Researchers gain new insights on river dynamics, which suggest that rivers may begin jumping course much farther in the coming years.
A river’s only consistent attribute is change. As the Greek philosopher Heraclitus remarked, “No man ever steps in the same river twice.” