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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.

We have carried on the hydrological investigation since 1966 in the Ogura basin located in the south of Kyoto, in order to clarify the urbanization effects on floodrunoff and flood disaster potentialities. This report is a summary of the research delivered as the last lecture at Disaster Prevention Research Institute, Kyoto University.This report is composed of the following contents.1) Flood disaster potentialities increase with the progress of urbanization. To cope with the urbanization in the upper area of the river Furu, the improvement of the river Furu become urgent.2) The impact of arterial roads concentration forecasted in the Ogura basin is caused by the construction of attached facilities such as gas stations, restaurants and so on. The construction of the attached facilities must be restricted severely in a low-lying basin.3) Extreme urbanization of a low-lying area may be obliged to construct a new drainage system because of the limit of the improvement of existing system.4) The result of DP calculation shows that the present drainage system is near to an optimal one, but that the system with several pump stations along the river Furu may become optimal if the land cost goes up and the channel improvement become expensive.

The effects of global warming on the hydrological cycle are examined by using the output data from the runoff model identified at the Wajima-Yanagida experimental catchment of 0.15 km^2 and the Eigenji Dam basin of 132 km^2.In this paper, the climate scenarios for cold and warm periods are constructed based on temperature and precipitation records for both the coldest and the warmest decades at meteorological stations located near the study catchments. These climate scenarios are inputed into the Long and Short Terms Runoff Models identified at both basins, respectively and simulated responses for cold and warm climate scenarios are compared. The results suggests that hydrological responses are more sensitive to precipitation changes than to temperature dhanges excepting the snowmelt season.

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.

We discuss the effects of global warming due to the increasing concentration of atmospheric GO2 and other trace gases on the hydrological cycle.First, the Long and Short Terms Runoff Model (LST Model) is applied to the Wajima-Yanagida experimental catchment of 0.15 km^2 and the Eigenji Dam basin of 132 km^2 to verify the applicability of the model and then to identify the model parameters.Next, under the hypothetical climate change scenarios of temperature increases and precipitation changes, hydrological responses in these catchments are simulated by using the LST model.As the results, the remarkable reduction in snow water equivalent is shown for both catchments and the major change in the seasonal distribution of runoff is observed for the Wajima-Yanagida catchment.

How to estimate the optimum volume of the front-pond at a pump station is afundamental but unresolved problem in the optimum design of drainage systems.The role of the front-pond to regulate the difference between the rates of inflowand outflow through pump station and to mitigate the intermittent pump operation, is being more important to cope with the increase of pumping capacity caused byurbanization or conversion of paddy field to upland field in a low-lying basin.This paper deals with the optimal design of front-pond volume considering twocomponents VF and VR. In which VF is the maximum volume to be stored beforepump operation, and VR is the allowable maximum volume to be stored after pumpoperation. These volumes are discussed using mass-curves for inflow and outflowto propose a simple method under the condition of non-intermittent pump operation.This method is examined using hydrographs obtained by applying the mathematicalmodels of kinematic wave for non-inundated area and dynamic wave for inundatedarea.As the result, it has been proved that it is almost impossible to completelyprevent intermittent pump operation for all hydrographs of various scales and theintermittent pump operation containing a proper rest time must be allowed.

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.

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.

We have carried on the hydrological investigation since 1966 in the Ogura basin located in the south of Kyoto, in order to clarify the urbanization effects on floodrunoff and flood disaster potentialities. This report is a summary of the research delivered as the last lecture at Disaster Prevention Research Institute, Kyoto University.This report is composed of the following contents.1) Flood disaster potentialities increase with the progress of urbanization. To cope with the urbanization in the upper area of the river Furu, the improvement of the river Furu become urgent.2) The impact of arterial roads concentration forecasted in the Ogura basin is caused by the construction of attached facilities such as gas stations, restaurants and so on. The construction of the attached facilities must be restricted severely in a low-lying basin.3) Extreme urbanization of a low-lying area may be obliged to construct a new drainage system because of the limit of the improvement of existing system.4) The result of DP calculation shows that the present drainage system is near to an optimal one, but that the system with several pump stations along the river Furu may become optimal if the land cost goes up and the channel improvement become expensive.

