1990.12.13

1988 (O) 791

Minshu Vol. 44, No. 9

Judgment concerning the defects in the administration of rivers for which new repair and maintenance were found unnecessary according to the Basic Plan for the Implementation of Construction Works

Case seeking compensation for loss or damage

Judgment of the First Petty Bench, quashed and remanded

Tokyo High Court, Judgment of August 31, 1987

1. The existence or absence of defects in the administration of rivers for which new repair and maintenance works were found unnecessary according to the Basic Plan for the Implementation of Construction Works should be determined based on whether or not the safety is secured sufficiently to prevent the occurrence of disasters that are predicted from the normal action of running water in the case of a flood of a scale specified in the plan.

2. The existence or absence of defects in river administration in the case where it has become possible to predict the risk of occurrence of flood damage after the implementation of repair and maintenance works should be determined based on whether or not the failure to take measures against the abovementioned risk during the period starting from the time when it became possible to predict the abovementioned risk until the flood damage occurred, by taking into consideration various circumstances such as the scale of past flood damages, frequency of flood damages, causes thereof, nature of damage, state of rainfall, configuration of the basin and other natural conditions, state of use of the land, and other social conditions, the urgency of repair and the degree thereof as well as financial, technical and social constraints on river administration in line with the relevant case.

3. The existence or absence of defects in the administration of the river parts wherein a permitted structure exists in the river channel should be determined with respect to the entirety of the relevant river parts.

Article 2, paragraph (1) of the State Redress Act



State Redress Act

Article 2, paragraph (1)

(1) When damage to another person is caused because of a defect in the placement or administration of a road, river, or other public structure, the State or public entity shall assume the responsibility to compensate therefor.

The judgment in prior instance is quashed.

This case is remanded to the Tokyo High Court.

Reasons 1 to 10 for a final appeal stated by the counsels for final appeal

1. The outline of the facts determined in the judgment in prior instance is as described below.

(1) At the time of September 1, 1974, the appellants (except for appellants A1, A2 and A3) as well as D (successor in litigant's status from appellant A1), E (successor in litigant's status from appellant A2) and F (successor in litigant's status from appellant A3) resided in the protected lowland area of district b, Komae City, Tokyo, along the left bank of Tama River or owned a land and house, etc. at that place and suffered damages caused by the flood in question (the "Flood"). The appellee administered Tama River.

2. Tama River extends to three prefectures, i.e. Yamanashi Prefecture, Tokyo Metropolis and Kanagawa Prefecture, and has been designated as a class A river pursuant to Article 4 of the River Act in 1966. Tama River has nine intake weirs for agro-industrial water around the middle basin. Recently, areas around the middle basin, including district b mentioned above, have been developed into residential areas at a rapid speed and areas around the middle and downstream basin have also become areas with high population density.

3. District b mentioned above is located in a place where Tama River slightly changes its direction from southeast to east and weir c (hereinafter referred to as the "Weir") is established in a river channel which is approximately 360m wide stretching over the district and the land ahead. In addition, from around 1934 to 1935, conventional banks were enlarged and new banks were constructed in areas in the vicinity of that district and the land ahead, thereby new banks were formed in sequence on the river side of the conventional banks in the vicinity of the left bank of the Weir. As a result, part of the conventional flood channel lying between the new banks and conventional banks became a protected lowland area, and in 1951 the Tokyo governor abolished the official use of river site with respect to the abovementioned portion.

On July 20, 1966, the Ministry of Construction formulated a Basic Plan for the Implementation of River-system Construction Works for Tama River (hereinafter referred to as the "Basic Plan"). According to the Basic Plan, the design high-water level of the area in the vicinity of district b mentioned above was specified to be 4,170m3 per second and the river part in the vicinity of this district was included in the repair work completed section under the Basic Plan; no repair plans were newly developed before the disaster in question (the "Disaster") occurred.

