Sediment Graph Research Articles

Regional validity of the parameters of a distributed runoff-erosion model in the semi-arid region of Brazil

The present paper examines the validity of the application of a distributed rainfall-runoff-erosion model on a regional basis in a semi-arid region of Brazil. The model tested is known as WESP (Water Erosion Simulation Program) developed by Lopes (1987). The model simulates the hydrograph and the sediment graph for individual events and thus, the model when properly calibrated can serve as a predictive tool for runoff and soil erosion on an individual or a continuous basis. The possibility of the existence of regionally applicable values for the parameters of the model WESP would be very interesting from the point of view of predictability of runoff and soil erosion from ungauged basins in the region. For this purpose, data collected in several experimental units in the experimental basin of Sume as well as in the experimental basin of Sao Joao de Cariri have been used. The model was calibrated and validated in each of the experimental units (consisting of erosion plots and micro-basins) and the average value from all of the units for each of the parameters was considered to be the regional value. With these average values, all the events in all the experimental units were simulated. The results show that the runoff and erosion values simulated with this single parameter set were very good in all the units, being well within the acceptable deviations.

A Simple Conceptual Model of Sediment Yield

The sediment graphs (time distribution of sediment yield) are very essential if the sediment transports the pollutants that are toxic at high concentrations, requiring determination of peak, rather than average sediment flow rate. In this paper, an effort has been made to develop a simple conceptual model of sediment yield based on Soil Conservation Service Curve Number (SCS-CN) method, instantaneous unit sediment graph (IUSG) method, and Power law and the performance is tested using real field data of Chaukhutia watershed of Ramganga river catchment (area = 452.25 km2). The proposed model is found to provide realistic estimates of temporal variation of sediment yield as well as total sediment yield during a storm event. The model is found to be most sensitive to parameter β followed by k, $\upalpha$ , A, and ns. A comparison is made with the existing IUSG based models of Kumar and Rastogi (J Hydrol 95:155–163, 1987) and Raghuwanshi et al. (J Hydraul Eng ASCE 120(4):495–503, 1994) for developing sediment graphs.

Soil erosion and sediment transport in the gullied Loess Plateau: Scale effects and their mechanisms

Scale effects exist in the whole process of rainfall-3-runoff-3-soil erosion-3-sediment transport in river basins. The differences of hydrographs and sediment graphs in different positions in a river basin are treated as basic scale effects, which are more complex in the gullied Loess Plateau, a region notorious for high intensity soil erosion and hyper-concentrated sediment-laden flow. The up-scaling method of direct extrapolation that maintains dynamical mechanism effective in large scale application was chosen as the methodology of this paper. Firstly, scale effects of hydrographs and sediment graphs were analyzed by using field data, and key sub-processes and their mechanisms contributing to scale effects were clearly defined. Then, the Digital Yellow River Model that integrates sub-models for the subprocesses was used with high resolution to simulate rainfall-3-runoff-3-soil erosion-3-sediment transport response in Chabagou watershed, and the distributed results representing scale effects were obtained. Finally, analysis on the simulation results was carried out. It was shown that gravitational erosion and hyper-concentrated flow contribute most to the spatial variation of hydrographs and sediment graphs in the spatial scale. Different spatial scale distributions and superposition of different sub-processes are the mechanisms of scale effects.

Determinant factors of sediment graphs and rating loops in a reforested watershed

Summary Sediment graphs and hydrographs were analyzed in a small, high-gradient reforested watershed in Mie Prefecture, Japan, which was instrumented to measure discharge and sediment transport. The study was conducted to recognize determinant factors on sediment graphs and hydrographs relationships, and corresponding rating loops using eight storm events that occurred in 2004. A cause-and-effect analytical approach was employed in the investigation of factors controlling individual hydrological events. The results showed that in a single event, the sediment peak preceded the peak discharge, following a clockwise hysteretic loop. The rating loops exhibited hysteresis with a greater suspended sediment concentration for a given discharge occurring on the rising limb rather than on the falling limb. Furthermore, the reduction in suspended sediment concentrations in a sequence of events and the falling limbs could mainly be associated with sediment exhaustion and contributions of throughfall and throughflow. We concluded that a combination of sediment availability, rainfall characteristics, soil water repellency, and contribution of different flow components control the variations in event-wise sediment graphs and rating loops in the study area. Understanding the relationship between controlling factors and sediment yield dynamics in the study area should greatly improve our understanding of sediment transport mechanisms and predictions in reforested watersheds, which should ultimately lead to better management of forest ecosystems.

