河口、海岸环境下床沙输运的初步实验研究

量测了在水深0.5m的情况下波浪、水流通过水平沙床所产生的床沙输移。实验波高为0.15m，周期分别为1.4和2.0s。首先量测纯波浪下的床沙输移，然后量测波流共同作用下，水流与波浪行进方向一致其稳定速度分别为0.02,0.04,0.06m/s时的床沙输移，结果表明，2个沙槽所得的总输沙率在波周期2.0s时最大，净输沙率在波周期1.4s时最大，将波叠加在速度为0.02m/s的水流上时，2种波型的净输沙率都增加约1倍，水流为0.04m/s和0.06m/s时2种波型的净输沙率分别都减少。     

Simulation of flow and solute coupled 2‐D problems with velocity‐dependent dispersion coefficient based on the network method

The governing equations of coupled density‐driven flow and solute transport problems in porous media, with velocity‐dependent dispersion coefficient, are strongly nonlinear and must be solved numerically. This contribution presents a network model, based on the network simulation method, capable of simulating the transient solution to this kind of problem efficiently and with a relatively low computational time. The mathematical model is formulated using the stream function and concentration variables. Simulation of the network model is carried out in the standard electric circuit simulation code, Pspice. The present model is first applied to simulate the original benchmark Henry problem, and the solution is compared with those obtained by other authors. A study of the grid size is also carried out. In addition, the modified version of Simpson and Clement of the Henry problem, as well as the groundwater flow in the closed desert basin of Pilot Valley, is studied using the proposed model. Copyright © 2011 John Wiley & Sons, Ltd.     

Calculation of diffusivities of passive fields in turbulent media

Abstract

The exact numerical and approximate analytical solutions of the simplest nonlinear integral equation with second order nonlinearity for the averaged Green function are presented. It is assumed that the turbulence is stationary, homogeneous, isotropic and incompressible. Numerous examples of turbulent spectra are considered (peak-like spectrum, spectra of Kolmogorov's type with different forms of “pumping” regions, stepwise spectra etc.). Special emphasis is given to investigating the case of so called “frozen” turbulence when the parameter ξ =u ₀τ/R→∞ where uτ₀,R ₀ are characteristic velocity, lifetime and space scale of turbulent pulsations, respectively. It is shown that these solutions allow us to calculate the turbulent diffusivities accurately for arbitrary spectra with any values of the parameter ξ. The results take into account the possible helicity of turbulence concerned only with scalar passive fields (number density and temperature).     

Real‐time monitoring and estimation of the discharge of flash floods in a steep mountain catchment

Synchronously and accurately estimating the flood discharges and dynamic changes in the fluid density is essential for hydraulic analysis and forecasting of flash floods, as well as for risk assessment. However, such information is rare for steep mountain catchments, especially in regions that are hotspots for earthquakes. Therefore, six hydrological monitoring sites were established in the main stream and tributaries of the 78.3‐km² Longxi River catchment, an affected region of the Wenchuan earthquake region in China. Direct real‐time monitoring equipment was installed to measure the flow depths, velocities, and fluid total pressures of the flood hydrographs. On the basis of field measurements, real‐time mean cross‐sectional velocities during the flood hydrographs could be derived from easily obtainable parameters: cross‐sectional maximum velocities and the calibrated dimensionless parameter K_h . Real‐time discharges were determined on the basis of a noncontact method to establish the effective rating curves of this mountainous stream, ranging from 1.46 to 386.34 m³/s with the root mean square errors of ≤10.22 m³/s. Compared with the traditional point‐velocity method and empirical Manning's formula, the proposed noncontact method was reliable and safe for monitoring whole flood hydrographs. Additionally, the real‐time fluid density during the flood hydrographs was calculated on the basis of the direct monitoring parameters for fluid total pressures and water depths. During the flood hydrograph, transient flow behaviour with higher fluid density generally occurred downstream during the flood peak periods when the flow was in the supercritical flow regime. The observed behaviour greatly increased the threat of damage to infrastructure and human life near the river. Thus, it is important to accurately estimate flood discharge and identify for fluid densities so that people at risk from an impending flash flood are given reliable, advanced warning.     

GIS Investigation of the relationship of sex and season on the population distribution of common bottlenose dolphins (Tursiops truncatus) in Charleston,South Carolina

ABSTRACT

The Charleston Estuarine System Stock (CESS) of common bottlenose dolphins (Tursiops truncatus) has been the focus of population monitoring for the past 20 years. Photo-id studies have determined abundance and survival estimates for this population, which exhibits high site fidelity in this area. However, fine-scale distribution, utilization patterns, and the driving forces behind these patterns are lacking. Using historical photo-id data and a novel application of geographic information system (GIS) analysis, the present study identified core use areas within Charleston Harbor, as well as patterns specific to sexes and seasons. Photo-id data of 319 dolphins sighted 11 times or more during 2004–2009 were analyzed. Heat maps were developed to examine spatial distributions using kernel density estimates (KDE) and were compared between sexes and seasons. Multiple high-density core use areas were identified for this population, with the most noteworthy near the mouth of the harbor toward the Atlantic Ocean. Fine-scale distribution varied across sexes, as well as seasons. Some areas were identified as more specifically inhabited by one sex, while other areas overlapped between sexes. Females were more tightly concentrated within their distribution while males were more dispersed. Although population distribution varied across seasons, sex distributions remained.     

