Assessment of disaster resilience capacity of hillslope communities with high risk for geological hazards

This study presents a novel preparedness assessment method for assessing hazard mitigation and environmental planning of hillslope communities. A professional questionnaire was utilized to weight each indicator. Communities in Hsinchu, Taichung and Nantou counties with debris flow hazards were taken as study samples. Debris flow risk and landslide susceptibility for each community were determined using Geographic Information System (GIS) technology and logistic regression analysis. Thus, a novel risk assessment method for evaluating disaster resilience capacity of hillslope communities was established. This method was then applied to assess casualties caused by Typhoon Herb in 1996 and Typhoon Mindulle in 2004. Additionally, the analytical results generated by this assessment method were discussed with the aim of developing references for implementation of risk analysis, increasing the effectiveness of disaster mitigation, and reducing future loss of life and property.     

Numerical Experiment on Two-Dimensional Line Thermal

The time evolution of a two-dimensional line thermal-a turbulent flow produced by an initial element with signifi-cant buoyancy released in a large water body, is numerically studied with the two-equation k - e model for turbulence closure. The numerical results show that the thermal is characterized by a vortex pair flow and a kidney shaped concentra-tion structure with double peak maxima; the computed flow details and scalar mixing characteristics can be described by self-similar relations beyond a dimensionless time around 10. There are two regions in the flow field of a line thermal: a mixing region where the concentration of tracer fluid is high and the flow is turbulent and rotational with a pair of vortex eyes, and an ambient region where the concentration is zero and the flow is potential and well-described by a model of doublet with strength very close to those given by early experimental and analytical studies. The added virtual mass coeffi-cient of the thermal motion is found to be approximat     

秦山核电站邻近水域的流况分析

本文分析了秦山核电站邻近水域各测站的实测流、潮流和佘流分布及季节变化。结果表明:测区内潮流为非正规丰日浅海潮流,其运动形式呈往复流。核电站二期工程取水口附近(L_1,18站)为一大流速区,而一期工程出水口周围(L_2,L_2′站)有一相对小的流速区。大流速区落潮流历时大于涨潮流历时,而相对小流速区则相反;大流速区的余流较小,而小流速区的余流大。在四个季节中,涨潮流速秋季最大,春季次之,夏季最小;落潮流速秋季最大,夏季次之,春季最小。余流冬、秋两季较大。在实测流中以潮流为主,径流和季风的作用也相当显著。     

How tides and river flows determine estuarine bathymetries

For strongly tidal, funnel-shaped estuaries, we examine how tides and river flows determine size and shape. We also consider how long it takes for bathymetric adjustment, both to determine whether present-day bathymetry reflects prevailing forcing and how rapidly changes might occur under future forcing scenarios.Starting with the assumption of a 'synchronous' estuary (i.e., where the sea surface slope resulting from the axial gradient in phase of tidal elevation significantly exceeds the gradient in tidal amplitude ), an expression is derived for the slope of the sea bed. Thence, by integration we derive expressions for the axial depth profile and estuarine length, L, as a function of and D, the prescribed depth at the mouth. Calculated values of L are broadly consistent with observations. The synchronous estuary approach enables a number of dynamical parameters to be directly calculated and conveniently illustrated as functions of and D, namely: current amplitude Û, ratio of friction to inertia terms, estuarine length, stratification, saline intrusion length, flushing time, mean suspended sediment concentration and sediment in-fill times.Four separate derivations for the length of saline intrusion, L_I, all indicate a dependency on (U_o is the residual river flow velocity and f is the bed friction coefficient). Likely bathymetries for `mixed' estuaries can be delineated by mapping, against and D, the conditions L<sub>I</sub>/L<1,E<sub>X</sub>/L<1 (E<sub>X</sub> is the tidal excursion) alongside the Simpson-Hunter criteria D/U<sup>3</sup><50 m<sup>−2</sup> s<sup>3</sup>. This zone encompasses 24 out of 25 `randomly' selected UK estuaries.However, the length of saline intrusion in a funnel-shaped estuary is also sensitive to axial location. Observations suggest that this location corresponds to a minimum in landward intrusion of salt. By combining the derived expressions for L and L_I with this latter criterion, an expression is derived relating D_i, the depth at the centre of the intrusion, to the corresponding value of U_o. This expression indicates U_o is always close to 1 cm s⁻¹, as commonly observed. Converting from U_o to river flow, Q, provides a morphological expression linking estuarine depth to Q (with a small dependence on side slope gradients).These dynamical solutions are coupled with further generalised theory related to depth and time-mean, suspended sediment concentrations (as functions of and D). Then, by assuming the transport of fine marine sediments approximates that of a dissolved tracer, the rate of estuarine supply can be determined by combining these derived mean concentrations with estimates of flushing time, F_T, based on L_I. By further assuming that all such sediments are deposited, minimum times for these deposition rates to in-fill estuaries are determined. These times range from a decade for the shortest, shallowest estuaries to upwards of millennia in longer, deeper estuaries with smaller tidal ranges.     

