Applied Mechanics and Materials Vols. 405-408

Abstract: Changes in stream flow and sediment load in the Buyuan River Basin is a focus due to its vital ecological niche in supply feeding and spawning habitats for upstream migrant fish species of Mekong River. Based on the precipitation and water discharge series data (19592008), and sediment load series data (19932008), the runoff and sediment discharge variation and its response to precipitation has been analyzed. The results shown that, during the study period of 19592008 at the Manan gauging station, annual runoff of Buyuan River has generally decreased, but not significant at the 95% confidence level. However, the decline trend of sediment load was obvious for gauged period from 1993 to 2008. The seasonal runoff distribution in the Buyuan River was uneven and demonstrated an observably unimodal distribution. Both water discharge and sediment load are largely derived from wet season (from Jun to Nov), especially in flood season from July to September. During the study period 1993-2008, both annual and monthly observed value of water discharge and sediment load had coincident changing processes. Double mass curves indicated decreasing precipitation was the main reason for runoff reduction in the Buyuan River Basin; declining rainfall and water discharge were two key factors for sediment load reduction. In 2002, however, sediment discharge undergone abrupt change due to huge peak discharge and two consecutive years strong precipitation in the Buyuan River Basin.

Abstract: Restricted by such factors as the size of test area, amount of work and water depth of model, hydraulic models are often made into distorted patterns, whereas the distorted models demand for roughening usually. The hydraulic model of comprehensive harness of Qian'an Reach of Luan River requires big roughness that general roughening technologies cant meet, so the plastic grass cushions were introduced. The preliminary experiment in flume, the preliminary experiment of the comprehensive model and the verification experiment of the comprehensive model proved the feasibility of the technology of roughening with the grass cushions in hydraulic model tests.

Abstract: This paper presents a statistics analysis of 1938-2012 data of daily discharge and water level collected from a gauging station on the Richelieu River in Southern Quebec, Canada. Using the most recent data, this paper aims to update flood characteristics from previous decades old analyses. Such update is important to the flood-prone region. The present analysis covers peak flow magnitude, duration, timing and, more importantly, their changes. The main findings are: There are no significant changes over time in average magnitude of floods, but there are increasing fluctuations between low and high peak discharges. The distribution of annual peak discharges shows a signifcaint shift of skewness from left to right; if this condition persists, future floods are expected to have a larger magnitude than historic flood events. The timing of peak discharges has not shown any significant trend of changes. A new flow rating curve has been obtained for discharge estimates.

Abstract: Reservoir sediment problem on sediment-laden river is the main puzzle problem in reservoir operation. Reservoir sedimentation, reservoir operation, reservoir sediment treatment and utilization and simulation of reservoir are analyzed in the paper. Difficulty is also provided during the research process. And reservoir sediment research on Yellow River is prospected. The paper can be helpful to provide the basis for reservoir sediment problem on sediment-laden river, and also point out the direction of reservoir sediment research on Yellow River.

Abstract: The protective structures on the shore often used in the river regulation and channel rectification works are divided into solid structures and permeable structures. The solid structures will cause an intensive change of the local flow condition, and lead to adverse impact as scouring of local foundation and edges; the permeable structures which can dissipate the flow energy are gradually popularized for use. Common permeable structures include the tetrahedron-like penetrating frame used for engineering and vegetation on the shore, etc. This paper takes the tetrahedron-like penetrating frame and vegetation for example, summarizes research on the behavior of water flow and sediment affected by permeable structures, discusses the similarities and differences as well as different effects of the functions of the solid structures and permeable structures, and finally concludes the features of application of permeable structures.