Conceptual model of sedimentgraph from flood events in a small agricultural watershed

Conceptual model of sedimentgraph from flood events in a small agricultural watershed A procedure for predicting the sediment graph (i.e. the suspended sediment flux), from a small river catchment by heavy rainfall, has been developed using the concept of an instantaneous unit hydrograph (IUH) and dimensionless sediment concentration distribution (DSCD). A formula for instantaneous unit sedimentgraph (IUSG) is presented, and a procedure for estimating the sediment routing coefficient, which is a key parameter of the IUSG, based on measured data of rainfall-runoff-suspended sediment is applied. Field data from a small, field sized agricultural basin, lacated in center of Illinois has been used for analizing lag times for runoff (LAG) and sediment yield (LAGs). Assumptions about sediment generated during rainfall events are discussed.

Development of a Storm Runoff Simulator: Part 3 – Sediment Mixing Device

Runoff simulators used in plot research have not effectively represented a natural hydrograph and sediment graph. Therefore, an improved runoff simulator is needed to better evaluate the performance of conservation buffers and similar practices. The objective of this study was to design, build, and test a prototype sediment mixing device that could be incorporated into the final design of a storm runoff simulator. Based on an engineering analysis, the simulator design constraints were a maximum water volume of 7580 L, a peak flow rate of 7.3 L s-1, a maximum sediment load of 882 kg, and peak sediment rate of 1.15 kg s-1. The sediment mixing device consists of an impeller agitated mixing tank to create a homogeneous slurry of fine silica sand and water. Slurry outflow is measured and controlled by an output control system operating under gravity flow conditions. A time-compressed 5-yr, 2-h SCS design storm with an eroded sediment mass of 442 kg and a peak sediment rate of 1.3 kg s-1 was used to verify performance. When reproducing the design sediment graph using a slurry concentration of 0.30 kg L-1 comparable efficiencies among repetitions were maintained; with root mean square error (RMSE) representing less than 4% error between the RMSE and the peak flow or sediment rate. Peak sediment rates were within 7% of the target rate. The prototype sediment delivery system uses fine silica sand to represent clay and silt sized particles, and is capable of producing varying sediment rates that match a design sediment graph.

A sediment graph model based on SCS-CN method

This paper proposes new conceptual sediment graph models based on coupling of popular and extensively used methods, viz., Nash model based instantaneous unit sediment graph (IUSG), soil conservation service curve number (SCS-CN) method, and Power law. These models vary in their complexity and this paper tests their performance using data of the Nagwan watershed (area = 92.46 km 2 ) (India). The sensitivity of total sediment yield and peak sediment flow rate computations to model parameterisation is analysed. The exponent of the Power law, β , is more sensitive than other model parameters. The models are found to have substantial potential for computing sediment graphs (temporal sediment flow rate distribution) as well as total sediment yield.

Dynamics of suspended sediment transport at field‐scale drain channels of irrigation‐dominated watersheds in the Sonoran Desert, southeastern California

AbstractSuspended sediment is a major source of pollution in irrigation‐dominated watersheds. However, little is known about the process and mechanisms of suspended sediment transport in drain channels directly connected to agricultural fields. This paper explains sediment dynamics using averaged 5 min flow discharge Q (m3 s−1) and suspended sediment concentration C (mg l−1) collected during one crop season in a small catchment containing a first‐order drain channel and its connected six agricultural fields within the Salton Sea watershed. The statistical properties and average trends of Q and C were investigated for both early (i.e. November) and late (i.e. January) stages of a crop season. Further in‐depth analysis on sediment dynamics was performed by selecting two typical single‐field irrigation events and two multiple‐field irrigation events. For each set of irrigation events, the process of suspended sediment transport was revealed by examining hydrograph and sediment graph responses. The mechanisms underlying suspended sediment transport were investigated by analysing the types of corresponding hysteresis loop. Finally, sediment rating curves for both hourly and daily data at early and late stages and for the entire crop season were established to seek possible sediment‐transport predictive model(s). The study suggests that the complicated processes of suspended sediment transport in irrigation‐dominated watersheds require stochastic rather than deterministic forecasting. Copyright © 2007 John Wiley & Sons, Ltd.

