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洪水を予測するうえで，水文量の空間分布をどの程度の分解能で流出予測に反映するべきかを検討する。水文量の空間分布を統計的に取り扱うことができる最大の流域面積を基準面積と定義し，分布型流出モデルを用いた数値シミュレーションによりその定量化を行う。基準面積に影響する要素として，降雨の空間分布，流域特性の空間分布，河道網の効果に着目し，それらが相互に関連して基準面積を決定づける内実を明らかにする。分析の結果，流域面積が150km2から1, 500km2の範囲では，基準面積は流域面積に関わらず絶対的な大きさで決まり，河道網の効果が主にその大きさを規定していることが分かった。また，わが国の実流域を対象とした洪水予測の例では，降雨分布の位置を陽に取り扱わないことによるピーク流量の差異を5％許容すると基準面積は300km2になることが明らかになった。, This paper investigates the appropriate spatial resolution to reflect hydrologic variabilities for flood simulation with rainfall-runoff models. It defines Model Building Unit (MBU) as a maximum catchment area in which statistical representation of the input variables is acceptable. Interactions among rainfall distributions, catchment distributions, and river cannnel effects determine the size of MBU. This paper clarifies the interactions and quantifies MBU by numerical simulations with a distributed rainfall-runoff model. The simulation results showed that MBU is restricted mainly by river channel effects and it is quantified as absolute size regardless the catchment scale if it is between 150 km2 and 1500km2. MBU is 300 km2 for 5% of allowable relative peak error.

都市の内水排除の排除施設を効果的に運用する場合、観測システムを明示的に考慮して運用ルールを決定することが重要であり、筆者らはルールの決定が部分観測下の最適制御問題として定式化でき, 有限な状態量の関数として定義可能であることを示した(田中他、1999)。しかし、複雑な内水排除システムでは厳密な最適制御ルールを求めることは難しい。本稿ではモデルの実用的な近似解法として観測方程式を用いた方法を提示する。, Major issues of urban drainage system control are design of control policy and monitoring system. Given a monitoring system , mathematical programming model to obtain an optimal control policy is formulated as a partially observable MDP problem. It was shown in the authors' previous paper (Tanaka, et.al. 1999) that the optimal operation policy takes the form of mapping from finite a point in state space to release volume. However, for real world problems, dimensions of state vectors tend to large enough as to prohibit direct application of the model. In order to cope with this problem, this paper presents an approximate method as to obtain sub-optimal operation policy under partially observable state information. This method contains an observation equation, which is formulated by considering hydrological characteristics. Numerical examples are also provided as to demonstrate its applicability to large-scale real world problems.

The Ogura low-lying basin located in the south of Kyoto has been urbanized rapidly in recent years. To cope with changes of flood runoff due to urbanization, the improvement of the River Furu was begun in 1971, and the Kumiyama Pump station with a pump of 30 m^3/s was constructed at the downstream end of the River Furu in 1973. Moreover, a pump of 30 m^3/s was added to this pump station in 1987, and the Joyo Pump station with two pumps of 5 m^3/s was constructed at Haccho located in the upstream of the River Furu in 1990.In addition to these counter-measures, several measures have been proposed in our previous papers. The latest paper showed an optimum plan of drainage systems along the River Furu from the viewpoint of minimum cost of construction.This paper deals continually with an optimum plan of drainage systems in the whole of the Ogura basin which consists of three sub-basins such as the Jodan, the Chudan, and the Gedan Zones from the viewpoint of minimizing a total amount of annual interests, depreciation, and maintenance of drainage equipment. In particular, two counter-measures against the increase of flood runoff due to urbanization in the Nakauchi and Ouchi sub-basins situated in the western part of the Gedan Zone are examined. The one of them is the improvement of existing drainage systems in these sub-basins connected with the Gedan Main Channel through two culverts, and the other is the separation of the drainage systems from the Gedan Main Channel after closing these culverts and constructing the new drainage pump station at the downstream end of the River Ouchi.As the result, it has been clarified that there is little difference in total amount of annual cost of these measures, and that the separating plan has an advantage of reduction of annual flood damage of paddy field in the Gedan Zone.

This paper presents a households' behavior model in drought time.In drought time, the difficulty of gaining the required amount of water increases and households are forced to reallocate their resources to produce water-dependent in-house services.In this paper, the difficulty induced by drought is expressed in terms of increased time to obtain a unit amount of water.A demand model is proposed to theoretically analyze the demand substitutions between different services as the time to gain water increases in drought time.It is shown that both the preferences for in-house services and the characteristics of households technology to produce in-house services determine the substitution patterns of the services and factor demands for inputs for the in-house services' production.

The Ogura low-lying basin located in the south of Kyoto has been urbanizedrapidly in recent years. To cope with changes of flood runoff due to urbanization, the improvement of the River Furu was begun in 1971 and the Kumiyama PumpStation with a pump of 30 m3/s was built at the downstream end of the River Furuin 1973. Moreover, a pump of 30 m3/s was added in the Kumiyama Pump Station in1987 and a new pump station is being constructed at the upper stream of the RiverFuru.In addition to those counter-measures, several measures have been proposed inour previous papers. These measures, however, are derived from the viewpoint ofhydraulic engineering without of careful consideration on the economical aspect.This paper deals with an optimum plan of drainage systems from the viewpointof minimum cost of construction by using the technique of the DynamicProgramming. Furthermore, the effects of urbanization, change of the price of landand the flood plain compensation on the optimum plan of flood control areexamined to give useful information for future strategy in the optimum design ofdrainage systems.

In the previous paper, we concluded that flood hydrographa from the whole river basin(4. 4 k㎡) can be calculated directly using hydrographs from the smaller sub-basin (0. 18k㎡) included in it, under the following assumptions1) The flood hydrographa from sub-basins which are same order as the specified sub-basin, are equal in runoff duration and proportional to their drainage areas in runoff intensity.2) The stream channels in the whole river basin are characterized by so-called linearchannel.This paper describes the application of these assumptions to the estimation of floodhydrographa in larger river basin of the River Chikugo being 537 kmi in area. It is shownthat the flood hydrographa at any location in the river basin can be estimated accuratelywhen the suitable specified sub-basin is selected, the proper propagation speed of floodflow is evaluated, and the movement of rainy area and the spacial distribution of amountof rain are taken account of.

