Matsuyama Plain

A plain in the center of central Ehime Prefecture. It is also called the Dogo Plain. It is an alluvial plain consisting of the Shigenobu River, Ishite River, Ono River, Yatori River, and other rivers, and covers an area of ​​about 100 square kilometers. The southern edge of the plain is the Ishizuchi Great Fault Escarpment, and the northeast is the Takanawa Mountains, with many granite and Tertiary collapsed terrains, and the rivers that run through the plain carry a lot of river load. As a result, the foothills around the plain are well developed with alluvial plateaus, river terraces, and alluvial fans. At the top of the fan are valley mouth (valley mouth) settlements such as Gunchu (Iyo City), Haramachi (Tobe Town), and Yokogawara (Toon City). The alluvial fan has a steep gradient of about 10/1000, and the underground water of the poor-water plateau forms springs at the end of the fan. This area has been developed a long time ago, and many of the place names are derived from the rows of stripes. In the northern part of the plain, there are several rows of sandbanks at Wake, Mitsuhama, and on the left bank of the mouth of the Shigenobu River, but the right bank of the Shigenobu River has been reclaimed and is now an airport and industrial area. The rough rivers of Ishite River and Shigenobu River have also been renovated several times since early modern times. There are several isolated hills in the northeastern part of the plain, and Matsuyama Castle is located on one of them, Katsuyama (131 meters), with the main urban area of ​​Matsuyama spreading out to the south of that.

[Kazuo Fukaishi]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

愛媛県中部の中心をなす平野。道後平野(どうごへいや)ともいう。重信(しげのぶ)川、石手(いして)川、小野川、矢取川などからなる沖積平野で、面積約100平方キロメートル。平野の南縁は石鎚(いしづち)大断層崖(がい)、北東は高縄(たかなわ)山地で、花崗(かこう)岩や第三紀層の崩壊地形が多く、平野を流れる河川は河川運搬物が多い。そのため平野周辺の山麓(さんろく)地帯には洪積台地、河岸段丘、扇状地がよく発達している。扇頂には郡中(ぐんちゅう)（伊予市）、原町(はらまち)（砥部(とべ)町）、横河原(よこがわら)（東温(とうおん)市）などの谷口（渓口）集落がある。扇状地の勾配(こうばい)は1000分の10程度で大きく、乏水性台地の伏流水は扇端で湧泉(ゆうせん)地帯となる。この地帯の開発は古く、条里にちなむ地名が多い。平野北部の和気(わけ)、三津浜(みつはま)、重信川河口左岸には数列の砂堆(さたい)があるが、重信川右岸は埋立地で空港や工場地域になっている。荒れ川の石手川、重信川も近世以来幾度か改修がなされた。平野北東部にいくつかの分離丘陵があり、そのうちの一つの勝山(かつやま)（131メートル）に松山城があり、その南側に松山市の主要市街地が広がっている。

［深石一夫］

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