The effects of global warming on the hydrological cycle are examined by using the output data from the runoff model identified at the Wajima-Yanagida experimental catchment of 0.15 km^2 and the Eigenji Dam basin of 132 km^2.In this paper, the climate scenarios for cold and warm periods are constructed based on temperature and precipitation records for both the coldest and the warmest decades at meteorological stations located near the study catchments. These climate scenarios are inputed into the Long and Short Terms Runoff Models identified at both basins, respectively and simulated responses for cold and warm climate scenarios are compared. The results suggests that hydrological responses are more sensitive to precipitation changes than to temperature dhanges excepting the snowmelt season.

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.

We discuss the effects of global warming due to the increasing concentration of atmospheric GO2 and other trace gases on the hydrological cycle.First, the Long and Short Terms Runoff Model (LST Model) is applied to the Wajima-Yanagida experimental catchment of 0.15 km^2 and the Eigenji Dam basin of 132 km^2 to verify the applicability of the model and then to identify the model parameters.Next, under the hypothetical climate change scenarios of temperature increases and precipitation changes, hydrological responses in these catchments are simulated by using the LST model.As the results, the remarkable reduction in snow water equivalent is shown for both catchments and the major change in the seasonal distribution of runoff is observed for the Wajima-Yanagida catchment.

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.

How to estimate the optimum volume of the front-pond at a pump station is afundamental but unresolved problem in the optimum design of drainage systems.The role of the front-pond to regulate the difference between the rates of inflowand outflow through pump station and to mitigate the intermittent pump operation, is being more important to cope with the increase of pumping capacity caused byurbanization or conversion of paddy field to upland field in a low-lying basin.This paper deals with the optimal design of front-pond volume considering twocomponents VF and VR. In which VF is the maximum volume to be stored beforepump operation, and VR is the allowable maximum volume to be stored after pumpoperation. These volumes are discussed using mass-curves for inflow and outflowto propose a simple method under the condition of non-intermittent pump operation.This method is examined using hydrographs obtained by applying the mathematicalmodels of kinematic wave for non-inundated area and dynamic wave for inundatedarea.As the result, it has been proved that it is almost impossible to completelyprevent intermittent pump operation for all hydrographs of various scales and theintermittent pump operation containing a proper rest time must be allowed.

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.

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.

It may be usefull to know the magnitude of the peak discharge of a record flood from a givendrainage area for the safety design of spillway of a dam and/or for the planning of precautionarymeasure for flood disasters in a river basin with different drainage area of the same hydrologicalcharacteristics and under the similar meteorological conditions. Unfortunately, however, thephysical or statistical characteristics of the regional maxima of flood peak has not hitherto beenstudied enough to sevre for the engineering practice in Japan.A study has been carried out from the point of view that the peak discharge of flood from ariver basin is the synthetic reflection of both characteristics of rainfall concentration in time andspace and of runoff of the basin. The basins of the River Obata in Kinki district, the River Tozuin Kii-Nanbu district and the River Ibi in Chubu district have been chosen in order to investigatethe DAD characteristics of heavy rainfalls. The equation of the peak discharge of flood from agiven drainage area has been obtained by combining the equations of DAD and the time of floodconcentration and drawn in a figure of log q (m3/sec/km2) to log A (km2). Such a curve has thenbeen slid to the log q direction to envelop flood peaks in the same district rivers. Every envelop-ing curve has shown good fitness far better than the Creager's curve.Finally, the parameters in the equation of enveloping curve have been examined and adjustedto set a common form of the equation in every district in Japan. The curves from the author'sequation show good fitness to record flood peaks in every district in Japan. They would be usedin Japan instead of the Creager's curves.

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.

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.

