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Frank Engelund's theory of meander flow, published in 1974, marked a major advance, fromuniform bend flow to flow in truly meandering channels. The paper also contains several errors andomissions, some of which are by no means trivial. Both the achievements and the shortcomings of thework have acted to stimulate subsequent research, which is analyzed in this light. It is concludedthat a paper of sufficient elegance, that touches at the heart of the problem at hand, may includemany errors and still represent an achievement capable of stimulating the next generation of creativeresearch. The resolution of the errors flows in part from the structural elegance of the theory.

筆者らが開発してきた, 山腹斜面流出系における一般的な流量流積関係式を集中化する手法を基礎として, 圃場容水量を考慮した流量流積関係式を集中化する方法について述べる。まずはじめに, 圃場容水量を考慮した流量流積関係式と, 基礎となる集中化手法の概要について説明し, つぎに, 圃場容水量を考慮した流量流積関係式に対する具体的な集中化手法を展開する。本流量流積関係式には, 関係する状態量として, 単位幅流量q, 水量hのほかに, 自由水分水量hfが媒介変数の形で含まれており, 基礎とする集中化手法をそのまま適用することができない。本論文では, 集中化の過程で行なうhによる積分操作をhfでの積分操作に置き換えることで, 本流量流積関係式の集中化を可能としている。最後に, 本流量流積関係式から導出された集中化モデルを大戸川流域と桂川流域に適用し, その結果を分布型モデルによる計算結果および観測結果と比較して, 本集中化手法の有効性と問題点を検証する。, This paper describes a method to lump a kinematic wave equation which considers field capacity of hill slope soil layer. The method is based on a method to lump a general kinematic wave equation, which has been developed by the authors. The kinematic wave equation considering field capacity and the method to lump a general kinematic wave equation are firstly shown, followed by the explanation on the method to lump the kinematic wave equation considering field capacity. This kinematic wave equation contains free water content hf in addition to discharge per unit width q and total water content h as relating state variables in the form of the parameter. Thus the lumping method which has been developed by the authors cannot be applied to this equation as it is. In this paper we develop a way to apply the lumping method to this equation by changing a variable of integration from h to hf in the lumping process. The lumped model derived from the kinematic wave equation considering field capacity is applied to simulate runoff processes of Daido River basin and Katsura River basin. Then effectiveness and problems of the lumping method are verified by comparing the results with the calculation results ofa distributed runoff model and the observation results.

海岸工学講演会で発表された論文の中から, 水理実験に関するものを抽出し, 波浪に係わる水理実験の変遷を調べることによって, 水理実験の今後の方向を検討した。その結果, 実験論文数の割合は, 今後減少していく方向にある。その中でも, 理論あるいは数値シミュレーション法の妥当性を調べる検証実験は, 電子計算機の処理速度の飛躍的な発達とともに最も多くなっており, 今後も増加する傾向にある。実験施設を整備していくにあたっては, 一様水路では不規則波造波装置が不可欠であり, 多方向不規則波造波機能を有した平面水槽の整備も併せて進めることが望ましい。, Historical change of hydraulic experiments was investigated statistically though the papers published in the proceedings of Japanese Conference on Coastal Engineering. The numeral rate of the papers on the hydraulic experiments has been dropping lately to about 30%. The confirmation experiments of the validity of theoretical analysis and numerical simulations has become major at present, comparing with other factors for hydraulic model tests. Since uni- and multi-directional random wave generators were developed, model tests in random wave have become predominant. The random wave generators in experimental flumes and basins have become inevitable facilities for hydraulic model tests.

This paper addresses the need for addition of a recreational use to multi-purpose reservoir development. The paper then proposes a systematic methodology of project evaluation where allocation of costs are combined with the assessment of benefits. Particularly, the method of evaluating the benefits of recreational use in multi-purpose reservoir development is closely discussed. It was determined that the application of the travel cost method was the most useful to the model situation assumed in this paper. Then, appropriate cost allocation schemes are discussed theoretically, based on the results from the benefits estimated for recreational use. The paper concludes with itemizing policy implications derived from this study and lists possible themes to be subject for further research.

The Ogura low-lying basin located in the south of Kyoto has been urbanized rapidly in recent years.In this basin, several counter-measures against changes of flood runoff due to urbanization have been completed or are continueing, such as the construction of the Kumiyama Pump Station with a pump of 30m^3/s in 1973 and the channel improvements to the River Furu since 1971. Moreover, a pump of 30m^3/s was added at the Kumiyama Pump Station in 1987 and the Jouyou Pump Station with the drainage capacity of 10 m^3/s composed of two pumps of 5 m^3/s, was constructed at a point of the upper stream of the River Furu in 1990.In the previous paper, we discussed an optimum plan of drainage system from the viewpoint of minimum cost of costruction, on the basis of drainage conditions in 1960.This paper deals continually with an optimum plan of drainage system in future on the basis of the present condition of drainage system.As the result, it has been clarified that the optimum plan of drainage system in future is the combination of the improvement of channels and the increase of pump capacities at the existing pump stations, and that the construction of new drainage equipments become difficult because mainly of high price of lands.

