土木学会論文集B1(水工学)
Online ISSN : 2185-467X
68 巻 , 4 号
選択された号の論文の303件中1~50を表示しています
水工学論文集第56巻
  • Yeonjoong KIM, Hajime NAKAGAWA, Kenji KAWAIKE, Hao ZHANG
    2012 年 68 巻 4 号 p. I_1-I_6
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Debris-flow breakers have advantage not only to reduce the energy but also to create suitable narrow area, cost-efficient, simply designed, easily repaired and maintained. It is known that two phenomena occur when a debris flow crosses the debris-flow breaker. First, infiltration happens as the process of deposition in the debris flow due to water drains through the permeable deck. Second, the pore water pressure changes on the debris-flow breaker. In this paper, fundamental experiments and numerical simulation are conducted to investigate debris-flow breakers. In addition, a methodology is proposed to assess the suitability of a variable deck shape and change of pressure on the deck according to separation of water. Numerical model to calculate travel length and deposit thickness of different sediments depends on opening size and blocking size. As a result, the optimum opening sizes for sediment A, B and C are 0.3cm, 0.3cm and 0.4cm for blocking size 1cm. Furthermore, the simulated results of the travel length and deposit thickness on the deck are also compared with experimental results.
  • MAHDI RAZAZ, KIYOSI KAWANISI
    2012 年 68 巻 4 号 p. I_7-I_12
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Determination of the size and settling velocity of particles in an estuary is important to prediction of many environmental issues. An underwater microscope has been used to measure near bed floc size in four cross sections along the mid reaches of the Ota Diversion Channel. Using an acoustic Doppler velocimeter (ADV) and a turbidity meter provided an effective non intrusive approach to measure the settling velocity of suspended particles and turbulence characteristics. The physical processes that control floc size differ in each measurement site. Turbulent motion and suspended sediment concentration SSC, however, exert the most effect on flocculation and floc break up processes. Turbulent kinetic energy TKE production and SSC were positively correlated in the all measured points.
  • Syed Iftikhar AHMAD, 知花 武佳
    2012 年 68 巻 4 号 p. I_13-I_18
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    In gravel bed rivers, shape of sediments has significant influence on the sediment transport. Sediment transport analysis was refined by extending the movement characteristics of different shapes of sediments. At first, the mean velocity of "i" sized particle: "Vpi" was analyzed for each Zingg's shape category "m" through the laboratory experiments. In the experiments, 4 to 32 mm sediments sampled in the Oppegawa River were colored and used at different flow conditions and bed slope. Moreover, more than 300 particles were analyzed through the Fourier analysis to get the shape roughness to compute the effective tractive force. Then, sediment transport data of the Big Wood River in USA was used to evaluate the modified approach. In the revised stochastic model with shape effect (SMSE), the significant harmonic order that can represent the significant difference of particle shape was calibrated. The results of analysis were found in reasonably good agreement with the measured quantities.
  • Puji HARSANTO, Nguyen Manh Minh TOAN, Hiroshi TAKEBAYASHI, Masaharu FU ...
    2012 年 68 巻 4 号 p. I_19-I_24
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    The purpose of this paper is to study the effect of bedload transport on the erosion rate characteristics of cohesive sediment. The results of flume experiment and the dynamic shear stress on the bed are discussed. The sediment feeding of the bedload transport rate is varied from 0 to 150% of the equilibrium sediment transport rate. Two kinds of sand, which have fine and coarse sediment size, are used to produce the bedload transport. The results show that the erosion rate of cohesive sediment will increase when the volume of the sediment feeding increase under the small rate conditions. However, after achieving a certain volume of the sediment feeding, the erosion rate of cohesive sediment will decrease. This tendency indicates that the relation between the volume of bedload transport and erosion rate of cohesive sediment is non-linear function.
  • Yeonsu KIM, Yasuto TACHIKAWA, Sunmin KIM, Michiharu SHIIBA, Kazuaki YO ...
    2012 年 68 巻 4 号 p. I_25-I_30
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    A short-term flood prediction algorithm with a 2D dynamic wave model and a particle filter is proposed to consider the uncertainties of hydrologic input data and channel roughness. The particle filter makes it possible to utilize a non-linear and non-Gaussian model for estimating time variant channel roughness and inlet flow uncertainty by considering sequentially updated water stages. The proposed method was applied to the Katsura River located in Kyoto, Japan, and it was verified first through a synthetic experiment. The experiment result shows that the algorithm successfully traces the hidden true values, which are the correct inlet discharges and Manning roughness coefficient, on a real-time basis. The prediction results were also compared with observed water stages, and they showed good agreements with the observed water stage.
  • Seungsoo LEE, Hajime NAKAGAWA, Kenji KAWAIKE, Hao ZHANG
    2012 年 68 巻 4 号 p. I_31-I_36
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Recently, there have been a lot of numerical models for prediction of urban inundation damage due to the climate change and heavy rainfall by using the combined drainage system. However, it is very difficult to estimate how much of discharge on the ground surface is drained hrough storm drains. Also,discharge coefficient of each formula is different depending on research groups. Hence in this study,laboratory scale experiments which can be fundamental experiments to measure the inlet discharge coefficients of weir and orifice into the storm drain are carried out and they could be divided into submerged and non-submerged cases. From the comparison between experimental and simulation data,each coefficients show good agreement in all the cases of steady state.
  • Mohammad MESHKATI SHAHMIRZADI, Tetsuya SUMI, Sameh KANTOUSH, Toshiyuki ...