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 western part of Sanin District, west Japan, was attacked by record severe rain stom, inwhich the maximum 1 hour rainfall was over 90 mm and the total over 600 mm, in July, 1983. Thispaper describes the meteoroogical conditions, damage and scientific characterristics of the disastersin order to provide information for countermeasures in future.

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.

In the previous paper, what criterion should be adopted in simplification of complicateddrainage channel networks was discussed fundamentally in order to apply the numericaltechnique of unsteady flow to simulate hydrographs of flood runoff in low-lying drainagebasin. As the result, it was disclosed that the channel networks could be simplified to thesecond order channel system.This paper deals with an actual example of flood runoff in the Ogura research basincomposed of hills, urban districts and mainly paddy fields. Flood runoff from non-inundatedwatersheds such as hills and urban districts is estimated by applying the kinematic wavemethod, and flood flow in low-lying basin is simulated by solving the unsteady flow equationnumerically after simplification of channel networks based on the criterion disclosed in theprevious paper.The results of runoff analysis show good coincidence with observed hydrographs, andverify the usefulness of the criterion for simplifying the complicated channel networks.

The previous paper has proposed a mathematical model of runoff put emphasis upon theprocesses of prompt and delayed groundwater runoff. This paper deals with a practical methodfor determining constants and curves required for the model to be applied in hydrograph analy-ses.The depth of active soil layer is estimated through changes of the soil moisture content andthe river discharge. Both the inifiltration rate and soil moisture flux curves being functionsof soil moisture content cannot but be determined after trial calculations. In order to save thetrial calculations, however, those curves are given on the basis of numerical solutions under somehypothetical rain and soil conditions. Applied examples are also shown for hydrographs at theoutlet of the Minegado experimental basin.

It is important to estimate impermeable coverage in a residential district in order to predictthe effect of urbanization on flood runoff, but we can hardly know the coverage without long spellsof and laborious investigation.A simple formula is proposed in this paper for estimating the impermeable coverage in aresidential district. The formula is composed of three terms such as the coverage in housinglots, the coverage by roads and the coverage in other lands, but the last one is negligible in manycases. The impermeable coverage in housing lots, which is the most important factor, is closelyrelated to the density of housing lots, but may be estimated considering the land use classificationwith slight loss of the accuracy. By the use of the formula, the impermeable coverage is able to beestimated in future, too.

Several fundamental problems in applying the kinematic runoff models such as the interflowmodel, the overland flow model and the composite model to flood runoff analysis are studied bydealing with the data in the Shimokari hilly watershed of 1.3 km2, the 93% area of which is coveredby bushes and bamboo groves. First, a detail watershed model composed of 62 blocks or 136 blocksis constructed. The model is then lumped considering the stream order based on both Strahlerand N1 systems for ordering. The geomorphological characterisitcs of these models are examinedfrom the hydrological viewpoint. Second, the applicabilities of the kinematic runoff models areexamined by searching their optimum model parameters in every watershed model. And thepractical formulae have been proposed for estimating the optimum model parameters. Third, aninstantaneous unit hydrograph is proposed theoretically considering the interflow model and theprobability distribution of slope lengths.

The Kagami Basin located in Shikoku District, west Japan, suffered severe disastersfrom flood caused by record heavy rainfall of 1835mm/6days in September 8-13, 1976, accompanied with 7617 typhoon.This paper discusses the flood control function of the Kagami Dam, flood processesin the down stream parts of the Kagami Basin, and some facters relating to the disasteron the basis of the results of runoff and flooding analyses. The flooding processes areanalyzed to fit the highest flood traces along the Rivers Kagami and Kooda and tosimulate hydrographs of water level observed at several points in the inundated areaby the method of trial and error of computation based on the mathematical models ofkinematic wave for non-inundated watersheds and dynamic wave for inundated area.

