Temporal Variation Of Sediment Yield Research Articles

Climatic and hydrogeomorphic controls on sediment characteristics in the southern Sierra Nevada

The magnitude of sediment yield from headwater catchments is controlled by the interactions among hydrology, geomorphology, and soil disturbance. In montane regions like the Sierra Nevada, snow is one of the main factors controlling the timing and magnitude of hydrological fluxes. However, the role of snow on modulating spatial and temporal variation of sediment yield remains unclear. Using 120-site years of sediment yield data from 10 headwater catchments (drainage area 50–475 ha), we examined the sediment yield characteristics across an elevational gradient (1,777–2,381 m elevation) in the southern Sierra Nevada. Across space and time, we calculated an average annual suspended sediment yield of 62 ± 147 Mg/km2. In contrast, the measured mean annual bedload yield from the study catchments was small, 1.1 ± 2.4 Mg/km2. A linear mixed-effects model showed that maximum annual discharge alone can only explain 24 % (marginal R2 = 0.24) of the variance in sediment yield. Similarly, the hypsometric integral, which is often used as a metric for erosion susceptibility, showed no predictive power (marginal R2 = 0.005). As much as 65 % of the variance in sediment yield can be explained by fixed effects when snow related drivers (i.e., center of flow timing and aspect) were included in the model along with maximum annual discharge, suggesting a strong influence of snowmelt. Moreover, the relationship between area normalized suspended sediment yield (Qs) and unit discharge (Q) was significantly different between rain and snow events (p = 0.001). Both average slope (α) and exponent (β) terms of the Qs=αQβ relationship across the ten catchments were higher for rainfall (α=5.8,β=1.84) than those for snowmelt (α=3.1,β=1.77) events. As the erosion severity and power were higher during rainfall than the snowmelt events, a shift in the precipitation form from snow to rain under a warming climate will likely increase sediment yield. These results provide critical insights on background sediment yield in the southern Sierra Nevada and likely changes under future climate.

Estimating Sediment Yield from Upland and Channel Erosion at A Watershed Scale Using SWAT

Sediment discharge is one of the main water quality concerns in integrated watershed management. A proper identification of sediment sources is therefore important to the success of watershed conservation programs. Since water quality monitoring data collected at the mouth of the watershed alone are typically not sufficient for identifying key sediment sources distributed in the watershed, hydrologic models can be applied to prioritize Best Management Practices (BMPs) implementation for sediment control in a watershed. In this paper, the Soil and Water Assessment Tool (SWAT) is applied to the South Tobacco Creek (STC) watershed in Canada to identify sediment sources and to estimate the spatial distribution of sediment yield from both upland and channel erosion processes. The model is calibrated and validated against observed flow and sediment data measured at fourteen edge-of-field and mainstream stations based on 20 years of land management data. Modeling results show that approximately 60 and 40 % of the sediment discharge at the mouth of the watershed are originated from channel erosion and upland erosion respectively. A high spatial and temporal variation of sediment yield is found in the watershed depending on climate, topography, land use, and soil conditions. These findings will be helpful for understanding the runoff and erosion processes and evaluating the cost-effectiveness of soil and water conservation programs at a watershed scale.

Changes in sediment discharge in a sediment-rich region of the Yellow River from 1955 to 2010: implications for further soil erosion control

The well-documented decrease in the discharge of sediment into the Yellow River has attracted considerable attention in recent years. The present study analyzed the spatial and temporal variation of sediment yield based on data from 46 hydrological stations in the sediment-rich region of the Yellow River from 1955 to 2010. The results showed that since 1970 sediment yield in the region has clearly decreased at different rates in the 45 sub-areas controlled by hydrological stations. The decrease in sediment yield was closely related to the intensity and extent of soil erosion control measures and rainstorms that occurred in different periods and sub-areas. The average sediment delivery modulus (SDM) in the study area decreased from 7,767.4 t/(km2 ·a) in 1951–1969 to 980.5 t/(km2·a) in 2000–2010. Our study suggested that 65.5% of the study area with the SDM below 1,000 t/(km2·a) is still necessary to control soil deterioration caused by erosion, and soil erosion control measures should be further strengthened in the areas with the SDM above 1,000 t/(km2·a).