The Ogura basin situated in south of Kyoto consists of three drainage zones such as the Joudanzone composed of hill and high land of 27.4km2, the Chudan zone of middle land of 6.3km2, and theGedan zone of low land of 18.7km2 contained the reclaimed land of 10.8km2. The Ogura PumpStation with 13 pumps of 48.9m3/sec in total capacity is in active at the outlet of the basin.The basin is rapidly being urbanized mainly in the Joudan zone to exceed 50% in area in thenear future. To cope with flood changes due to the urbanization, the improvement of the RiverFuru being the drainage channel of the Joudan zone was began in 1971, and the Kumiyama PumpStation with a pump of 3Om3/sec was built at the end of the River Furu in 1973. These counter-measures, however, are not enough yet to deal with floods in the future.This paper discusses a desirable least counter-measure continuing the previous paper to mitigateflood disasters in the future, analyzing the flood behaviour by the kinematic runoff model and thedynamic tank model under a dangerous rainfall condition for every return period.As the results, the following two measures are proposed. (1) Increasing the pump capacity of60m3/sec to do 9Om3/sec in total at the Kumiyama Pump Station, and enlarging the side weir to 8times as large in length as the present to do 200m in total in the downstream of the River Furu to spillflood water temporary into the reclaimed land. (2) Increasing the pump capacity of 30m3/sec at theKumiyama Pump Station, enlarging the side weir to do 200m in length in the downstream of theRiver Furu, and setting a new multi-purpose retarding basin of 47.7ha in the middlestream of theRiver Furu. This retarding basin is divided into three lots to expect the effective land utilization.The lowest lot of 11.Oha is used for minor floods, the middle lot of 22.Oha for floods over 5 years returnperiod, and the highest lot of 14.7ha for severe floods over 30 years return period.

The main objective of this paper is to investigate relationships between characteristics of riverflooding and damages of houses in flooded districts. The Misumi River was flooded by the heavyrains in July 23, 1983. As the river meanders in mountain area, the estimated flooding dischargewas over some three times of its capacity at the lower reaches of the river.It is well known that number of houses swept away or severely ruined by flooding is relatedto loss of human life. In this paper, the destruction processes of wooden houses by flooding areconfirmed with the eyewitness evidences of the inhabitants. When the depth of flooding is over theceiling of the first floor, the wooden houses can be easily swept away downwards. Thehydraulic force of the simulated current contributes to the occurrence of wooden house swept awayor severely ruined.

The Ogura basin located in the south of Kyoto is divided into three drainage sub-basins suchas the Joudan of hill and higher land of 27.4 km2, the Chudan of 6.3 km2, and the Gedan of lowerland of 18.7 km2 contained the reclaimed land of 10.8 km2. The Ogura Pump Station built in 1943at the outlet of the basin has thirteen pumps of 48.9 m3/s in total capacity at present.The basin has been urbanized rapidly in recent years. To cope with changes of flood runoffdue to the urbanization, the improvement of the River Furu being the drainage channel of theJoudan was begun in 1971, and the Kumiyama Pump Station with a pump of 30 m3/s was builtat the downstream end of the River Furu in 1973. These counter-measures, however, are notenough yet to deal with runoff water in the future.In order to make up reasonable flood control plan in the future, we cannot help expecting theeffect of the temporal ponding of runoff water in the reclaimed land. Several proposals describedin previous papers were also based upon this principle under the assumption that almost all part ofthe reclaimed land would be utilized as paddy fields. This assumption, however, may not alwaysbe applicable in the future because of the changes of the socio-economical conditions in recentJapan.In this paper, we propose to classify farm into zones of three classes such as Zone A with thenon-inundation probability of 1/10-year, Zone B of 1/5-year except Zone A, and Zone C with highprobability of inundation which is used only as paddy. A flood control plan is examined to in-crease Zones A and B.The flood control plan proposed in this paper is as follows: 1) For the Joudan: Adding thepumping capacity of 60 m3/s at the Kumiyama Pump Station, and enlarging the side weir in theRiver Furu to 250 m in length being tenfold at present to spill flood flows into the reclaimed land.2) For the Chudan: Reconstructing the side weir at the Main Channel point in the ChudanChannel to spill runoff water into the reclaimed land, and improving the Chudan Channel partly.3) For the Gedan: Adding the pumping capacity of 30 m3/s at the Ogura Pump Station, construct-ing a new drainage channel under the elevated high speed way of the Keiji Bypass Road, andimproving the Main Channel.

It is very significant to estimate a probable maximum discharge of a flood, which willoccur in the specified river basin, in the sence of prevention of water hazards. Manyformula of the specific discharge of flood peak have been proposed but most of them areobtained empirically after plotting observed flood peaks against drainage area on a graphpaper. This paper describes the occurrence condition of flood peak in relation to rainfallpattern and system of stream net, and the curve on a log-log paper, which will give theprobable maximum specific discharge of flood peak because this curve is derived from thepast records of extremely large and heavy rainfalls.

本報告は，21 世紀COE プロジェクトの一研究課題である「都市水害の危険度評価技術とその社会的応用に関する研究」に係わる以下のような研究テーマに関して2005 年に行った研究の成果を概述したものである．1）河床変動に伴う生態の生息条件評価手法の開発，2）適切なダム操作による洪水制御，3）地下空間の浸水予測モデル，4）岸沖方向の海底床形状による津波の変形に関する実験的研究．, The present paper describes tentative results which have been obtained from the following research topics in our COE project on Risk Assessment Technology of Flood in Urban Area and Its Practical Application: 1) Methodological development for assessing habitat condition associated with bed variation, 2) Flood control by appropriate dam operation, 3) Prediction model for inundation of underground spaces, and 4) Experimental investigation on tsunami transformation due to a cross-shore shape of a sea bottom