This paper deals with a longitudinal mixing of particles which are instantaneously releasedin a bounded turbulent shear flow. The movements of particles are described in view of theLagrangian particle analysis. The similarity of concerned phenomena to the turbulent diffu-sion by continuous movements in a uniform turbulent flow is studied. The discrepancy oftwo phenomena is also shown with some discussions. In the mixing the Lagrangian auto-correlation function plays the most important role. Some auto-correlation functions in aturbulent shear flow are introduced and their dependency on a released position and traveltime is discussed. The discussion gives useful information of estimating the Lagrangianauto-correlation function in a turbulent shear flow. Finally, the model of the Lagrangianauto-correlation function proposed by the authors in the other paper is referred, and thegeneral features of longitudinal mixing given by the proposed model are compared withthe past knowledge experimentally obtained.

This paper presents the results of experimental and theoretical investigations on theprocesses of transport and deposition of suspended sediments in the channel with a floodplain. In the interaction region between the flow in a main channel and the flow in aflood plain, suspended sediments are mixed laterally as well as longitudinal momentum offlow. Almost of the sediments transported to the flood plain are deposited and are transportedas bed load because the turbulence on the flood plain is small. In this paper the concentrationdistribution of suspended sediments and transverse distribution of deposition-rate and bed loadon a flood plain are measured, and the processes that suspended sediments are diffused tothe flood plain and deposited there as suspended sediments are transported downstream areinvestigated. Then, the numerical method to calculate the distributions is proposed underthe condition of steady and uniform flow. This method is verified by comparing the theoreticalresults with experimental ones.

In the previous paper'~, we discussed the process and mechanism of the progressionof the local scour in the alluvial curved channels on the basis of the experimental studies, and developed the theoretical analysis for the variation of lateral bed profiles at the initialstage of scour.This paper proposes an analytical approach for the progressive stage of scour, whichdescribes the longitudinal variation of bed profile with time along the outside wall ofcurved reach. The fundamental equations derived in this analysis include two unknownfactors. The one is characteristics of flow pattern near the scour hole, and the other isthe variation of stream width near the outside wall or longitudinal profiles of lateralscour front with time. Concerning to these problems, we discuss the results of themeasurements of flow direction and velocity near the bed and the observation of Dunes(Bars) in the curved reach.

In order to establish the mechanics of scour downstream of a culvert and anoutlet and to discuss the method for preventing from scour, it is necessary, firstof all, to analyze the characters of flow close to a bed, especially the boundarylayer developing there. The first part of this paper, therefore, presents an analysisof the boundary layer growth in a wall jet issuing from a submerged outlet, basedon the momentum equation for a boundary layer connecting with two-dimensionalfree turbulent jets. Characters of diffusion of a wall jet, boundary layer growthand resistance laws are discussed on the basis of the experimental results of walljets, and it is cleared that comparisons between the experimental results and thetheoretical ones are satisfactory for practical purpose.The main purpose of the paper is to obtain some fundamental data for estimat-ing the length of apron of a submerged outlet under the condition that the sedi-ment bed downstream of aprons is not scoured absolutely by action of flow. In thesecond part, the criterion for scour from the wall jet in the region having a con-stant maximum volocity is discussed by using the results obtained in the first part.The experimental results of the criterion are compared with the theoretical re-lationships, and an empirical formula for the criterion is proposed on the basis ofthe both results. In addition, some considerations on the design of the length ofapron are briefly described.

This paper describes the internal structure of curved flows based on measurements of threedimensional velocity components in the curved reaches of smooth rectangular channels underconditions of subcritical flows.Considering the properties of three voriticity components observed, the flow through acurved section was divided into three regions: the generated region, the developed region andthe fully developed region of secondary flow. The magnitude of secondary flow predicted fromthe longitudinal vorticity equation was confirmed by the experimental results in the generatedregion. Further, the radial distribution of tangential velocity measured in the fully developedregion supported the theory of pervious papers.

There are many complicated hydraulic problems on surface flow over agricultural landsin low areas. This paper deals with the resistance coefficient in transitional flow from inopen channels to at or near state of still water.At first, in order to discuss the variation in resistance coefficient in such flows, the rela-tion between the resistance coefficient and hydraulic factors with respect to the flow at thecritical slope is obtained. The equations (16), (17) and (18) are developed from the exper-imental results using the rectangular open channel.Moreover, the relation between the resistance coefficient and the Froude number isdiscussed. In case of turbulent flow, it is well known that the resistance coefficient increaseswith the Froude number, and here it is also found that the trend of increase in the resistancecoefficient even at the Froude number less than 10 1 is recognized. Since, however, the ex-periment has not been enough to discuss in detail, the definitive conclusion is suspended inthis paper.

