The influence of changes in tidal asymmetry on residual sediment transport in the Western Scheldt

This study fits into a wider research program from RWS RIKZ concerning the exchange of sediment between the coast and the tidal basins, Western Scheldt and Wadden Sea, which are the largest basins along the Dutch Coast, over different time-scales. For both basins, questions about the evolution of the import/export at the mouth recently arose. In case of the Western Scheldt, which is the subject of this study, mainly the uncertainty about the future developments after the change from import to export at the mouth was noticed in the 1990s, which necessitated a more detailed study of this area.     

Conditions when anisotropy is negligible for solute transfer in sediment beds of lakes or streams

To reduce the complexity and save computation time, an isotropic and a scalar dispersion model are explored and compared to the anisotropic advection/dispersion model to study the interstitial flow in a stream and lake sediment induced by a periodic pressure wave. In these systems, the solute transport is controlled by the ratio (R = a/(LS)) of the pressure wave steepness (a/L) to the stream slope (S), and the dispersivity ratio (λ = α_L/L) that measures the longitudinal dispersivity (α_L) relative to the pressure wave length (L). Through a series of numerical experiments, the conclusion is reached that a scalar dispersion model can be applied with satisfactory results for advection-dominated transport, i.e. when R ?  0.1 and λ ? 0.01, or λ ? 0.0001, i.e. Peclet number (Pe) ? 10000; an isotropic dispersion model can be applied when R ? 10 or λ ? 0.001, and the full anisotropic advection/dispersion model has to be applied when R > 10 and λ > 0.001.     

Effects of Caragana Korshinskii Kom. Cover on runoff,sediment yield and nitrogen loss

Soil erosion is serious in the Loess Plateau of China. Deposition of the eroded sediment in lakes or rivers may lead to eutrophication, because the sediment carries a lot of nutrients. Field experiments were conducted to study soil erosion and loss of nitrogen (N) from a 15o hillslope with 30% (low) or 80% (high) coverage of the shrub Caragana korshinskii Kom. A bare soil plot was used for the comparison. The results showed that Caragana korshinskii cover significantly reduced runoff and soil erosion. In comparison to the bare soil plot, the vegetation covered plots had about 20% less runoff and 65% less sediment. In general, the concentration of N in both runoff water and the eroded sediment decreased with time and approached a steady value. However, the species of nitrate nitrogen (NO3) was exceptional which increased with time slightly. The soil erosion caused an N loss of about 250 mg/m2 for the bare soil plot, the low coverage of Caragana korshinskii reduced the N loss by 20% and the high coverage of Caragana korshinskii reduced the N loss by 40%. Moreover, the amount of total N in eroded sediment was 2 to 3 times higher than the value in runoff water. In the total N loss, the organic N was about 75-80%. Nevertheless, inorganic N in runoff water was 5 to 10 times higher than the value in eroded sediment. The species of NO3 was obviously higher than the species of ammonium nitrogen (NH4). NO3 was the main species of inorganic N loss and was about two thirds of total. The organic N was the main species of N in the eroded sediment.     

Sediment removal efficiency of siphon dredging with wedge-type suction head and float tank

Siphon dredging with a float tank and different siphon suction heads, including the plain-type and wedge-type with/without side holes, through flume experiments were used to investigate the reservoir sediment removal efficiency. The experiment revealed maximum suction pressure and velocity when the distance from the suction head to the bed was about 25% of suction head diameter. Suction pressure decreased rapidly as the distance from the suction head to the bed increased to 50% and 100% of suction head diameter. Suction pressure achieved by wedge-type suction head was only 16.9-17.6% of that around plain-type suction head, and the velocity around wedge-type suction head was 64.7-68.4% of that around plain-type suction head. However the plain-type suction head was easily clogged doe to its long bobbing period. The average bobbing period for the plain-type suction head was about 105-263% that of the wedge-type suction head. The sediment removal efficiency was achieved when float tank diameter was 3-4 times that of the suction head. Flow discharge and sediment removal increased as the suction head diameter and side hole diameter increased, respectively. The most efficient side hole area was an area within 15% of suction head area. Totally, the optimal sediment removal efficiency was the wedge angle of 20° with 3 side holes. The efficiency of sediment dredging by siphon suction with a suction tube passing through the dam bottom was better than that with suction passing over the top of the dam. The wedge-type siphon suction with a float tank is preferable for sediment dredging in small reservoirs because it is inexpensive and efficient.     

