High water

The rise and fall of sea levels due to tides refers to the state in which the sea level has risen to its maximum. It is also called high tide. In contrast, when the sea level has fallen to its maximum, it is called low tide. Normally, high tide and low tide occur twice a day, but there is a difference in the height of high tide, and when distinguishing between them, the higher is called high tide and the lower is called low tide.

The time and height of high tide changes daily, but the tidal range is large around the time of the new moon and full moon, resulting in high high tides. During the seasons from summer to autumn when the average tide level is high, if a spring high tide coincides with a high tide or abnormal tide level, the damage caused by flooding and inundation can become even greater, so caution is required.

[Masami Okada]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

潮汐(ちょうせき)による海面の昇降で、海面が上昇しきった状態をいう。高潮(こうちょう)ともいう。これに対して、下がりきった状態を干潮(かんちょう)という。通常は満潮と干潮がそれぞれ1日2回生じるが、満潮時の高さに差があり、それを区別するときは高いほうを高高潮(こうこうちょう)、低いほうを低高潮(ていこうちょう)とよぶ。

　満潮の時刻と高さは日々変化するが、新月と満月のころは潮差が大きく、高い満潮となる。夏から秋にかけて平均潮位が高い季節に、大潮の満潮と、高潮(たかしお)や異常潮位が重なると、浸水・冠水の被害が一段と大きくなるので注意を要する。

［岡田正実］

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