As described in a previous paper', the flow through a simple curved open channel maybe divided into three regions a generated region, a developing region and a fully developedregion of secondary flow.In the first part of the present paper, the existence and the properties of these regions arereexamined by a series of experiments shown in Table- 1 . From the longitudinal distributionsof three mean vorticity components observed, it was found that the flow in the curved reach hasthe characteristics of the generated region and the developing region, and the fully developedregion will be never reached in many practical cases.In the second part, the vertical distributions of radial velocity with or without the effects ofbed wall friction are discussed. Considering small perturbations from a flow as a free vortex, thedistributions of radial velocity are derived from longitudinal vorticity equations for a laminar anda turbulent flow. The experimental results within the generated region support the theoreticalconsiderations.

A method of numerical analysis for three dimensional unconfined seepage flow was proposed inthe previous paper. Then, few examples for engineering application of the method are shown inthis paper. First, the result calculated for the flow in the three dimensional earth dam was discussedin comparison with the result obtained as two dimensional flow. Moreover, three dimensionalcharacters of ground water flow in a wide alluvial fan are examined using the results calculated bythe method and observed data.

階段式魚道型水路では，流下方向にのみ水面が振動する1次元的な波が発生する場合と水路横断方向にねじれを伴った2次元的な波が発生する場合があることが知られている。しかし，水面振動発生のメカニズムについては十分に解明されていないものと考えられる。本研究では，隔壁上層と隔壁下層の流体の交換速度を仮定した簡易モデルを用い，不安定波動の発生機構について理論的に考察した。また，水理模型実験を行い，水面振動特性について実験結果と比較することでモデルの検証を行った。, In this paper, the unsteady water surface oscillations in a ladder fishway type flume are investigated. In the previous studies, a few patterns of water surface oscillations were observed and the countermeasures have been taken to prevent the oscillation. However, the fundamental mechanism of generation of unsteady waves is not clarified yet. In this study, laboratory experiments were firstly conducted to examine the oscillation characteristics and obtain the fundamental data. Then, a simple theoretical model on the unsteady wave generation was developed by assuming the exchange velocity between the surface and pool regions. The model was verified by comparing the theoretical results with the laboratory experiments.

市街地および地下空間における洪水氾濫に関する研究を行ってきた結果，浸水時の地下空間の危険性が明らかとなった。その対策として，地下空間からの避難が最重要であるが，避難困難度に関する定量的な評価があまりなされていなかった。本報は，実物大の階段模型および地下室のドア模型を用い，浸水時の避難体験実験をするとともに，水深，流速などの水理量および避難時の脚部に作用する力の計測などを行い，地下空間からの避難に関する定量的な検討を行った。その結果，階段実験では地上水深0.3m，ドア模型ではドア前面水深0.4mが、避難困難となる水深であることが知れ，今後の防災対策に有用な知見を得た。, Many floods caused by heavy rainfalls and typhoons hit Japan in recent years, and some floods attacked fully urbanized areas. Tokyo, Nagoya and Fukuoka were inundated by urban floods, and some parts of flood water intruded into underground spaces. During the floods, underground shopping arcades and subway stations were inundated. The inundation in underground space is one of problems to resolve urgently. One of effective measures to reduce the damage of flood disaster is quick evacuation from the underground spaces. In this paper, evacuation from underground spaces has been tested by using real scale models of staircases and doors. From the results, it found that water depth of 0.3m on the ground is a critical depth for evacuation from underground space through staircases and 0.4m deep in front of the door is the limit to open the door.

大陸規模の河川流域における洪水を予測するためには, 洪水を水循環の中の現象の一部として捉えモデル化する必要がある。そのためには, 気象モデルと水理・水文モデルとの結合を念頭においた流出シミュレーションシステムを構築することが重要となる。そこで, 対象流域を気象モデルでのグリッド位置・大きさを想定したグリッド型の流域に分割し, 各々のグリッド流域に集中型モデルを適用してそれらを相互に結合することによって流域全体の水移動を表現する流出シミュレーションシステムを構築する。このシステムをタイ国チャオプラや川流域に適用しシステムの性能を検証する。, To predict flood or drought disasters and future water resources for large river basins, it is very important to combine atmospheric models, hydrological models and flow routing models. In this paper, a method to build a macro scale rainfall runoff model is presented and a method to generate channel network data sets, which are essential for making flow routing models, from the River Course Data Set in the DCW(Digital Chart of the World) and the GLOBE(Global Land One‐km Base Elevation) data sets is presented. A macro scale rainfall runoff model for the Chao Phraya River Basin is made and runoff simulations are carried out.