2004年（平成16年）10月20日に，大阪市付近に上陸した台風23号により由良川沿川の四市一町（福知山市・舞鶴市・綾部市・宮津市・大江町）は，浸水家屋約1700戸，浸水面積2600haに達する大きな被害を受けた。この台風23号は福知山上流域で流域平均2日雨量276mmの降雨をもたらし，福知山水位観測所では，昭和28年に福知山市内で浸水家屋数約3800戸に達する大災害をもたらした台風13号に次ぐ水位が観測された。本研究では，こうした大規模洪水が物理的な背景にもとづいた分布型降雨流出モデルで適切に再現できるかを検討している。ここではまず2004年洪水を分布型流出モデルにより再現した。次に，2004年洪水を再現可能なモデルが過去の小中規模洪水を適切に再現するかを検討した。その結果、同じモデルパラメータの値を用いて，同地域においては中小洪水から計画規模に匹敵するような大洪水まで概ね良好に再現できることがわかった。, This paper analyzes the Yuragawa river flood by Typhoon No.23 on 19-22 October 2004 which brought the large number of casualties and loss of asset especially at the downstream region of the Yuragawa catchment. First, the discharge-hydrograph at Fukuchiyama during the flood is reproduced by a distributed rainfall-runoff model. The simulated discharge-hydrograph after the parameter adjustment shows a good fit with the observed discharge-hydrograph. Afterwards, the model with the same parameter is applied to two past-medium-size floods, which also exhibit the good performance of the model. From these applications, it is clarified that the physically-based distributed rainfall-runoff model has a high potential to reproduce floods of any size in the catchment.

足羽川流域においては，2004 年7 月に梅雨前線の集中豪雨によって河川の流下能力を大幅に超える洪水が発生し，流域の各所で激甚な被害を被った。本研究においては，足羽川中流部の水害の実態を詳細に調べ，山地河川の水害の発生構造を検討した。その結果，谷底平野の形態，河道湾曲部における土地利用，橋梁や取水堰などの河道内の構造物，土石の堆積による河床上昇，各地区内にある道路や鉄道線路の状態が水害の発生に大きな影響を与えることがわかった。また，得られた知見に基づいて考えられる治水対策について述べた。, Severe flood disasters due to heavy rainfall occurred in the Asuwa River basin on July 18, 2004. In this paper, the flood disasters in mountainous area of the basin are discussed by investigating the aerial photographs taken after the flood and the results of precise field surveys. The main conclusions are that the aspects of flood disaster are characterized by the following points; (1) the characteristics of flood plains in valley, (2) land usage around river channels, (3) obstructing effect by bridges and barrages, (4) sedimentation in river channels and (5) the role of roads for inundation.

通年においてわが国へ上陸する台風はは2～3個であるのに対して，昨年（2004年）は10個にも達し，観測史上最大の個数であった．台風0416と0418号では瀬戸内海に大きな高潮が発生し，多くの犠牲者が出るとともに，多大な被害を被った．また，高知沿岸を走った台風0423号では防潮堤のパラペットが破壊され，越波による浸水で数名の死者が出た．さらに，台風による集中豪雨によって河川が氾濫して，福井県や新潟県で多くの住民が避難生活を余儀なくされた．そこでは河川堤防の決壊が氾濫水域を拡大し，大量の土砂を堤内地に運び込み，被害を拡大させた．このような氾濫災害の発生は，わが国が水害に対して十分に対応できていないことを如実に示していると言える．本報告は，このような氾濫災害を軽減するために21世紀COEプロジェクトの一環として行ってきた研究のうち，現在までに得られた成果の一部を概述したものである．, Last year of 2004 large and various disasters happened due to landing-on of the quite large number of typhoons and the local heavy rainfalls. Thus, our countermeasure against water related disasters is not sufficient even now. The present paper describes following tentative results which have been obtained in our COE project: 1) Quantitative effect of collaborative flood control by a group of dams, 2) Inundation of underground space in urban area, 3) New prediction procedure of suspended load, 4) Storm surge disasters in Korea and 4) Coastal damages of storm barriers and breakwaters.

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.

福岡市では1999年6月29目午前に1時間雨量として観測史上最大の77mmの豪雨を記録し, 市内を流れる2級河川御笠川が氾濫した。氾濫水は都市機能の集中するJR博多駅周辺にまで流下し, ビルの地下, 地下街, 地下鉄駅構内に多量の氾濫水が浸入するという都市域特有の水害が発生した。本報は, この水害の現地調査結果ならびに水理検討結果をとりまとめたものである。また, 今回の水害の調査結果をもとに, 地下空間を含む都市の水害対策についてハード・ソフトの両面から若干の提言を行っている。, Heavy rainfall occurred in Fukuoka Prefecture in the morning of 29 June, 1999. The hourly rainfall from 8 to 9 a.m. amounted to 77mm in Fukuoka city. This heavy rainfall and the consequent overtopping flow from the Mikasa river caused inundation in the wide area of the city. The inundating flow invaded into underground space, namely, the underground space in buildings, the subway station and the underground shopping mall, which caused heavy damages.This paper summarizes the field surveys of Fukuoka flood and treats some hydraulic studies concerning it. The countermeasures against urban typed flood are also considered.

本研究では, DAD(Depth-Area-Duration)解析を用いた可能最大降雨(PMP)の推定方法と, PMPと分布型流出モデルを用いた可能最大洪水(PMF)の推定方法を提案する。那珂川流域を覆う2つのレーダー雨量計で得られた雨量データを, 45個の地上雨量計を用いて補正する。レーダー雨量計は, 地上雨量計が捕らえられなかった局所的豪雨を検知し得ることが示された。レーダー雨量を用いてDA関係を求める新しい方法として, 面積固定法と雨量固定法を考え, 両者によって得られるDAD式の違いを検討している。その際, DAD式(最適な包絡線)を求める非線形最適化アルゴリズムを開発した。求めたDAD式に基づき, 最大の洪水を引き起こすと思われる豪雨の時空間分布を設定して, それを分布型流出モデルに入力することにより, 那珂川流域における物理過程に基づくPMFの推定を行った。, This paper describes a procedure of estimating the PMP (Probable Maximum Precipitation) using DAD (Depth-Area-Duration) analysis and the PMF (Probable Maximum Flood) using the PMP and a distributed hydrological model. Radar data obtained from two radars, which cover the Naka river basin in Japan, are calibrated with 45 ground raingages. The radar data detected the local extreme rainfall which ground raingages could not catch. In calculating DA relationship with the radar data, two new methods, constant area and fixed rainfall methods, are proposed. The difference of DAD equations given by the two methods is studied. A nonlinear optimization technique has been developed to determine parameters of DAD equations, optimal envelops. The spatiotemporal distribution of storm, which is expected to cause the maximum flood, is set up based on the DAD equation. Inputting it into the grid-cell based distributed runoff model produces the physically-based PMF estimate for the Naka river basin.