    2012 年 68 巻 4 号 p. I_37-I_42
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Air injection could be a possible solution to prevent blockage along the transport pipeline which commonly occurs during the operation of dredger system. The present paper seeks to investigate the influence of air injection on the performance of dredger system by injecting variant air concentrations. To achieve this purpose, the experiments were conducted under various operating condition such as: initial pump pressure (0.196, 0.294, 0.490 and 0.706 MPa), sediment grain sizes (2, 5, 10 mm, Mixed and Large), transport sediment concentrations (0.8% to 8.5%) and air concentrations (0, 25, 40, 60 and 100 nl/min). The experiments showed that the risk of pipeline blockage is higher in case of fine sediment compared with coarser sizes. Furthermore, the air injection into the system is more effective for lower initial pump pressure (0.196 and 0.294 MPa). Also, the lowest pressure gradient along the transport pipeline was observed for the specific air concentration ranges from 40 to 60 nl/min and specific sediment concentration ranges from 3.5% to 6%.
  • Bambang WINARTA, Hitoshi TANAKA
    2012 年 68 巻 4 号 p. I_43-I_48
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    This paper reports on continues an experimental investigation of characterizing transition to turbulence for solitary wave boundary layer in a smooth bed condition. A series of experiments has been carried out using a closed conduit generation system over the Reynolds number (Re) range 5.64 x 105 - 7.34 x 105. Additionally, the instantaneous velocities were measured by a Laser Doppler Veloci-meter (LDV) over 50 wave numbers and at 17 to 22 points in the vertical direction. The turbulence intermittency has been analyzed based on experimental data. Moreover, momentum method has been employed for calculating bottom shear stress for all cases. And then, the turbulence intensity is plotted to give clearly description how turbulence generated in the various values of Re. The phase difference obtained from the present experiment has an excellent agreement with the result of previous studies. Inconsistency critical (Re) (Recr) can be found in solitary wave case in terms of phase difference, this observable fact is different with sinusoidal wave case which has consistency in Recr.
  • Hyung Suk KIM, Ichiro KIMURA, Yasuyuki SHIMIZU
    2012 年 68 巻 4 号 p. I_49-I_54
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Laboratory experiments and numerical simulations were conducted to investigate interactions of flow and sediment with vegetation. Four experimental and numerical cases were carried out with three patch densities and without a patch. Vegetation patch was located at middle of a channel. For un-vegetated condition, channel widening with bank erosion occurred, but for vegetated channel, bank erosion took place opposite the patch and sediment was deposited downstream of the patch in both experiments and numerical simulations. In experiments, local scour occurred around the patch and scour depth increased with patch density. However, 2D shallow flow model did not reproduce such phenomena. This was due to three dimensional effects such as reinforcement effects and horseshoe vortex caused by individual stems. Nevertheless, numerical results reasonably agreed with experimental results.
  • Feng CAI, Akihiro TOMINAGA
    2012 年 68 巻 4 号 p. I_55-I_60
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    A box groyne is composed of various types of single groyne to satisfy the different river ecological requirements. Fewer studies are available for the flow structure around box groyne with different single shaped groyne. The flow velocity near typical box groynes with a longitudinal block, which is composed by straight and L-shape groyne, are measured by PIV (Particle Image Velocimetry) under emerged flow in horizontal plane. The paper shows experimental results of flow patterns for this box groyne. Due to the longitudinal block of box groyne limits the generation and development of the large coherent structure in the groyne field, flow periodicity and the capacity of mass exchange with main stream are significantly different between these types of box groyne. The placement of block obviously influences the number and scale of circulating flow inside the box groyne field, because of the distribution difference of vortex structure in longitudinal profile of mixing layer.
  • Amir-Reza MANSOORI, Hajime NAKAGAWA, Kenji KAWAIKE, Hao ZHANG, Akbar S ...
    2012 年 68 巻 4 号 p. I_61-I_66
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    In the present study, three-dimensional flow structure around two simple series of groynes with different shapes of head was investigated using a numerical model known as SSIIM. The model solved the fully three-dimensional, RANS equation to simulate flow upstream, downstream of the groynes as well as their embayment in which a fully complex 3D flow is governing. Two case studies were considered: a simple series of straight groynes and a simple series of groynes with T-shape head. The reattachment length was computed and by illustrating the hydrodynamic of flow at different longitudinal, transverse and vertical sections, an attempt was made to give a 3D understanding of flow around a simple series of T-shape groynes and to highlight its differences with the similar series of groynes with I-type head which is the typical form of groynes in practical designs. Finally, in this study an in-depth discussion about the physics of flow was done in order to compare the performance of a series of T-shape groynes with that of straight ones based on the primary objectives of the design of the groynes.
  • Manoj LANGHI, Takashi HOSODA, Subhasish DEY
    2012 年 68 巻 4 号 p. I_67-I_72
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    To examine the characteristics of unsteady open channel flow, one-dimensional depth-averaged velocity deformation model is developed. The fundamental form of streamwise velocity in a power series of depth is initially assumed, and the formula for friction velocity is derived. The coefficients of the power series are later evaluated by using the unsteady equation of motion. The applicability of the model is tested using experimental data. The numerical model showed reasonably good agreement with the experimental data. A new approach to reproduce the velocity deformation in the vicinity of free surface using the comparison of velocity distribution of numerical model and uniform velocity distribution of Engelund model is also presented.