過去に提案されている水田モデルは大きく、川長期流出計算を対象とするもの.121短期洪水流出計算を対象とするものの二つに分類される。本研究では、それぞれの代表的モデルである複合タンクモデルと低平地タンクモデルを組み合わせた新しい水田モデルを構築した。ついで、この新しい水田モデルを構造的モデル化法によって要素モデル化し、木津川上流域に適用した。, Paddy field runoff models proposed until now are mainly classified imito two groups: (1) models which simulate long‐term rummoff taking into accoumit irrigation and drainage, and (2) models which simulate short‐term flood runoff takimig imito account overflow on a levee. In this paper, we develop the new paddy field runoff model integrating the Complex Tamik Model and the Diffusive Tank Model, which are representative models of each group, respectively.Then, we build the miew paddy field runoff element model by usimig OHyMoS (Object‐oriented Hydrological Modeling System), and apply it to Kizu River basin in Japan.

本研究は山地河川の長期流出特性の変化をタンクモデルの係数変化として検証したものである。大域的最適化手法であるSCE‐UA法は, ノイズを含むデータを用いた場合にもモデルの最適同定を行うことができる。タンクモデルの同定において, 安定した結果を得るためには約10年程度の同定期間のデータが必要であった。永瀬ダム流域の解析では, 最近, 第1タンクの上流出孔係数の値が小さく同定されることが認められた。, In this paper, daily streaniflow data of a moutainous river was examined to get the change of long‐term runoff characteristics as that of runoff model parameters. The SCE‐UA which is a global optimization method is the mbust tool against to measurement noises and it is capable of solving the tank model efficiently and steadily.To get stable parameters of tank model, it was necessary to use the data for about 10 years duration. Through the present analysis for the daily data in the Nagese Dam basin of monobe river, it was indicated that the upper runoff coefficient of the first stage of a standard tank model was estimated smaller than ever.That seems to correspond to the increase in the evapo‐transpiration of the watershed.

本報は大阪湾水理模型を使用し、湾内の流動特性について実験的手法により検討したものである。実験では、異なる5段階の水深に抵抗板を持つフロートを用いて、それぞれ抵抗板の水深における流動を捉えた。水深別の流動特性の比較より、潮流の流速・流向が大きく変化する海峡部付近では水深方向に流動の違いが見られたが、それ以外の領域では流動特性の水深方向変化は小さいものであることが知れた。また、海峡部での流入・流出に際して、主流部に偏りが見られることがわかった。, This paper shows some experimental results of tidal currents using a hydraulic model.Inner tidal currents in the model were observed using a flow visualization technique.A tracer has a submerged cross-shaped plate which is set 5, 10, 15, 20 and 25m below the water surface in the prototype scale. It is found that vertical velocity distribution is not uniform in the regions near straits.

複断面流れの構造は。水路の平面形状および横断面形状に支配されるとと童)に, 低水路水深によって孟)変化する。この流れ特有の構造は, 速度の異なる低水路流れと高水敷上流れが相互に干渉する低水路側岸近傍に見られる。ここでは, 水路側壁の形状(直線水路, 蛇行水路)と低水路形態(直線, 屈曲, 蛇行)の組合せで分類し、4種の複断面 水路(直線・直線, 直線・屈曲, 直線・蛇行, 蛇行・蛇行)における実験結果を用いて低水路側岸近傍の三次元流況の差異について検討した。その結果, 混合形態と二次流構造でそれぞれの流れが分類されること。いずれの流れにおいても低水路水深によって構造が変化するr構造の水深依存性」が見られることが指摘された、, Flow structure in a compound open channel is investigated here with experimental results by flow visualization.Three dimensional stnmcture in four types of compound open channel: a straight comnpound channel, a comupound channel with sinuous and meandering main channel, and a mneandering compound channel, are discussed.The results show that fluid Inixing and secondary flow are key‐phenomnena when we discuss on the structures, and that the structures are different each other in shallow cases of flood plain and deeper cases in all four channels, which is an universal characteristics called as the depth dependence of the flow structure in this paper.

既往洪水から同定された貯留関数パラメータは洪水ごとに異なる値を示す。したがって現に起こりつつある洪水に適合するモデルパラメータは, 一般には過去に同定したモデルパラメータとは一致しない。適合しないモデルパラメータを用いた場合は当然, 良い予測結果は得られない。そこで, 貯留関数パラメータが洪水ごとに変化することを考慮するために, 複数の予測更新システムを同時に実行してそれらの重みを逐次更新する手法を導入した実時間流出予測手法を提案し, 実流域に適用してその効果を検証する。, The storage function method developed by Kimura is often used for short‐term runoff simulation, and some on‐line prediction methods which use the storage function method incorporating forecast updating using Kalman filterimig have beemi developed by several investigators including the authors. In this paper, the framework of our flood runoff pmediction muethod is introduced and treatment of uncertainty of model parameters of the storage function method is newly devised.In the new method, a number of filters with different parameters are rumi simultaneously, and the probability distribution assigned to these filters is updated by using Kalman filtering with real‐time observation data. The results of application of this treatment show that the new treatment enhances the prediction accuracy.

