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。     

滨州市海岸带工程地质特征分析

根据该次工程地质调查和钻探工作取得的大量数据,结合收集的钻孔资料,对研究区土体工程地质层进行了系统研究,并依据地层沉积年代、成因类型、地层结构、工程力学性质,对研究区陆域地表以下,海底以下50m深度范围内的土层进行分层研究,并对各层工程地质特征进行了分析,对区内软土分布范围、饱和砂土液化进行了综合研究,为滨州海岸带港口及重大工程规划建设提供系统的基础地质资料和决策依据。     

Displacement ring load Green's functions for saturated porous transversely isotropic tri‐material full‐space

Based on the Biot's poroelastic theory and using scalar potential functions both the ring load and point load displacement Green's functions for a transversely isotropic saturated porous full‐space composed of an upper half‐space, a finite thickness middle layer and a lower half‐space is analytically presented for the first time. It is assumed that each region consists of a different transversely isotropic material. The equations of poroelastodymanics in terms of the solid displacements and the pore fluid pressure are uncoupled with the help of two scalar potential functions, so that the governing equations for the potential functions are either a second order wave equation or a repeated wave‐heat transfer equation of sixth order. With the aid of Fourier expansion with respect to circumferential direction and Hankel integral transforms with respect to the radial direction in cylindrical coordinate system, the response is determined in the form of line integrals in the real space, followed by theorem of inverse Hankel integral transforms. The solutions degenerate to a single phase elastic material, and the results are compared with previous studies, where an excellent agreement may be observed with the results provided in the literature. Some examples of displacement Green's functions are finally given to illustrate the solution. Copyright © 2016 John Wiley & Sons, Ltd.     

Comparison of different methods describing the peak runoff contributing areas during floods

In the last few years, the scientific community has developed several hydrological models aimed at the simulation of hydrological processes acting at the basin scale. In this context, the portion of peak runoff contributing areas represents a critical variable for a correct estimate of surface runoff. Such areas are strongly influenced by the saturated portion of a river basin (influenced by antecedent conditions) but may also evolve during a specific rainfall event. In the recent years, we have developed 2 theoretically derived probability distributions that attempt to interpret these 2 processes adopting daily runoff and flood‐peak time series. The probability density functions (PDFs) obtained by these 2 schematisations were compared for humid river basins in southern Italy. Results highlighted that the PDFs of the peak runoff contributing areas can be interpreted by a gamma distribution and that the PDF of the relative saturated area provides a good interpretation of such process that can be used for flood prediction.     

Three‐dimensional time‐harmonic fundamental solutions for a fluid‐saturated poroelastic half‐space with partially permeable free surface

By virtue of a pair of scalar potentials for the displacement of the solid skeleton and the pore fluid pressure field of a saturated poroelastic medium, an alternative solution method to the Helmholtz decomposition is developed for the wave propagation problems in the framework of Biot's theory. As an application, a comprehensive solution for three‐dimensional response of an isotropic poroelastic half‐space with a partially permeable hydraulic free surface under an arbitrarily distributed time‐harmonic internal force field and fluid sources is developed. The Green's functions for the poroelastic fields, corresponding to point, ring, and disk loads, are reduced to semi‐infinite complex‐valued integrals that can be evaluated numerically by an appropriate quadrature scheme. Analytical and numerical comparisons are made with existing elastic and poroelastic solutions to illustrate the quality and features of the solution. Copyright © 2016 John Wiley & Sons, Ltd.     

Steady flow to a partially penetrating blind‐wall well in a confined aquifer

Wells in aquifers of loose collapsible sediment are cased so that they have a blind wall and gain water only from the bottom. The hydraulic gradient established at the bottom of these wells during pumping brings the aquifer materials in a quicksand state, which may cause abrasion of pipes and pumps and even the destruction of well structure. To examine the quicksand occurrence, an analytical solution for the steady flow to a partially penetrating blind‐wall well in a confined aquifer is developed. The validity of the proposed solution is evaluated numerically. The sensitivity of maximum vertical gradient along the well bottom in response to aquifer and well parameters is examined. The solution is presented in the form of dimensionless‐type curves and equations that can be easily used to design the safe pumping rate and optimum well geometry to protect the well against sand production. The solution incorporates the anisotropy of aquifer materials and can also be used to determine the hydraulic conductivity of the aquifer. Copyright © 2012 John Wiley & Sons, Ltd.     

Effects of hillslope topography on hydrological responses in a weathered granite mountain,Japan: comparison of the runoff response between the valley‐head and the side slope

To evaluate the effects of hillslope topography on storm runoff in a weathered granite mountain, discharge rate, soil pore water pressures, and water chemistry were observed on two types of hillslope: a valley‐head (a concave hillslope) and a side slope (a planar hillslope). Hydrological responses on the valley‐head and side slope reflected their respective topographic characteristics and varied with the rainfall magnitude. During small rainfall events (<35 mm), runoff from the side slope occurred rapidly relative to the valley‐head. The valley‐head showed little response in storm runoff. As rainfall amounts increased (35–60 mm), the valley‐head yielded a higher flow relative to the side slope. For large rainfall events (>60 mm), runoff from both hillslopes increased with rainfall, although that from the valley‐head was larger than that from the side slope. The differences in the runoff responses were caused by differences in the roles of lower‐slope soils and the convergence of the hillslope. During small rainfall events, the side slope could store little water; in contrast, all rainwater could be stored in the soils at the valley‐head hollow. As the amount of rainfall increased, the subsurface saturated area of the valley‐head extended from the bottom to the upper portion of the slope, with the contributions of transient groundwater via lateral preferential flowpaths due to the high concentration of subsurface water. Conversely, saturated subsurface flow did not contribute to runoff responses, and the subsurface saturated area at the side slope did not extend to the upper slope for the same storm size. During large rainfall events, expansion of the subsurface saturated area was observed in both hillslopes. Thus, differences in the concentration of subsurface water, reflecting hillslope topography, may create differences in the extension of the subsurface saturated area, as well as variability in runoff responses. Copyright © 2007 John Wiley & Sons, Ltd.     

