Sakawa River

A river that flows through the Ashigara Plain in western Kanagawa Prefecture. It is 46 km long and has a drainage area of ​​582 square km. It originates from two rivers, the Ayuzawa River, which collects water from the eastern slope of Mt. Fuji, and the Kawauchi River in the western Tanzawa Mountains. In Matsuda Town, it joins the Shijuhasse River, which flows down from the western part of the Hadano Basin, and empties into Sagami Bay in Odawara City. In the past, it was also called the Mariko River. This river carries a large amount of sediment, and has created an alluvial fan over almost the entire Ashigara Plain, with deltas only found in a small area near the river mouth. Floods have occurred frequently since ancient times, but it is well known that the main stream was blocked by volcanic ash that fell during the eruption of Mount Hoei in the mid-Edo period, and then flowed out all at once during the rainy season the following year, breaking the levee at the valley mouth, and it took 18 years to restore. It is also widely known that a flood that occurred downstream in the late Edo period caused great hardship for the affected villages, but they were rebuilt using Ninomiya Sontoku's Houtokushiho method. Modern industries such as film, photographic materials such as photographic paper, textiles, and printing were developed in the downstream basin, using the abundant underground water from the alluvial fan. In addition, in order to secure water resources within Kanagawa Prefecture, the Sakawa River Comprehensive Development Project was carried out, which built the Sakawa Dam (Miho Dam when completed) upstream of the Kawachi River to store water and then took water from the Iizumi Water Intake Weir downstream. The Sakagawa River has also long been known for its abundance of natural sweetfish, making it one of the best fishing spots in the metropolitan area.

[Yukio Asaka]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

神奈川県西部の足柄平野(あしがらへいや)を流れる川。延長46キロメートル。流域面積582平方キロメートル。富士山東斜面の水を集める鮎沢(あゆさわ)川と、丹沢(たんざわ)山地西部の河内(かわうち)川の2川を源とし、松田町で秦野(はだの)盆地西部から下る四十八瀬(しじゅうはっせ)川をあわせ、小田原市で相模(さがみ)湾に注ぐ。古くは丸子(まりこ)川ともよばれた。この川は土砂の搬出量が多く、足柄平野のほとんど全域にわたって扇状地をつくり、三角州は河口近くの小地区にみられるにすぎない。そして、昔からたびたび洪水が起こったが、江戸中期の宝永(ほうえい)山の爆発のときに降った火山灰で本流がせき止められ、それが翌年の梅雨期の増水で一挙に流出し、谷口部の堤防を決壊し、復旧に18年間もかかったことは有名。江戸後期に下流部で起こった洪水では被災村落がひどく困窮し、二宮尊徳(にのみやそんとく)の報徳仕法で復興したことも広く知られている。下流流域では扇状地の豊富な伏流水を利用して、フィルム、印画紙などの写真材料や繊維、印刷などの近代工業がおこった。また、神奈川県内の水資源確保のため河内川上流に酒匂ダム（完成時は三保ダム）をつくって貯水し、下流の飯泉(いいいずみ)取水堰(しゅすいぜき)で取水する酒匂川総合開発事業が行われた。また、酒匂川は古くから天然アユの豊富さで知られ、首都圏有数の好釣り場となっている。

［浅香幸雄］

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