4. The Weir was developed by improving the water intake facility using conventional temporary structures such as wire cylinders made from bamboo for the purpose of water irrigation to areas around the downstream basin of the right bank and was completed by Kanagawa Prefecture in 1949 by obtaining permission from the Tokyo governor, who was the then river administrator (Articles 17 and 18 of the former River Act) in 1947. Later, the authority to administer the Weir was transferred to Kawasaki City. The Weir, which is 3.1m high and 297m long, was established across the river channel from the abovementioned district b and the land ahead to district c, Kawasaki City, Kanagawa Prefecture, and the land ahead on the right bank side. It was a permeable dam having a wicket consisting of quintuple gates and a five-tier stair-like fixed portion which was 200m long on both the right and left banks. The right bank side of the Weir was fixed to the levee immediately downstream from the water intake, while on the left bank side of the Weir, the extended part of the fixed portion was fitted into the underground of an approximately 45m wide flood channel for a length of 15m oriented towards the main body of the levee from the low-water revetment, and its upper edge was located approximately 1m below the ground surface of the flood channel. In addition, on the low-water channel side of the flood channel in the left bank to which the Weir was fixed, small levees: three sides of which were covered by stone-lined concrete, were established from a point approximately 260m on the upper stream side of the Weir to the point approximately 20m on the downstream side along the side edge, the front slope of the small levees was structured in an integrated manner with the low-water revetment which was covered by stone-lined concrete and which extended from the upper stream to the downstream of the Weir.

5. In the Tama River basin areas, it started raining from the night of August 30, 1974, and the rainfall became heavier from around 7:00pm on August 31, 1974, and didn't stop until the evening of September 1, 1974. This rainfall caused increased running water from August 31, 1974, in the vicinity of the Weir, eventually destroying part of the revetment of the attaching portion in the downstream on the left bank of the Weir around noon of September 1, 1974. Later, the small levees were also destroyed, causing overflow water from the small levees on the upper stream part of the Weir and loss of filling earth from the damaged parts of the abovementioned revetment of the attaching portion. As a result, the coating works of the revetment, which had become hollow as a result of loss of filling earth, were repeatedly damaged, promoting damage to the revetment, while causing erosion in the flood channel of the attaching portion mentioned above from the downstream to the upper stream and promoting damage to the small levees. In addition, as a result of the action of the water current flowing down from the flood channel to the eroded part, the abovementioned erosion expanded and extended to the upper stream side of the abovementioned fit-in part of the Weir. Moreover, with the overflow water from the small levees, a watercourse detouring around the upper stream side of the abovementioned fit-in part was formed, and this detouring watercourse expanded as a result of the scouring action of the water current and eroded the foot of the slope of the main body of the levee. Later, the running water level became lower than the foot of the slope of the main levee but the depth of the detouring watercourse became lower than the bed height of the movable part of the Weir, and thus, the water force of the detouring watercourse continuously eroded the main body of the levee without any reduction in force, eventually breaking down and washing out the levee and thereby continuously eroding the protected lowland area. As a result, a disaster occurred from midnight of August 1, 1974 to 3:00p.m. of August 3, 1974, washing out an approximately 3,000m2 residential area in the protected lowland area and 19 houses owned or resided by the appellants (hereinafter referred to as the "Disaster"). The total amount of rainfall from its start to end was the largest scale since 1913 and the scale of the flood was almost the same as those of the floods, etc. that occurred in 1910 and 1947.

6. The revetment of the attaching portion on the left bank of the Weir was damaged by the floods that occurred in 1958 and 1965. In 1965, there was no overflow from the small levees but the revetment of the attaching portion and small levees in the downstream on the left bank of the Weir were damaged and a cavity was generated as a result of the filling earth in the tip of the breaking hole of the small levees being washed out; the state of this disaster was almost the same as the initial state of the Disaster. In both cases, the scale of the flood was far below the design high-water level described in the Basic Plan, which was later developed, and repairs made after the disasters were limited to construction works to restore the facilities to their original shapes and structures.

7. The main body of the Weir, revetment of the attaching portion of the Weir, small levees and connection form of the main body of the Weir, the protection works of the flood channel, etc. cannot be said to have been incompatible with the safety standard for structures under the technology level as of 1949, when the Weir was established. However, it may be interpreted that the general technology level in river engineering at the time of the Disaster following the subsequent improvements in disaster prevention technologies is shown in the eighth draft of the Cabinet Order on Structures, which had been prepared as a draft of the Cabinet Order on Structure of River Administration Facilities, etc. based on Article 13, paragraph (2) of the River Act and was then tested. According to such draft, at the time of the Disaster, the structures of the Weir and the revetment of the attaching portion were in a state where they could not be recognized as being sufficiently safe against the normal action of running water. Specifically, the Weir was in the following state: [i] the weir height had become high beyond necessity; [ii] there was room to improve the ratio of the movable part of the weir to the length of the main body of the weir; [iii] it had become clear that the fixed part of the weir was in a condition causing hindrance to the flow of running water due to being installed in the cross-section area of running water of the design high-water level; and [iv] there was room to improve the coating works of the revetment of the weir attaching portion. These flaws caused the Disaster.

