A geospatial framework to estimate depth of scour under buildings due to storm surge in coastal areas

Hurricanes and tropical storms represent one of the major hazards in coastal communities. Storm surge generated by strong winds and low pressure from these systems have the potential to bring extensive flooding in coastal areas. In many cases, the damage caused by the storm surge may exceed the damage from the wind resulting in the total collapse of buildings. Therefore, in coastal areas, one of the sources for major structural damage could be due to scour, where the soil below the building that serves as the foundation is swept away by the movement of the water. The existing methodologies to forecast hurricane flood damage do not differentiate between the different damage mechanisms (e.g., inundation vs. scour). Currently, there are no tools available that predominantly focus on forecasting scour-related damage for buildings. Such a tool could provide significant advantages for planning and/or preparing emergency responses. Therefore, the focus of this study was to develop a methodology to predict possible scour depth due to hurricane storm surges using an automated ArcGIS tool that incorporates the expected hurricane conditions (flow depth, velocity, and flood duration), site-specific building information, and the associated soil types for the foundation. A case study from Monmouth County (NJ), where the scour damages from 2012 Hurricane Sandy were recorded after the storm, was used to evaluate the accuracy of the developed forecasting tool and to relate the scour depth to potential scour damage. The results indicate that the developed tool provides relatively consistent results with the field observations.     

Social vulnerability in the context of bushfire risk at the urban-bush interface in Sydney: a case study of the Blue Mountains and Ku-ring-gai local council areas

In the recent past, Australia has experienced several catastrophic hazard events and the frequency and intensity of such events is expected to increase in the future. Natural hazards can rarely be fully prevented, yet their losses can be minimized if the necessary preparedness and mitigation actions are taken before an event occurs. Identification of vulnerable groups is an important first step in any preparedness and emergency management planning process. Social vulnerability refers to population characteristics that influence the capacity of a community to prepare for, respond to and recover from disasters. Factors that contribute to social vulnerability are often hidden and difficult to capture. This study analyzes the relative levels of social vulnerability of communities at the urban?Cbush interface in the Blue Mountains and Ku-ring-gai local council areas in New South Wales (NSW), Australia. We tested whether a standardized social vulnerability index could be developed using a pre-existing set of indicators. We created an exploratory principle component analysis model using Australian Bureau of Statistics 2006 census data at the Census Collection District (CCD) level. We identified variables contributing to social vulnerability and used the component scores to develop a social vulnerability index. Finally, the social vulnerability index was mapped at the CCD level. Our results indicate that both contributors to and the level of social vulnerability differ between and within communities. In other words, they are spatially variable. They show different spatial patterns across the areas, which provides useful information for identifying communities that are most likely to experience negative disaster impacts due to their socio-demographic characteristics.     

A new magnitude category disaggregation approach for temporal high‐resolution rainfall intensities

Simulation of quick runoff components such as surface runoff and associated soil erosion requires temporal high‐resolution rainfall intensities. However, these data are often not available because such measurements are costly and time consuming. Current rainfall disaggregation methods have shortcomings, especially in generating the distribution of storm events. The objectives of this study were to improve point rainfall disaggregation using a new magnitude category rainfall disaggregation approach. The procedure is introduced using a coupled disaggregation approach (Hyetos and cascade) for multisite rainfall disaggregation. The new procedure was tested with ten long‐term precipitation data sets of central Germany using summer and winter precipitation to determine seasonal variability. Results showed that dividing the rainfall amount into four daily rainfall magnitude categories (1–10, 11–25, 26–50, >50 mm) improves the simulation of high rainfall intensity (convective rainfall). The Hyetos model category approach (Hyetos_Cat) with seasonal variation performs representative to observed hourly rainfall compared with without categories on each month. The mean absolute percentage accuracy of standard deviation for hourly rainfall is 89.7% in winter and 95.6% in summer. The proposed magnitude category method applied with the coupled Hyetos_Cat–cascade approach reproduces successfully the statistical behaviour of local 10‐min rainfall intensities in terms of intermittency as well as variability. The root mean square error performance statistics for disaggregated 10‐min rainfall depth ranges from 0.20 to 2.38 mm for summer and from 0.12 to 2.82 mm for the winter season in all categories. The coupled stochastic approach preserves the statistical self‐similarity and intermittency at each magnitude category with a relatively low computational burden. Copyright © 2014 John Wiley & Sons, Ltd.     

