At the early decade of this century, the warming of world-wide climate with its peak in the fifth decade, especially in the middle and high latitude regions in the northern hemisphere, was reported by some climatologists and meteorologists. It was also cofirmed in Japan by H. Arakawa (1936) for the period of fifty years preceding to 1935. In this paper, the writer intends to make clear the temperature trend for thirty years since 1936 as related to the world-wide change, influence of urban development on the secular variation of its temperature and some other subjects. The main results obtained are summarized as follows:
1) As is shown in Fig. 1., annual temperature in Tokyo is approximately expressed by the following simple equation,
θ=a+bt
where θ is an annual temperature for the t th year, a and b the numerical constants. In this paper t is reckoned in such a way as 1, 2, 3 ……for 1951, 1952, 1953……and -1, -2, -3, ……for 1950, 1949, 1948……respectively.
The same equation can be adopted at all the places in Japan. The most probable values for a and b are determined for fifty seven stations in Japan by the method of least squares (Table 1.)
Excepting a few places, magnitude of a which means the average annual temperature for this thirty years becomes larger than that for the preceding fifty years which is shown by the numerical figures enclosed by brackets. In Tokyo, for example, it grew up to 14.8°C or 0.9°C higher than the preceding period. Also as for b which means the average amount of temperature rise per year, similar trend is recognized with a more striking tendency.
Namely it increased very rapidly since the preceding period in some giant cities as are given in the following examples:
Tôkyô from 0.009° to 0.032°C/year
Ôsaka 0.015 0.029
Kyôto 0.010 0.032
Hence the magnitude of b grew up two-or threefold and at Kanazawa it became eighteen times larger.
2) As already mentioned, rapid increase of temperature was experienced in the entire world. Mitchell, J. M. (1961) calculated the average rise of temperature for the zonal areas between every ten degree of latitude. Meanwhile, the average increase of temperature at fourty eight places in Japan from Kagoshima in the south and Akita in the north between 30° and 40° N. was 0.8°C, which is nearly equal to the results obtained by Mitchell. In the northern part of Japan, mainly occupied by Hokkaido, however, temperaure for this period still increased against the remarkable decrease of average temperature for the belt area between 40° and 50° N. This was probably due to the fact that the greater part of this latitude belt was invaded by the cold air-mass from the Arctic region, whereas the Japanese Islands were left alone being covered by the relatively warm air tongue as is shown in Fig. 2. More important fad t is that the subsequent fall of temperature since about 1940 in many countries in the middle and high latitudes was far delayed in Japan, faintly appearing in the latest years of this period. It is probably concluded in Fig. 2. that the warming in Japan was maintained until recent years, not influenced by the cold air invasion now extending to the east and south and therefore, the winter cold in Japan might become more severe in the near future.
3) The fact that the development of urban temperature relates to the size and population of the city was confirmed by Duckworth and Sandberg (1954) in three cities with a mutually different area and population near the San Francisco Bay in the U.S. In this paper the urban size is represented by its population for convenience sake and it is clearly recognized in Fig. 3. that the increasing rate of temperature is closely related to the square root of population for the cities with a population of less than 500, 000.