  • Fatima JAHRA, Yoshihisa KAWAHARA, Fumiaki HASEGAWA, Takuya YAMAMOTO
    2012 年 68 巻 4 号 p. I_73-I_78
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    The present study investigates the solute transport mechanism in a vegetated compound channel. In this paper three-dimensional numerical simulations involving solute transport models in a partially vegetated open channel flows are presented. Vegetation zones were prepared fully covering the floodplain and as a vegetation belt on one side of a compound channel to identify the mixing mechanism. For flow simulation a non-linear k-epsilon model coupled with a vegetation model is used. For solute transport an eddy diffusivity model and an algebraic scalar flux model by Daly-Harlow are implemented and the performance of each model is evaluated. The numerical results are favorably compared with the experimental observations in terms of solute concentration. It is found that Daly-Harlow model taking into account the anisotropy of turbulence shows better performance over an eddy diffusivity model in complex flow fields.
  • ADRIANO COUTINHO DE LIMA, NORIHIRO IZUMI
    2012 年 68 巻 4 号 p. I_79-I_84
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    The turbulent flow in a wide rectangular open-channel with lateral vegetation is studied by performing a weakly nonlinear stability analysis. The vegetation acts as a source of drag forces which provide resistance to the flow, such that there is an inflection point in the depth-averaged streamwise velocity. The generated instabilities may grow into discrete horizontal vortices centred at the edge of the vegetated region. The growth rate expansion method is applied with the multiple scale perturbation technique to the governing normalized Navier-Stokes equations. The small perturbation is added to a parameter related to the vegetation density.
  • Kim-Cuong NGUYEN, Motohiko UMEYAMA, Van-Uu DINH
    2012 年 68 巻 4 号 p. I_85-I_90
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    The article presents the investigation of morphological changes and simulation of circulation in the Hai Phong area, Vietnam using remote sensing and measured data for a period of 1965-2005. During this period, the shoreline and sea bottom relief have changed considerably. The circulation and the tendency of sediment transport were simulated by developing a modeling system. In the system, three-dimensional thermo-dynamic primitive equations were used to investigate current velocity, water level, and the sediment transport. A special computing procedure was applied to the river boundaries because the tidal range in the area is approximately 4 m. In addition to the model study, a record of field survey for the wave climate is presented in a period from 2005 to 2006. The result suggests that the wave energy is small throughout a year, and the wave-induced current is negligible in the Hai Phong estuary. This study was extended to study turbidity in the Do Son beach area.
  • Jie WANG, Hiroshi ISHIDAIRA
    2012 年 68 巻 4 号 p. I_91-I_96
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Impacts of human activities and climate variability on streamflow and sediment have long been an issue for concern. It is critical to quantify the contribution of climate change and human activities on the change of streamflow and sediment flow, which can provide a scientific basis for future land conservation and river ecological conservation. In this study, Pettitt mutation method was employed to detect trends and changes in annual streamflow. SWAT model simulation method was then applied to separate different effects from climate change and human activities. Based on sediment rating curve, one well fitted curve between sediment and runoff was introduced to simulate the suspend sediment. Results indicated that effects of human activities on streamflow accounted for more than 50% both in the Laichau and Tabu catchments. Human activities are the main factor to affect the changes of streamflow and sediment flow into the Hoa Binh Reservoir.
  • Tetsuya OGATA, Oliver C. SAAVEDRA VALERIANO, Chihiro YOSHIMURA, Winai ...
    2012 年 68 巻 4 号 p. I_97-I_102
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Predictions of variations in global and regional hydrological cycles and their response to changes in climate and the environment are key problems for future human life. Therefore, basin-scale hydrological forecasts, along with predictions regarding future climate change, are needed in areas with high flood potential. This study forecasts hydrological process scenarios in the upper Chao Phraya River basin using a distributed hydrological model (DHM) and precipitation scenarios from three general circulation models modified by the H08 model. First, discharge was simulated by the DHM using the observed rainfall from 2007 to 2009 and then, future discharge scenarios from2010 to 2040 were forecast.
  • Ichiko INAGAKI, Dian SISINGGIH, Sri WAHYUNI, Ratih Indri HAPSARI, Keng ...
    2012 年 68 巻 4 号 p. I_103-I_108
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    The purpose of this paper is to highlight the importance of people's response and their perceptions of urban flood to establish effective policies and strategies for disaster management. Tulungagung Regency, Indonesia, was focus of the study. The data were obtained from field investigation and interview survey. It is interesting to note that most of respondents recognized themselves to be in high risk of flood, however they prefer staying at home rather than evacuation during flood event. They voluntarily establish emergency countermeasures. The study revealed that overall, attitudes towards urban flooding in this study area was positive, although knowledge of their flood prevention and flood risk was poor. Therefore, the information obtained on the perceptions both of flood disaster and flood risks could be more effective tools in the hands of policy makers in determining the appropriate strategy for disaster prevention, particularly in sustainable urban flood management.
  • Romeo Jr. GILBUENA, 河村 明, Reynaldo MEDINA, 天口 英雄, 中川 直子
    2012 年 68 巻 4 号 p. I_109-I_114
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Identification of priority areas for flood disaster risk reduction (FDRR) management is critical and often tedious to both planners and decision-makers. Requests for additional resources, infrastructures and capability enhancement may require a quantifiable basis for budget allocation. In Metro Manila, Philippines, flooding is a perennial problem, thus requires a regular assessment of FDRR management. This study provides a simple approach to address this requirement using a multi-criteria gap analysis method. This is demonstrated using the results of the assessment made by the local government units (LGUs) in Metro Manila at the aftermath of an extreme flood event in 26 September 2009. Results show that gaps ranging from very small to medium-scale exist in the management system of the LGUs. Serious attention must be given to land use planning and flood mitigation measures. Flood hazard mapping should also be a priority in most local government units. Efforts must also be made to improve flood warning dissemination.
