Wakayama Plain

Located in the northwest of Wakayama Prefecture and included within the Wakayama City area, this is the largest plain in the prefecture. The entire plain formed by the Kinokawa River, which flows west along the southern foot of the Izumi Mountains, and the Ryumon Mountains, is called the Kinokawa Plain, while the area downstream from the narrow section about 15 kilometers upstream from the river mouth is generally called the Wakayama Plain. During the Jomon period, it was an inlet, but it is thought that the shoreline gradually receded due to sea regression and sedimentation of the Kinokawa River. There are old river channels such as the Wakagawa River, Donyu River, and Suiken River that tell the story of the changes in the river course, as well as hills that were once islands in the sea, such as Mt. Nagusa, Mt. Saika, and Okayama, the site of Wakayama Castle. The three rows of sand dunes stretching from north to south that once marked the shoreline are now surrounded by urban areas or have disappeared due to landfill.

[Yoichi Koike]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

和歌山県北西部、和歌山市域に含まれる県内第一の平野。和泉(いずみ)山脈南麓(ろく)を西流する紀ノ川が龍門(りゅうもん)山地との間に形成した流域平野全体を紀ノ川平野とよび、河口から約15キロメートルさかのぼった狭隘(きょうあい)部から下流の部分を一般に和歌山平野とよぶ。縄文時代には入り江であったが、海退と紀ノ川の堆積(たいせき)によって汀線(ていせん)がしだいに後退したと思われ、和歌川、土入(どにゅう)川、水軒(すいけん)川など流路の変遷を物語る旧河道や、名草(なぐさ)山、雑賀(さいか)山や和歌山城跡の岡山など、古くは海中の島であった丘陵が点在する。かつての汀線を示す南北に延びる三列の砂丘も、いまは市街地に取り囲まれたり、埋立てによって姿を没している。

［小池洋一］

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