the relative size of the tsunamis that deposited each sand bed, we employed tsunami flow inversion. Our results show that the older sand bed was produced by higher flow speeds and depths than those in 2015. Anthropogenic evidence along with 137Cs and 210Pb dating constrains the age of the older tsunami to the last ∼110 years. We suggest that the older sand bed was deposited by the large tsunami in 1922 CE sourced to the north of our study site. This deposit represents the first geologic evidence of a pre-2015 tsunami along the semi-arid north-central Chile coast and highlights the current and continuing tsunami hazard in the region. • First geologic record of pre-2015 tsunami inundation in north-central Chile. • Stratigraphic and grain-size analyses characterize the 2015 and one older tsunami deposit. • 137Cs, 210Pb, and historical analyses show that the older tsunami was deposited in 1922 CE. • Tsunami and tidal modeling show the 1922 tsunami was higher and faster than the 2015 tsunami. [ABSTRACT FROM AUTHOR]