Kurushima Strait

A strait in the mid-western part of the Seto Inland Sea, between Imabari city in Ehime Prefecture and Oshima, between Itsukinada and Hiuchinada. It is an important western shipping route connecting the Chugoku region and Shikoku, with as many as 1,500 ships passing through it every day. It is a difficult spot for ships to navigate, with currents reaching speeds of 8 to 10 knots, and there have been many marine accidents. The fast currents and complex changes are related to the distribution of islands and the underwater topography, and it is as famous as the Naruto Strait and the Kanmon Strait. Ships can only navigate through it one way, as per the Specific Waters Navigation Act (1952). Of the waterways, the Naka Channel (between Umajima and Nakatojima, 450 meters wide) is navigated with the tide, the Nishi Channel (between Kojima and Umajima, 870 meters) is navigated against the tide, and the Higashi Channel (between Mushijima and Oshima, 600 meters) has many reefs and is impossible for large ships to navigate. There are eight lighthouses, five light beacons, and four light buoys in the strait for safe navigation, and a tidal signal station at Nakatojima that indicates changes in the tides.

[Kazuo Fukaishi]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

瀬戸内海の中西部、愛媛県の今治(いまばり)市と大島間、斎灘(いつきなだ)と燧(ひうち)灘との間にある海峡。中国地方と四国を結ぶ西の重要航路で、1日に1500隻もの船舶の航行がある。8～10ノットにも達する潮流があり船舶航行の難所で、海難事故も多い。潮流が速く、複雑な変化をするのは島の分布や海底地形が関係し、鳴門(なると)海峡、関門海峡と並んで有名である。船舶の航行は特定水域航行令（1952）により一方交通方式がとられる。水路のうち中水道（馬(うま)島と中渡(なかと)島の間で、水道の幅450メートル）では順潮航行、西水道（小島と馬島間、870メートル）では逆潮航行が行われ、東水道（武志(むし)島と大島間、600メートル）は暗礁が多く大型船の航行は不能である。海峡には安全航行のため灯台8、灯標5、灯浮標4、中渡島には潮流変化を表示する潮流信号所などがある。

［深石一夫］

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