There exist several low lands in danger of flooding in the down-stream reaches of the Niyodoriver. Flood disasters there are not independent of flood flows in the Niyodo river, but the floodflows are not simple because the Niyodo river basin is large as 1460 km2 in area in the upstreamof Ino which is the key water gauge station for river plannings.In this paper, the statistical characteristics of heavy rainfalls are examined for the flood flowsover 3000 m3/s at Ino, by applying the principal component analysis. On the basis of the results, the correlation between average rainfall over a sub-basin and flood peak discharge at Ino isexamined to show that the flood peak is mainly governed by the rainfall in the middle zone of thebasin.

The characteristics of flood runoff in the Taiko-daira golf course, Kyoto, of 0.051 km2and the Tsudaka pastureland, Okayama, of 0.23 km2 are examined in this paper, to getfundamental data for establishing the methodology for the prediction of runoff changes dueto the development of watersheds. The results obtained are summarized as follows.(1) The retention capacity of rainwater in the golf course is almost the same as orlarger than those in forest watersheds. This characteristics is regarded as the effect ofspiked golf shoes beyond the influence of surface geology. The characteristics of rainfallretention in the pastureland, one third of which is occupied by groves yet, is similar tothat in the golf course.(2) The land use coefficient C in the Kadoya-Fukushima's formula for estimating thetime of flood concentration in the golf course is C=120 which is near to the standard value, but the one in the pastureland C=140 to be smaller than the standard value.(3) The maximum values of the peak runoff coefficient are regarded as 0.60-0.65 inboth areas.(4) The values of the parameter k of the kinematic runoff model in both areas arealmost the same, and they correspond nearly to one fourth of the ones in natural mountainwatersheds.

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.

A self-recording water-stage or rainfall gauge exposed under the severe meteorologicalconditions for several years has sometimes troubles in the accuracy of time. These troubles are aptto cause fundamental faults in hydrological researches especially in a small or urbanized watershed.In order to mitigate the influence of such troubles, we have developed a device to recordrainfall data simultaneously on self-recording charts of a water gauge without the fundamentalremodeling of the water gauge. Four types of the device are introduced in this paper.Types A and B are both mono-response style to the signal from a tipping backet rain gauge, but the former records the signal in one side and the latter in both sides to the base line. Types Cand D are both response-cumulating style, but the former is used for a water gauge with the one-scale type of recording chart and the latter for two-scale type. Types A and B have difficulty inreading data of high-intensity rainfall, because they are designed as a time-marker. On the otherhand, types C and D are useful for high-intensity rainfall.

This paper discusses the interrelations of three typical flood runoff models, such as the tanksmodel of series type, the storage function model and the kinematic runoff model, through the resultsof flood runoff analysis in the River Shimokari of natural hilly watershed, and the River Tenjin ofurban area. The optimum parameters of the tanks and storage function models are estimatedby applying the Powell's conjugate gradient method. The main results are summarized as follows:Runoff from the first tank of the tanks model in the Shimokari basin is equivalent to surfacerunoff and subsurface runoff, that from the second tank to interflow, and that from the third andfourth tanks to groundwater runoff.The tanks model composed of the two tanks gives the accurate results in the sense of engi-neering practice in the Tenjin basin where surface runoff is the most important component.There exist several tanks models obtained by the optimization technique. The models arediffer from each other in the parameters but show almost the same relation between storage anddischarge.The storage function models in both basins correspond to the kinematic runoff model foroverland flow of the Manning's or Chezy's type. The parameters of the storage function modelare estimated from the kinematic runoff model or the practical formula for the time of concentration, and yet the estimated values are closer to the optimum parameters.Comparing the tanks and storage function models in both basins, it is clear that the storageeffect on direct runoff of the Tenjin basin is less than that of the Shimokari basin.

The urbanization of forest and agricultural areas near big cities is being accelarated with theadvance of the overpopulation from the cities in modern Japan. The urbanization of a watershed, however, is apt to promote the flood potential in the watershed or its down stream areas.This paper discusses the effect of urbanization on the flood potential generally but quantitativelyfrom the view point of engineering practice. The discussion is carried out through the followingitems: Changes in the detention and storage capacity of rain water on the ground surface and inthe surface soil layer; changes in roughness and gradient of the slope surface; changes in theconcentration time, the peak runoff coefficient and the peak dischage of flood runoff; and theground subsidence in an alluvial fan.Moreover, several counter-plans to prevent or mitigate flood disasters due to urbanizations areproposed from the view points of engineering practices and social policies.

