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Most process-based sediment dynamic models are based on the concept of sediment transport capacity (TC) of flow. Relationships between sediment TC and its characterized variables are found to vary widely, depending on the characteristics of a watershed and the underlying hydrological processes. This study has aimed to incorporate various widely used sediment transport capacity equations (TCEs) in a process-based sediment dynamic model, and to evaluate their relative performances in estimating suspended sediment dynamics at a river basin scale. The paper describes the modelling approaches and their application to a case study area (Abukuma River Basin, Japan), and then elaborates various parameters used in different TCEs with their useful impacts on modelling outcomes. The results of the case study have demonstrated that some of the TCEs are not suitable for simulating basin scale sediment dynamics. The TCEs that consist of more hydraulic parameters representing the flow and sediment transport processes have produced better outcomes. [ABSTRACT FROM AUTHOR]

Abstract: We investigated the dam-break problem for Herschel–Bulkley fluids: a fixed volume of a viscoplastic material (a polymeric gel called Carbopol ultrez 10) was released and flowed down an inclined flume. Using Particle Image Velocimetry techniques, we measured the velocity profiles far from the sidewalls, the front position as a function of time, and the flow depth evolution at a given place. The experimental data were compared to three models of increasing complexity: the kinematic wave model, an advection diffusion model (lubrication theory), and the one-layer Saint-Venant equations. Surprisingly, the best agreement was obtained with the simplest model (kinematic wave model) even though it could not capture the details of the head profile (regarded as a shock wave, i.e., a discontinuity). Lubrication theory (the advection diffusion model) performed well from a qualitative viewpoint. Computed velocity profiles and depth evolution were in reasonably good agreement with data, but this model overestimated initial acceleration, which resulted in a systematic difference between theoretical and experimental curves of the front position over time. This shortcoming was not fixed when using a more elaborate model (Saint-Venant equations), rather it was exacerbated. The relatively modest performance of the more elaborate models was intriguing (for Newtonian liquids, the best agreement was obtained with the most sophisticated model). [Copyright &y& Elsevier]

Bed load transport is a key process in maintaining the dynamically stable channel geometry for restoring the form and function of river ecosystems. Bed load consists of relatively large sediment particles that are moved along the streambed by rolling, sliding or saltation. Currently, various empirical correlations are used to estimate bed load transport rates since no single procedure, whether theoretical or empirical, has yet to be universally accepted as completely satisfactory in this aspect. Bed load particles are primarily sourced from river bed materials or banks. The amount of bed load and its spatial distribution contributes significantly to river bed level changes. Hillslope sediment contribution, mostly available to the river in the form of suspended load, also plays an important role in river bed level changes. This study aims to analyse different bed load equations and the resultant computations of river bed level variations using a process-based sediment dynamic model. Analyses have revealed that different bed load equations were mainly deduced from the concept of relating bed shear stresses to their critical values which are highly factored by the slope gradient, water discharge and particle sizes. In this study, river bed level variations are calculated by estimating total surplus or deficit sediment loads (suspended loads and bed loads) in a channel section. This paper describes the application of different widely used bed load equations, and evaluation of their various parameters and relative performances for a case study area (Abukuma River Basin, Japan) using a basin-scale process-based modelling approach. Relative performances of river bed level simulations obtained by using different bed load equations are also presented. This paper elaborates on the modelling approaches for river bed load and bed level simulations. Although verifications were not done due to unavailability of field data for bed load, qualitative evaluations were conducted vis-à-vis field data on flow and suspended sediment loads as well as the bed loads presented in different past studies. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a finite element method based soil erosion and sediment yield model has been developed for overland and stream flow. The one dimensional conservation of mass of sediment flow equation has been solved based on kinematic wave flow approximation and Galerkin''s based numerical solution. Various thematic maps required for the model are prepared using Geographical Information System (GIS). Land use/Land cover is extracted from remotely sensed data. The proposed finite element based distributed model has been used for the estimation of soil erosion and sediment outflow by discretizing the watershed into small grids. The soil erosion and sediment outflow model has been developed and applied to Khadakohol watershed located in Nashik district of Maharastra state, India. Part of the available data has been used for the model calibration and the other part for model validation. The simulated results of the watershed have been compared with the observed data and found to be satisfactory. [Copyright &y& Elsevier]

