I live on the DesPlaines River. How is a river’s “flood phase” determined?
It is believed that the flood stage is the time when water begins to overflow the riverbank. However, this is not necessarily true. In fact, the flood phase is the point at which the natural bank overflow of a river or stream first introduces a potential risk of flood damage to the area. Therefore, it depends not only on how much water flows away from its shore. In many cases, the actual flooding stage can be several feet above shore as no significant property damage occurs until the water level reaches higher levels. Input from local officials and emergency managers is used to establish flood thresholds.