In mountainous rivers, huge rocks are scattered on river bed which have been supplied by debris flows or side slope failure caused by heavy rainfalls or earthquakes.The rocks can not be transpoted by medium or small floods, and affect stream channels variation and sediment runoff.In this paper, flume tests are conducted to investigate the process of channel variation where gravels are set along the banks of the stream channels in order to clarify the relationship between arrangement of rocks and stream channel variation.Numerical simulation model is also proposed to calculate the channel variation, and the results of the calculation are compared with the data obtained from the flume tests.

The three-dimensional river-bed configurations were measured by a echo-sounder attached to a cross-type float which was tagged from the top of the bridge, and almost simultaneously, time series of photographs were taken of the flow patterns on the flow surface during a flood stage in the Hii River. Photograph data were analyzed by picture processing technique to obtain the mean velocity in water surface of flood flows.5 series of measurements were made from 1993 to 1995. In this paper, by using the obtained data, the characteristics of bed configulations and their time variations were examined in relation to the time variation of flow depth, resistance and velocity.

By the development of the mathematical modeling for overland flooding flow, inundation flow can be treated in hydraulic manner. A map denoting hazard area due to flood or predicting the distribution of maximum overland flood depth is released by river administration. From these aspects, establishment of refuge system in a sheltered area against flooding has become a new research subject.This paper deals with a modeling of refuge system at a supposed inundation area in terms of network theory and considers effects of refuge measures and residents behaviour during refuge. First, the distribution of the residents requiring refuge and the allocation of suitable refuges are examined. Next, using the residents behaviour model during refuge, and taking into account of inundation flow characteristics and refuge execution rate by residents, several simulations are conducted which can express the temporal situation of refuge. Based on the above results, the effects of refuge system and some tasks to be solved are discussed.

This paper deals with the numerical analysis of channel processes resulted from bank erosion. In order to analyze the channel processes, it is necessary to develop a numerical model which is available to calculate unsteady open channel flow in a changing boundary with time. Therefore, a moving boundary fitted coordinate system was introduced to analyze the channel processes. The model is applied to compute the channel processes for the experiments with straight, circular and meandering channels. In the case of straight channels, the computed results were in good agreement with the experiments. In the case of circular channel, the model is improved to simulate the experimental results by introducing secondary flow component. In the case of the meandering channel, the volume of the bank erosion computed by the model is much smaller, and the probable reason of this discrepancy has been discussed based on the detailed experimental results of channel profiles and flow properties.

The aim of this study is to reveal fundamental flow behaviors in an estuary into which a river flows.The fresh water of river expands three dimensionally in the estuary, affected by buoyancy force due to salt water.Estuary topography, discharge of river and density difference between fresh and salt waters play dominant roles for flow field characteristics.As the first stage of study, the present paper deals with the numerical procedure to analyze the flows near the river mouth and in the estuary, and simulation using simplified estuary model.Simulation results show that radially expanding flow in surface layer is associated with radially converging flow in lower layer, and a prominent shearing layer characterize the whole flow field.

This paper deals with the surging phenomena with the propagation of multiple interfaces between open channel free surface flows and pressurized pipe flows, which can be seen due to the rapid change of flow discharge in the sewer network system, the tailrace tunnel of hydropower plants, etc.The circular pipe with multiple vertical shafts is used as the experimental set-up to investigate the fundamental characteristics of phenomena.The temporal and spatial variations of the pressure and depth in the pipe after the instantaneous interception of discharge are measured under some hydraulic conditions.The maximum elevetion of water surface at vertical shafts is related to the hydraulic variables such as the discharge and the position of vertical shafts.It is tried to reproduce the phenomena numerically by means of the simulation model proposed by authors. The numerical results are compared with the laboratory tests to make sure the applicability of the model.

It is well known that the secondary flow can be observed in a straight open channel, however, it is elusive to be detected because of its small magnitude and unstableness. The secondary flow is investigated experimentally or numerically by many researchers. In this paper vortex motions induced by the secondary flow are classified on the basis of its cause; velocity gap, flow boundary and bed-generated turbulence, and discussed by using the results of 3-D LDA measurements, flow visualization in a transverse cross section and an algebraic stress model (Naot-Rodi model). It is found that there are some difference between the time-mean secondary flow obtained by LDA and N-R model and the instanteneous secondary flow by the flow visualization.

