Nayoro Basin - Nayorobonchi

Located in the north central part of Hokkaido, this basin opens into the upper reaches of the Teshio River. It lies long from north to south between the Kitami Mountains to the east and the Teshio Mountains to the west, and structurally it forms a corner of the lowlands that run north to south through central Hokkaido, connecting with the Tonbetsu Lowland to the north and the Kamikawa Basin to the south. The basin floor is 100 to 160 meters above sea level, and the Teshio River flows north, collecting tributaries such as the Kenbuchi River and the Nayoro River, and its river terraces jut out like plateaus near Chiebun and Shibetsu. From the north, it can be divided into the Bifuka Basin, the Nayoro Basin in the narrow sense, and the Kenbuchi Basin. It has an inland climate with a significant temperature difference, and in winter, along with the Kamikawa Basin, it is the coldest in the lowlands of Hokkaido. The basin floor was developed into a rice paddy field during the Taisho period, and the Kenbuchi Basin was a peat bog, but land improvement work progressed after the Second World War, and the Bifuka Basin is now the northern limit of paddy rice cultivation. Lumber-related industries are located close to the forestry area.

[Jiro Okamoto]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

北海道中央部北寄りに位置し、天塩川(てしおがわ)上流域に開ける盆地。東の北見山地、西の天塩山地の間に南北に長く横たわり、構造的には北の頓別(とんべつ)低地、南の上川(かみかわ)盆地に連なって北海道中央部を南北に走る低地帯の一角を形成している。盆地床の標高は100～160メートル、天塩川が剣淵(けんぶち)川、名寄川などの諸支流を集めて北流し、その河岸段丘が智恵文(ちえぶん)と士別付近で台地状に張り出して、北から美深盆地(びふかぼんち)、狭義の名寄盆地、剣淵盆地に区分することができる。寒暖差の著しい内陸的気候を示し、冬は上川盆地とともに道内低地ではもっとも低温となる。盆地床は大正期に造田が進み、剣淵盆地は泥炭地であったが、第二次世界大戦後に土地改良が進み、美深盆地は水稲の北限地となっている。林業地帯を控えて木材関連工業が立地している。

［岡本次郎］

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