Sagami River

It originates from Lake Yamanaka in Yamanashi Prefecture, flows northeast through the Tsuru Basin, enters Kanagawa Prefecture, flows southeast, then turns south and empties into Sagami Bay. It is a Class A river. It is the largest river in Kanagawa Prefecture, with a length of 109 km and a drainage area of ​​1,680 square km. In Yamanashi Prefecture upstream, it is called the Katsura River, and after entering Kanagawa Prefecture, it becomes the Sagami River, and near its mouth it is also called the Banyu River. Along the way, it joins with tributaries such as the Doshi River, Nakatsu River, and Koayu River. River terraces have developed along the coasts of the main river and its tributaries. During the Edo period, the river was used as a waterway from the present Midori ward of Sagamihara to the river mouth, transporting rice, cocoons, timber, firewood, and charcoal, and transporting soy sauce, fish, dried sardines, and other goods downstream. After the Second World War, the Sagami Dam (Lake Sagami) and Shiroyama Dam (Lake Tsukui) were built and are now used for various purposes, including flood prevention, power generation, drinking water, industry, and agriculture. The upper and middle reaches of the river have long been known as sweetfish fishing spots, and the two new artificial lakes are popular as lakeside sightseeing spots in the Keihin area, as well as practice and competition areas for water sports (boating, canoeing, etc.). The river basin sewerage system project has almost covered the left and right banks of the middle and lower reaches, and projects are underway to convert the levees on both banks into multi-purpose levees that can be used as roads in addition to waterproofing, and to green the areas outside the levees and develop them into sports and recreational areas. Additionally, in the Miyagase area upstream of the Nakatsugawa tributary, there is the large Miyagase Dam (full operation began in 2001). Upstream in Yamanashi Prefecture, there are many scenic spots with waterfalls and rapids caused by lava erupting from Mt. Fuji. The old Sagami River bridge pier (Chigasaki City, nationally designated historic site) on the opposite bank of Banyu near the river mouth is made up of 11 large piles that emerged from the rice fields when the surrounding area subsided during the Great Kanto Earthquake, and is said to be a bridge built in the Kamakura period.

[Yukio Asaka]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

山梨県の山中湖に源を発し、都留(つる)盆地を北東へ流れ、神奈川県へ入って南東へ、さらに南に向きを変えて相模湾へ注ぐ川。一級河川。神奈川県内最大の河川で、延長109キロメートル。流域面積1680平方キロメートル。上流の山梨県では桂川(かつらがわ)とよばれ、神奈川県へ入ってからは相模川となり、河口付近は馬入川(ばにゅうがわ)ともいわれる。途中で道志(どうし)川、中津川、小鮎(こあゆ)川などの支流を合する。本・支流の沿岸に河岸段丘が発達する。江戸時代には、現在の相模原市緑(みどり)区から河口まで、下り荷では米、繭、木材、薪炭(しんたん)、上り荷ではしょうゆ、魚類、干鰯(ほしか)などの輸送水路として使われていた。第二次世界大戦後、相模ダム（相模湖）と城山ダム（津久井湖(つくいこ)）が建設されて、洪水防止をはじめ、発電、飲料、工業、農業用など多目的に利用されている。上・中流部は古くからアユ釣り場として知られ、新しい両人造湖は京浜の湖水観光地、また水上スポーツ（ボート、カヌーなど）の練習場、競技場としてもにぎわっている。中・下流の左右両岸地域に流域下水道事業がほぼ行き渡り、また両岸の堤防を防水のほか道路としても利用する多目的堤防に改造する事業、堤外地を緑化してスポーツやレクリエーション地区として整備する事業なども行われている。また、支流の中津川上流の宮ヶ瀬地区には大規模ダムの宮ヶ瀬ダム（2001年全面運用開始）がある。上流の山梨県内には、富士山の噴出溶岩にかかる滝や急流の景勝地が多い。河口に近い馬入の対岸にある旧相模川橋脚（茅ヶ崎(ちがさき)市、国指定史跡）は、関東大地震のとき付近一帯が沈降した際、水田中から現れた11本の大杭(おおくい)で、鎌倉時代に架けた橋ではないかといわれる。

［浅香幸雄］

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