The objective of this study is to develop a soil erosion and sediment yield model based on the kinematic wave approximation using the finite element method, remote sensing and geographical information system (GIS) for calculating the soil erosion and sediment yield in a watershed. Detachment of soil particles by overland flow occurs when the shear stress at the surface overcomes the gravitational forces and cohesive forces on the particles. Deposition occurs when the sediment load is greater than the transport capacity. Beasley et al.'s (Trans ASAE 23: 938-944, 1980) transport equations for laminar and turbulent flow conditions are used to calculate the transport capacity. The model is capable of handling distributed information about land use, slope, soil and Manning's roughness. The model is applied to the Catsop watershed in the Netherlands and the Harsul watershed in India. Remotely sensed data has been used to extract land use/land cover map of the Harsul watershed, and other thematic maps are generated using the GIS. The simulated results for both calibration and validation events are compared with the observed data for the watersheds and found to be reasonable. Statistical evaluation of model performance has been carried out. Further, a sensitivity analysis has also been carried out to study the effect of variation in model parameter values on computed volume of sediment, peak sediment and the time to peak sediment. Sensitivity analysis has also been carried out for grid size variation and time step variation of the Catsop watershed. The proposed model is useful in predicting the hydrographs and sedigraphs in the agricultural watersheds. [ABSTRACT FROM AUTHOR]

The article discusses the effect of moving storms on the attainment of equilibrium discharge. The author states that even though rainfall is assumed spatially uniform in conventional hydrological modelling for use in rainfall-runoff simulations. Moving storms have been shown to have a heavy influence on flow hydrographs. The study in the article used criteria for attainment of the equilibrium discharge from watersheds subjected to moving storms were examined. The author explains that non-linear numerical kinematic-wavemodels have been developed to simulate runoff from an overland plane and from a V-shaped catchment.

Abstract: We investigate in this paper the effect of plane and profile curvatures on the soil moisture distribution and related fluxes obtained from field experiments. Today, there is a need also to confirm the theoretical approaches of the kinematic wave approximation with the real field measurements. Within a research project dedicated to the model-based description of runoff formation processes, field measurements of soil moisture dynamics and numerical simulation, using one simply formulated kinematic wave model, are combined. It is shown that the measurement of the soil moisture movement downwards within a hillslope can be interpreted by the kinematic wave model and vice versa how the model can be validated in its physical explanations by the field measurements. It is revealed that the soil moisture fluxes can be described by kinematic waves crossing the soil mantle of the hillslope. Based on these analyses it is shown that the two topographic characteristics plane and profile curvatures of the hillslope control the subsurface and saturation flow. The obtained results are related to the previous theoretical analysis of Fan and Bras [Fan Y, Bras RL. Analytical solutions to hillslope subsurface storm flow and saturation overland flow. Water Resour Res 1998;34(4):921–7], Troch et al. [Troch PA, Paniconi C, van Loon EE, Bijkerk B, Hilberts A. Behaviour of a hillslope-storage Boussinesq model for subsurface storm flow and saturation overland flow. International Workshop on Catchment, Wageningen 2000; Poster] and Troch et al. [Troch PA, van Loon C, Hilberts A. Analytical solutions to a hillslope-storage kinematic wave equation for subsurface flow. Adv Water Resour 2002;25:637–49] which have shown considerable progress in the modelling using the kinematic wave approximation. [Copyright &y& Elsevier]