This paper deals with the possibility of simplification of runoff model in a low-lying drainagebasin composed mainly of paddy fields. First, the method of numerical calculation of unsteadyflow at a junction of channels and the effect of the weir length of a pond on hydrographs at theoutlet of channel networks are discussed. Next, the possibility of simplification of complicatedchannel networks model is examined for the case that the boundary condition at the outlet of thenetworks is given by discharge assuming the pump drainage system. As the result, it has beendisclosed that a complicated channel networks can be simplified to the second order channel system.

As the results of infiltration test and soil survey in slopes of the Shimokari watershed, it was disclosed that the final infiltration capacity is too large in view of the soii characterand that a large number of crack and hole is formed in soil layer by active and dead roots.On the basis of these facts, a mathematical runoff model composed of surfase runoff, interfiow, rapid and slow groundwater runoff is discussed in this paper. The surface runoffand interfiow are treated as the kinematic wave in surfase of slope. The rapid groundwaterrunoff is simulated as the component supplied through cracks and holes, and the slowgroundwater runoff is solved as the vertical percolation in unsaturated capillary zone.The applicability of this model is examined to simulate runoff for the period of fourmonths in the Minegado experimental watershed of 12. 95 ha in area which is part of theShimokari watershed.

Several optimization techniques are examined experimentally for finding what technique canbe utilized as a powerful tool for the parameter identification of three typical runoff models such asthe series tanks model, the storage function model and the kinematic surface runoff model. Thetechniques examined here are as follows: The conjugate direction method proposed by Powellnamed here the Powell method for short. The conjugate gradient method developed by Davidon, Fletcher and Powell called as the DFP method. The QG method combined the techniques ofquasi-linearization and golden section.It is pointed out that the standardization of variables is very usefull in applying the Powelland the DFP methods for the identification of a set of model parameters different in order. Atechnique for standardizing variables by a set of initial values is proposed and named as the SPand SD methods, respectively.It is shown that both SP and SD methods are excellent for the optimal identification of theseries tanks model with sixteen unknown parameters, and that both SP and Powell methods arevery useful for finding optimal parameters of the storage function model with three unknownparameters and also of the kinematic surface runoff model with two unknown parameters.Moreover, a simple method is proposed for estimating the lag time in the stroage function, and the interrelation between the storage function and the kinematic surface runoff models issuggested based on the identified parameters.

The infiltration tests have been carried out at three field plots in an urban area by theequipment of artificial rainfall type developed by the authors for trial. The infiltration curvesobtained by these field tests have been simulated numerically on the basis of the Richards equationby the method of trial and error for finding the hydraulic properties corresponding to the type ofsurface soil in a field plot.Considering the result of this infiltration study, the runoff characteristics have been examinedin the Kita-Ogurayama residential basin. The results obtained are as follows: The base flow isonly composed of domestic sewage, and groundwater runoff from pervious area is negligible. Run-off from an impervious lot is almost 100 percent. Runoff from a pervious plot occurs only forrainfall over 20 mm in depth, and depends upon the moisture condition of surface soil. Theeffective rainfall intensity for runoff from the pervious plot is able to estimate by solving theRichards equation.These results have been applied to the analysis of runoff from the Kita-Ogurayama residentialbasin. Runoff hydrographs simulated by the kinematic runoff model show good agreements withobserved ones.