本報では急傾斜都市における土砂動態を考慮した氾濫解析法を提示した。上流部の山地部では流出流量と土砂濃度のハイドログラフを求め, それより下流域の都市部に対する境界条件とした。都市部では全領域を河川, 道路, 堤内地に属性分けすることによって都市の諸要素を考慮に入れた非構造格子法を用いて, 土砂を含んだ二次元氾濫解析を行った。本モデルを神戸市の生田川流域に適用し, 土砂流出を考慮した場合としない場合の解析結果を比較し, 土砂を考慮した場合では考慮しない場合に比べて, 浸水深, 氾濫規模はともに大きく, より危険であるという知見が得られた。したがって土砂生産の盛んな河川流域の都市では, 土砂の影響を考慮した氾濫解析の必要性が確認できた。, This paper treats the inundation flow analysis in steep slope cities considering the effects of sediment.A computational river basin is divided into mountainous area and urban area. The hydrographs of discharge and sediment concentration in mountainous area are imposed as the boundary conditions of upstream end in urban area. The above model is applied to Ikuta River basin in Kobe. The results show that the extent of inundation is much severer than that of the case without considering sediment. So it has been found out that sediment influences inundation flow behavior considerably in the river basin with much sediment.

1998年の7月から8月にかけて中国の長江で大洪水が発生した.洪水の原因は異常な豪雨にあるが, 亜熱帯高圧帯が長江に沿って移動し, 下流の洪水流出と上流のそれとが重畳したこと, 洞庭湖・ポーヤン湖の容積が減少したために洪水調節能力が低下したこと, 洪水の疎通能力を低下させるような輪中や建物が堤外地に多数造られたこと, 河床上昇により洪水規模の割には水位が高くなったこと等により, 長期間の高水位を持続し, 本川堤防の決壊や輪中堤の決壊, 多数のパイピングや漏水等が発生した.ここでは, 今回の洪水の原因と特徴, 被害の概要, 長江の治水計画, 洪水対策等について報告する。, A great flood occurred at the Changjiang River, China in July and August, 1998. The primary cause of the flood is an extraordinary heavy rainfall brought by the subtropical high which moved along the Changjiang River. Owing to the rainfall, a flood runoff at the upstream fell on the runoff at the downstream, resulting in the great flood of a long duration. The decrease of water storage capacity of the Dongting Lake and Poyang Lake due to reclamation also magnified the flood scale.A flood water level was higher comparing the flood water discharge due to decrease of flood discharge capacity by the construction of a large number of buildings and circle levees which are called as "yuan" in Chinese in the riverside lands, as well as due to aggradation of the river bed. In this paper, the results obtained by the hearing and the field survey concerning the cause of the great flood, flood control planning of the Changjiang River, the aspects of flood and flood disasters, and countermeasures in future, are reported.

本論文は, 1998年8月下旬に生起した那珂川流域の豪雨・洪水災害について若干の考察を行ったものである。災害発生直後の9月上旬から3月上旬までの間に現地調査・資料収集などを行うとともに, 豪雨データのDAD解析, それに基づく流出解析によって起こりうる極大な流量の推定を行った。今回の事象は, これまでの当該地域の豪雨・洪水の記録を更新する未曾有のものであることが明らかになった。, Based on field investigation, this paper describes the outline of storm and flood disaster that has occurred in the Nakagawa basin in August 1998.The flooding in the Yosasagawa River and the Kurokawa River, the upper reaches of the Nakagawa was brought by a record-breaking severe storm. The resultant flooding was one that exceeds design flood. Using ground-based rainfalls at more than twenty locations and radar raingauge data, the authors have conducted the DAD analysis and derived the probable maximum precipitation (PMP) in the basin. On the basis of the DAD analysis, hydrological simulation using the grid-cell based distributed runoff model has given the probable extreme (plausible maximum) flood.

従来より, 平面2次元流れを解析するにはデカルト座標系が主として用いられてきた。しかし, 都市域での氾濫解析にこれを適用すると, 都市域には道路や建造物, さらには中小河川や連続盛土など氾濫水に大きな影響を及ぼす要素が数多く存在するために, これらの影響を考慮した解析が困難になる。そこで本報では, 対象領域を任意形状の格子に分割することのできる非構造格子を用いた氾濫解析法を展開し, これを実際の都市域へ適用した。その結果, このモデルが中小河川からの氾濫水の排出や, その堤防や連続盛土による氾濫水の遮断を考慮した氾濫解析を行うのに有効であることがわかった。, In analysis of two-dimensional overland flood flow, Cartesian coordinate has been used most popularly. However, in application of the coordinate to urban area, some difficulties arise for treating urban geographical factors - streets, buildings, small rivers or continuous dike -, which have large influence on inundation flow. Then in this paper, an inundation flow model using unstructured meshes which can divide the computational region into arbitrary shapes of meshes is developed, and applied to urban area.Consequently, it is found that this model can take small rivers and continuous dike into account and can be applicable for predicting an inundation flood hazard in urban area.

本報は, 大阪市北区の「梅田」地下街を対象として, 地上部における洪水氾濫とその氾濫水の地下空間への浸水過程を解析したものである。地上部の洪水氾濫解析においては平面二次元モデノセを, 地下空間の浸水解析においては一次元ネットワークモデルに地下街の天井高を考慮できるスロットモデルを組み込んだ数学モデルを適用した。数値シミュレーションの結果, 予想され得る氾濫水の地下空間への浸水過程がこのモデルによって表現されることが知られた。スロットモデルを用いた場合の計算精度の向上が今後の課題である。, This paper treats a numerical analisys of overland flood flow intrusion into underground space in urban area. A one‐dimensional network mathematical model to express inundation flow in underground space linked with a two‐dimensional overland flood flows by river bank collapse is developed and applied to Umeda underground market in Osaka city.For the pipe flow condition in underground space, a slot model is also applied. The obtained results show that the model exploited here can simulate the aspects of inundation flow into underground space fairly well.