Efficacy of Time-Area Method in simulating temporal variation of sediment yield in Chehelgazi watershed, Iran

Efficacy of Time-Area Method in simulating temporal variation of sediment yield in Chehelgazi watershed, Iran The proper prediction of temporal and spatial variation of sediment yield from the watershed is a need for sediment control, river engineering and soil and water conservation studies. The present study was therefore planned to simulate the sediment graphs for Chehelgazi watershed in Gheshlagh dam upstream in Kurdistan Province, Iran, by using Time-Area Method. Towards this attempt, the study watershed was divided into 7 time-area segments based on the time of concentration. The soil erosion in each segment was estimated using the USLE and then routed to the main outlet using sediment delivery ratio as a function of land slope in two adjacent time-areas. The temporal variation of sediment was ultimately predicted with the help of lag time of sediment arrival to the outlet and the concept of superposition for 11 storm events, which occurred during winter 2006 and spring 2007. The comparison between estimated sediment graphs with corresponding observed ones verified the weak capability of the model in simulation of sediment graphs under consideration. The results also verified the calibration necessity of the model to achieve appropriate estimation for important components of the sediment graphs. The results of the calibration finally proved the considerable capability of the model in predicting of total volume of sediment yield with respective estimation and verification errors of 30.93 and 33.40%.

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.

Spatial and temporal variation of sediment yield in the landscape: Example of Huanghe (Yellow River)

Regional scale relations between specific sediment yield and drainage basin area in the Huanghe basin reveal varying landscape sedimentary dynamics. Declining specific sediment yield with area is typical of disturbed agricultural areas, while increasing yields indicate the remobilization of stored sediment by bank and floodplain erosion along major tributaries. Using the developed relations, areally‐adjusted sediment yield maps are created over the entire Huanghe basin. Maps of the Loess Plateau for periods before and after 1970 reveal major changes in sediment yield, indicating that land management may have a major effect on sediment dynamics within a short period of time.

Event-based Sediment Yield Modeling using Artificial Neural Network

In the present study, a back propagation feedforward artificial neural network (ANN) model was developed for the computation of event-based temporal variation of sediment yield from the watersheds. The training of the network was performed by using the gradient descent algorithm with automated Bayesian regularization, and different ANN structures were tried with different input patterns. The model was developed from the storm event data (i.e. rainfall intensity, runoff and sediment flow) registered over the two small watersheds and the responses were computed in terms of runoff hydrographs and sedimentographs. Selection of input variables was made by using the autocorrelation and cross-correlation analysis of the data as well as by using the concept of travel time of the watershed. Finally, the best fit ANN model with suitable combination of input variables was selected using the statistical criteria such as root mean square error (RMSE), correlation coefficient (CC) and Nash efficiency (CE), and used for the computation of runoff hydrographs and sedimentographs. Further, the relative performance of the ANN model was also evaluated by comparing the results obtained from the linear transfer function model. The error criteria viz. Nash efficiency (CE), error in peak sediment flow rate (EPS), error in time to peak (ETP) and error in total sediment yield (ESY) for the storm events were estimated for the performance evaluation of the models. Based on these criteria, ANN based model results better agreement than the linear transfer function model for the computation of runoff hydrographs and sedimentographs for both the watersheds.

NUMERICAL SIMULATION OF SURFACE EROSION AND SEDIMENT YIELD FROM BARE HILLSIDE

Erosion process of bare hillside was investigated experimentally and numerically in the present study. Experiments were conducted on the model hillside with the artificial rainfall in the experimental flume. The numerical simulation model has been developed to predict the erosion process and to understand it more deeply. The numerical model was applied to the phenomenon which occurred on the slope in the experimental flume. Based on the comparison between the experimental results and the numerical ones, the validity of the present numerical model was verified. The process of channel network evolution and the head migration of the gully were investigated on the basis of this numerical analysis. Temporal variation of sediment yield from the hillside was also studied.

Changes in the fine sediment dynamics of the Ouse and Tweed basins in the UK over the last 100–150 years