  • Cho Thanda NYUNT, Hiroki YAMAMOTO, Akio YAMAMOTO, Toshihoro NEMOTO, Ma ...
    2012 年 68 巻 4 号 p. I_115-I_120
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Climate change impact assessments for regional or local studies are mainly based on the general circulation models GCMs under the different emission scenarios. Downscaling of selected GCM after bias-correction can address the gap of resolutions with some merits and limitation for application at basin-scale hydrologic simulation. This paper describes how to select the appropriate GCMs and how to develop bias-correction and downscaling method for GCMs precipitation. Bias-corrected scheme removes the large bias of GCMs precipitation. This method of downscaling is also comparable to the basin scale mean intensity,annual precipitation and inter-annual monthly precipitation. All of corrected GCMs rainfall presented the increasing trend not only in extreme rainfall but also in seasonal climatology in the Kalu Ganga basin in near future.
  • Cindy SUPIT, 浩一郎 大串
    2012 年 68 巻 4 号 p. I_121-I_126
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    The SWAT model has been used to estimate the impact of dam constructions on annual and peak stream flow rates in Kase River, Japan. A new multipurpose dam, Kase River dam has been constructed just downstream of another old agricultural dam, Hokuzam dam. The watershed area is set up 197.735 km2 that accounts for 54% of the entire area of the Kase River Basin. The model was calibrated and validated for stream discharge data from 2008-2009 by using Nash-Sutcliffe to model performed evaluation. Simulated data from the model for the period 2008 - 2009 were used in order to investigate the response of stream flow to dam constructions in Kase River basin. Using sensitivity analysis dominant parameters affecting water flow, the four most sensitive parameters of flow were selected and adjusted. The best fit was achieved with R2 = 0.86 and NSI= 0.84 at Furuyu outlet just downstream after the new dam. The result from the scenarios analysis shows that an annual runoff decreases consistently from the disappearance of dam by the value of 1.40-11.59 m3/s to 0.83-8.89 m3/s and 1.18-11.35 m3/s respectively during appearance of Hokuzam dam only and appearance of Hokuzam and Kase dam in the watershed. Since both dams' impoundments, peak flow rates at Furuyu have decreased by 23.45% from current condition. The results of this study enhance the understanding of stream flow consequences of dam constructions associated with impoundment, while these estimates could aid a decision maker to optimize water supply and demand and further water quality management in this basin.
  • Pingping LUO, Kaoru TAKARA, APIP APIP, Bin HE, Daniel NOVER, Yosuke YA ...
    2012 年 68 巻 4 号 p. I_127-I_132
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Human activities have led to changes in land use, environmental conditions and climate. Land use change has significant impacts on hydrology and other water related problems. In this study, the assessment of land use change is used to explore the effects of human activities on hydrologic response under the paleo-environment and the present conditions by using a grid-based distributed hydrologic model. According to the results of land use change analysis, forest area decreased, but the areas of building types A and B increased from 1843 to 1902. Due to increasing building area and decreasing forest area and rice fields, the peak discharge is increasing and arriving earlier. Projected rainfall-runoff hydrographs suggest that rainfall may peak early (in the third hour) leading to earlier peak discharge or rainfall could peak later (in the eighth hour), leading to larger and later peak discharge. This study offers guidance for future urban planning and flood risk management.
  • Patricia Ann JARANILLA-SANCHEZ, Lei WANG, Katsunori TAMAGAWA, Izumi HA ...
    2012 年 68 巻 4 号 p. I_133-I_138
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    The Yoshino River provides the main water source for agricultural, industrial and domestic activities in Shikoku Island. This study aims to identify the impacts of climate change in the basin by identifying its temporal effects in the future using climate scenarios and the Water and Energy Budget-based Distributed Hydrological Model (WEB-DHM). Using spatially distributed gauge rainfall, the model was calibrated at Sameura dam for 1984. Bias correction was done for precipitation using GCM climate scenarios (from SRESA1b for the years 1982-2000 and 2046-2064). Focusing on possible water deficits, the standard anomaly index (SA) identified possible droughts in the observed (1982-2000), past and future GCM ensemble outputs. Results show that historical moisture deficits can be simulated. Past and future simulations on basin average rainfall and discharge show future maximum values to be much higher than past indicating increases in wet conditions that may have possible effects on water availability in the future.
  • Ratih Indri HAPSARI, Satoru OISHI, Kengo SUNADA
    2012 年 68 巻 4 号 p. I_139-I_144
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Ensemble short-term rainfall-runoff prediction in urban river basin is presented. An ensemble rainfall prediction is built by perturbing initial condition of the extrapolation model. The five ensemble members are subsequently considered as uncertain input of the distributed hydrological model. GLUE method is used to calibrate the rainfall-runoff model and quantify the uncertainty. Four sensitive parameters of rainfall-runoff model are considered. The set of behavioral simulations develop an ensemble of flood prediction. This approach allows a cascading of uncertainty from rainfall prediction to the flood prediction. The methodology is demonstrated throughout case studies in Kofu urban river basin, Japan. Having demonstrated the plausible results, this approach could serve as a reliable and effective method for estimating the uncertainty range of short-term prediction of runoff dynamics for operational flood disaster prevention in urban area.