1991年度から3ヶ年の予備的調査研究を経て, 1994年度よりインドネシア共和国中部および東部ジャワ島を中心に「洪水および地形変動による災害とその防御」に関する研究を推進している。主要なテーマは, (1)ジャワ島東部における洪水・土砂流出の評価と水害に関する研究および(2)インドネシアにおける海岸侵食に関する研究であって, これらは現地観測, 資料の収集・解析ならびに理論解析を駆使しながら推進され, これまでに興味あるいくつかの知見を得ている。本稿は, 1994年以後の研究によって得られた主要な成果について総括的に報告したものである。, This project has been conducted since 1994, with attention focused on flood and sediment hazards in central and east Java, Indonesia. It aims at developing methods for predicting floods and associated sediment phenomena such as sediment yields, river changes and beach erosions, including preferable countermeasures against flood hazards and coastal changes. Valuable results have been obtained from observations, data analyses and numerical simulations. This paper describes parts of them as well as the problems to be conducted.

本報は, 中国南東部およびベトナムの大都市の水災害の現状をとりまとめるとともに, 今後の治水対策のあり方について若干の提言を行ったものである。中国広東省に位置する深堀市, 広州市, ベトナムのハノイ市, ホーチミン市を対象とし, それらの都市を悩ます水害, 特に内水災害の実態を述べるとともに, 現在取られている対策について言及している。また将来の治水対策への提言として, ポンプ場の整備のようなハードな対策に加えて, 流域の保水・遊水機能の確保や土地利用規制といったソフトな対策を加えた総合洪水対策の必要性を説いている。, This paper treats urban flood disaster and its control at Shenzhen city, Guangzhou city in China and Hanoi city, Ho Chi Minh city in Vietnam.Present situations of flood disaster there are described and the relation between flood occurrence and rainfall is examined.The causes of flood and the countermeasures against mt are also discussed.In the future, comprehensive measures by both structural and non‐structural facilities are considered to be significant.

Residual currents are known to be responsible for the transport of mass, pollution and sediment, despite their magnitudes are small relative to those of tidal currents.The residual currents in the previous research have been obtained by averaging temporal variation of velocity at a fixed point. To study the transport processes, however, handling the phenomena from Lagrangian viewpoint is necessary.Many factors like tide, wind and density are related to residual currents. In case of Osaka Bay, additionally, the existence of currents running toward the east in the Seto island sea (the constant flow) is pointed out in the previous studies, and the currents has influence on transport processes.This paper shows some experimental results, which take the constant flow into account, of the residual currents in Osaka Bay using a hydraulic model test and a tracer method.

This paper deals with effects of shape of a dropshaft intake to energy dissipation and air transport control. First, free-surface swirling flows in vertical dropshafts are modeled and their solutions are derived. With these solutions, the energy dissipation effects of the dropshafts are examined by the vertical change of vertical momentum flux and kinematic energy, and some results of practical use are obtained. Next, the relations between the dropshaft shape and air entrainment are examined through dimensional analysis. Three types, that is, standard vortex flow dropshaft, helicoidal-ramp dropshaft and vortex flow dropshaft with contraction are analyzed. A hydraulic parameter influencing air entrainment is found and the excellence of the helicoidal-ramp dropshaft is clarified.

Now various kinds of high resolution remote sensors are available, such as Landsat TM (spatial resolution 30 m × 30 m), SPOT HRV (20 m × 20 m) and ADEOS AVNIR (16 m × 16 m) launched in 1996. It is significant to quantify the accuracy of interpretation or classification on high resolution remotely sensed images. This paper assesses land cover classification accuracy quantitatively for four remotely sensed images acquired almost simultaneously with various sensors with different spatial resolutions: Landsat TM, SPOT HRV, JERS OPS (18 m × 24 m), Airborne multispectral scanner (AMSS: 6.25 m × 6.25 m), and false remotely sensed images produced by three degradation algorithms. These false images have 10-m to 30-m resolution resampled from the 6.25-m AMSS image. The authors also produce the 16-m false AVNIR image by a degradation algorithm, and predict the classification accuracy of ADEOS AVNIR images.

The Meghna river, one of Bangladesh's major rivers, flows through the easter part of that country, eroding its banks at many points, and this erosion has been assumed an alarming magunitude since the enormous floods of 1987 and 1988.This paper describes the characteristics of flood flows in downstream of the Meghna river, which were clarified by analyses of water level data at seven gauging stations, and river channel process near the Meghna Bridge site that was surveyed during 1989-1992.Changes in water levels and their correlations showed tidal effects during dry seasons and complicated loops reflecting ground levels in floodplains.Retreat of river bank in a meandering reach up- and down- stream of the Meghna Bridge has proved deeply related to the river bed erosion, especially a severe local scour close to a ferry pier.There, local bed scour and extreme bank erosion have repeated by turns.Numerical simulations of flood flows were carried out in the reach by a 2-D finite element method for shallow water flows.The calculated result showed a significant influence of the ferry pier upon plane velocity distributions.

This paper presents an algorithm for mathematical simulation model to estimate the influences of bay-area reclamation on flood efflux in a esuary by means of finite difference numerical method. To be applied a new three-dimensional model is emphasized for the analysis of the flow structure and density effect. Following the basic equations, the numerical model using leap-frog scheme is derived in detail.After the calibration of the eddy viscosity and diffusivity, a good agreement is realized between the observed and calculated water stages. A simulation study is also made to predict water stage rise clue to reclamation and the density difference is found to play effective roles.

Failure of landslide dams is one of the main causes of severe flood disaster.Discharges resulting from dam failures can be much larger than those originating from mere strong rainfall. This fact, however, has been only qualitatively known and the quantitative analysis which enables to calculate the process of development of overflow channel on the dam body and the hydrograph of discharge has not existed. This paper, at first, proposes an empirical method to estimate the life span of a landslide dam. Secondly, a system of equations to be used in the numerical simulation of the process of failure and estimation of the discharge hydrograph is given. Comparison of the calculated results to those of the flume experiments proves the method is promissing.