II. The court of prior instance dismissed the appellants' claims based on the abovementioned facts. The summary of the reasons is as described below.

1. Repair projects as described in the Basic Plan are incomplete throughout the country and even river parts for which repairs have been completed under the abovementioned plan only have safety against floods of a design high-water level for overflow-type breaking of levees and are not completely free from the risk of permeation-type breaking of levees or scouring-type breaking of levees caused by river channel damage. Accordingly, even river parts for which repairs have been completed under the Basic Plan are not guaranteed to have absolute safety against a flood with a flood discharge less than the design high-water level and fall under the category of insufficiently improved rivers which require further repairs to realize an ideal river administration. In addition, there are characteristic features and various constraints in river administration as presented in the judgment rendered in what is generally called the Daito flood damage lawsuit (the judgment of the First Petty Bench of the Supreme Court of January 26, 1984, Minshu Vol. 38, No. 2 at 53), and thus, the transient safety presented in the abovementioned judgment is sufficient for the safety required of rivers for which repairs have been completed under the Basic Plan.

In addition, the details of the transient safety mentioned above should be determined according to the determination criteria presented in the abovementioned judgment (the criteria described in III.1. below).

2. Generally, it is not preferable to have structures in river zones in terms of water control, and it is necessary to adjust the proper use of river and the purpose of water control. Thus, establishment of structures is subject to the relevant river administrator's permission (Article 26 of the River Act and Article 17 of the former River Act). While river administrators should give permission based on the premise that sufficient response measures that are found safe against the normal action of running water are provided, in light of the knowledge and technology level in river engineering as of the time, once a structure is established based on a permission, river administrators bear the responsibility to secure river safety under the given condition that such structure has been established.

A permitted structure established by a person other than the river administrator will be maintained and administered independently from the river by the person who has received permission for establishment but the river administrator still has the right to impose a supervisory disposition (Article 75, paragraph (2) of the River Act). Thus, if a river disaster is caused by any flaws inherent in a permitted structure, the river administrator will not be exempted from liability even if he/she was not directly involved in the maintenance and administration of the permitted structure. In addition, if the safety of river is impaired by any flaws inherent in a permitted structure, the river administrator may respond by issuing an order for repair of the structure based on the right of supervisory disposition or by implementing repair and enhancement works for the river facilities he/she administers or by using both such measures. However, there are constraints on issuing the abovementioned repair order such as the necessity to meet the given requirements. Nevertheless, there is no substantial difference in the characteristic features of river administration and the degree of various constraints associated therewith based on whether the subject to administration is a permitted structure or a river administration facility. Therefore, even if a permitted structure is the subject of administration, the existence or absence of defects in river administration should be determined based on whether transient safety is ensured or not.

3. As described in I.7 above, there was room for improvement of the Weir at the time of the Disaster. However, there are generally technical constraints in changing the structure each time in association with the improvement of the technology level while maintaining the functions of permitted structures once established, and also the social drawbacks of substantially increasing the costs to be borne by administrators. As such, except for the case where it is specifically and clearly predicted that neglecting technological backwardness would cause disaster to a protected lowland area, if the river part in which a permitted structure is located, as a whole, is found to have the safety level approvable in light of general standards for river administration and socially accepted ideas, it is unnecessary to immediately take improvement measures to adapt to the latest technological level and would be sufficient to reconstruct the permitted structure to adapt to the technological level at that time during any appropriate opportunities such as reconstructions to be made at a later date.

The requirement for issuing an improvement order based on the river administrator's right of issuing a supervisory disposition as prescribed in Article 75, paragraph (2), item (v) of the River Act, which stipulates that "when there is unavoidable necessity concerning public benefits," refers to the case where it is specifically and clearly predicted that neglecting a technological backwardness would cause a disaster in a protected lowland area or would at least lead to a situation where the river part in which a permitted structure is located, as a whole, is found to lack the safety level approvable in light of general standards for river administration and socially accepted ideas.

Accordingly, in determining whether or not any defects can be found in the river administration in relation to the fact that improvement measures were yet to be started, even if a permitted structure is the subject of improvement measures, it would be sufficient if the existence or absence of what is generally called transient safety is examined with respect to the river part in the vicinity as a whole, as in the case where the river itself or the river administration facility is the subject of improvement measures.

