Inhibitability of soil loss and sediment concentration during consecutive rainfalls from experimental plots treated by endemic microorganisms

Consecutive rainfalls, due to changes in antecedent moisture, alter soil erosion processes, necessitating the implementation of suitable soil loss control methods. Biological soil microorganism approaches have been applied to control soil loss. However, information on the involvement of microorganisms in the soil loss and rill erosion processes has yet to be supplied. In this study, the individual and combined inoculation of cyanobacteria and bacteria was investigated during five consecutive rai...     

Base flow separation for soil erosion simulation in a granitic forested headwater catchment using a process-based model,GeoWEPP

Distributed erosion models, which simulate the physical processes of water flow and soil erosion, are effective for predicting soil erosion in forested catchments. Although subsurface flow through multiple pathways is dominant for runoff generation in forested headwater catchments, the process-based erosion model, Geo-spatial interface for Water Erosion Prediction Project(Geo WEPP), does not have an adequate subsurface component for the simulation of hillslope water flow. In the current study, t...     

Modeling uncertainties of reservoir flushing simulations

Every dam or barrage construction affects the watercourse and the retention of sediment that previously was carried by the river, which can lead to siltation of the reservoir and obstruction of water intakes over time, reducing their capacities. However, the information available regarding the effect of sediment and drawdown parameters, sediment management at reservoirs, as well as different equational approaches, is scarce. The current research aims to evaluate the effect of parameters associated with numerical modeling of sediment management in reservoirs considering scenarios with different drawdowns, transport equations, sediment size distributions, and thickness of the initial sediment layer. The case study of the Aimorés Hydropower Plant (HPP) is used, applying the Delft3D-FLOW model for two-dimensional modeling. All parameters influenced the volume of mobilized sediment, among which the initial layer thickness was the parameter that resulted in the greatest changes in simulated results. In general, the results show that the uncertainties in the input parameters outweigh the uncertainties between the techniques, which found large variations in results when evaluating the use of different transport equations. These results indicate the importance of proper estimation of model parameters for predicting effects with accuracy and the need for such studies before planning and management operations are evaluated to avoid environmental harm and energy waste.     

Modelling aeolian sand transport and morphological development in two beach nourishment areas

The aeolian sand transport model SAFE and the air flow model HILL were applied to evaluate cross‐shore changes at two nourished beaches and adjacent dunes and to identify the response of aeolian sand transport and morphology to several nourishment design parameters and fill characteristics. The main input of the model consisted of data on the sediment, tide and meteorological conditions, and of half‐yearly measured characteristics of topography, vegetation and sand fences. The cross‐shore profiles generated by SAFE–HILL were compared to measured cross‐shore profiles. The patterns of erosion and deposition, and the morphological development corresponded. In general, the rates of aeolian sand transport were overestimated. The impact of parameters that are related to beach nourishment (namely grain size, adaptation length and beach topography) on profile development was evaluated. Grain size affected the aeolian sand transport rate to the foredunes, and therefore the morphology. Adaptation length, which is a measure of the distance over which sediment transport adapts to a new equilibrium condition, affected the topography of the beach in particular. The topography of a beach nourishment had limited impact on both aeolian sand transport rate and morphology. Copyright © 2000 John Wiley & Sons, Ltd.     

Detecting significant sediment motion in a laboratory flume using digital video image analysis

A video analysis method for monitoring sediment transport and sorting processes in a laboratory flume is presented. Video taken through the glass side‐wall of a laboratory flume is captured using a digital CCD (charge‐coupled device) camera and significant movements between individual frames are detected using image analysis. This method involves direct subtraction of the brightness numbers of pixels in sequential video frames, followed by thresholding to produce binarized images of significant change, above the inherent level of system noise. Experimental results showing dilation of a gravel framework and rapid infiltration of fines just prior to entrainment are discussed. Copyright © 2000 John Wiley & Sons, Ltd.     

滦县地磁场井下观测系统抗干扰效果

近距离铁磁性物质干扰(农田耕作、基建等)、直流供电干扰(高压直流输电、地电阻率观测等)是地磁场地面观测的主要干扰方式。在滦县地震台布设地磁场井下观测系统,检验井下观测的抗干扰效果,结果发现,地磁场井下观测可抑制近距离铁磁性物质干扰,但无法抑制直流供电干扰(可通过避让一定距离解决),该分析结果为未来地震监测手段的选取提供技术参考指标和依据。     

Difference between static and dynamic angle of repose of uniform sediment grains

In the investigation of sediment transport, it is necessary to differentiate various definitions of angle of repose (AoR) available in the literature. The static AoR, composed of upper and lower angle of slope, forms just before and after slope instability, while the dynamic AoR can be observed when sediment grains are moving continuously down an inclined plane. In the present study, a series of laboratory experiments was conducted to measure static and dynamic angle of repose for uniform natural sedi-ments with median diameter of 0.28–4.38 mm. The results show that the different slope angles have different characteristics. The upper and dynamic AoR increase slightly with increasing grain diameter, while the lower AoR is not sensitive to changes in sediment size and may assume a constant value. The average of the upper and lower AoR is equivalent to the dynamic AoR, and the difference between them increases with increasing grain diameter. The present study suggests that the different angles of repose should be treated with caution when applying in investigations of bedload transport, dune migration and local scour development.