River Meanders and Flooding
Date: Summer 2012
I would like to know how do the meanders in a river contribute to flooding? If there is a meander, is there more chance of a flood?
Streams can be classified by age. Immature streams have narrow floodplains, are generally straight, fast-flowing, and have numerous small waterfalls. Mature streams have very wide floodplains, numerous meanders, slower moving water, and no waterfalls. Over time, the meandering river carves wide floodplains. If abundant rainfall occurs, especially if associated with rapid snow melt, then the water in the stream can easily overflow its banks and cause widespread flooding (because the floodplains are quite wide).
It's not the meanders that increase the likelihood flooding, but meandering streams have wide floodplains so a flood could cover great areas.
Leslie Kanat, Ph.D.
Professor of Geology
Johnson State College
Meanders occur when rivers flow over very flat terrain. So if the river's flow rate increases, there is no place for the water to go but out of its channel. A river in a deep gorge can still flood, but its water will not spread out over as much area.
Richard E. Barrans Jr., Ph.D., M.Ed.
Department of Physics and Astronomy
University of Wyoming
Rivers meander because the land over which they flow is flat.
Rivers that do not meander, have relatively straight courses, have a definite grade down hill.
Meandering rivers have wider areas between which the meanders drift, so if a larger volume of water (a flood where a river overflows its banks) came down a meandering river, it would have more room to spread out over than a river that had a direct course. That is, a meandering river would have a greater area to accommodate a larger volume of water.
But overall, the local environment is the best determining factor.
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Update: June 2012