Transport and retention of Escherichia coli in a mixture of quartz,Al‐coated and Fe‐coated sands

Transport and retention of Escherichia coli through the mixture of quartz, Al‐coated and Fe‐coated sands was examined using column experiments to investigate the effect of geochemical heterogeneity on bacteria transport. The first set of the experiments was performed in quartz, Al‐coated and Fe‐coated sand mixtures (coated sand: 0, 5, 10, 25, 50, 100%) to examine the influence of positively‐charged sand grains on bacteria transport. The second experiments were carried out to observe the impact of pH (range 6·74–8·21) on bacteria transport in the mixture of quartz 50% and Fe‐coated sand 50%. The third experiments were conducted to analyse the effect of ionic strength (0, 50, 100, 200 mM) on bacteria transport in the mixture of quartz 50% and Al‐coated sand 50%. The first experiments show that bacterial mass recoveries were in the range of 3·6–43·4%, decreasing nonlinearly as the content of Al‐ and Fe‐coated sands increased. In the second experiments, the bacterial mass recoveries were in the range of 35·5–79·2%, increasing linearly as the solution pH increased. In the third experiments, the mass recovery was 3·4% at 0 mM. As the ionic strength increased to 50mM, the mass recovery decreased to 0%. When the ionic strength increased further to 100 and 200 mM, no bacterial mass was recovered as in the case of 50 mM. It indicates that in the mixed medium of quartz 50% and Al‐coated sand 50% both positive (increment of bacterial adhesion) and negative (decrement) effects of ionic strength may be counterbalanced, minimizing the impact of ionic strength on the bacterial adhesion. This study helps to understand the role of metal oxides and solution chemistry in the transport of bacteria in geochemically heterogeneous media Copyright © 2008 John Wiley & Sons, Ltd.     

Evaluating fine sediment mobilization and storage in a gravel‐bed river using controlled reservoir releases

Two controlled flow events were generated by releasing water from a reservoir into the Olewiger Bach, located near Trier, Germany. This controlled release of near bank‐full flows allowed an investigation of the fine sediment (<63 µm) mobilized from channel storage. Both a winter (November) and a summer (June) release event were generated, each having very different antecedent flow conditions. The characteristics of the release hydrographs and the associated sediment transport indicated a reverse hysteresis with more mass, but smaller grain sizes, moving on the falling limb. Fine sediment stored to a depth of 10 cm in the gravels decreased following the release events, indicating the dynamic nature and importance of channel‐stored sediments as source materials during high flow events. Sediment traps, filled with clean natural gravel, were buried in riffles before the release of the reservoir water and the total mass of fine sediment collected by the traps was measured following the events. Twice the mass of fine sediment was retained by the gravel traps compared with the natural gravels, which may be due to their altered porosity. Although the amount of fine sediment collected by the traps was not significantly related to measures of gravel structure, it was found to be significantly correlated to measures of local flow velocity and Froude number. A portion of the traps were fitted with lids to restrict surface exchange of water and sediment. These collected the highest amounts of event‐mobilized sediments, indicating that inter‐gravel lateral flows, not just surface infiltration of sediments, are important in replenishing and redistributing the channel‐stored fines. These findings regarding the magnitude and direction of fine sediment movement in gravel beds are significant in both a geomorphic and a biological context. Copyright © 2006 John Wiley & Sons, Ltd.     

The timing and magnitude of changes to Hortonian overland flow at the watershed scale during the post-fire recovery process

Extreme hydrologic responses following wildfires can lead to floods and debris flows with costly economic and societal impacts. Process-based hydrologic and geomorphic models used to predict the downstream impacts of wildfire must account for temporal changes in hydrologic parameters related to the generation and subsequent routing of infiltration-excess overland flow across the landscape. However, we lack quantitative relationships showing how parameters change with time-since-burning, particularly at the watershed scale. To assess variations in best-fit hydrologic parameters with time, we used the KINEROS2 hydrological model to explore temporal changes in hillslope saturated hydraulic conductivity (K_sh) and channel hydraulic roughness (n_c) following a wildfire in the upper Arroyo Seco watershed (41.5 km²), which burned during the 2009 Station fire in the San Gabriel Mountains, California, USA. This study explored runoff-producing storms between 2008 and 2014 to infer watershed hydraulic properties by calibrating the model to observations at the watershed outlet. Modelling indicates K_sh is lowest in the first year following the fire and then increases at an average rate of approximately 4.2 mm/h/year during the first 5 years of recovery. The estimated values for K_sh in the first year following the fire are similar to those obtained in previous studies on smaller watersheds (<1.5 km²) following the Station fire, suggesting hydrologic changes detected here can be applied to lower-order watersheds. Hydraulic roughness, n_c, was lowest in the first year following the fire, but increased by a factor of 2 after 1 year of recovery. Post-fire observations suggest changes in n_c are due to changes in grain roughness and vegetation in channels. These results provide quantitative constraints on the magnitude of fire-induced hydrologic changes following severe wildfires in chaparral-dominated ecosystems as well as the timing of hydrologic recovery.