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1. The delta plain of Nobi, one of the great delta plains in Japan, extends at the head of Bay of Ise and is formed by three rivers named the Kiso, the Nagara and the Ibi. These rivers run in braided streams on the delta, forming many islands like areas surrounded by their natural levees in the former times. These islands like areas had been developed into “Wadju”, the enclosed areas with a complete set of levees through adding artificial levees and modification of their river courses. Takasu Wadju, the biggest one located in the middle of the plain, was studied on the development of “Kabu-Ido” as they called, authorized artesian wells for irrigation by the community. The details of natural relief of the Wadju are as following: It has 0-3 meters in height above sealevel and is higher in the northeast portion (more than one meter high) and lower in the south-west portion (less than one meter high), contrasting each other.
2. Due to the recent land improvement taken place after World War II the labor productivity of rice agriculture has considerably been raised by means of water control enabled by mechanized pumping facilities for both irrigation and drainage. In the former times it was usual that the higher portion of the area had been suffered from drought and at the same time the lower portion from flooding. In addition to this, frequent break-downs of the levees by river floods had brought many difficulties to the inhabitants. For these accounts they made great efforts to bore artesian wells to get underground water for rice-fields and domestic use on the higher portion, while the people of the lower, always suffered from too much water, had continued to stabilize rice production by constructing “Horiageda” as they called, through lifting rice-field level higher with mud dug out.
As the artesian wells on the higher portion increased its number the increased amount of water discharged to the lower area intensified damages to rice plants due to deep water. It is natural that a dispute on the development of artesian wells had arisen between the inhabitants of the lower area and the higher, because the interest of artesian wells was entirely against each other. As the result of negotiation, a compromise was reached with the following terms that the people of the lower area recognized those wells already established as the authorized wells with some limitations, so called as “Kabu-Ido” on one side, and the people of the higher portion who had obtained benefit from those wells would pay charge for maintaining drainage canal and for improving its capacity as a compensation for the dis- charged water.
From this viewpoint “Kabu-Ido” is considered as a kind of social system of water utilization created on the opposition and contradiction of their interests conserning the irrigation water originated from artesian wells and its discharge among the inhabitants. This contradiction was based upon differences in height of the area.
3. The introduction of artesian wells into the Wadju area was at the earliest period of 19 century. It was the beginning of dispute when they bored many wells to get water at the great drought in 1852-1853 on the higher portion. The numbers of artesian wells were recorded so many as to attain to 484 in 1854, according to the investigation of Kasamatsu office belonging to the Central Government of Tokugawa which administered the works of irrigation. In negotiation among the inhabitants they agreed to set an investigation period extending over six years in order to examine whether these wells were to be continued or abolished.
Against to their expectation, it was favorable for rice production for the former three years, while it was unfavorable owing to bad weather for the latter three years.

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This research aims to clarify the actual conditions pertaining to recent inundation disasters in the southern part of Yamashiro Basin and to find out the means to prevent or diminish them.
This region is a valley plain which was formed by Kizu River. There are moreover, alluvial fan, natural levee and abandoned course. The area can be divided into ten landform types.
Due to the construction of a dam in the upper reaches of Kizu River and taking of the river sand, the river bed has become lower and as a result inundation disaster in the region has been somewhat reduced. However, this has had ill effects on the irrigation and drinking water.
The advancing urban use of land has produced new kinds of inundation disasters. They are as follows:
(a) Since large scale fill-ups are formed in regions which are often inundated the area and the time of the inundation disaster has changed very much.
(b) Arable land has become marshy area because of poor drainage caused by fill-ups.
(c) Inundation disaster occurs in totally new areas due to desolation or development of the upper drainage basin.
The advance of city people to the farm villages where they construct their houses has lessened the cooperative spirit of the old villages. This coupled with the reduction of labor force has promoted inundation disasters.
Inundation disaster occurs in flood plains, back swamps and abandoned courses but if this is analyzed minutely it does not necessarily conform with the configuration of the land sur-face. Rather, it is more closely related man-made constructions.
The following is a summary of the causes and areas of inundation disasters in this region and the means of preventing them.
(1) The back water of Kizu River causes damage to the areas along the dikes of the river. Sendo, Taga and Hirao are model examples. The damages in these areas will be solved if the drainage is moterized. But since the burden is largely on the farmers it could not be said that this is the best solution.
(2) Seepage water and upstream flood are remarkable in spots along Fudo River, Naruko River, Minamitani River, Tenzin River and Sibutani River through the right-hand area of Kizu River and in Yamamatsu River through the left-hand area. Dikes, full equipment in the river bed and digging of the river bed could possibly prevent seepage water but considered from the point of view of balance of the drainage basin the first solution is the safest.
(3) Tanabe, Tsukamoto, Kamikoma and Kizu are inundated when there is a flood because of incomplete construction of draianage channels. If the drainage channels are built straight, the inside widened and dug deeper floods can be reduced to a certain degree. However, if the gate which is directly connected to the drainage channel is not changed into a water pump a basic solution cannot be hoped for.
(4) The swamps formed by the fill-ups are distributed in Kizu, southern Kamikoma, Kusauchi and Terada. These artificial swamps have a very short formative history. Powerful and appropriate laws passed by the national and district administrative authorities are necessarty to lessen this problem.
(5) In Nagaike, Ikyuoka and Degaito the devastation or changes in the drainage basin causes inundation disasters. Like (4) this is man-made and there is no proper means of prevention besides appealing to the consciene of man.

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