  • Xiao LI, Minjiao LU
    2012 年 68 巻 4 号 p. I_145-I_150
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    The objective of this study is to find an efficient way to optimize parameters in the Xinanjiang model automatically. According to the time scale dependent sensitivities, a multi-step optimization scheme is developed with the help of the SCEM-UA algorithm. Some case studies were designed to test the efficiency of the scheme. The tests show this scheme under ideal condition could converge to the true values of parameters to be optimized. For the actual practice, the multi-step optimization scheme is capable of searching the optimum parameter set for the Xinanjiang model, and the simulation results are acceptable.
  • Temur KHUJANAZAROV, Yutaka ICHIKAWA, Jun MAGOME, Satoru OISHI
    2012 年 68 巻 4 号 p. I_151-I_156
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    In this paper, a web-based platform for arranging, storing, and geospatial visualization of hydrological data with a goal of research collaboration is presented. The platform, which helps researchers arrange their own data and visualize data from observations in their area of interest, is used as a working environment for planning and conducting research activities. Although there are many good structured data archiving projects based on open/closed distributed in situ data by institutional observation stations, they do not cover all the needs of usable data. The researchers generally collect large amounts of data in the studied regions and create their own collection of information within their project or research theme. However there are very few ways to organize all this information and even less to share it. In this paper, we propose a platform to cover this gap and give options for sharing data used in research activities among researchers.
  • Shakil AHMAD, Kazuaki NISHII, Toru TAMURA, Tetsu OHTA, Eiji IKOMA, Mas ...
    2012 年 68 巻 4 号 p. I_157-I_162
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    By data analysis, an attempt has been made to identify the associated processes which support the Pakistan Summer Monsoon (PSM) mature phase in comparison with pre-monsoon phase. We found that during pre-monsoon phase, the subsidence associated with upper level strong convergence suppresses the convective activities around Pakistan. However, during the PSM mature phase, (1) the mid-upper tropospheric warming which causes the reversal of meridional temperature gradient (MTG), further gets strengthened and expands, and (2) the subsidence significantly weakens associated with the weakening of the upper level convergence and vortex stretching around Pakistan. Simultaneously, the low level trough around Pakistan becomes stronger enough for the maturity of PSM, together with the deflected southeasterly and southwesterly moisture flux from the Bay of Bengal (BoB) and Arabian Sea (AS) increases to intrude over Pakistan. The current finding will be useful for understanding the processes associated with the anomalous tropospheric conditions during extreme PSM events.
  • Keisuke NAKAYAMA, Carlos BEITIA, Erick VALLESTER, Reinhardt PINZON, Jo ...
    2012 年 68 巻 4 号 p. I_163-I_168
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    The paper describes trends in climate change indices in the Republic of Panama by using long-term meteorological data sets from the Panama Canal and MRI-AGCM. Simple precipitation intensity index from eleven climate change indices shows the same trend, increasing at six meteorological stations around the Panama Canal. Forward projection (from 2080 to 2099) was carried out by using MRI-AGCM3.1S and 3.2S, which demonstrates an increase in simple precipitation intensity index in the entire area of Panama. The increase in simple precipitation intensity index may suggest that stronger precipitation will occur more frequently in the future in Panama.
  • Martin GOMEZ GARCIA A., Toshio KOIKE
    2012 年 68 巻 4 号 p. I_169-I_174
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    The available satellite-derived estimates of rainfall, product of various algorithms, reveal unsystematic errors when compared to in-situ measured data. This acknowledgement, its low resolution, and the impossibility of spatially distribute the bias correction make these estimates useless for accurate basin-scale hydrological modeling. An initial downscaling scheme is presented in this paper, which main basis is the linkage of characteristics of in-situ measurements with the inter-scale relationships of statistical parameters that describe the spatial distribution of local fluctuations of rainfall intensity. The results show the next path along which later research should be conducted in order to take advantage of these datasets.
  • Dwi Prabowo Yuga SUSENO, Tomohito J. YAMADA
    2012 年 68 巻 4 号 p. I_175-I_180
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    This research deals with the use of geostationary satellite based rainfall estimation for characterizing storm severity. The objectives of this research are to estimate storm rainfall intensity by using Multi-functional Transport Satellite (MTSAT) blended with C-band rainfall radar data and to show the severity of the identified storm rainfall intensity by representing its return period map. A regional frequency analysis (RFA) method developed by Hosking and Wallis (1997) is used to define the frequency distribution of long-term hourly maximum rainfall over Hokkaido Island. RFA indicates that Generalized Normal/Log Normal three parameters (GNO/LN3) is suitable to describe the frequency distribution of long-term hourly maximum rainfall over Hokkaido Island. Characterization of severity of 24 August 2010 storm event has been performed over Ishikari river basin, Hokkaido according to estimated rainfall using MTSAT data. Even though the return period map shows underestimation in comparison with the current situation of flood event in Ishikari river basin, this information is useful for flood control and mitigation.
  • Do Hoai NAM, Keiko UDO, Akira MANO
    2012 年 68 巻 4 号 p. I_181-I_186
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Many reservoirs are operational with single objective like hydropower reservoirs. Its objective function is to maximize water availability for power generation. While objective functions related to vulnerability, for example flood control, are not prioritized or at very limited capability. In many cases, improper reservoir operation may produce extra flood threats downstream because of dam safety issues. This paper presents inflow forecast for real-time flood control based on combination of downscaled precipitation from the global NWP model using local scaling method and a distributed rainfall runoff model. Altitudinal dependence of rainfall is utilized to determine the basin average scaling factor. Results show that inflow prediction based on precipitation forecast using the local scaling factor exhibits significant improvement. It has demonstrated an added value in reservoir inflow prediction for flood control practices, especially in unobserved, remote catchments, that aims to reduce downstream flood.