Volcanological and petrological evolution of Marsili Seamount (southern Tyrrhenian Sea)

A swath bathymetric survey was conducted on Marsili Volcano, the biggest seamount in the Tyrrhenian Sea. It stands 3000 m above the surrounding oceanic crust of the 3500 m-deep Marsili back-arc basin and is axially located within the basin. The seamount has an elongated shape and presents distinctive morphology, with narrow (<1000 m) ridges, made up of several elongated cones, on the summit zone and extensive cone fields on its lower flanks. A dredging campaign carried out at water depths varying between 3400 and 600 m indicates that most of Marsili Seamount is composed of medium-K calc-alkaline basalts. Evolved high-K andesites were only recovered from the small cones on the summit axis zone. Petrological and geochemical characteristics of the least differentiated basalts reveal that at least two varieties of magmas have been erupted on the Marsili Volcano. Group 1 basalts have plagioclase and olivine as dominant phases and show lower Al, Ca, K, Ba, Rb and Sr, and higher Fe, Na, Ti and Zr with respect to a second type of basaltic magma. Group 2 basalts reveal the presence of clinopyroxene as an additional phenocryst phase. In addition, the two basaltic magmas have different original pre-eruptive H₂O content (group 1, H₂O-poor and group 2, H₂O-rich). Moreover, comparison of the compositional trends and mineralogical compositions obtained from MELTS [Ghiorso, M.S., Sack, R.O., Contrib. Mineral. Petrol. 119 (1995) 197–212] fractional crystallization calculations reveal that the evolved andesites can only exclusively be derived from a low-pressure (0.3 kbar) fractionation of magmas compositionally similar to the least evolved group 2 basalts. Finally, we suggest that the high vesicularity of the basalts sampled at relatively great depths (>2400 m) on the edifice is governed by H₂O and, probably, CO₂ exsolution and is not a feature indicative of shallow water depth eruption.     

Atmospheric Precursors of and Response to Anomalous Arctic Sea Ice in CMIP5 Models

This study examines pre-industrial control simulations from CMIP5 climate models in an effort to better understand the complex relationships between Arctic sea ice and the stratosphere, and between Arctic sea ice and cold winter temperatures over Eurasia. We present normalized regressions of Arctic sea-ice area against several atmospheric variables at extended lead and lag times. Statistically significant regressions are found at leads and lags, suggesting both atmospheric precursors of, and responses to, low sea ice; but generally, the regressions are stronger when the atmosphere leads sea ice, including a weaker polar stratospheric vortex indicated by positive polar cap height anomalies. Significant positive midlatitude eddy heat flux anomalies are also found to precede low sea ice. We argue that low sea ice and raised polar cap height are both a response to this enhanced midlatitude eddy heat flux. The so-called "warm Arctic, cold continents" anomaly pattern is present one to two months before low sea ice, but is absent in the months following low sea ice, suggesting that the Eurasian cooling and low sea ice are driven by similar processes. Lastly, our results suggest a dependence on the geographic region of low sea ice, with low Barents–Kara Sea ice correlated with a weakened polar stratospheric vortex, whilst low Sea of Okhotsk ice is correlated with a strengthened polar vortex. Overall, the results support a notion that the sea ice, polar stratospheric vortex and Eurasian surface temperatures collectively respond to large-scale changes in tropospheric circulation.     

STAMP: spatial–temporal analysis of moving polygons

Research questions regarding temporal change in spatial patterns are increasingly common in geographical analysis. In this research, we explore and extend an approach to the spatial–temporal analysis of polygons that are spatially distinct and experience discrete changes though time. We present five new movement events for describing spatial processes: displacement, convergence, divergence, fragmentation and concentration. Spatial–temporal measures of events for size and direction are presented for two time periods, and multiple time periods. Size change metrics are based on area overlaps and a modified cone-based model is used for calculating polygon directional relationships. Quantitative directional measures are used to develop application specific metrics, such as an estimation of the concentration parameter for a von Mises distribution, and the directional rate of spread. The utility of the STAMP methods are demonstrated by a case study on the spread of a wildfire in northwestern Montana.      

Structure of the crust and upper mantle in Canada

The seismic probing of the crust and upper mantle in Canada started in 1938 and since then has involved many government and university groups using a wide variety of techniques. These have included simple profiling with both wide and narrow station spacing, areal time-term surveys, detailed deep reflection experiments, very long-range refraction studies and the analysis of surface wave dispersion between stations of the Canadian Standard Network.

A review of the published interpretation leads to the general conclusion that:

1. (1) P_n-velocities vary from a value possibly as low as 7.7 km/sec under Vancouver Island to 8.6 km/sec and higher in the extreme eastern part of the shield and some parts of the Atlantic coast.

2. (2) Large areas of Canada have a crustal thickness of 30–40 km, with Vancouver Island, the southwestern Prairies, the Lake Superior basin and parts of the eastern shield of Quebec being thicker. No continental area in Canada is known to have a crust thinner than 29 km.

3. (3) The Riel discontinuity — a deep intra-crustal reflector and sometime refractor, is widely reported in the Prairies and Manitoba. It is not seen to the north in the vicinity of Great Slave Lake, nor in the Hudson Bay, Lake Superior and Maritime regions, nor in the interior of British Columbia. It may be present in some areas of the eastern shield.

4. (4) As experiments have become more detailed, crustal structures of greater complexity have been revealed. The concept that crustal structure becomes simpler with increasing depth is apparently unfounded.

Long-range refraction studies suggest that the Gutenberg P-wave low-velocity channel is poorly developed under the Canadian Shield. The analysis of the dispersion of surface waves, however, suggests that the channel is better developed for S-waves, and is present throughout the country. The lid of the channel is deepest under the central shield and shallowest under the Cordillera.