Machine Learning Approach to Predict Sediment Load – A Case Study

In this study, a novel machine learning technique called the support vector machine (SVM) method is proposed as a new predictive model to predict sediment loads in three Malaysian rivers. The SVM is employed without any restriction to an extensive database compiled from measurements in the Muda, Langat, and Kurau rivers. The SVM technique demonstrated a superior performance compared to other traditional sediment‐load methods. The coefficient of determination, 0.958, and the mean square error, 0.0698, of the SVM method are higher than those of the traditional method. The performance of the SVM method demonstrates its predictive capability and the possibility of the generalization of the model to nonlinear problems for river engineering applications.     

Submerged hydraulic jump with sediment-laden flow

In this experimental study,the effect of suspended sediment concentration on the characteristics of a submerged hydraulic jump in a rectangular channel has been investigated,based on the sediment conce...     

鄂尔多斯盆地环县地区上三叠统延长组长63砂层组沉积微相特征及新认识

通过岩心的详细观察,结合测井、录井资料综合分析,在环县地区上三叠统延长组长6₃砂层组中,识别出了三角洲前缘、前三角洲和深湖3种亚相,和水下分流河道、支流间湾、河口砂坝、远砂坝、前三角洲泥、砂质碎屑流沉积、浊流沉积、液化流沉积、滑塌沉积和深湖泥10种微相。编绘了一系列沉积微相连井剖面图和长6₃砂层组的沉积微相平面展布图,表明研究区西部、北部及东北部发育三角洲前缘亚相,研究区中部和东南部发育深湖亚相。在深湖亚相中除了深湖泥外,发育大量的砂质碎屑流和浊流等重力流沉积。作者首次提出了源于浅水区的砂级沉积物是通过前三角洲上的一系列水道搬运至深湖区形成重力流沉积的。综合以上研究成果,建立起了该区的沉积模式。论文最后分析了研究区的油气潜力,指出水下分流河道和砂质碎屑流沉积两种微相的储集性能最好。由于本区砂体横向尖灭现象普遍,可形成一些规模较大的岩性圈闭,是岩性油气藏勘探的有利目标区。     

铜锈环棱螺( Bellamya aeruginosa ) 生物扰动对藻华水体沉积物微生物群落结构的影响

应用磷脂脂肪酸(PLFAs)法测定了不同密度铜锈环棱螺生物扰动下沉积物表层微生物群落结构的变化。结果表明,与对照组相比,含螺处理组PLFAs总生物量有了明显的升高,且与底泥总有机碳(TOC)含量变化趋势有很高的相关性(r=0.541)(P<0.05)。实验过程中细菌/真菌值发生显著变化,中密度处理组的细菌/真菌值显著高于其它实验组(P<0.05),说明中密度螺影响下细菌生长较真菌更快,细菌生物量显著升高。主成分分析(PCA)显示,低、高密度螺处理下沉积物的微生物群落结构与对照组相似,而中密度螺处理组(3个螺/培养柱)(相当于196ind/m2)能够使沉积物微生物群落结构产生明显变化。     

Assessment of Water Quality in the Elbe River at Flood Water Conditions Based on Cluster Analysis,Principle Components Analysis,and Source Apportionment

An assessment of water quality measurements during a spring flood in the Elbe River is presented. Daily samples were taken at a site in the middle Elbe, which is part of the network of the International Commission for the Protection of the Elbe River (IKSE/MKOL). Cluster analysis (CA), principal components analysis (PCA), and source apportionment (APCS apportioning) were used to assess the flood‐dependent matter transport. As a result, three main components could be extracted as important to the matter transport in the Elbe River basin during flood events: (i) re‐suspended contaminated sediments, which led to temporarily increased concentrations of suspended matter and of most of the investigated heavy metals; (ii) water discharge related concentrations of pedogenic dissolved organic matter (DOM) as well as preliminary diluted concentrations of uranium and chloride, parameters with stable pollution background in the river basin; and (iii) abandoned mines, i.e., their dewatering systems, with particular influence on nickel, manganese, and zinc concentrations.