Braided channels which are generally produced in mountain streams, vary spatially and temporally. The channel processes are composed of widening phase, bifurcating phase and merging phase.In this paper, flume tests are conducted to investigate widening and bifurcating phenomena in order to clarify the mechanism of such channel variation. According to the results, a straight channel irregularly widen and bifercate with development of a bar formed in the channel.Numerical analysis is also presented to predict the channel bed variation in a stream channel with non-uniform width. The result simulated by the numerical model compare well with the data obtained from flume tests.

The velocity distribution together with a stage discharge curve obtained by experiments for a compound open channel are discussed. The distribution of the velocity between the main channel and the flood plain is founded to be closely related to two mixing processes which are dominated by shearing and secondary flows. A new method is proposed for calculating a stage discharge curve which shows good agreement with experimental data.An application of the turbulence models is also discussed in this paper. The results obtained by the models are compared with the accurate data of turbulece data by using a 3-component LDA. The model results show good agreements with experimental data in a rectangular open channel, but not enough in a compound open channel.

In genaral, tidal exchange of water in a semi-enclosed sea area is the result of currents induced by wind and density and horizontal residual circulation associated with the geometry of the basin.This paper describes the tidal exchange phenomena governed by the horizontal mean circulation in the system.Two approaches were used for analyzing the tidal exchange.One is a physical experiment and the other is a numerical simulation based on the ADI method. It was found that exchange of water between adjacent circulations was determined mainly by the scale and velocity of circulations and the time during the streamlines of the circulation were kept closing.

In the previous paper^1)- the authors presented a bed-load equation which was derived from their constitutive relations of debris flow. The equation underestimates somewhat the bed-load rate in the range of non-dimensional shear stress smaller than 0.2.This paper discusses a refinement of the constitutive equations in smaller range of shear stress, but greater than the critical value of initiation of sediment movement.A bed-load equation, then, is derived from the refined constitutive relations.The formula is tested in terms of the data obtained from flume tests carried by using both of sand particles and glass beads.

This paper describes the "Multi Layers Mesh Model" representative of distributedrunoff system model. The horizontal space of watershed is divided by mesh or gridsize and the vertical zone under the ground surface consists of A, B, C and D layerscharacterizing the soil structure of forest.After the estimation of many parameters necessary for model making, this modelwas applied to Hinachi experimental watershed of 4.07 ha in area size and showed agood agreement with the observed data. Moreover this model was used in order toestimate the effect of deforestation on runoff regime.Key words: multi layers mesh model, evapotranspiration, deforestation, sensitivityanalysis

This paper deals with the numerical simulation study of flow and associatedwater quality distribution effected by the topographical feature in a reservoir. Themathematical models for the simulations are deduced from the hydrodynamicprinciples by means of the curvilinear orthogonal coordinate system. They aredeveloped into the numerical models by making use of the integral technique withrespect to a block obtained from homogeneous property of the flow field. Thenumerical simulations concerning the two-directional multi-layered flow in astratified reservoir are practiced by means of the finite difference method in terms ofthe staggered schemes. The results obtained through the simulations agree with theknowledge from the past experiences and the usefulness of the proposed proceduresis successfully verified.

In a compound open channel, the interaction between main channel and floodplain flow is the most important phenomenon to be clarified. This interactionaffects the resistance to flow and sedimentation on the flood plain.To carry on the research of the interaction, it is necessary to clarify the flowstructure in this region. Strong secondary flows near the boundary, which wereindirectly showed by Sellin or another researchers, have been investigated inexperimental compound open chnnels in this paper. In spite of elusiveness of thesecondary flows, many attractive photographs were obtained by the refinedtechniques to visualize the flow in a cross section. Characteristics of the secondaryflow and interaction between main channel and flood plain flows were discussedhere.

When a river dike breaks down, the flowing water of higher level in a stream channel runs outabruptly from the part of breaking. The motion of water which runs out in an inland area hasbeen studied by hydraulic experiments or by numerical calculations of difference equations. How-ever, hydraulic behavior of the flowing water in a stream channel, control position of the wholeflow pattern and so on after dike breaking are remained unsolved.This paper describes the results obtained after hydraulic experiments on the motion of waterdue to breaking of a river dike. It is one of the available results obtained that, after several secondsfrom breaking, the discharge rate of outflow from the broken dike is proportional to 3/2 power ofthe initial depth of water and remains constant.

This paper deals with the mixing phenomena in a main flow direction within a bounded turbulentshear flow in view of Lagrangian aspect.Data obtained by numerical simulations are analized through application of Taylor's classicturbulent diffusion theory by continuous movements: Main objectives are to disclose the relations ofLagrangian properties, such as Lagrangian auto-correlation coefficient, integral time scale and dis-persion coefficient with Eulerian Flow properties and also to obtain differences of these Lagrangianproperties between two and three dimensional turbulent shear flows.As results of this study, it is concluded that the auto-correlation coefficient in a three dimensionalturbulent shear flow is quite different from that in a two dimensional one, and that the lateral non-uniformity of velocities averaged in a vertical direction and the lateral turbulent intensity are mosteffective on the longitudinal mixing in three dimensional turbulent shear flows.