In a compound open channel the flow velocity on the flood plain and it in the main channel are different, and a mixing zone exists between the two flows.It is necessary to clarify the flow structure in this region for investigating the interaction between main channel and flood plain flows.In this paper it is the objectives to clarify the fluid mixing in this region and compare the mixing with it in the 2 -D mixing layer by using the flow visualization results on the water surface and in a cross section of the flow.The analogy between the fluid mixing in a compound open channel and it in the 2 -D mixing layer has been recognized from the results.

In Japan, big cities such as Tokyo, Osaka and Nagoya cities are situated on thelowland called delta plain, and it is not rare that they have comparatively largeunderground spaces used for markets and subway stations.Recently, it has been said that sea water level might rise from 20 cm to 100 cm in21st century because of the global greenhouse effects, thus it is apprehended thatthere will be some danger of the large-scale inundation caused by a storm surgeand/or reduction of the discharge capacity at the river mouth.If these phenomena will occur in future at big cities, where population, privateand public properties and so-called life-lines are concentrated, following unknownproblems will arise: what kind of disaster will occur not only on the ground butalso under the ground, how is the mechanism of occurrence of inundation in theunder ground space, what kinds of the countermeasures against inundation in theunder ground space are effective and whether the evacuation systems designedconsidering the cases of earthquake and fire can still work well in case ofinundation in the underground space.In this paper, a method to simulate the inundation in an underground spacelinked with a simulation of an overland flood flows caused by a storm surge orriver bank breach is presented. The validity of this simulation method is checkedby experiments. Consequently, the experimental data are well explained by thecalculation.

This paper discusses some properties of the optimum parameters of the two typical floodrunoff models, such as the kinematic model with two parameters and the storage functionmodel with three parameters. The optimum set of the parameters is identified under thechi-square criterion of errors by the SP (Standardized Powell) method which is one ofthe mathematical optimization techniques. Both flood runoff models are applied to simulatehydrographs at the outlets of the Echi mountain river watershed of 108 km2, the Shimokarihill river watershed of 1.3km2, and the Tenjin urban watershed of 2.6km2. Main resultsare summarized as follows:1) From the parameter relating to the flow regime, it has been clarified that the Manninglaw is applicable to the kinematic model for flood runoff of peak discharge larger than4 m3/sec/km2.2) The optimun parameters of the storage function model are related to the ones of thekinematic model. The formulae combining them are obtained theoretically under someassumptions and proved by optimum parameters obtained.3) The functional expression of trough in the response surface composed of parameters isgiven experimentally and theoretically under some assumption. This result suggeststhe possibility of the development of the new technique for parameter optimization.

昭和49年7月, 6～8日及び24～25日の2回にわたり, 近畿』東海地方の各地に豪雨があり多くの災害が発生した。三重県では, 前期に伊勢市を中心として南勢地方が, 後期に中・北勢地方がいずれも記鐸的な集中豪雨に見舞われ, 全県各地で土砂災害や中小河川の破堤, 氾濫災害を起こしている。災害の要因, 被災のメカニズムは各所で異なるから, それぞれについて調査分析が望まれるが, 今回は前期豪雨の中心地で洪水被害の大きかった伊勢市勢田川流域の内水氾濫の素因分析を行ってみた。伊勢市の水害の第1素因はいうまでもなく驚威的な豪雨にある。14時間に619mm, 7時間に482mmという豪雨はこの地方では例のないものであったといわれる。しかし日本全国のどこの中小河川でも, この程度の集中豪雨に見舞われたならば, まず例外なく大災害を起こすであろう。それだけに, 中小河川計画はどうあるべきかという基本的な問題をこの災害は提起している。・一r…」さてほとんどすべての中小河川の例に洩れず, 勢田川では出水氾濫過程を示す資料はほとんど得られていない。そこでわれわれは痕跡, 聞き込み調査結果を手掛りとして, 主要地点における出水ハイド・グラフの数値的再現を試みた。これにより被災の物理的メカニズムを明らかにすることができ, 今後の災害対策に基本的な寄与ができると考えたからであるるここで用いた解析モデル, 手法は今後のこの種の問題の解明に有用な示唆を与えるものと信じているが, これに対し大方の批判が得られれば幸である。, Ise City faced to Isa Bay, Middle Japan, was attacked by record local heavy rainfall of619 mm during the duration of 14 hours, especially 482 mm during the duration of 7 hours, in July 7, 1974, and several places suffered severe disaster from flood. Flooded damage wasthe most intense in residential district along the River Seta.This paper discusses the flooding processes and, some (actors relating to the disasteron the basis of the results of runoff analysis. Flood hyArographs of discharge and waterlevel at several points are estimated applying the mathematical models of kinematic wavefor non inundated watersheds and dynamic wave fat inundated areas, The calculation forestimating the hydrographs is repeated to simulate flood traces l.n several places assumingthe water level condition at the outlet of the River Seta because no recording gauges ofwater level have been installed. The results of calculation are coincident with all floodtraces within the error of few centimeters.

The Uji river basin of 13.9 km2 is mainly composed of mountains. The narrow and lowerplain of 2.2 km2 along the Uji river is used mostly as paddy fields and partly as urban areas.The urbanization is recently advancing mainly along the Uji river in spite of the dangeroustopographical condition from flood. Several flood prevention works had been hurriedly carried outafter severe disasters in 1975 and 1976.This paper discusses the storage capacity of a retarding basin in relation to pumping capacitywhich are required for absorbing the effects of future urbanization on flood. A new methodutilizing a functional expression for flood runoff hydrographs is introduced to find a quasioptimum capacity of drainage facilities before the detailed examination using a model for floodsimulation. It is emphasized, as one of the results, that the urbanization of this area is undesirablebecause the enlargement of the ponding storage capacity is limited by the topographical condition.

The Nakashima River which runs through midle of Nagasaki City has overflowed its banksowing to the heavy rainfall of more than 400mm per 7 hours from 17:00 to 24:00 in July 23, 1982.In this paper, based on the fact-finding survey, river characteristics related to the bed slopes, river width and capable discharge were examined, and the flooding processes, inundated area andthe distribution of its water depth were reported.To simulate this flood event, a simple runoff analysis was carried out at first, then usinghydrographs obtained by this analysis as input data, unsteady two dimensional overland floodflow in Nakashima basin was analyzed by the numerical simulation method. Calculated resultsconcerning to the water depth and the flow direction showed relatively good agreement withobserved ones. The effect of the tide level was also investigated.