  • Azinoor Azida ABU BAKAR, Minjiao LU
    2012 年 68 巻 4 号 p. I_187-I_192
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    A new equation to estimate annual canopy evaporation with depth of storage capacity effects was evaluated in this study. The inputs to derive the equation were: the precipitation data with a different temporal resolution ranging from one hour to twenty four hours; and the depth of storage capacity varies from 0.1 to 10.0 mm. The estimated annual canopy evaporation from the equation was compared with interception loss measured from others locations in Japan and around the globe. The results shows that annual canopy evaporation can be estimated by taking account the effects of depth of storage capacity into the equation. The equation can be applied to several locations across Japan and around the world.
  • Kunio WATANABE, Sagar KATTEL, Shinji TAKEUCHI, Wael E. MAHMOD
    2012 年 68 巻 4 号 p. I_193-I_198
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Spatial distribution of pore pressure change is the good information to know the effect of construction works on groundwater flow. It has been pointed that the pore pressure change at an arbitrary point can be well evaluated from the data measured at other points by using linear and non linear models. Furthermore, it has been clarified that soft computing techniques such as Artificial Neural Network (ANN) and Genetic Algorithm (GA) are the powerful tool to evaluate the parameters included in these models. In this paper, the change of pore pressure in the rock mass around the site of Mizunami underground research Laboratory (MIU) was analyzed by the linear model. GA was used for estimating parameters in the model. It was found that this technique can be used for the evaluation of spatial distribution of pore pressure change.
  • YUREANA WIJAYANTI, TAKASHI NAKAMURA, KEI NISHIDA, EIJI HARAMOTO, YASUS ...
    2012 年 68 巻 4 号 p. I_199-I_204
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Major ions and stable isotopic measurements were utilized in order to investigate the groundwater recharge and nitrate pollutant transformation of shallow alluvial groundwater aquifer. The spatial distribution and multivariate analysis of ions, combined with stable isotope analysis were performed. The result showed that precipitation contributed to the whole year groundwater recharge. Pollutants were transported from the land surface through an infiltration of precipitation. Sources of nitrate are from ammonium fertilizer, manure and septic waste. According to the ion and isotope characteristics, both denitrification and mixing process could take place. The statistical correlation and cluster analysis coupled by spatial analysis approach, based on isotope and ion data could be utilized for a quick assessment of groundwater recharge and nitrate pollution dynamics in an alluvial fan.
  • Felix MUTUA, Lei WANG, Akio YAMAMOTO, Toshihoro NEMOTO, Masaru KITSURE ...
    2012 年 68 巻 4 号 p. I_205-I_210
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Using a physically-based distributed hydrological model (WEB-DHM), this study investigated the likely impacts of climate change on Nyando river basin in Kenya. Analysis of the East African regional climate indicates a weakening in the westerlies and a projected increase in precipitation. A simple statistical method was applied to downscale General Circulation Model (GCM) precipitation to the basin scale. At this scale the GCMs predict a relatively drier basin with two of the selected models projecting a 9% decrease in annual rainfall. The bias-corrected and downscaled GCM precipitation data was then used to drive the WEB-DHM to project future changes in streamflow. There′s a projected decrease in annual discharge with a likely increase of floods in the months of July and August.
  • Sujan KOIRALA, Hannah YAMADA, Pat YEH, Taikan OKI, Yukiko HIRABAYASHI, ...
    2012 年 68 巻 4 号 p. I_211-I_216
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    With the withdrawal for anthropogenic uses in addition to climatic changes, the sustainability of groundwater resources is under question. Global-scale land surface models commonly used for water resources assessment, however, simplify or completely neglect the groundwater processes making them inapplicable for groundwater resources assessment. In this study, a groundwater representation is implemented into a global-scale LSM, the MATSIRO, enabling it to simulate the major groundwater variables namely, groundwater recharge, water table depth, and low flow. The estimated global groundwater recharge (29900 km3/yr) corresponds well with GSWP-2 mean baseflow (30200 km3/yr). Global distribution of water table depth is found to be mainly controlled by climate and soil properties. The comparison of simulated and observation-based daily flow duration curves in selected global river basins reveals that the simulation of low flow improves significantly with the groundwater representation.
  • Hannah G. YAMADA, Sayaka YOSHIKAWA, Sujan KOIRALA, Shinjiro KANAE
    2012 年 68 巻 4 号 p. I_217-I_222
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    In order to assess future global water resources, it is necessary to comprehend the past and current water withdrawal trends and distribution. This study presents an estimate of global water withdrawal from 1950 to 2000 in 0.5 resolution by fully utilizing past and current withdrawal statistics as well as Historical equipped Irrigation Map (HIM) and a historical population data. By comparing our results to one from a physically simulated model, we could have an idea of whether a country has an agricultural water withdrawal larger than its crop requirement or not. Validation of a country scale distribution showed good agreement for the agricultural and domestic sector.
