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91.
Present‐day understanding of rill dynamics is hampered by a lack of detailed data on velocity distributions in rills. The latter are dif?cult to collect with traditional techniques due to the very low water depths and the relatively high ?ow velocities in rills. The objectives of this paper were to investigate the feasibility of miniaturized acoustic Doppler velocimeter (mADV) measurements in rill ?ow and to explore longitudinal variations in ?ow velocities and their relationship with rill bed morphology. Detailed data on longitudinal ?ow velocity were required to achieve these objectives. A 1·8 m long rill was formed freely in a ?ume at 5° slope and 0·001 m3 s?1 discharge. Rill topography was characterized by an alternation of steps and pools. The ?ume surface was then ?xed to preserve rill roughness. A topographical scanning of the entire ?ume surface was made. Velocity was measured with a mADV along the rill, and at different depths. Flow depth in a longitudinal direction was also measured using an elevation gauge. A strong relationship exists between rill topography and ?ow hydraulics. Over steps, ?ow was unidirectional and rapidly accelerating until a threshold Froude number (Fn) value between 1·3 and 1·7 was reached and a hydraulic jump occurred leading to the formation of a pool. In the pool, the ?ow pattern was multidirectional and complex. The ?ow was subcritical when leaving the pool and accelerated over the next step until the threshold Froude number value was again reached. Energy loss in the rill was concentrated in the pools, mainly due to the action of a hydraulic jump. This mechanism of energy dissipation appeared to be an essential factor in rill formation and bedform evolution. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
92.
Ernesto R. Rodríguez Flores Rafael Gmez Díaz Ramn E. Rodríguez Taboada 《Journal of Atmospheric and Solar》2005,67(17-18):1728
Based on high-resolution (0.3 arcsec) observations, we studied the behavior of solar granulation in the neighborhood of a sunspot. The bright granules’ spatial distribution and the granules’ surface density as a function of distance from the center of the sunspot umbra were determined.Bright granules distribute delimiting cells of dimensions in the mesogranular scale. The mean diameter of these cells does not show significant variation with the variation of the magnetic field of the sunspot. The granules’ surface density does not show significant variation with distance to the sunspot umbra. Both results point to a very weak, if any, influence of the sunspot magnetic field at distances greater than 20 arcsec. 相似文献
93.
Rafael D. Guerrero III 《GeoJournal》1996,40(1-2):69-72
Laguna de Bay is the largest lake in the Philippines bordering metropolitan Manila, the nation's capital and the industrial hub of the country. As a multiple-use resource the lake is of prime importance for its fisheries, as a transport route and as a water source for the cooling of industrial plants and for irrigation. The lake is also envisaged to supply the domestic water needs of the basin in the year 2000. With rapid urbanization, industrial development and deforestation of its watershed, Laguna de Bay has been stressed with sedimentation, overexploitation of its fisheries and pollution. Various management strategies have been adopted by government to address such human impacts. Among the major programs are the installation of a hydraulic control structure, implementation of a zoning and management plan and the formulation of a master plan. There is need for an integrated approach for the management of the Laguna de Bay basin for its sustainable development. 相似文献
94.
Jingfeng Wang Rafael L. Bras Dara Entekhabi 《Stochastic Environmental Research and Risk Assessment (SERRA)》1997,11(2):95-114
Large-scale fields of soil moisture are forced by atmospheric precipitation and radiative forcing. When these forcing factors
are themselves influenced by surface and soil moisture processes, the result is a nonlinear land-atmosphere system with inherent
feedback mechanisms that may strongly modulate variability in climate. Given such feedbacks, simple randomness in the forcing
factors may be manifested as a complex statistical signature in the surface hydrology. In this paper, we investigate the impacts
of non-Gaussian and colored-noise on the probability distribution of soil moisture resulting from the statistical-dynamical
land-atmosphere interaction model of Rodriguez-Iturbe et al. (1991). Persistence of hydroclimatologic anomalies as characterized
by the correlation time scale of soil moisture is discussed. 相似文献
95.
The inelastic response of one-storey systems with one axis of asymmetry subjected to bi-directional base motion is studied in this paper. The effect of the system parameters on response is also evaluated: uncoupled torsional-to-lateral frequency ratio, stiffness eccentricity, and yield strength of the lateral resisting elements. The ensemble of earthquake records used consists of 15 two-component strong ground motions. The response to uni-directional excitation is considered first to examine the influence of the system parameters and to serve as a basis to examine the results of the bi-directional case, which are presented in terms of average spectra for bi- over uni-directional lateral-deformation ratios. It is shown that the effect of inelastic behaviour is, on the average, noteworthy for stiff structures, in turn, the same structures are the most affected by the action of bi-directional ground motions. The effect of the relative intensity of the two orthogonal ground motion components is also studied. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
96.