Application of LICOM to the numerical study of the water exchangebetween the South China Sea and its adjacent oceans

1 IntroductionThe South China Sea (SCS) is the largestmarginal sea in the western Pacific (see Fig. 1). It con-nects with the SCS through the Taiwan Strait, with thePacific through the Luzon Strait, with the Sulu Seathrough the Mindoro and Balabac Straits and with theJava Sea and Andaman Sea through the Sunda Shelf(For convenience, here we refer to the section at 1.5°N,Fig. 2). It is shown that the seasonal SCS circulation ismostly affected by the summer/winter monsoon, andthe no…     

一个南海热带气旋发展的环流特征分析

本文用ECMWF2.5×2.5网格点资料通过一个例子,对有利于南海热带气旋发展的环流场作了详细的分析,发现几点事实:(1)扰动在风的垂直切变较大的环境中仍可发展。(2)扰动位于中、低空西南急流左侧,高空南支东风急流右侧时,有利发展。(3)中,低空西南急流形成了扰动环流的强风潮,强风潮从扰动南侧入角,并包围扰动的东半圆。(4)扰动中、低层的入流和高层的外流呈现严重的不对称性。(5)当扰动发展到一定强度时,对南海热带季风环流圈的加强起到正反馈作用。     

Fluid flow equations governing primary oil migration as a separate phase

A mathematical model of primary oil migration as a separate phase out of compacting shales is presented. During burial and oil generation, source rock porosity decreases and oil saturation increases until residual oil saturation is reached. At this stage oil is expelled out by capillary and excess fluid pressure gradients. The model is a system of differential equations which relate changes in oil and water saturation in time to water and oil flow out of the source rock during burial. An additional set of equations for periods of erosion of overburden are also provided. The equations can be numerically solved by finite difference method. If oil and water flow is to be simulated during oil generation, then at each time step, changes by oil generation in oil and water saturations and porosity must be calculated. The solution procedure is briefly outlined.     

Simulation of green water flow on deck using non-linear dam breaking theory

Experiments carried out with models of floating production, storage and offloading platforms (FPSOs) showed that the flow of water over the deck edge, onto the deck resembled a suddenly released wall of water rather than a breaking wave. Therefore green water flow onto the deck was simulated using dam breaking theory, but the theory’s shallow-water assumptions may be limiting. In this paper a non-linear dam breaking problem is formulated. Equations of motion in the Lagrangian form are used and the solution is sought as an infinite series in time. Comparisons with the shallow water approximation are carried out.     

Decadal Variability of Subsurface Temperature in the Central North Pacific

Decadal variability of subsurface temperature in the North Pacific has been investigated. Two dominant regions were found; the central subarctic region (CSa) and the north-eastern subtropical region (NESt). In CSa, cooling (warming) of wintertime subsurface temperature corresponds to the large (small) temperature gradient and southward (northward) shift of subsurface temperature front, associated with the increase (decrease) of positive wind stress curl and the southward (northward) shift of curl τ zero line with 2 years delay. It is suggested that the relocation of subtropical-subarctic boundary plays an important role. In NESt, importance of heat flux through the sea surface and heat divergence in the Ekman layer is also discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

A Computational Model for Velocity Separation in Shallow Sea

Based on the hydrodynamical feature and the theoretical velocity profiles of tidal flow and vvind-induced flow in shal-low sea, a computational model is established for the first time, which can separate observed velocity into tidal velocity and wind-induced velocity by use of the least square method. With the model, not only the surface velocities of tidal flow and vvind-induced flow are obtained, but also the bed roughness height is determined and the wind velocity above the wa-ter surface is estimated. For verification of the model, the observed velocity in the Yellow River Estuary and the laborato-ry test is separated, then it is applied to the Yangtze River Estuary. All the results are satisfactory. The research results show that the model is simple in method, feasible in process and reasonable in result. The model is a valid approach to analysis and computation of field dala, and can be applied to separate the observed velocity in shallow sea; at the same time, reasonable boundary conditions of th