Japan fisheries have caught about 400-500 thousands tons of tuna per year recently-equivalent to 62%-65% of the world's total catch. Tuna fishing plays a major role in total, and, although it had an early origin, it has prospered greatly in recent years. Since the abolition of the McArthur Line in 1952 following World War II, Japanese fishermen built larger boats and expanded their fishing grounds to include the Eastern Pacific, the South Pacific Ocean, and the Indian Ocean. This expansion of the industry was due mainly to the following-governmental policy (support and promotion); technical progress; enlargement of the overseas market and of the internal processing market for fish sausage; and the enlarged fishing companies which developed to catch tuna following on World War II.
The chief tuna ports are Misaki (Kanagawa prefecture), Yaizu, and Shimizu (both in Shizuoka prefecture) which together are responsible for 78% of Japan total tuna landing. I can find some facts illustrated in the table of the quantity of tuna landed at each port. While the amount landed in Misaki was the highest of three until 1954, it has declined in importance since 1957. Yaizu became pre-eminent in 1955. Shimizu began to increase after 1957 and left Misaki behind in 1961. Such changes in the volume of the tuna handled at these ports are caused by certain characteristics of each which reflect the growth of the tuna fishing industry.
Misaki, With its many powerful brokers, was a distributing centre for fish to Edo (Tokyo). Having a good natural harbour and being near to the fishing grounds, this port grew to a large tuna fishing centre particularly after 1928 when the new harbour was constructed and motor-powered boats gathered there. Great fishing companies with head offices in Tokyo, made this port their base for operations.
For this reason, and for the fact that Misaki was not damaged during World War II, it was the first to recover after the war. With the pioneer spirit brought from many old fishing villages before the war, the tuna fishermen expanded their fishing grounds to the Indian and Atlantic Oceans. Fishing boats catching tuna in the Atlantic, landed their catch directly to countries on the Atlantic sea-board. This resulted in a decline in the catch handled in Misaki, but, owing to changes in the cost structure of the Atlantic fishing, the boats again returned to Japan leading to an increase in 1966 and following years. However, Misaki handles mainly fresh and has poor facilities for precessing fish-a weak point.
Shimizu is more of a seashore industrial city than a fishing port. Originally it was the main port of the Tokai region, and following on the Meiji period, harbour works were carried out on a large scale, and many great plants were located here. Being near fishing grounds, fishing boats entered the port for landing their catch-mainly albacore with white meat which the Japanese dislike. Canning of the albacore, combining with the orange cultuation near Shimizu, prospered especially after 1928 when the export to U.S.A. commenced. The existence of such industries and the famous ship yards for fishing boats are conditions which favour Shimizu as a tuna-landing port. But the processing of fish is not so prevalent, nor are the brokers so powerful here. Tuna fishing boats of this port are comparatively large, but there are not such a great number.
As long-range fishing became common, and the landing of refrigerated tuna for export increased, Shimizu, of the three ports, became pre-eminent as a trading port. Many foreign trade companies extended their businesses to this port, and controlled many tuna fishing boats by loaning money to them. These companies land refrigerated tuna from fishing boats controlled by them to their own warehouses without passing through the fish market, and they export refrigerated tuna to Europe and North America by liners or their own

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最近の水害常習地は,宇治川下流右岸の淀駅周辺および東高瀬川・砂川合流点より名神高速道路に至る低湿地である。両地域共古代より流路の変遷や土地利用の変化が激しく,治水工事が繰り返されて現在に至っている。とくに宇治川下流の三川合流地点は,河道の付け替えと決潰の繰り返しにより,合流点がしだいに下流へ移動し,その付け替え跡である淀駅周辺の複雑な地形と,最近急速に進展した宅地化が,洪水災害の危険度を高める原因となっている。
宇治川・桂川・東高瀬川・鴨川に囲まれたうち水地帯の旧集落は,ほとんど例外なく自然堤防や旧河道の堤防跡,高い盛土上にさらに各家の能力に応じた嵩上げ工事を行なって建てられている。
昭和33年以後に速度をはやめた宅地化による流出率の変化に治水対策が追いつかず,浸水地区が増加する傾向が見られる。1967年には176mm/day程度の降水量のため各所で床下床上浸水の被害を受けている。これは宅地業者による利潤追求のみを目的とした宅地化がその要因であり,東高瀬川右岸一帯,宇治川右岸下流域の交通の便のよい安価な低地には,水害危険度の高い住宅地が多く見られる。
低地洪水災害に大きい影響を与える山手の宅地化は,雨水の流出率を非常に大きくし,治水工事計画変更の主因になっている。このためになされた東高瀬川の改修計画は,ある程度の効果を挙げうるものとみられ,それが完成すればたいていの豪雨(日雨量300mm/day以下)に耐えられるが,短時間降水(30mm/hr以上)に対しては高瀬川の改修のみでは浸水を防ぐことは不可能である。
洛南湛水排除計画は,計画基準に短時間降水をとらず269.7mm/3 dayを基準にしているため,これ以上宅地化が進行し,市街地が増加すれば大幅に計画を変更せねばならなくなる。
治水計画の参考となる危険地域の想定図によると,地盤高,排水能力,宅地化の進展,家屋密集度から見た悪条件が重なっている地域は,次の三か所である。(1)淀駅周辺,(2)新旧国道1号線の分岐点付近,(3)高瀬川と七瀬川の合流点。
以上の地域を中心とする宅地化の進展の傾向を早くつかみ,宅地化の後を追わず先を回るような計画を立てなければ,浸水災害問題の解消は望めないと思う。この研究がそのために役立つことを切に望むしだいである。

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