Rafael Almar Alexandre Nicolae Lerma Bruno Castelle Timothy Scott 《Ocean Dynamics》2018,68(7):899-909
The reflection of incident gravity waves over an irregular swash zone morphology and the resulting influence on surf zone dynamics remains mostly unexplored. The wave-phase resolving SWASH model is applied to investigate this feedback using realistic low-tide terraced beach morphology with well-developed beach cusps. The rhythmic reflection generates a standing wave that mimics a subharmonic edge wave, from the superimposition of incident and two-dimensional reflected waves. This mechanism is enhanced by shore-normal, narrow-banded waves in both direction and frequency. Our study suggests that wave reflection over steep beaches could be a mechanism for the development of rhythmic morphological features such as beach cusps and rip currents. 相似文献
97.
How does anisotropy in bedrock river granitic outcrops influence pothole genesis and development?
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Pothole formation and development may be influenced by joint sets and other heterogeneities within bedrock, as well as by hydraulics. Previous research indicates that most potholes found in rivers of the mountainous Spanish Central System exhibit preferred orientations associated with dominant joints and correlate more strongly with variations in substrate resistance than with hydraulics. Weathering and erosion weaken rock surfaces, which leads to decreased mechanical resistance. We start from the hypothesis that different mechanisms of pothole formation may create around the pothole a distinctive signature in terms of ultrasound pulse velocity and surface hardness. We develop a conceptual model and test it using potholes for which we know the mechanism of formation, demonstrating that the spatial and statistical distributions of dynamical mechanical properties and surface hardness of a pothole may provide insight into its genesis. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
98.
Stamatis-Christos Batelis Mostaquimur Rahman Stefan Kollet Ross Woods Rafael Rosolem 《水文研究》2020,34(13):2843-2863
Groundwater is an important component of the hydrological cycle with significant interactions with soil hydrological processes. Recent studies have demonstrated that incorporating groundwater hydrology in land surface models (LSMs) considerably improves the prediction of the partitioning of water components (e.g., runoff and evapotranspiration) at the land surface. However, the Joint UK Land Environment Simulator (JULES), an LSM developed in the United Kingdom, does not yet have an explicit representation of groundwater. We propose an implementation of a simplified groundwater flow boundary parameterization (JULES-GFB), which replaces the original free drainage assumption in the default model (JULES-FD). We tested the two approaches under a controlled environment for various soil types using two synthetic experiments: (1) single-column and (2) tilted-V catchment, using a three-dimensional (3-D) hydrological model (ParFlow) as a benchmark for JULES’ performance. In addition, we applied our new JULES-GFB model to a regional domain in the UK, where groundwater is the key element for runoff generation. In the single-column infiltration experiment, JULES-GFB showed improved soil moisture dynamics in comparison with JULES-FD, for almost all soil types (except coarse soils) under a variety of initial water table depths. In the tilted-V catchment experiment, JULES-GFB successfully represented the dynamics and the magnitude of saturated and unsaturated storage against the benchmark. The lateral water flow produced by JULES-GFB was about 50% of what was produced by the benchmark, while JULES-FD completely ignores this process. In the regional domain application, the Kling-Gupta efficiency (KGE) for the total runoff simulation showed an average improvement from 0.25 for JULES-FD to 0.75 for JULES-GFB. The mean bias of actual evapotranspiration relative to the Global Land Evaporation Amsterdam Model (GLEAM) product was improved from −0.22 to −0.01 mm day−1. Our new JULES-GFB implementation provides an opportunity to better understand the interactions between the subsurface and land surface processes that are dominated by groundwater hydrology. 相似文献
99.
González Juan González Gabriel Aránguiz Rafael Melgar Diego Zamora Natalia Shrivastava Mahesh N. Das Ranjit Catalán Patricio A. Cienfuegos Rodrigo 《Natural Hazards》2020,101(1):231-253
Natural Hazards - This paper presents an investigation of the collapse of a 325-year-old multi-tiered heritage temple during the 2015 Gorkha earthquake in Kathmandu, Nepal. The research comprises a... 相似文献
100.
Romo-Morales Diana Moreno-Rodríguez Verónica Molina-Freaner Francisco Valencia-Moreno Martín Ruiz Joaquín Minjárez-Osorio Christian Hernández-Mendiola Ernesto del Rio-Salas Rafael 《Natural Resources Research》2020,29(4):2773-2786
Natural Resources Research - Mining is an important activity in Mexico; however, despite its economic benefits, it carries potential environmental risks, including mine spills. On August 6,... 相似文献