13e SESSION DU COMITÉ CONSULTATIF KARACHI 4–15 NOVEMBRE 1957

Abstract

Event-based methods are used in flood estimation to obtain the entire flood hydrograph. Previously, such methods adopted in the UK have relied on pre-determined values of the input variables (e.g. rainfall and antecedent conditions) to a rainfall–runoff model, which is expected to result in an output flood of a particular return period. In contrast, this paper presents a method that allows all the input variables to take on values across the full range of their individual distributions. These values are then brought together in all possible combinations as input to an event-based rainfall–runoff model in a Monte Carlo simulation approach. Further, this simulation strategy produces a long string of events (on average 10 per year), where dependencies from one event to the next, as well as between different variables within a single event, are accounted for. Frequency analysis is then applied to the annual maximum peak flows and flow volumes.

Citation Svensson, C., Kjeldsen, T.R., and Jones, D.A., 2013. Flood frequency estimation using a joint probability approach within a Monte Carlo framework. Hydrological Sciences Journal, 58 (1), 1–20.     

土壤热参数及其影响因素测试分析

热性质是岩土体基本的物理性质之一,用以评价热量在其中的保持、传导和分布状况,以导热系数、比热容和热扩散系数最为常见,这些参数也是地热能管理与开发、工程冷冻开挖、寒区工程设计与施工的重要参数。已有研究表明,土壤热参数与土质、来源、含水率、密度等因素有关。通过广东湛江某工地粉质黏土和黏土的热参数测试结果分析发现：随含水率的增大,粉质黏土导热系数和热扩散系数的变化趋势是先增加至最大值,然后减小,而比热容基本呈线性增大。干密度对粉质黏土导热系数的影响与含水率大小有关,当含水率不超过20.0%时,其随干密度的增加而增大,而当含水率超过27.5%后,其随干密度的增加有减小趋势;当含水率在24.5%（液限）左右时,基本没有规律可循。干密度对粉质黏土热扩散系数影响规律不明显。黏土的导热系数和比热容都随含水率和干密度的增加而增大;热扩散系数随含水率的升高整体表现为非线性增加至稳定,在低含水率下干密度的影响不明显,在较高含水率下随干密度的增加热扩散系数先增大后减小。较大颗粒的存在导致粉质黏土的导热性较黏土复杂。     

Sediment density flow distribution on wave-influenced deltas

Deltas are at the transition between fluvial and marine sedimentary environments where sediment density flows are often triggered during high river discharge events, forming submarine channels and sediment waves. On wave-influenced deltas, longshore currents are particularly efficient at transporting sediment alongshore, reducing the likelihood of sediment density flows from occurring at river mouths. This study describes four deltaic sedimentary systems at different stages of their evolution on a formerly glaciated continental inner shelf of eastern Canada in order to better understand the distribution of sediment density flows on wave-influenced deltas. Three types of settings are recognized as being prone to sediment density flows: (i) in the early stages of wave-influence and on large deltas, converging longshore currents can lead to offshelf sediment transport; (ii) on wave-influenced to wave-dominated deltas, a sandy spit can re-route the river mouth and sediment density flows form where the spit intersects the delta lip; (iii) in advanced stages of wave-dominated deltas and during their demise, rocky headlands are exposed and can intersect the slope, where off-shelf sediment transport occurs. These types of sediment density flows were all characterized by debris flows or surge-type turbidity currents which have limited offshore run-out. More rarely, hyperpycnal flows form at the river mouths, especially where the river incises glaciomarine clays prone to landsliding in the river, which increases fine-grained fluvial suspended sediment concentration. Overall, these results highlight the predominance of fluvial-dominated deltas during a phase of relative sea-level fall combined with high sediment supply. However, as soon as sediment supply diminishes, wave action remobilizes sediment alongshore modifying the distribution and types of sediment density flows occurring on wave-influenced deltas.     

气象产品的广义联合偏差修正方法及其应用

卫星气象产品、气候模式预测数据通常与地面观测数据存在偏差,为保证数据的可靠性和合理性,需要对其进行偏差校正,但偏差校正过程往往受具体区域气象特征、方法本身假定等因素的影响,导致修正效果不佳。为此,本文提出一种广义联合偏差修正方法,相较于现有研究最常用的单变量QM修正方法以及固定多变量修正顺序的JBC修正方法,该方法充分考虑到流域尺度降水和气温双变量的时空相关性,并结合其对径流的主导作用对变量修正顺序进行动态调整,实现了QM法和JBC法的优势互补。在澜沧江-湄公河流域的应用表明：考虑降水、气温相关性可显著改善降水和温度极值的修正效果,尤其是5、6月份,修正后气象与实测数据的纳什系数提升了0.5以上;考虑气象要素的修正次序显著降低了修正后的降水和温度频率分布及均值偏差;利用修正后的气象数据驱动分布式水文模型时,部分月份的径流模拟精度提升了54.3%。