This paper deals the two-dimensional numerical simulation method of flows andassociated dispersion in the horizontal plane by means of the generalized curvilinearcoordinate system. Basic mathematical models for flows and convective-dispersionof contaminants are derived in the generalized curvilinear coordinate system. Theyare represented in the conservation forms and as simple as those in the Cartesiancoordinate system. Finite differece forms of these equations are obtained by the in-tegral method and they have the second order accuracy in a time coordinate andthe third order accuracy in space coordinates. The algebraical numerical grid gener-ation method is also introduced. The usefulness and the accuracy of these proposedprocedures are successfully examined through the comparative study of numericalresults with the analytical solution for a 2-D convective dispersion phenomenon.They are also applied to the numerical experiments for 2-D flows and the trans-verse dispersion of contaminants in a model river. The results obtained are agreedwith the knowledge obtained in the past study and the usefulness of the proposedmethod is verified.

The statistical laws of geomorphologic properties in river basins, using the stream magnitude, are shown, postulating the topological randomness and the randomness of link lengths and theirassociated areas. The relations of various methods concerning channel classifications suggest-ed in the past, are statistically disclosed with the use of topological randomness and a new methodin terms of stream link order is proposed. The empirical laws of drainage composition basedon the stream order are theoretically obtained from the laws using the stream magnitude thatare proposed in this paper.

Phisically-based runoff models are generally classified into two groupes: distributed parametermodel (DPM) and lumped parameter model (LPM). In this paper, we present a framework toevaluate LPM's, while a DPM is regarded as a prototype and used to simulate discharge datacontaining only random errors.Akaike's information criterion (AIC) is incorporated into the evaluation framework; so thatour method can be used to determine the order of a hierarchical model and to compare varioustypes of models.Tank cascade model (TC), Sugawara-type tank model (TANK) and Kimura's storage functionmodel (KSFM) are evaluated for several storm-flood data simulated. Though KSFM givesminimum AIC values for each data, the values of the model parameters vary with the flood.The framework presented here is important to evaluate LPM's and establish a proper LPM.

The outline of the recent investigations on the turbulence characteristics in free surface shearflows, performed by the staffs in the Ujigawa Hydraulics Laboratory, is described in this paper, which is consisted of the following two main parts.Firstly, the spectral similarities of the turbulence energy, the Reynolds stress and the con-vective process are obtained for the productive, the inertial and the viscous subrange respective-ly, through the technique of dimensional analysis. The validity of these similarities are examinedby the experimental data.Secondly, the vertical distribution of parameters on fhe turbulence field in a two-dimensionalfree surface shear flow is investigated both theoretically and experimentally, and the followingresults are obtained. The mean velocity distribution is good approximated by the well-known log-arithmic law, but the Karman constant and the integral constant are differ from these of pipe flow.The vertical distribution of the turbulence intensity, the Eulerian integral scale and the energydissipation rate are represented in form of universal functions, whose functional forms aredetermined experimentally.

Before and behind bed protection works in natural rivers, bed roughnessabruptly changes from smooth to rough and/or rough to smooth. This paper dealswith water surface profiles and turbulent structures of open channel flows producedby sudden changes in bottom roughness experimentally and theoretically.Changes in vertical distribution of sediment concentration under the fullysuspended condition are also discussed. The transition of flow depth was found tobe mainly depend on the bed slope and classified into three types of flow patterns.In the downstream reach after roughness change, distributions of the velocity andturbulence property vary with development of the internal boundary layer, in whichthe transfer of turbulence energy by convection and vertical diffusion play dominantrole in the turbulence energy budget. The calculated results of the k-e andsediment transport models agree well with the experimental ones.

Because the long range runoff system is essentially the stochastic one, it is necessary todisclose not only the deterministic characteristics but the stochastic laws contained in theprocces of rainfall-runoff. From this point of view, T. Takasao and S. Ikebuchi have intro-duced the concept of entropy defined by Shannon to describe the rainfall-runoff system.The objective of this paper, expanding their study, is to define the transmission rate of therunoff system with due regard to that it is a lag system and to find out the transition pro-bability among the runoff states on the assumption of maximum entropy and maximumacquired informatiom content. The applying results of these probabilities to Yura River Basinare good agreement with natural stream records.

In a curved channel there are spiral motions occurred by centrifugal force. And in an openchannel that consists of a main channel and flood plains, the flow has a complex turbulent structurebecause of interaction between flow in a main channel and it in flood plains. So it is difficult to clarifycharacteristics of an open channel flow in bend with flood plains.In this paper it is the objective to elucidate the turbulent structure of this flow by measurementsof velocity and flow visualization. From experimental results it is comfirmed that three independentspiral motions exist in bend with two flood plains.

