河川かせん Common Noun English jmdict 1 noun (common) (futsuumeishi) rivers 河川は豪雨で氾濫しました。 The rivers were flooded by the heavy rain.
河川氾濫かせんはんらん Noun English jmdict 1 noun (common) (futsuumeishi) flooding caused by overflowing of rivers (e.g. breaching levee banks)