本研究は、（明治29年(1896)7月洪水）以降の明治30年(1897)から昭和30年(1955)までの59年間の年最大二日雨量について、近年の代表的な台風性と前線性の複数洪水の中から、降雨特性が類似した近年洪水を選定し雨量の時間分布を仮定して、流出計算により年最大流量を推定するとともに、推定した流量群に、先に推定した洪水最大流量、昭和31年(1956)から現在までの年最大流量をくわえ、連続した105個の標本をもとに水文統計処理し、洪水の流量確率を求め、洪水の位置づけを明らかにするものである。

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本研究は， (明治29年 (1896) 7月洪水) 以降の明治30年 (1897) から昭和30年 (1955) までの59年間の年最大二日雨量について，近年の代表的な台風性と前線性の複数洪水の中から，降雨特性が類似した近年洪水を選定し雨量の時間分布を仮定して，流出計算により年最大流量を推定するとともに，推定した流量群に，先に推定した洪水最大流量，昭和31年 (1956) から現在までの年最大流量をくわえ，連続した105個の標本をもとに水文統計処理し，洪水の流量確率を求め，の洪水の位置づけを明らかにするものである.

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This study is conducted as part of the study on estimation of the peak discharge of “the Yokota-Gire Flood” in July 1896, one of the historical floods in the Shinano River Basin. This study analyses relationship between rainfalls and discharges of relatively large floods since 1956 with well recorded rainfalls and flood discharges, and particularly compares the Yokota-Gire Flood with the flood in September 1982, in which the similar amount of rainfall was recorded despite the difference of the number of precipitation stations exists. Making clear the characteristics of hourly and spatial distribution of the rainfalls which caused large floods in the Shinano River Basin, not only helped to improve the accuracy of the peak discharge estimation of the Yokota-Gire Flood and to verify its validity, but also clarified the statistical positioning of the Yokota-Gire Flood through rainfall characteristics.

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This study estimated the safety degree of flood control at Yattajima, the Tone River, Japan to verify effects of additional dams. Rainfall events considered are Catherine Typhoon in 1947, Ise Bay Typhoon in 1959, the Typhoon No. 15 in 1981, and the Typhoon No. 5 in 1998. The storage function method was used for runoff analysis, which showed good agreement between observed and computed discharges. Using the spatiotemporal rainfall pattern of Catherine Typhoon, this study simulated rainfall-runoff at each time stage; 1959 with two dams, 1981 with five dams, and 1998 with six dams (the same as present situation), and evaluated the effect of these added dams on flood control in terms of the decrease of peak discharge at Yattajima. The decreases estimated were 513-1, 253 m³/s for the 1959 situation; 2, 025-2, 765 m³/s for 1981; and 2, 233-2, 973 m³/s for 1998. It is also verified that the present situation with six dams can cope with 200-year floods, which is significant improvement because the past situation without dams could cope with 100-year floods.

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The author clarified the characteristics of the Tsurumi River Flood Prevention Cooperative, located in urbanized area in the middle and lower reaches of a small river, judging from the standpoints of imposing on the expense. But she has not referred to those of cooperatives located in agricultural area in the lower reaches of a large river. Then she intended to clarify the characteristics of the Johgoh Flood Prevention Cooperative located in the lower reaches of the Shinano River from the view points of analyzing cooperative rules and Its system of determining the membership fee. As a result of analyzing its rules, it was revealed that the Johgoh Flood Prevention Cooperative bore a close parallel to regular water use cooperatives, and that it has an obligation to bear the expense of river improvement works of Shinkawa Drainage Regular Water Use Cooperative. As a result of analyzing its system of determining the membership fee, it was revealed that frequently inundated arears nearby intake works of drainage rivers are highly imposed. On the contrary less inundated areas nearby irrigation rivers situated at comparatively high ground are less imposed. Consequently the frequency of inundation caused by shortage of irrigation water prescribes the grades of imposition. The reasons are as follows: first the difference between regular water use cooperatives which aimed for irrigation and flood prevention cooperatives which aimed for flood controll cannot be definitely clarified yet. Because irrigation and drainage are not separated in the low and marshy area under study. Second, when prefectural river improvement works came into operation in the study area after the enforcement of Water Act, the Johgoh Flood Prevention Cooperative was established as the one to bear local expenses allocated for the works. It could get higher rate of prefectural subsidy and bigger authority than regular water use cooperative. Therefore, the Johgoh Flood Prevention Cooperative with such given financial aid and authority has accomplished the river improvement works of itself and the improvement works which the Shinkawa Drainage Regular Water Use Cooperative was supposed to accomplish. And this put an end to the troubles in connection with drainage between two cooperatives for long years.