This paper deals with a formula for estimating the concentration time in a river basin, the-oretically and practically. The concentration time is defined as the time required for disturbanceof rainwater to propagate from the top of slope located at the remotest portion of the basin in thesense of dynamics to the outlet. Based on this definition, the equation for the concentration timeis derived from the kinematic wave theory to emphasize being a function of the average effectiverainfall intensity or peak discharge and of the area of watershed. By applying an approximatemethod to estimate the concentration time, the hydrological data in 18 natural river basins of0.13-740 km2 are examined to propose a practical formula for the concentration time. Theformula is also modified to extend its applicability to grazing and urban watersheds.

This paper discusses the changes of flood risk due to urbanization by the form of floodfrequency in the Ogura basin of 52km2 situated in south of Kyoto City. The urban area ofthe basin was under 8% in 1965. But the urbanization is now rapidly going on mainly inhill and high land of the watershed of the River Furu. The urban area has been extendedto 35% in these ten years and anticipated to exceed 50% in the near future. To copewith this tendancy, the improvement of the River Furu was began in 1971 and the Kumi-yama Pump Station with a pump of 30m3/sec was built at the end of the River Furu in 1973.The characteristics of flood runoff and inundation for the past, present and future urbanstates are analyzed by applying the kinematic surface runoff model and the dynamic tankmodel under the several rainfall conditions satisfied the given return periods in one-daydepth and under the given drainage facilities.Noticeable results obtained are as follows:1) The flood risk is increased by the urbanization. For example, the flood risk in thefuture becomes 50 times at a point of the middle reach and 4 times in the lowest paddyfield in the downstream of the River Furu compared with the one in the past, respectively.2) At the present before finishing the river improvement, the flood risk is decreasedslightly in the downstream compared with the one in the past, but increased 30 times inthe middle reach.3) In the future after finishing the river improvement, the flood risk is decreased largelyin the middle reach compared with the one in the past, but increased 3 times in thedownstream and a new counter-plan is demanded.

This paper discusses the effects of urbanization on flood in the Ogura basin situated in southof Kyoto City. The Ogura basin, the catchment area of which is 52 km2, is rapidly being urban-ized mainly in hill and high ground zone. The urban area of the basin was under 8% in 1965.But the urban area has been extended to 35% in these ten years and anticipated to exceed 50% inthe near future.First, the flood runoff characteristics in the present have been examined by applying thekinematic surface runoff model for a non-inundation sub-basin and the dynamic tank model pro-posed by the authors for a back water reach of channel flow and an inundation zone, and decidedthe principle of the watershed modeling and the parameters of the mathematical models.After then, the flood runoff analyses have been performed to find the effects of the futureurbanization on flood assuming the past heavy rainfall conditions in August, 1959, and July, 1972, whose return periods are regarded as 30 years in maximum one-day depth and 10 years in three-day depth and as 10 years in maximum one-day depth and 30 years in three-day depth, respectively.The urbanization effects have been evaluated by the form of changes in the runoff volume, thepeak discharge or water level at a point and the operation time of drainage pumps. As the results, the necessity of the precautionary measure for flood disaster has been pointed out.

From the 20th to 23rd in July 1983, heavy rainfall attacked the large area in San-in Districtsand the flood with vast discharge was generated in the Misumi River. The level of flood waterreached about 2 meters beyond the top of embankments and the whole fluvial areas were flooded.Everything on the area - embankment, river-walls, bridges, agricultural plains, houses etc. -were destroyed or were given serious damages.The authors surveyed the river basin after the flood and examined the aerial photographsto find out some features with which river constructions were destroyed. They also conductedsome experiments to confirm them. In this paper, the results of the survey and the experimentsare described.

URBANIZATION EFFECTS ON FLOOD RUNOFF ANDINUNDATION CHARACTERISTICS IN OGURA BASIN (7)-FLOODING PROCESSES CAUSED BY RECORD HEAVY RAINFALL INJULY, 1986 AND COUNTER-MEASURES AGAINST ITS FOOD-By Mutsumi KADOYA and Takao MASUMOTOSynopsisPart of new residential area and low-lying arable land in the Ogura basin located inthe south of kyoto suffered inundation damages caused by record heavy rainfall such as257mm (return period: 1/50years) in 24 hours and 332.5mm(1/l00years) in 48 hours, in July21-22, 1986.To cope with changes of flood runoff due to the rapid urbanization of this area, theimprovement of the River Furu begun in 1971, and the Kumiyama Pump Station with apump of 30m3/s was built at the downstream end of the River Furu in 1973. In additionto those counter-measures, several promising measures have been propsosed in previouspapers4) 6).Almost all of these plans, however, are based upon the states that the improvement ofthe River Furu had been completed. It seems as if the heavy rainfall of this time struckthis weakness of the area to bring the disaster.This paper discusses the flood behavior of this occasion analyzed by the kinematicrunoff model and the diffusive tank model, and effects of urbanization on this flooding toshow the existence of the weak points to be improved. Moreover, several flood control planswhich are expected as the emergency measures are examined by using the rainfall patternof this time.

Bangladesh suffered, sequentially in 1987 and 1988, severe damages caused by the flooding ofits three major rivers, the Brahmaputra, Ganges and Meghna, and the stagnation of rainfall in thelow-lying areas. About 40 and 84 percent of the whole country were inundated, and 25 and 45 mil-lion people were affected, respectively, in 1987 and 1988. Death toll in each year is estimated to bemore than 1500.Based on our field study and data collection in December 1987 and April 1989, we inversti-gated the severe flood disaster from the aspects of meteorology, geomorphology, hydrology, riverengineering and sociology in order to contribute to planning the structural and non-structuralcountermeasures against the flood hazards. This paper summarizes the results of these investiga-tions, and mainly describes characteristics of hydrographs in the major rivers and inundation pro-cesses, the river channel process in the Brahmaputra, the damage to water works and living, andthe relief and rehabilitation activities during the 1987 and 1988 floods.