4. During the past 25 years from the completion of the Weir to the occurrence of the Disaster, no disaster caused by flood affecting the protected lowland occurred in the vicinity of the Weir. In the vicinity of the Weir, running water was gently curving but the course of river was stable and the running water did not hit the left bank. Moreover, there was a flood channel that was as wide as approximately 45m and thus, it had a configuration from which one could hardly imagine that any impact would be caused to the main body of the levee even if the revetment of the attaching portion on the left bank of the Weir was damaged; no one suggested the possibility of occurrence of a disaster such as the one that occurred in this case. In addition, even if the high necessity of conducting repair works arising from the fact that areas around the river basin were urban areas is taken into consideration, in light of the facts that the river facilities in the Tama River basin were maintained at a high rate in comparison to other rivers and that not a few parts of the urban river parts of the Tama River system were under repair based on repair plans, in order to find the necessity to implement repair works in the surrounding areas of the Weir on a priority basis, there must have been special circumstances supporting the urgent necessity outweighing that of other parts. Furthermore, in general, when taking into account that there are social constraints such as the necessity to obtain consent from person with the water right to implement repair works of a weir or the adjunct facilities thereof, unless there are special circumstances such that it can be specifically and clearly predicted that neglecting the current condition would cause a disaster in a protected lowland area, no defects can be found in river administration in relation to the river administrator's failure to order improvement of a permitted structure or to implement repair works of the river by itself.

5. As such, with regard to Tama River around the Weir before the Disaster, when examining whether or not there were any situations where it could specifically and clearly be predicted that neglecting the current condition would cause a disaster in the protected lowland area, a positive determination cannot be made as described below.

It was predictable that the revetment of the attaching portion, flood channel and small levees, etc. in the left bank of the Weir would be affected by a flood of a scale at the design high-water level. However, even if it could be predicted that the individual structures in the river channel would be affected by a disaster, such prediction is different from predicting the possibility of such disaster developing into a disaster affecting the protected lowland area. Moreover, Japan had never experienced a disaster where the filling earth of a revetment and small levees of a part which was not exposed to water was scoured by colliding water, destruction of small levees proceeded beyond the fit-in part of a weir, a flood channel was eroded from the downstream to the upper stream and a detouring water course was formed, as in the case of the Disaster, and thus, the mechanism of occurrence of the Disaster could not have been predicted from the knowledge of river engineering that was available before the Disaster occurred. In addition, the partial breakage of the revetment on the left bank of the Weir in 1958 and that of the revetment and small levees in 1965 were both caused by a flood of a scale far below the design high-water level. Although the situation of disaster in 1965 was almost the same as the initial situation of the Disaster, as of the time of the Disaster, there was no knowledge on the following facts: when running water in the flood channel flows into a broken part of the revetment of the attaching portion in the downstream of the Weir, erosion will rapidly proceed to the upper stream direction, and the filling earth of the small levees, which are not affected by colliding water, will be washed out. Furthermore, it was impossible to predict the occurrence of the Disaster even based on the experience of past disasters in other rivers.

6. For the reasons described above, there were no special circumstances where it could be specifically and clearly predicted that neglecting the current condition would cause a disaster in the protected lowland area before the Disaster. Therefore, Tama River around the affected parts in question had the safety level approvable in light of general standards for the administration of rivers of the same kind and scale and socially accepted ideas, and no defects can be found in river administration in relation to the fact that improvement measures were yet to be started.

III. However, the abovementioned determination cannot be upheld for the following reasons.

1. The defects in the placement or administration of a public structure as prescribed in Article 2, paragraph (1) of the State Redress Act refer to a state where the public structure lacks the safety level which it should normally have and is likely to cause harm to others. Existence of such defects should be determined in a specific and individual manner by comprehensively taking into consideration various circumstances such as the construction, use, locational environment and state of use of the public structure. Administration of rivers is not started on the premise that they have the normally required safety level from the beginning but instead is expected to gradually improve their safety level through water control projects. Thus, even if a river does not have the safety level sufficient enough to prevent flood damages which can normally be predicted and avoided, a defect cannot be immediately found in the river administration and there is no choice but to find that the safety level required of a river is that corresponding to the stage of repair and maintenance works of the river in the process of water control projects that have generally been performed. It is appropriate to interpret that the existence or absence of defects in the administration of rivers should be determined by comprehensively taking into consideration various circumstances, such as the scale of past flood damages, frequency of flood damages, causes thereof, nature of damage, state of rainfall, configuration of the basin and other natural conditions, state of use of the land, and other social conditions, the urgency of repair and the degree thereof, and based on the standard as to whether or not the river has safety level approvable in light of general standards for the administration of rivers of the same kind and scale and socially accepted ideas under various financial, technical and social constraints in river administration (the judgment of the First Petty Bench of the Supreme Court of January 26, 1984, 1978 (O) No. 492, No. 493 and No. 494, Minshu Vol. 38, No. 2 at 53; the judgment of the First Petty Bench of the Supreme Court of March 28, 1985, 1982 (O) No. 560, Minshu Vol. 39, No. 2 at 333). The abovementioned criteria for determining defects in river administration presented by the court of this instance should be applied to this case and thus the part of the determination made by the court of prior instance suggesting this point should be found justifiable.

