Applied Mechanics and Materials Vols. 212-213

Abstract: Aiming at the existing problems in the models of water resources allocation, the concept of friendly allocation of water resources was put forward, and based on the principles of basic water use guarantee, preference of status in quo, fairness and high efficiency, the friendly subfunctions were established and an integrated model of water resources allocation was proposed with maximizing friendly function of water resources allocation. As a case study, the proposed allocation model was applied in Fuhuan River Basin in China, and the results indicated that the model was rational and effective, which provides a new method for water resources allocation in the river basin.

Abstract: Dinh An Estuary is one of Bassac River’s estuaries as a part of the Mekong delta. The navigation channel entrance, however, has a limited nautical depth due to the presence of a highly dynamic offshore bar at the estuary. Ship’s size sailing on the Bassac River is therefore limited to 5,000 DWT in optimal conditions. It needs to dredge twice a year and a lot of money paid for keeping the channel. Sometimes, the channel was deposited intermediately after dredging. In this paper, according to the specific morphodynamic conditions at the estuary, the advantages and drawbacks for the proposed regulation schemes are established. Four regulation schemes are numerically investigated and analyzed with respect to the behavior of each scheme to improve the water depth in the navigation channel.

Abstract: Bases on the expansion of Geordie Coefficient, a analysis method for water consumption fairness have been set up, and the Geordie coefficients are calculated to describe the influence of population, GDP, water quantity on water use of China in 2009. Then water demand coefficient is put forward to estimate the reasons for unfairness of water use. Moreover, Geordie coefficient of the North and South of China is analyzed. The results show that Geordie Coefficient represents unfairness of water use, which result from the unfair factors, including population, GDP, and water quantity. The research can provide reference for reasonable configuration of the water resources.

Abstract: Nanchang rail transit project line1 was programmed to drill through the Ganjiang river bottom of the reach approximately 700m downstream from the Nanchang Bridge. The prediction of maximum erosion depth of the river bed at the tunnel location was strongly needed. This paper described the composition and evolution of the river bed in the engineering reach, established a 2-D flow and sediment mathematical model to calculate and analyze the river bed evolution at the tunnel location, selected the typical hydrological years of erosion calculation, catastrophic floods and a long series of hydrological years as the hydrological conditions, and finally obtained the maximum erosion depth under different hydrological conditions. These results will provide technical reference for the tunnel design.

Abstract: In these years, the global climate change has caused the increase in storm and drought frequency. In August 2009, Taiwan experienced its worst floods in 50 years after Typhoon Morakot struck almost the entire southern region. During the three-day event, Typhoon Morakot brought copious amounts of rainfall, peaking at 2,500 mm, which triggered severe flooding throughout the region. The Kaoping River Basin was one of the most impacted regions in southern Taiwan. A huge amount of sediments and debris flowed into the Kaoping River Basin, which caused high concentration of suspended sediment in the river causing the shut down of water treatment plants. In addition, the Kaoping River receiving significant biochemical oxygen demand (BOD) and ammonia loads from hog farms and domestic wastewaters and resulted in the deterioration of water quality. The Water Quality Simulation Program (WASP)/EUTRO model was used to simulate the fate and transport of water quality pollutants and develop water quality management strategies. The developed strategies are able to effectively control the pollutants and improve the Kaoping River water quality.

Abstract: Effect of shrub on runoff and sediment yield and its hydraulic mechanism of shrub were studied under rainfall intensities of 45, 87 and 127mm/h with 20°slope gradient using simulated rainfall experiment. the results showed that average runoff rates ranged from 39.7 to 126.0 L/min for bare plots and 0.77 to 4.83 L/min for shrub plots, and the runoff rates from shrub plots were much less than from bare plots. Average sediment yields varied from 3636.7 to 9436.3 g/min for bare plots and from 28.0 to 421.6 g/min for shrub plots. The critical flow shear stress of 1.65 N/m2 on shrub slope and 0.861 N/m2 on bare slope were got under experiment condition. The sediment yield increased with the increase of flow shear stress. The experiment results are meaningful for quantifying runoff and sediment reduction and deepening soil erosion mechanical process also.

Abstract: The deposition rate of the delta decreased when seawards sediment decreased. The critical values of sediment concentration mean the concentration which kept balance of erosion and deposition. According to the topography data of Yangtze estuary between 1958 and 2007, the change process of the isobaths is established. Based on the datum line of east longitude 122°17′, the empirical relation between the erosion/deposition rate of delta and the sediment amount was built and the critical values were calculated. The trend of the change of sediment concentration was also forecasted. The isobaths of -10 m, -15 m and -20 m have been eroded from 2000 to 2007 because of the decrease of the sediment discharge into the sea. The critical values of the isobaths of -10m, -15m, -20m is 24.88, 24.23, 20.40 million tons per year and the numbers are decreasing in the deep sea.

Abstract: The effect of spatial distribution of rainfall is considered to be main uncertain factor for hydrologic simulation. Based on calibration and validation of the SWAT model, using the 15 rainfall stations data ，analyzed the effect of spatial distribution of rainfall on runoff modeling in Xixi Watershed of Jinjiang basin. The results show that the difference of the rainfall spatial distribution is very obvious by calculating standard deviation. The effect of the difference of rainfall spatial distribution to simulation results is significant by comparing runoff simulation of different years in which the average of all rainfall stations precipitation was similar. The uncertain spatial distribution of rainfall must be considered in the hydrological simulation.

Abstract: Demarcation of fresh- and saline-water interface is important in water supply engineering in coastal regions. A resistivity imager system was employed to investigate the saline water intrusion to freshwater table at selected coastal locations in Sri Lanka. This is the first such attempt in Sri Lanka using the above technique. Systematic geo-resistivity investigations were carried out at randomly selected sites at Mundel and Rekawa coastal areas. Measured and calculated values generally show good agreement, especially in Mundel area, where the current penetration is good. The results indicate a possibility of using resistivity imager system to demarcate the saline and fresh water interfaces and intermixing zones, especially in the wet zone.

Abstract: The wave breaking forces can exacerbate sediment transport, and lead to erosion of the seabed, coastal deformation and destruction of coastal structures. The experiment is carried out in a wave flume with a 1:30 sloping sandy seabed. A wide range of measurements from the regular wave runs are reported, including time series of wave heights, changes of bed profile. The video records are analysed to measure the time development of the seabed form and the characteristics of the orbital motion of the sand in the wave breaking region. The location and wave height at wave breaking point is measured by experiment. Formation and evolution of sand ripple and sand bar are studied under the breaking waves. It is found that effect of bed surface on wave breaking zone is more significant than wave non-breaking.