Several problems have been examined to propose the practical methods for applying themathematical optimization technique to the identification of the series tanks model with sixteenunknown parameters for the long term runoff analysis. The data used are the daily ones ofprecipitation and runoff for the period of 1973-1979 in the Eigenji Dam basin of 132 km2 and of1975-1976 in the Ichinotani basin of 0.13 km2. On the basis of numerical experiments, the SDFP(Standardized DFP) method has been chosen as the optimum identification technique to be usedhere under the Chi-Square criterion of errors to be minimized.The results of practical examination are summarized as follows:1) The water balance constraint is indispensable for identifying the model, by which goodaccuracy is expectable in the period of prediction, too.2) The data of drought years, even if their length is short, are effective for the model identificationof good accuracy.3) Excluding the data of runoff greater than a given level from the evaluation of errors is fairlyeffective if no data of drought period are available for the model identification.4) Permitting the one-day shift back of observed runoff is effective for improving the model, because the influence of night rainfall cannot be neglegible.5) Excluding the data of runoff in snow season from the error evaluation may be permittedbecausc of the uncertainty in the estimation of snowfall.

This paper discusses the effects of urbanization of upstream districts on flood runoff and inunda-tion characteristics of down stream low-lying area in the Ogura basin situated in south of KyotoCity. The basin was a quiet suburb agricultural district and the residental districts were onlyfew percent in area before about 1965. In the basin, however, the urbanization is rapidly goingon mainly in hill and high ground zones and urban lots are extended to thirty five percent inarea for these ten years.The flood runoff analyses are performed for heavy rain storms in July, 1972, and Augnst, 1959, under both land states in 1972 and 1959, by applying the kinematic surface runoff modelfor a non-inundation zone and the dynamic tank model developed by the authors for the backwater region of a channel and the inundation zone.The urbanization effects are evaluated quantitatively by the form of changes in the runoffvolume, the peak discharge or water level at a point and the operation time of a pump. It isalso mentioned of the flood control effect of paddy field extant along the River Furu which isthe drainage channel of hill and high ground zones.

There remain many problems unsolved in the application of the mathematical optimizationtechniques to the parameter identification of the series tanks model with sixteen unknown parametersfor runoff analysis. This paper discusses some of these problems fundamentally by the techniquesof numerical experiment. The results are summarized as follows:1) The chi-square criterion is generally recommended as the objective function for the pur-pose of finding a set of optimum parameters of the model.2) The efficiency of the SP method (Standardized Powell method) is sometimes affected bythe ordering of variables.3) The SP method by an optimum ordering system may be more powerful than the SDFPmethod (Standardized Davidon-Fletcher-Powell method) for the purpose.4) The true model is easily searched by using the data of drought years, but not by the onesof rainy years.5) The efficiency of the standardization system is not seriously affected by the initial set ofparameters chosen in the common sense.

In order to investigate basically the processes of rainfall infiltration, surface and groundwaterrunoff in connection with soil moisture behaviour, a slope lysimeter was constructed in 1970. Thispaper describes the detail of the lysimeter equipments, the physical characteristics of soil filled upin the lysimeter.The lysimeter has four containers of 7.0 m in length, 1.45 m in width, 1.7 m in depth and 5%in slope. Two kinds of sandy soil have been filled up in two blocks, each of which is composed oftwo containers. The physical characteristics relating to soil moisture movement were measuredby special apparatuses designed by the authors.Hydrological observations have been carried on under the bare slope and natural meteorologicalconditions since July, 1971.

A peculiar type of urbanization due to the plan of arterial road networks isforecasted in the Ogura basin located in the south of Kyoto.Several countermeasures against changes of flood runoff due to the urbanizationin recent years have been completed or are continuing in this area, such as theconstruction of the Kumiyama Pump Station with a pump of 30 m3/s in 1973 and thechannel improvements to the River Furu since 1971. In addition, as a momentumwith the flood disaster caused by record heavy rainfall in July, 1986, a pump of 30m3/s was added in the Kumiyama Pump Station in 1987 and the construction of anew pump station is being planned at the upper stream of the River Furu. Thesemeasures, however, are derived on the basis of the present urbanization of the area.This paper discusses the influence of this peculiar urbanization on flood risk bysetting several urbanization stages such as Future I-IV, on the basis of floodsimulation by the kinematic runoff model and the diffusive tank model. Further-more, several countermeasures for every stage of the urbanization are examined bythe simulation model.