Observational research of sediment yield and transport have been carried out in mountainbasin called Ashiaraidani (7.2km2), which is located in the Northern Japan Alps Range.This paper presents some results of the observations on runoff characteristics, on rate ofsediment yield and transport, and on stream channel variations before and after floods inthe Hirudani basin (0.85 km2). These major observational research efforts have produceda bedload equation that can be used in gravel-bed steep channels with stair-like sequencesof pools and chutes.The process and mechanism of sediment transport during a flood in the Ashiaraidanistream channel were partially revealed through the observation of flows and channel variationson the stream by the TV camera.

This paper describes an experimental investigation of the profiles of mean velocitiesand some turbulence properties in a two-dimensional free surface shear flow. The exper-iments were performed under the condition of greater aspect ratio than 10, to obtain thetwo-dimensional flow in a rectangular open channel.The experimental results show that the mean velocity profiles are well described bythe logarithmic distribution, and that the Karman constant k and the integral constantAs, Ar may be treated as constants which are independent of the Reynolds number, theFroude number and the relative roughness height. However, the values of theses con-stants in a free surface shear flow are somewhat different from these in a pipe flow, andthe following values may be recommended, that is, k=0.33, As=2.2 and Ar=8.3.According to the Reynolds number similarity, the turbulence properties are normalizedwith the flow depth, the friction velocity and the local mean velocity. And the verticaldistribution of the normalized turbulence properties, such as, the turbulence intensity, theEulerian mean scale, the energy dissipation rate, the Taylor's dissipation scale, the Kol-mogorov's lacal scale, the Lagrangian mean scale and the turbulent diffusion coefficientare described by the universal function of the relative depth, respectively.

This paper concerns with the mass transfer processes of dissolved materials inserted as aninstantaneous line source in the open-channel flow reviewing the lateral diffusion in concentra-tion. Experimental studies made in a rectangular laboratory flume consist of two series.Data obtained were treated by the statistical analysis like the lateral distribution of con-centration, first moment, second moment, peak concentration, and so on, with results of newknowledges in the statistical characteristics of mass transfer and in the practical application ofone-dimensional mass transfer analysis in open-channel flows.

This paper describes what effect topography of a natural watershed has on therunoff properties. In small mountainous watersheds, it is very important to take ac-count of the effect of topography on runoff. To examine this effect, we take twosteps. The first is geometric modeling of a natural watershed. A natural watershedis modeled as a group of slope element models. They are covered with an A-layerwith uniform thickness and are described by using spline functions based on thedata from a topographic map. The second is modeling of surface and subsurfaceflows by the kinematic wave equations considering the A-layer, the change of slopewidth and slope gradient. By applying this kinematic wave quations to a slope ele-ment model, the hydrograph in a slope element is simulated.These methods are applied to the Arakawa experimental basin. It is revealedthat slope elements in the shape of valley have great influence on runoff.

In this paper dominant characteristics of the local scour near a cylindrical pier are investigatedon the basis of wide ranged experimental data. And an attempt is performed to explain its char-acteristics by making use of a simple model which is constructed in consideration of only the vortexof the stagnation plane and the continuity of the sediment in the same plane. Secondary, by dis-cussing the existing experimental results and proposals together with their applicability, anothermethod of estimation of the equibilium scour depth is proposed.

This paper deals with characteristics of the resistance coefficient and the vertical distributionsof velocity and concentration of free surface shear flows with suspended sand particles, as a firststage of research program for hydraulics of multi-phase flows.Main results obtained through the experimental investigation are as follows; 1) The resis-tance coefficient of a sediment-laden flow over smooth bed increases with, while that of a flow overrough bed decreases, with increasing of sediment concentration. 2) The vertical distribution ofmean velocity in the outer region is confirmed to be logarithmic for a sediment-laden flow as sameas a clear water flow. 3) It should be noticed that, in a sediment-laden flow over smooth bed, decreasing of velocity near the bed results larger velocity gradient compared to a clear water flow, and that, in a sediment-laden flow over rough bed, increasing of velocity near the free surfaceresults larger velocity gradient. 4) The Karman constant of sediment-laden flow over bothsmooth and rough beds becomes larger than that of a clear water flow. The integral constant of alogarithmic velocity distribution for a flow over smooth bed decreases with increasing of sedimentconcentration, but that for a flow over rough bed increases with increasing of sediment concentra-tion. 5) The characteristics of turbulence of a sediment-laden flow is also changed from thatof a clear water flow, especially in the region near the bed, where the turbulence intensity andthe energy dissipation rate become larger. 6) Non-uniform lateral distribution of sedimentconcentration may be described by the connection with large-scale turbulent motion such as asecondary flow. That is, high and/or low speed streaks are seemed to correspond with low and/orhigh sediment concentration, and these characteristics should be more investigated in details.