2. During the period after the development of the Basic Plan and until the Disaster occurred, new repair and maintenance works were found unnecessary for the river parts in question (the "River Parts") in light of the matters specified in the Basic Plan. Thus, they can be regarded to be in the same conditions as rivers for which repair and maintenance works were conducted in accordance with the Basic Plan for the Implementation of Construction Works. In this case, the defects in the administration of such river parts are in question.

The safety level corresponding to the stage of repair and maintenance works, as regards rivers for which the Basic Plan for the Implementation of Construction Works was developed and repair and maintenance works have been conducted in accordance with said Basic Plan or for which new repair or maintenance works were found unnecessary in accordance with said Basic Plan, should be interpreted as referring to a safety level sufficient to prevent the occurrence of a disaster which is predicted from the normal action of running water in a flood of a scale specified in said Basic Plan. In light of the characteristic features of river administration presented in the determination criteria described above, rivers for which repair and maintenance works have been conducted should have a safety level sufficient to prevent the occurrence of flood damages which can be normally predicted and be avoided in light of the level of disaster prevention technologies at the time based on a flood of a scale assumed at the stage where such repair and maintenance works were conducted. This is because defects in river administration cannot be questioned even if flood damage has occurred but the risk of occurrence of such flood damage could not have been normally predicted from a flood of a scale assumed at the stage where repair and maintenance works were conducted for the river.

In addition, even if the risk of occurrence of a flood damage could have been normally predicted at the time of occurrence thereof, if the abovementioned risk could not have been predicted at the stage where repair and maintenance works were conducted and such prediction became possible as a result of changes in the environment of the river and river basin after such repair and maintenance works were conducted, increase in the knowledge in river engineering or improvement of disaster prevention technologies, defects cannot be immediately found in river administration. This is because there are various constraints on river administration as shown in the abovementioned determination criteria regarding taking measures to remove or diminish the abovementioned risk and a reasonable period of time is required to take the abovementioned measures, and moreover, whether the failure to take measures against a risk which could have been predicted from the time when it became possible to predict that risk until the occurrence of the water disaster falls under defects in river administration should be determined by taking into consideration the various circumstances and constraints shown in the abovementioned determination criteria in line with the relevant case.

3. Next, in this case, the Weir, which is a permitted structure, existed in the river channel prior to the development of the Basic Plan and erosion occurred in the flood channel due to the flaws in the Weir and revetment of the attaching portion thereof upon the occurrence of a flood of a scale at the design high-water level specified in the Basic Plan, eventually resulting in the breaking of the levee.

As described above, the existence or absence of defects in river administration with respect to river parts in which a permitted structure exists should be determined based on whether or not the river parts, as a whole, have the safety level shown in the abovementioned determination criteria and should not be determined based solely on the necessity of conducting repair works for the abovementioned structure by separating the administration of the abovementioned structure from that of the river parts as a whole. When a permitted structure other than a river administration facility exists in a river channel, as explained by the court of prior instance, a river administrator is responsible to secure safety of the river through exercise of the right to issue supervisory disposition for the structure or implementation of repair and improvement works for the river facilities which it administers, on the condition that the abovementioned structure exists, even if the river administrator does not have the right to administer the structure itself. This is because, when the safety level which the river part should have has come to be impaired due to flaws in the structure and other requirements are satisfied, defects should be found in the river administration with respect to the river parts in which the abovementioned structure exists.