AbstractSediment cores (collected from nine headwater lakes and reservoirs in their catchments and adjacent areas and from ten floodplain sites in the middle and lower reaches of the two river systems) have been used to reconstruct changes in suspended sediment yields, rates of sedimentation and suspended sediment sources for the Ouse and Tweed catchments in the UK over the last ca 100–150 years in response to recent environmental change. For the small lake/reservoir catchments in or adjacent to the Ouse basin, average sediment yields for the recent period (1963–95) were generally found to exceed those for the period prior to 1963, by up to 94%, suggesting that sediment yields have increased over time. For the equivalent lake/reservoir catchments in and adjacent to the Tweed basin, sediment yields were generally lower in the period since 1963. In both basins, sediment yields over the past 100–150 years were characterized by considerable temporal variability, which was seen to reflect, at least in part, the significant changes in land use and land management that occurred within their catchments. No clear links between the variability of sediment yields and changes in climate were apparent. Changes in sediment source reconstructed for one of the lakes appeared primarily to reflect catchment disturbance during afforestation in the 1940s. Average rates of overbank sedimentation for the ten floodplain sites varied considerably between sites. For those cores collected from the Ouse basin there was no consistent temporal trend, and average sedimentation rates for the period extending from ca 1895 to 1963 were broadly similar to those for the period since 1963. For the Tweed basin, sedimentation rates for all three cores were higher prior to 1963, reflecting the increased soil erosion and sediment yields associated with the conversion of pasture to arable land in the immediate post‐World War II period and the ditching and planting operations associated with afforestation in the 1940s. Substantial downcore variability in the source of the overbank sediment, considered in terms of both source type and spatial location, was found in both river basins. This was seen to reflect land‐use change, including land drainage, the conversion of pasture to arable land, afforestation, and increased cereal production. The evidence provided by the floodplain cores again showed little indication of any influence linked to climate change.Although the detailed patterns of temporal variation of sediment yield, overbank sedimentation rate and sediment source reconstructed from the sediment cores collected from the lake/reservoirs and floodplain locations are site specific, there is a general consistency between the changes in sediment dynamics reconstructed for the headwater catchments (based on the cores collected from the lakes and reservoirs) and the equivalent evidence for the middle and lowland reaches of the catchments (provided by overbank floodplain deposits). Despite significant changes in climate, and, more particularly, land use over this time period, the general lack of evidence of substantial changes in downstream sediment yield and rates of overbank sedimentation over the last ca 100–150 years in the Ouse and Tweed basins suggests that their sediment dynamics have been generally insensitive to recent environmental change. This finding has important implications when considering the likely response of these, and similar, UK river basins to future environmental change. Copyright © 2003 John Wiley & Sons, Ltd.

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.

Estimation of temporal variation of sediment yield from small catchments through the kinematic method

Abstract A method is proposed for estimation of temporal variation of the sediment yield for single storm-events in small catchments. The kinematic wave equations are used for simulation of overland flow whereas continuity equation for sediment and expressions for sediment detachment and transport are used to compute the sediment yield. The method is based on numerical solution of these equations through a non-uniform spatial grid formed by time-area segments of the catchment. Carefully collected data of 12 experimental catchments from varying climates and ranging in size from 0.002 km2 to 92.5 km2 are used for calibration and verification of the proposed method. The observed sediment yields during the storm events studied hererin varied from about 0.003 tonnes to 800 tonnes. The method developed in the present study depends on calibration against a record of past conditions. Therefore, it can not be used directly to predict the future changes in catchment land use or climate. However, the present method can be used for estimation of sediment yield in other such ungauged catchments which have similar hydro-meteorological conditions and for which other information are available.

Temporal Variation of Sediment Yield by Debris Flows at the Mizunashi River in Unzen Volcano

Temporal Variation of Sediment Yield by Debris Flows at the Mizunashi River in Unzen Volcano

Temporal Variation of Sediment Yield

Estimates of temporal variation of the sediment yield are required for studies of reservoir sedimentation, river morphology, and soil and water conservation. In this paper, a method is proposed for prediction of the variation of sediment yield with time. This method is based on the assumption that the time-area curve of a catchment can be used to obtain the catchment response to an input. The sediment delivery ratio in a catchment is considered to be the function of land slope, area, and extent of forest cover. Carefully collected data from the experimental catchments are used for calibration and verification of the proposed method. The present method is found to produce realistic estimates for the total sediment yield.

Rill sediment transport on a Prince Edward Island (Canada) fine sandy loam

In order to determine the temporal variation of sediment yield under conditions of freezing, rill erosion tests were conducted on beds of a fine sandy loam soil subjected to surface flow under various conditions of freezing, mulching, surface compaction, and slope. During a 20-min test period, runoff samples were collected at six sampling times to measure sediment yield. Freezing, mulching, and slope had significant ( P< =0.05) effects on sediment yield. Generally, sediment yield decreased with time, although treatment units subjected to freeze-thaw (frozen at the start of the tests) or compaction showed an initial rise. The sediment yield of the latter treatments were best described by non-linear ( R 2=0.807 to 0.969) regression models. In examining sediment size grades <600 μm, only the <38 μm fraction showed significant differences in individual sample mass among sampling times. For this size grade there was a significant decrease in sediment yield for the 7% slope ( R 2=0.901) and for bare surface ( R 2=0.614) at later sampling.