  • Pedro Luiz Borges CHAFFE, Yosuke YAMASHIKI, Kaoru TAKARA, Maho IWAKI
    2012 年 68 巻 4 号 p. I_223-I_228
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Areas with seasonal snow cover are very susceptible to climate change, the correct estimation of snow distribution is essential for water resources management in such places. The objective of this work was to estimate snow accumulation and melt in the Ane River basin, which is located in the North part of Lake Biwa and has seasonal snow cover. We show how the combination of Satellite products, simple point SWE measurements, point and distributed snowmelt models can be useful for estimating the spatial distribution of SWE. The temperature index model calibrated with the point measurement was used for estimating spatially distributed snow cover and compared with MODIS snow product. This method showed good agreement with observed snow cover, but there still room for improvement.
  • Maheswor SHRESTHA, Lei WANG, Yukiko HIRABAYASHI, Toshio KOIKE
    2012 年 68 巻 4 号 p. I_229-I_234
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    A newly developed physically based distributed biosphere hydrological model with three layered energy balance snow melt module (WEB-DHM-S) has been implemented at point scale to evaluate the forest snow processes at Fraser Experiment Forest site (USA) for two snow seasons (2003-2005). Results illustrate that the model is capable of representing the sub-canopy snow depth and snow water equivalent well with average correlation coefficient of 0.9. Energy fluxes are analyzed in detail for above canopy and below canopy snow processes. It can be concluded that the radiation energy is dominant in above canopy where sensible heat flux is dominant in addition to the radiation energy in sub-canopy snow processes. Furthermore, the sensitivity runs against the interception capacity shows that the interception capacity plays a major role in canopy snow sublimation.
  • Sixto A. DURAN-BALLEN, Maheswor SHRESTHA, Lei WANG, Kohei YOSHIMURA, T ...
    2012 年 68 巻 4 号 p. I_235-I_240
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    A physically based distributed hydrological model (WEB-DHM-S) was used for modeling 3 years of time series, from 2006 to 2008, for the Puna Tsang River Basin and to compare the results with the observed measurements. Furthermore, with additional inputs of initial snow cover area, snow depth, glacier area, and temperature, WEB-DHM-S can simulate the snow and glacier melt flow contribution to the stream discharge accurately. By adjusting the air temperature from the JRA-25 datasets, the model can simulate the seasonal snow melt and accumulation. This study may benefit the community in Bhutan by providing reliable predictions of flow regimes in the rivers due to climate change. It may provide a physically based modeling of the snow and glacier melts; and further assessment of the impact of GLOFs.
  • Luminda GUNAWARDHANA, So KAZAMA
    2012 年 68 巻 4 号 p. I_241-I_246
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    This study estimated the climate change impacts on future water resources availability in the Tagliamento River in Italy. The results from ten GCM scenarios were linked with the mesoscale climate using the stochastic weather generator technique. The tank model, which produced 84‰ agreement for observed and simulated water discharges in present climate, was used to simulate river discharges in three time periods in future. According to our results, 2.3° and 2.7°C warming in annual average minimum and maximum temperatures can be expected in 2080–2099 compared to observations in 1991–2010 period. Markedly, the rate of frost day decrease in lower elevation areas is 262‰ higher than that in the higher elevation areas. The change in precipitation pattern is minor in near future but likely to be significant in further climates. Consequently, the occurrence of low flow events will be more than two folds and decrease in monthly river discharge will be as high as 33‰ in 2080–2099 compared to 1991–2010 period.
  • Tong LIU, 木内 豪
    2012 年 68 巻 4 号 p. I_247-I_252
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    On outer-tropical glaciers, mostly in Peru and Bolivia, ablation and accumulation occur all year round whereas maximum in wet seasons. This study investigated glacier mass balance and catchment scale water balance of Glacier Tuni and Huayna Potosi, which locate at the west side of Bolivian Andes. Remote sensing and hydrological methods have been applied to conduct glacier mass balances monthly and annually in recent years. With remote sensing method, glacier volume change has been derived based on glacier area change obtained utilizing cloud free Landsat Thematic Mapper (TM) scenes. Results of commonly negative glacier mass balance have revealed that glaciers in this region are retreating. Despite of interests on glaciological aspects, water balances of glacierized catchments have been carried out. Except for in a few months glaciers got positive mass balance, glaciers continuously contributed to discharge.
  • 盧 敏, 田中 仁, Mohammad Bagus ADITYAWAN, 真野 明, 有働 恵子
    2012 年 68 巻 4 号 p. I_253-I_258
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    On March 11, 2011, the Great East Japan Earthquake generated huge tsunami waves, and severe devastating damages have been induced on the East Japan coastal area. Several video images taken during this tsunami event in Sendai Plane were collected and analyzed to estimate celerity of tsunami propagated into river and land area. It was found that the tsunami celerity in river attained to 25km/h to 30km/h with slow reduction in the upstream direction, whereas in the land area, celerity shows distinct reduction with distance from the shoreline due to predominant resistance on the ground. Furthermore, tsunami-induced velocity is estimated from measured water level variation along the Sunaoshi River. Temporal variation of velocity is successfully estimated along the river by applying the conservation equation.
  • Sabaruddin RAHMAN, Akira MANO, Keiko UDO
    2012 年 68 巻 4 号 p. I_259-I_264
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Boussinesq type equation has been coupled with sediment transport model to simulate sediment transport in a wave flume. A new eddy viscosity model has been applied to calculate wave decay as well as suspended sediment concentration. A bed load transport formula based on an energetic transport of Bagnold-type model combined with suspended load model was validated under the condition of a spilling wave. The applicability of both eB and cf has been investigated. The result indicated that two sets of parameters cf = 0.017 with eB = 0.21 and cf = 0.003 with eB = 1.03 calculated a similar bed level change. Comparison of calculated and measured bed level change is fairly good in offshore and near breaking point. However, the model cannot predict accretion in swash zone.
