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71.
The role that family and household structure, size, and ethnic/racial composition play in increasing or decreasing vulnerability to natural hazards, which has been missing from the literature, is investigated. The study first reviews the conceptual foundations of the relationships between families/households and natural hazards vulnerability and then employs a principal components analysis to uncover spatial variations in the vulnerability of families and households to hurricane storm surge hazards in Sarasota County, Florida. The analysis identifies and maps five principal components that explain approximately 83% of the variance in family/household population: nuclear families/households; Black families/households; nonfamily, young adult group households; Hispanic families/households; and Asian families/households. Comparison of storm surge risk maps with the locations of these families/households shows the relative vulnerability of each of these family/household categories, with elderly householders living alone on exposed barrier islands being the most vulnerable. The research suggests that family and household structures integrate several socio-demographic vulnerability indicators central to most social vulnerability assessments. Results indicate that future research and hazard mitigation policies should focus on families and households as core analytical units. Findings also suggest that recognizing the diversity of families and households is important to reducing vulnerability to natural hazards. 相似文献
72.
Yi Qiang Nina S.-N. Lam 《International journal of geographical information science》2016,30(9):1832-1852
ABSTRACTUnderstanding human dynamics after a major disaster is important to the region’s sustainable development. This study utilized land cover data to examine how Hurricane Katrina has affected the urban growth pattern in the Mississippi Delta in Louisiana. The study analyzed land cover changes from non-urban to urban in three metropolitan areas, Baton Rouge, New Orleans-Metairie, and Hammond, for two time periods, pre-Katrina (2001–2006) and post-Katrina (2006–2010). The study first applied a focal filter to extract continuous urban areas from the scattered urban pixels in the original remote sensing images. Statistical analyses were applied to develop initial functions between urban growth probability and several driving factors. A genetic algorithm was then used to calibrate the transition function, and cellular automata simulation based on the transition function was conducted to evaluate future urban growth patterns with and without the impact of Hurricane Katrina. The results show that elevation has become a much more important factor after Hurricane Katrina, and urban growth has shifted to higher elevation regions. The elevation most probable for new urban growth increased from 10.84 to 11.90 meters. Moreover, simulated future urban growth in this region indicates a decentralized trend, with more growth occurring in more distant regions with higher elevation. In the New Orleans metropolitan area, urban growth will continue to spill across Lake Pontchartrain to the satellite towns that are more than 50 minutes away by driving from the city center. 相似文献
73.
Plant fossils from the volcano-clastic marine deposits of the Coniacian Hidden Lake Formation of James Ross Island in Antarctica are described based on their macromorphology. Stratigraphic positions of fossiliferous horizons and details of the lithostratigraphic situation of the middle part of the Hidden Lake Formation are published for the first time. The flora consists primarily of leaf impressions and petrified wood. There are also small amounts of mesofossils, dispersed cuticles and charcoalified wood. The megafossils typically occur fragmented, underpinning their allochtonous origin. The plants are described in systematical order. This contribution in contrast to earlier observations reports a high diversity of pteridophytes (11 taxa) and conifers (6 taxa). Angiosperms representing families Nothofagaceae, Atherospermataceae, probably Lauraceae and Sterculiaceae are the most abundant and common plant groups of the flora (12 taxa). The presence of the tropical fern family Marattiaceae and rarity of the genus Nothofagus are of interest, arguing for the prevalence of a warm temperate to tropical humid climate during the Coniacian in this part of Antarctica. 相似文献
74.
Harry F.L. Williams 《地球表面变化过程与地形》2012,37(8):901-906
There is a paucity of information on the regional distribution and magnitude of hurricane storm surge sedimentation. This study assesses the spatial extent and magnitude of Hurricane Ike's (2008) storm surge sedimentation and discusses implications for the role of hurricanes in marsh aggradation. The characteristics of the storm surge deposit, including thickness, inland penetration, volume and mass, were determined for 15 transects across marshes bordering the Gulf of Mexico in south‐eastern Texas and south‐western Louisiana. The deposit is up to 0·85 m thick, extends up to 3·6 km inland, and has an estimated volume of about 13·7 million m3 and an estimated mass of about 16·2 million metric tons. This level of sedimentation is one to two orders of magnitude larger than other potential sources of marsh sedimentation, including annual riverine inputs and inputs from alongshore sediment transport. The study findings add support to a growing body of evidence that hurricanes may be the predominant sediment source for long‐term aggradation of many coastal marshes bordering the Gulf of Mexico. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
75.
76.
R.T. McCall J.S.M. Van Thiel de Vries N.G. Plant A.R. Van Dongeren J.A. Roelvink D.M. Thompson A.J.H.M. Reniers 《Coastal Engineering》2010
A 2DH numerical, model which is capable of computing nearshore circulation and morphodynamics, including dune erosion, breaching and overwash, is used to simulate overwash caused by Hurricane Ivan (2004) on a barrier island. The model is forced using parametric wave and surge time series based on field data and large-scale numerical model results. The model predicted beach face and dune erosion reasonably well as well as the development of washover fans. Furthermore, the model demonstrated considerable quantitative skill (upwards of 66% of variance explained, maximum bias − 0.21 m) in hindcasting the post-storm shape and elevation of the subaerial barrier island when a sheet flow sediment transport limiter was applied. The prediction skill ranged between 0.66 and 0.77 in a series of sensitivity tests in which several hydraulic forcing parameters were varied. The sensitivity studies showed that the variations in the incident wave height and wave period affected the entire simulated island morphology while variations in the surge level gradient between the ocean and back barrier bay affected the amount of deposition on the back barrier and in the back barrier bay. The model sensitivity to the sheet flow sediment transport limiter, which served as a proxy for unknown factors controlling the resistance to erosion, was significantly greater than the sensitivity to the hydraulic forcing parameters. If no limiter was applied the simulated morphological response of the barrier island was an order of magnitude greater than the measured morphological response. 相似文献
77.