Suspended Sediment Flow Routing by Discrete Linear Models

Discrete Linear sediment models were developed using sediment mobilized and direct sediment flow graphs of Chaukhutia watershed of the Ramganga reservoir catchment, India, and applied for sediment flow routing. The parameters of the models were estimated by Lagrangian method. The sediment graphs computed by these models compared with remarkable accuracy to the measured sediment graphs. The average values of integral square error, coefficient of efficiency and ratio of mean error to the mean observed output for four parameter sediment discharge model are 5.991 %, 97.183% and 0.0022 respectively. For three parameter sediment discharge model, the average value of relative error in estimated peak is 6.976%.

Artificial neural networks for estimating daily total suspended sediment in natural streams

Estimates of sediment loads in natural streams are required for a wide spectrum of water resources engineering problems from optimal reservoir design to water quality in lakes. Suspended sediment constitutes 75–95% of the total load. The nonlinear problem of suspended sediment estimation requires a nonlinear model. An artificial neural network (ANN) model has been developed to predict daily total suspended sediment (TSS) in rivers. The model is constructed as a three-layer feedforward network using the back-propagation algorithm as a training tool. The model predicts TSS rates using precipitation (P) data as input. For network training and testing 240 sets of data sets were used. The model successfully predicted daily TSS loads using the present and past 4 days precipitation data in the input vector with R2=0.91 and MAE=34.22 mg/L. The performance of the model was also tested against the most recently developed non-linear black box model based upon two-dimensional unit sediment graph theory (2D-USGT). The comparison of results revealed that the ANN has a significantly better performance than the 2D-USGT. Investigation results revealed that the ANN model requires a period of more than 75 d of measured P-TSS data for training the model for satisfactory TSS estimation. The statistical parameter range (xmin−xmax) plays a major role for optimal partitioning of data into training and testing sets. Both sets should have comparable values for the range parameter.

Tank Model for Sediment Yield

A tank model consisting of three tanks was developed for prediction of runoff and sediment yield. The sediment yield of each tank was computed by multiplying the total sediment yield by the sediment yield coefficients; the yield was obtained by the product of the runoff of each tank and the sediment concentration in the tank. The sediment concentration of the first tank was computed from its storage and the sediment concentration distribution (SCD); the sediment concentration of the next lower tank was obtained by its storage and the sediment infiltration of the upper tank; and so on. The SCD, caused by the incremental source runoff (or the effective rainfall), was obtained by the theory of the instantaneous unit sediment graph (IUSG) and a sediment routing function. Using the SCD, the sediment yield was computed from the tank model as well as by the IUSG model. The sediment yield obtained from the tank model was then compared with that from the IUSG model. Finally, the tank model was verified on an upland watershed in northwestern Mississippi.

Estimation of temporal variation of sediment yield using GIS / Estimation de la variation temporelle de l'exportation sédimentaire grâce à un SIG

A GIS-based method is proposed for computation of temporal variation of sediment yield during isolated storm events. Data from three Indian catchments, namely Karso and Nagwa in Jharkhand and Kharkari in Rajasthan, have been used. The Integrated Land and Water Information System (ILWIS) GIS package was used for (a) catchment discretization into cell areas using grid networks, (b) evaluation of the spatial variation in catchment topographical characteristics and land use, and (c) presentation of the results obtained. The process of sediment delivery from grid cells to the catchment outlet is represented by the topographical characteristics of the cells. Unit sediment graphs for the catchments are derived by translation of the sediment yield from the grid cells and routing through a linear storage reservoir. The proposed method is found to provide satisfactory estimates of the temporal variation of sediment yield during isolated storm events. The total sediment yield of a storm event may also be computed using the proposed method.

2D Unit Sediment Graph Theory

The erosive behavior and fundamentals of the black-box analysis of a catchment are briefly discussed, and the potentialities of functional series are considered as a model. Then a physically significant nonlinear functional model, called a “2D unit sediment graph,” is developed for predicting the river suspended-sediment concentration or yield from the current and antecedent effective precipitation events. The model represents the overall behavior of the catchment, and hence, does not require separation of excess rainfall, direct runoff, and washload. Comparative applications are performed for the 2D unit sediment graph model and the first- and second-order functional series. Unusually good predictions are produced by the 2D unit sediment graph model. The model represents the factors affecting the erosive behavior by its response functions (unit sediment graphs); hence, it is expected to predict the sediment concentration or yield with sufficient accuracy if the catchment conditions in the calibration per...