The Kusaka and the Hage basins located in Shikoku District, west Japan, sufferedagain severe disasters from flood caused by record heavy rainfall accompanied with 7617typhoon, following to 7505 typhoon in August, 1975. The rain falled continuously duringthe period of September 8～13 and the areal depths in both basins amounted to 1, 019mmand 881mm, respectively.This paper discusses the flooding processes and factors relating to the disasters. Theflooding processes are analyzed to simulate hydrographs of water level observed at somepoints in both basins by the method of trial and error of computation based on themathematical models of kinematic wave for non-inundated watersheds and dynamic wavefor inundated areas. Hydrographs of flooded water level are also estimated under somehypothetical drainage facilities to suggest some means for preventing or mitigating suchthe disasters from flood.

Recently, in order to prevent a disaster due to a flood, embankments, reservoirs for flood control, divergent channels and so on have provided in a river basin. This paper, first of all, discribes a flowdiagram of occurrence of disasters in such a complicated river system, which is characterised by twosub-systems of the runoff process of rainfalls and the flood control by reservoirs, and of the decisionprocess of destruction of protection works against floods. It is pointed out that this flow diagram isvery helpful to determine a design criterion of protection works and to set up a flood forecastingand warning system.Next, after discussing a runoff process of rainfall in a river basin, the synthetic method of floodforecasting is proposed by the use of a combination of tank model and modified time-are-concentra-tion diagram. Lastly, an example of evaluation of destruction probabilities of embankments in theneighbourhood of confluence of two tributaries and a proposal of the relationship between designfloods for upstream area and downstream area in a river basin are presented in the light of the flowdiagram of occurrence of disasters.

The Kusaka and the Hage basins located in Shikoku District, west Japan, suffered severedisasters from flood caused by record heavy rainfall of 676 mm and 552 mm in areal depths, respectively, in August 16～17, 1975, accompanied with 7505 typhoon.This paper discusses the flooding processes and factors relating to the disasters to suggestsome means to prevent such the disasters. The flooding processes are analyzed to simulatethe highest flood traces in several places along rives in the basins by the method of trial and errorof computation based on the mathematical models of kinematic wave for non-inundated water-sheds and dynamic wave for inundated areas. Hydrographs of flood water level are also esti-mated under some hypothetical drainage facilities to give a suggestion of policy for preventingor mitigating disasters from flood.

The Ogura basin situated in south of Kyoto City consists of three drainage zones, suchas the Joudan zone composed of hill and high land of 27.4km2, the Chudan zone of middleland of 6.3km2, and the Gedan zone of low land of 18.7km2 contained the reclaimed land of10.8km2. The Ogura Pump Station with 13 pumps of 48.9m3/sec in total capacity is inactive at the outlet of the basin.The basin is rapidly being urbanized mainly in the Joudan zone to exceed 50% in thenear future. To cope with the urbanization, the improvement of the River Furu being thedrainage channel of the Joudan zone was began in 1971, and the Kumiyama Pump Stationwith a pump of 30m3/sec was built at the end of the River Furu in 1973. These counter-plans, however, are not enough to deal with flood in the future.This paper discusses a desiable counter-plan to mitigate flood disasters in the future, assuming the rainfall condition of 100 years return period and analyzing the flood behaviourby the kinematic surface runoff model and the dynamic tank model.The counter-plans examined are as follows: 1) The increase of pump capacity at theKumiyama Pump Station, 2) the enlargement of side weir in the downstrem of the RiverFuru to spill flood water temporary into the reclaimed land, 3) the creation of a retardingbasin and 4) the radical improvement of the side weir with lowering its crest. As theresult, the fouth or the second plan has been proposed with the increase of pumps of 30m3/sec or 60m3/sec, respectively.

Because flood disasters cannot be prevented perfectly by engineering works only, it isimportant to keep flood damage from escalating by an act of flood prevention.In this paper, the announcement criterion of meteorological alarm and/or warning, and theinformation system of order for refuge are discussed on the basis of results of opinionaireinvestigations.The results obtained are as follows;(1) Almost all of people got weather informations, but were not ready for refuge. Con-sequently it is necessary to improve warnings to get public attention.(2) About fifty percents of people did not get an order for refuge, so the informationsystem of order for fefuge has to be improved and it is necessary to send order as soon aspossible for making refuge more safety.

Shimane and Hiroshima Prefecture were attacked by severe rain storms in July, 1988. Landslides, debris flows and floodings occurred. These districts have been frequently suffered fromthe disasters caused by heavy rain.This paper describes the meteorological conditions, damages, and scientific characteristics ofthe disaster in order to prevent or to mitigate the disasters frequently occurred.

Since various kinds of rainfall-runoff models have been developed, the evaluation of themhas become one of the most important problems. What kind of model should be used fora specific hydrological problem? In this paper, a stochastic method of evaluating rainfall-runoff models is presented. First, the properties of stochastic input-output transformationof hypothetical slope and slope-channel systems are studied by using the kinematic wavemodel and the Monte Carlo simulation technique. Second, the so-called storage functionmodels, which are regarded as ones obtained by simplifying the kinematic wave model, are evaluated by the method considering whether the models preserve the stochatic proper-ties of the system or not. Since rainfall-runoff phenomenon is physical and stochatic, the method presented here is appropriate and useful.

The runoff phenomenon of a heavy rainfall in a river basin is divided briefly into thetransformation process from rainfall to outflow on mountain slope and the propagationprocess of water resulting from the above outflow in river channel. As the part of theresearch of such a runoff, this paper describes the physical background of the propagationspeed of flood waves in an actual river channel, and consists of two parts.In the first part, the change of propagation speed of a flood wave passing through alocation of river channel is discussed. As the results, it is found out that the flood wave ischaracterized remarkably as a uniformly progressive flow at the rising stage, and that thepropagation speed at a location of river channel holds nearly constant regardless of changeof discharge, because the relationship between the cross-section area of the flow and thedischarge shows approximately linear.In the second part, the change of propagation speed of a flood wave along a river courseis examined. The river bed configuration is divided into mountainous river bed, dune bedtype-I and dune bed type-II, and the formulae of flow resistance for each bed configurationis discussed in the light of open-channel hydraulics. It is obtained from the discussions thatthe mean velocity of a flood flow, corresponding the propagation speed, has a tendency toincrease from upstream to downstream in a mountainous region, that is, in the range ofmountainous river bed, and to decrease slightly form upstream to downstream in a alluvialregion, that is, in the range of dune bed type-I or type-II.