Ephemeral sand waves in the hurricane surf zone 总被引：2，自引：0，他引：2
Andrew B. Kennedy K. Clint Slatton Tian-Jian Hsu Michael J. Starek Kittipat Kampa 《Marine Geology》2008,250(3-4):276-280
Airborne bathymetric LIDAR observations along the Florida panhandle after Hurricane Dennis (2005) show the first unequivocal observations of surf-zone sand wave trains.
These are found in depths of 5m along the trough of the hurricane bar, where hindcasts show strong longshore currents only during severe storms. The waves extend over tens of kilometers of coast after Dennis but are absent from the same area in four other datasets. Observed wavelength to water depth ratios are comparable to river dunes and tidal sand waves but height to depth ratios are smaller, with the largest wave heights around 0.1 times the water depth. The sand wave generation mechanism is hypothesized to be from wind-and-wave-induced longshore currents, which were hindcast to be large during Dennis, with destruction from water wave orbital velocities. 相似文献
78.
Present criteria for acceptable grass covered levee overtopping are based on average overtopping values but do not include the effect of overtopping duration. This paper applies experimental steady state results for acceptable overtopping to the case of intermittent wave overtopping. Laboratory results consisting of velocities and durations for acceptable land side levee erosion due to steady flows are examined to determine the physical basis for the erosion. Three bases are examined: (1) velocity above a threshold value, (2) shear stress above a threshold value, and (3) work above a threshold value. The work basis provides the best agreement with the data and a threshold work value and a work index representing the summation of the product of work above the threshold and time are developed. The governing equations for flow down the land side of a levee establish that the flows near the land side levee toe will be supercritical. Wave runup is considered to be Rayleigh distributed with the runup above the levee crest serving as a surrogate for overtopping. Two examples illustrating application of the methodology are presented. Example 1 considers three qualities of grass cover: good, average, and poor. The required levee elevations for these three covers differ by 1.8 m. The results for Example 1 are compared with the empirical criteria of 0.1 liters per second per meter (l/s per m), 1.0 l/s per m, and 10.0 l/s per m. It is found that the required crest elevation by the methodology recommended herein for the “poor” cover is only slightly lower than for the criterion for average overtopping of q=10.0 l/s per m but significantly lower than for the overtopping criterion of 1.0 and 0.1 m/s per m. Example 2 considers two durations of the peak surge with the result that the longer duration peak surge requires a levee that is higher by approximately 0.8 m. 相似文献
79.
W.C. Seabergh 《Ocean Engineering》2010,37(1):48-58
A 1:50 scale physical model was constructed for the 17th Street Canal region, New Orleans, on the southern coast of Lake Pontchartrain, as part of the Interagency Performance Evaluation Task Force (IPET) study of Hurricane Katrina. The purpose of the 1350 m2 physical model that represented about 3.4 km2 of the local area was to aid in defining wave and water velocity conditions in the 17th Street Canal during the time period leading up to the breaching of the floodwall within the Canal. In the immediate period following this disaster, there were many hypothesis of failure put forth in the media. Some of these hypothesis indicated wave action may have been the underlying cause of the failure of the 17th Street Canal floodwall. Some performed numerical work with inappropriate boundary conditions, which indicated strong wave-generated currents may have caused erosion along the floodwalls. This physical model study indicated a number of wave-attenuating processes occurring as waves approached the location of the breach. Wave height reduction resulted due to: (1) refraction of wave energy over the shallower submerged land areas surrounding the harbor away from the canal; (2) reflection of energy off vertical walls in the region between the entrance to the canal near the Coast Guard Harbor and the bridge; and (3) interaction of the wave with the Hammond Highway bridge, including reflection and transmission loss. Wave heights near the lakeside of the bridge were 0.3-0.9 m in height, reduced from 1.8 to 2.7 m wave heights in the open lake. Waves on the south side of the bridge, near the breach, were further reduced to heights below 0.3 m. These results supported the conclusion that waves were not a significant factor for the 17th Street Canal floodwall failure. Other IPET investigations determined floodwall failure was of a geotechnical nature due to the high surge water level. The physical model also provided calibration information for numerical wave models. The effects of debris on flow and waves after the breach was formed were also investigated. 相似文献
80.
Wave and combined wave-and-surge overtopping was significant across a large portion of the hurricane protection system of New Orleans during Hurricane Katrina. In particular, along the east-facing levees of the Mississippi River-Gulf Outlet (MRGO), the overtopping caused numerous levee breaches. This paper will focus on the MRGO levees, and will attempt to recreate the hydrodynamic conditions during Katrina to provide an estimate of the experienced overtopping rates. Due to the irregular beach profiles leading up to the levees and the general hydrodynamic complexity of the overtopping in this area, a Boussinesq wave model is employed. This model is shown to be accurate for the prediction of waves shoaling and breaking over irregular beach profiles, as well as for the overtopping of levees. With surge levels provided by ADCIRC and nearshore wave heights by STWAVE, the Boussinesq model is used to predict conditions at the MRGO levees for 10 h near the peak of Katrina. The peak simulated overtopping rates correlate well with expected levee damage thresholds and observations of damage in the levee system. Finally, the predicted overtopping rates are utilized to estimate a volumetric flooding rate as a function of time for the entire 20 km stretch of east-facing MRGO levees. 相似文献