  • Mohammad SOLTANIASL, Kiyosi KAWANISI, Mahdi RAZAZ
    2012 年 68 巻 4 号 p. I_265-I_270
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    In the present paper, the cross-correlation, multiple regression, salinity and velocity decomposition techniques were employed to analyze the short and long-term variations of salinity and flow rate in the Ota estuary. We considered the effect of the freshwater discharge, the tidal range, the activities of wind and the mean sea level on the salinity variations. Although the freshwater discharge plays the most important role in the variations of salinity, the results show high correlation between the along-channel component of the wind and the estuarine salinity changes. The direction of the net salt transport was landward during spring tides and low flow conditions. Though, the direction of net salt flux was seaward during most part of the observation period.
  • Duc Hoang NGUYEN, Motohiko UMEYAMA, Tetsuya SHINTANI, Chikashi NAKAZA
    2012 年 68 巻 4 号 p. I_271-I_276
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    We investigate changes in the longitudinal salinity distribution in the Red River estuary (RRE), where the channel shape and size greatly vary as a function of tidal amplitudes. A theoretical salt intrusion model was applied to analyze the salinity along the channel, considering the topographic characteristics. The model was originally developed based on the tidally averaged cross-section. In this study, assuming topographic parameters that exponentially vary under different tidal conditions, we could estimate the spatial and temporal distribution of the salinity using a modified model. The extension of the salt intrusion model agrees satisfactorily with field data that measured in the RRE during the dry seasons in 2006 and 2008. This finding indicates the applicability of the modified model for the further investigation in estuaries having more complex topography.
  • Sha LOU, 多田 彰秀, 田井 明, 矢野 真一郎, Shuguang LIU
    2012 年 68 巻 4 号 p. I_277-I_282
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Because of the serious mercury pollution in 1950s, many measures and researches for pollution control have been implemented in not only Minamata Bay but also the Yatsushiro Sea. In this paper, the effect of river's outflow and wind stress on flow field will be presented by numerical simulation in order to reveal the characteristics of flow currents in the Yatsushiro Sea. It is pointed out that among three rivers, the Komenotsu River has the most effect on flow field in Minamata Bay. Wind stress could enhance the fluidity in the southern part of the Yatsushiro Sea. In particular, the northeast-southwest wind has more influence on the Yatsushiro Sea than the north-south wind. Under all the four cases of wind stress, strong currents obviously appear along the east coastline in surface's residual flow fields and the returning currents are found in bottom layer. It could change the characteristics of flow currents in Minamata Bay and be important for the transportation of mass in water areas.
  • 辛 卓航, 木内 豪
    2012 年 68 巻 4 号 p. I_283-I_288
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    To reveal the anthropogenic influences on thermal environment in urban rivers, stream temperatures from 1990 to 2010 of the Tama River were investigated. Both the long-term and longitudinal changes of stream temperature, as well as flow rate, effluent temperature and volume, and water and energy budget were revealed. Stream temperature in winter season increased significantly at points where the temperature and discharge volume of effluents from wastewater treatment plants increased over the past 20 years. The different longitudinal variations in upstream temperature between winter and summer seasons were found primarily due to the flow rate decrease. Water and energy budget analysis suggested that the anthropogenic heat inputs from the wastewater were the dominant warming factor both in winter and summer seasons in downstream segments, while other factors such as groundwater recharges, and air-water and water-sediment interactions were contributing to suppress the stream water warming.
  • Duong HAI THUAN, Makoto UMEDA, Masahiko MATSUKAWA, Hitoshi TANAKA
    2012 年 68 巻 4 号 p. I_289-I_294
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Artificial neural network (ANN) is applied to a predictive model for the intermittent occurrence of taste-and-odor problem in the source of drinking water in Kamafusa Reservoir, Japan. To predict the temporal variation of 2-methylisoborneol (MIB) concentration, which triggers taste-and-odor problem, ten-year data of water quality from continuous water quality monitor as well as using the microscopic analysis data of planktonic cyanobacteria. The model examined in this paper is capable of reproducing the trend of evolution of MIB concentration and hence the intermittent occurrence of taste-and-odor events observed in Kamafusa Reservoir. Thus the model can be used as a decision-making tool for reservoir management office in measuring and treating the quality of water.
  • Atas PRACOYO, Makoto UMEDA, Hitoshi TANAKA, Mikio SASAKI, Masayasu NAG ...
    2012 年 68 巻 4 号 p. I_295-I_300
    発行日: 2012年
    公開日: 2013/03/26
    ジャーナル フリー
    Some areas in Lake Jusan disparate extremely in population of Corbicula japonica (Yamato shijimi), and this disparity remain constant every year, indicating variation of mortality rate. Most of the low population areas are located in the deeper area where silt-clay concentration is high. Population growth simulation by using dynamic energy budget (DEB) model is used to identify the difference of mortality rate. The results show that the rate varies from 0.001 to 0.01 and this variation tends proportional to the population density. Effect of silt-clay content was not identified for the concentration lower than 26%. Although water depth is shallower than a maximum suitable depth, but in bottom layer in the deeper area, DO always lower than 3 mg.l-1 in summer. This low DO represents low pH, indicating that dissolution mortality occurs every year in Lake Jusan
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