Hillslope response has traditionally been studied by means of the hydraulic groundwater theory. Subsurface flow from a one-dimensional hillslope with a sloping aquifer can be described by the Boussinesq equation [Mem. Acad. Sci. Inst. Fr. 23 (1) (1877) 252–260]. Analytical solutions to Boussinesq''s equation are very useful to understand the dynamics of subsurface flow processes along a hillslope. In order to extend our understanding of hillslope functioning, however, simple models that nonetheless account for the three-dimensional soil mantle in which the flow processes take place are needed. This three-dimensional soil mantle can be described by its plan shape and by the profile curvatures of terrain and bedrock. This plan shape and profile curvature are dominant topographic controls on flow processes along hillslopes. Fan and Bras [Water Resour. Res. 34 (4) (1998) 921–927] proposed a method to map the three-dimensional soil mantle into a one-dimensional storage capacity function. Continuity and a kinematic form of Darcy''s law lead to quasi-linear wave equations for subsurface flow solvable with the method of characteristics. Adopting a power function of the form proposed by Stefano et al. [Water Resour. Res. 36 (2) (2000) 607–617] to describe the bedrock slope, we derive more general solutions to the hillslope-storage kinematic wave equation for subsurface flow, applicable to a wide range of complex hillslopes. Characteristic drainage response functions for nine distinct hillslope types are computed. These nine hillslope types are obtained by combining three plan curvatures (converging, uniform, diverging) with three bedrock profile curvatures (concave, straight, convex). We demonstrate that these nine hillslopes show quite different dynamic behaviour during free drainage and rainfall recharge events. [Copyright &y& Elsevier]

This study implemented kinematic wave and dynamic wave approximation of flood routing for a prismatic rectangular channel. The results of the two methods were compared by differences in maximum flow depth, and the applicability of kinematic wave equation was discussed. The influences of hydraulic and geometrical factors on the applicability of kinematic wave equation were considered. It was found that a portion of the numerical results violated existing criteria used to indicate the applicability of kinematic wave equation, particularly when geometrical and hydraulic factors were considered together. This is because the characteristics of upstream inflow were rarely or incompletely considered in these criteria. Therefore, the present study proposed a new criterion. The theoretical influence of all factors was considered using three parameters, namely, K F 0 2 , η t s / T 0 ′ and Q b o t t o m / Q p e a k ( K ,   F 0 ,   η t s ,   T 0 ′ ,   Q b o t t o m , and Q p e a k represent the kinematic wave number, Froude number, the time span of discharge exceeding 90% of maximum discharge in hydrograph, wave travel time in the channel, base flow discharge, and peak discharge, respectively, while the subscript 0 represent the value of reference discharge). The influences of these three parameters were illustrated by the momentum equation of one-dimensional Saint-Venant equation. The numerical results showed that the value of η t s / T 0 ′   (K F 0 2) D could be used to determine the relative error ξ h of kinematic wave equation. In addition, for each Q b o t t o m / Q p e a k the value of η t s / T 0 ′   ( K F 0 2) D used to depict the same relative error ξ h was different. This new criterion was validated using two real case studies, and it showed a good performance. [ABSTRACT FROM AUTHOR]

An essential factor in the propagation of drought, from meteorological drought to groundwater drought, is the delay between a precipitation event and the groundwater recharge reaching the groundwater table. This delay, which mainly occurs in the vadose zone of the hydrological cycle, is often poorly studied. Therefore, this paper proposes a method for estimating the spatially distributed delay in the vadose zone using the kinematic wave approximation of Richards' equation combined with the van Genuchten–Burdine and Brooks–Corey parametric model. The modeling was approached (1) using a detailed parametrization of soil and geological layers and (2) using lumped hydraulic and physical properties of geological layers. The results of both approaches were compared against the physically based flow model Hydrus-1D. This analysis shows that using a detailed parametrization of soil and geological layers results in good comparison, with a Nash–Sutcliffe efficiency of 0.89 for Brooks–Corey and 0.80 for van Genuchten–Burdine. The delay result of the Brooks–Corey model was incorporated into the groundwater recharge time series from 1980 to 2013 to analyze the effect of this delay on groundwater drought. The results show that the delay in the vadose zone influences groundwater drought characterization features such as the number, duration, and intensity of drought events. [ABSTRACT FROM AUTHOR]