In addition, needless to say, even if repair and maintenance works are conducted only for a permitted structure or river administration facilities connected thereto to remove or diminish a risk arising from the existence of the structure, there are various financial, technical and social constraints presented in the abovementioned determination criteria. However, the degree of such constraints should normally be considerably smaller in comparison to that in the case where river administration facilities existing in broader river basins are to be repaired and maintained, and thus, the abovementioned circumstances should also be taken into consideration in determining the existence or absence of the safety level presented in the abovementioned determination criteria.

4. When examining this case based on the explanations made above, the following findings can be made.

The necessity to conduct new repairs and maintenance was not found for the River Parts in light of the matters specified in the Basic Plan after its formulation, and thus, the scale of a flood assumed at the time of occurrence of the Disaster should be a flood of a scale at the design high-water level specified in the Basic Plan. The issue in this case is whether or not there were any defects in the river administration regarding the River Parts as a whole including the Weir in relation to the breaking of the levee that occurred in the River Parts due to the flaws in the Weir and the revetment of the attaching portion. Accordingly, in examining the existence or absence of defects in river administration in this case, it should first be examined whether or not it could have been predicted that breaking of the levee would be likely to occur in the River Parts due to the flaws in the Weir and revetment of the attaching portion from the normal action of the running water of a scale at the design high-water level specified in the Basic Plan. If this is affirmed, after determining the point of time when the abovementioned prediction became possible, it should be specifically determined in line with this case, as to whether the failure to appropriately take such measures as the exercise of the right to issue a supervisory disposition with respect to the Weir or implementation of repair and maintenance works for the river administration facilities connected to the Weir had led to the situation where the River Parts lacked the safety level approvable in light of general standards for the administration of rivers of the same kind and scale and socially accepted ideas, even if various constraints presented in the abovementioned determination criteria are taken into consideration from the time when prediction of such risk became possible before the time of occurrence of the Disaster.

5. However, in applying the abovementioned determination criteria, the court of prior instance failed to make the following consideration or examination: [i] although it should have been taken into consideration whether the River Parts had a safety level corresponding to the stage of repair and maintenance works therefore as described above, the court failed to make such consideration, while finding that the River Parts were those for which repair works had been completed under the Basic Plan but regarding them to be in the same condition as insufficiently repaired rivers; [ii] although the differences in the method of river administration and various constraints associated thereto between permitted structures and river administration facilities should have been taken into consideration when examining the existence or absence of defects in river administration with respect to the River Parts as a whole, in this case where a disaster occurred in the river parts in which a permitted structure existed, the court failed to make such consideration, while holding that no substantial difference can be found in the characteristic features of river administration and degree of various constraints associated thereto depending on whether or not the subject of administration is a permitted structure or a river administration facility; and [iii] although it should have been specifically examined in line with this case as to whether a disaster in the protected lowland area could have been predicted based on the normal action of a flood of a scale at the design high-water level specified in the Basic Plan as of the time of the Disaster, the court failed to make such examination, while establishing its own criteria that measures such as the exercise of the supervisory right or improvement and maintenance to address flaws in a permitted structure or river administration facilities connected thereto are required to be taken "when it is specifically and clearly predicted that neglecting the current condition will cause a disaster in the protected lowland area," and holding that this case does not meet the criteria described above. In conclusion, the court of prior instance determined that there were no defects in the river administration in question.

As such, the determination made by the court of prior instance is one which only denied defects in the river administration in question without applying the abovementioned determination criteria and making examination in line with the specific case with respect to the safety level which the River Parts should have had as a whole, including the Weir and the revetment of the attaching portion, although it should have made such application and examination; the court of prior instance erred in the construction and application of Article 2, paragraph (1) of the State Redress Act and its determination must be found illegal for failing to thoroughly examine the defects in the administration of rivers. Moreover, the facts determined by the court of prior instance are insufficient to find that the facts related to the abovementioned explanations were found based on the flaws in the Weir and the revetment of the attaching portion.

4. For the reasons described above, the abovementioned illegality in the judgment in prior instance obviously affects the judgment and the arguments claiming this intent are well-grounded. The judgment in prior instance should inevitably be quashed without the need to determine the remaining points. In addition, in this case, it is appropriate to remand this case to the court of prior instance to have these points explained above be further examined.

Accordingly, in accordance with Article 407, paragraph (1) of the Code of Civil Procedure, the Court unanimously decides as set forth in the main text.

Justice OHORI Seiichi

Justice TSUNODA Reijiro

Justice OUCHI Tsuneo

Justice YOTSUYA Iwao

Justice HASHIMOTO Shirohei