Abstract: Hydraulic conductivity (K) and scale effects in basalt in the dam area of Xiluodu hydroelectric station were investigated by three kinds of field hydraulic tests with different test scale, 2608 water pressure tests in single borehole, 54 water seepage tests in adit and groundwater tracer test. Statistical results show the high heterogeneity of fractured rock and K difference between two neighboring test intervals are often more than two orders of magnitude. However, there is a strong decreasing trend of hydraulic conductivity with the increase of vertical depth. Moreover, these three kinds of hydraulic test results demonstrate that hydraulic conductivity increases with the increase of test scale in heterogeneous basalt and the heterogeneous degree of K decreases with the increase of test scale. K from water seepage test in adit, with the test scale of 1-2 m, is dispersed from 0.00024 m/d to 3.46 m/d. K from water pressure test in single borehole, with the test scale of 4-7 m, is 0.0002-1.04 m/d. K from groundwater tracer test, with the test scale of 70-145 m, is concentrated between 0.46 m/d and 2.1 m/d. High heterogeneity of fractured rock and multi-level of fractures are thought as the major reason resulted in scale effects of hydraulic conductivity.

Abstract: An experiment was carried out to determine the effect of mulched drip irrigation under water deficit on leaf area index (LAI), leaf area duration (LAD), dry matter (DM) and relative growth rate (RGR) of potato in an arid environment. Five water deficit treatments and a full irrigation control were established to subject potato to various levels of soil water deficit at different crop growth stages. The result indicated that potato LAI and LAD at all the determined growth stages were not reduced under water deficit regulation. Additionally, the DM and RGR at starch accumulation were not significantly decreased under water deficit either. Therefore, medium soil water deficit regulated at 55%~65% of field capacity with mulched drip irrigation at potato tuber initiation could be used to effectively improve leaf area index, leaf area duration, dry matter and relative growth rate of plants.

Abstract: To improve the soil condition in coastal area, subsurface drainage projects with different depth and space were established, and the materials were bellows combining with 40g/m² geotechnical cloth and forage; in the study, the economic benefits were evaluated, and the soil samples before and after one typical rainfall were taken and observed. Results showed that the subsurface drainage system was proved to be feasible, with the EIRR of about 14.3%, ENPV of about 2697 $/hm², and EBCR of about 1.36. On the other hand, subsurface drainage projects decreased the contents of Cl^- in different soil layers significantly, especially T4, which obtained the optimum results, decreasing Cl^- of each soil layer by more than 50% after the rainfall. From the observation results of the deeper soil, it was discovered that the lower depth was negative to the Cl^- elimination in deeper soil layer. In practical, 0.9m depth and 10m space was appropriate for the application. Besides, the management and improvement of later stage were also important, in the reality situation of project conducted, the sludge elimination of the drainage pipes should be regarded as chief issue in later utilization of the drainage project.

Abstract: In order to meet the requirements for flood prevention, the blocked river channel of a certain phosphate mine area which located in the Three Gorges Reservoir area requires to be regulated. The river channel has the features of mountain-rivers. The flood prevention standard of the river channel is designed to prevent 50-year flood according to the local meteorological and hydrological data. The gravity gabion retaining walls has been used to support side slopes, the Reynolds gabion cushion has been used to protect the bottom, and the reinforced Mack mattresses has been employed to protect slopes. The results indicate that the minimum cross sectional area of the river is 25.743 m² under the condition of 50-year flood, which is lower than the designed maximum cross sectional area of the river 31 m², meaning that the design of the river channel meets the flood prevention requirements. In addition, the special material composition and structure features of gabion structures do not only overcome the defects of the traditional structure which features stereoplasm imperviousness and is prone to aging and failures, but also are characterized by good foundation adaptability and ecological features. This project can be referred to similar projects as the new ideas in river regulation of mine mountain areas.

Abstract: China is a country with frequent floods from ancient periods, caused by its complicate topology, higher in western regions, lower in eastern regions, consisting of three kinds of terraces, and precipitation variance at different seasons in a common, heavy or scare year. Challenges from floods are increased together with climate change, land use change and urbanization development, particularly, extreme rainfall events occurring with a high frequency. Four kinds of flood damage data time series including affected area, damaged area, dead population and collapsed houses from 1950 to 2010 from Bulletin of Flood and Drought Disaster in China in 2011 will be applied to trend analysis of floods by MK test. The results indicate that affected area and damaged area have significant upward trend, dead population has significant downward trend, damaged houses has no significant upward or downward trend. Keywords: Trend Analysis; Flood Damage; Mann-Kendall Test; Data Series