Parameter Identifiability for Three Sediment Entrainment Equations

A process-based erosion model is used to study parameterization problems of sediment entrainment equations in overland flow areas. One of the equations for entrainment by flow is developed based on a theory of excess stream power, while the other two relate to excess hydraulic shear. The investigation is conducted in two steps. The first step examines parameter optimization for simulated data sets where the parameter values are known. In the second step, parameter optimization for the most robust equation is examined using experimental data from rainfall simulator plots. Results demonstrate that although the model is capable of estimating total sediment yields with relatively small errors in parameter estimates, the converse is true when the optimization is performed for sediment concentrations. Although sediment yields calculated from simulated sediment concentrations match well with observed data, the parameter estimates generally underestimate sediment concentrations on the rising limb of the sediment graphs, and they overestimate them on the falling limb. This difficulty might be related to structural problems in the model, and unique solutions for parameter estimates cannot be obtained.

Input output models for estimating suspended sediment flow

Linear discrete input-output models were developed for estimating sediment discharge hydrographs from the Chaukhutia watershed comprising an area of 452.25 km2 of the Ramganga reservoir catchment. The causative factors such as sediment mobilized, direct runoff and excess rainfall water was used as input to the models and sediment discharge as the output. The parameters of these models were estimated from rainfall hyetographs, direct runoff hydrographs and direct sediment flow graphs by Lagrangian's method. The generation and prediction performance of these models were assessed based on pattern recognition technique and using the criteria of accuracy. The computed sediment graphs were in closer agreement with measured sediment flow graphs. The average values of coefficient of efficiency and relative error in estimated peak for sediment mobilized-sediment discharge model were more than 96.0% and less than 7.6 %, respectively whereas for direct runoff-sediment discharge model the values were more than 79.0% and less than 18.8%, respectively. For rainfall excess-sediment discharge model these values were more than 57.0% and less than 29.0, respectively.

Prediction of sediment yield by coupling Kalman filter with instantaneous unit sediment graph

An instantaneous unit sediment graph (IUSG) model in conjunction with Kalman filter was investigated for prediction of sediment yield from an upland watershed in Northwestern Mississippi. The state vector of the watershed sediment yield system was constituted by the IUSG and then the sediment yield was estimated by the IUSG model using Kalman filter. The initial values of the state vector were assumed as the average of the IUSG values and the initial sediment yield estimated from the average IUSG. The IUSG model using Kalman filter with a recursive algorithm accurately predicted sediment yield from watershed W-5, Mississippi. The filter allowed the IUSG to vary in time, increased the accuracy of the IUSG model, and reduced physical uncertainty of the sediment yield process in the watershed. Copyright © 1999 John Wiley & Sons, Ltd.

Prediction of sediment yield by coupling Kalman filter with instantaneous unit sediment graph

Prediction of sediment yield by coupling Kalman filter with instantaneous unit sediment graph

The European Soil Erosion Model (EUROSEM): a dynamic approach for predicting sediment transport from fields and small catchments

The European Soil Erosion Model (EUROSEM) is a dynamic distributed model, able to simulate sediment transport, erosion and deposition over the land surface by rill and interill processes in single storms for both individual fields and small catchments. Model output includes total runoff, total soil loss, the storm hydrograph and storm sediment graph. Compared with other erosion models, EUROSEM has explicit simulation of interill and rill flow; plant cover effects on interception and rainfall energy; rock fragment (stoniness) effects on infiltration, flow velocity and splash erosion; and changes in the shape and size of rill channels as a result of erosion and deposition. The transport capacity of runoff is modelled using relationships based on over 500 experimental observations of shallow surface flows. EUROSEM can be applied to smooth slope planes without rills, rilled surfaces and surfaces with furrows. Examples are given of model output and of the unique capabilities of dynamic erosion modelling in general. © 1998 John Wiley & Sons, Ltd.

Satellite remote sensing for soil erosion modelling using the ANSWERS model

Abstract The distributed parameter model ANSWERS was used to predict runoff and soil loss from three agricultural watersheds in the arid zone of India. Model input parameters such as landform, drainage, soil and land use/land cover were derived from Landsat Thematic Mapper false colour composites and limited ground truth. The model predicted hydrographs and sediment graphs within acceptable limits. ANSWERS underpredicted the total soil loss by factors of 2.6 to 3.6. Reasons for these results are discussed.

Modelling sediment transport in stream channels in the arid zone of India

AbstractEphemeral channels in arid regions convey larger amounts of sediment than perennial channels in humid regions. Sediment graphs at the outlet of channels have been derived by the standard sediment rating curve technique and by a lumped model based on the instantaneous unit sediment graph (IUSG) concept. The IUSG gives estimates of sediment transport that are better than those derived with the sediment rating curve as it takes into account the availability of erodible material within the channel bed.