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明治時代は列強諸国に追いつくために，富国強兵や国土開発が盛んに行われた。そのなかで，基幹政策となる水管理事業では，度重なる水害（明治三大水害など）に対して，順調に治水体制や治水施設の整備が行われた。治水制度として，河港道路修築規則の制定が行われ，事業として直轄の低水・高水工事が始まり，治水に重点が置かれた事業が展開された。日本人技師による築堤や放水路建設が特徴的で，治水においても近代化へ進んでいった。河川改修工事では機械化が図られ，行政主体の水防活動が行われた。このように，当時の水害，治水技術，洪水対応技術などをはじめとする明治時代のすぐれた水管理技術を調べて，水管理に関する経験や実績より，現代でも有効な考え方や技術を整理・分析した。

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Once, Niigata was the Canal City. The canals covered the town and rowboats were coming and going. However, these canals were filled in at the time of the rapid economic growth of the Showa 30s. Although the reclamation of the canals and the Shinano River have an important meaning in Niigata's city formation, there is no detailed research, studies nor data on this process. In this research, the process in which the canals are lost from Niigata is clarified toward the revitalization of the canals expected in the future.

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Frequently innundated Nishikanbara Area in Niigata Prefecture changed into fertile rice fields as a result of many flood control works. The main works are Ohkohzu Floodway of the Shinano River, improvement works of other small rivers and national irrigation and drainage improvement works in Nishikanbara Area.
In June, 1978 when these works were almost completed, a large-scale inundation caused by poor drainage occurred in Nishikanbara Area. At that time the drainage system consisting of many pumps controlled by Nishikanbara Land Reclamation Union was almost completed. Total amount of precipitation was over the maximum estimated by the drainage system. But damage of the flood that inundated only rice fields was much slighter than that caused by the past flood of the Shinano River.
In addition to low and swampy parts that have been frequently inundated, the author found a few new types of irregular inundation spots.
The first type is caused by land subsidence resulting from pumping up ground water including natural gas. This type of inundation was found on the left bank side of the Nakanokuchi River, and total amount of subsidence from 1951 to 1975 was from 100 centimeters to 220 centimeters. Annual amount of subsidence became much less but at present subsidence continues.
The second type is found on natural levees and comparatively high altitude spots. This type of flooding spots are located at terminations of small-sized irrigation waterways.
The third type is found at back swamps. This type of spots are located along small-sized drainage waterways or at terminations of them. These spots are also adjacent to collective tableware factories removed from central part of Tsubame City on account of pollution and enlargement of business.
The reasons of the second and third type of floods are presumed as follows.
1. Maintenance works of small-sized irrigation or drainage waterways became slack because of increasing part-time farmers and decreasing full-time farmers. Most of part-time farmers work for factories or companies located in near cities where they can commute.
Waterways covering large or medium-sized area are maintained directly by Nishikanbara Land Reclamation Union. However small-sized waterways which benefit the area below 20 hectare have to be maintained by landowners.
Futhermore farmers comming from other areas to cultivate their farm land in Nishikanbara Area have increased in number. They sold their farm land near their residential site in rapidly urbanizing area for example in Niigata City, and purchased substitutive farm land in Nishikanbara where they can come to work easily by car in a short time. They tend to neglect maintenance of irrigation or drainage waterways, since they are not habitants.
2. Diversion of agricultural land have progressed. This diversion area from 1967 to 1977 was 1133 hectare which came under 5 percent of Nishikanbara Area. Agricultural lands have been diverted into residential or factory sites. Especially in southern part of Nishikanbara Area, many rice fields were diverted into factories, because it is adjacent to Tsubame and Sanjo Cities noted for tableware industry. Drainage from these factories have increased and flowed into drainage waterways managed by farmers or Nishikanbara Land Reclamation Union.
Nishikanbara Land Reclamation Union began to allot the expense for drainage to factories and municipal corporations in 1973. It was one of the earliest attempt in Japan. Also all the member of Nishikanbara Land Reclamation Union must bear the running cost of drainage and irrigation pumps. The expense in 1978 increased by 6.91 times in comparison with that in 1968.
Countermeasure for flood is determined by a scale and feature of past big floods. But flexible countermeasures corresponding with changes of the area are needed.

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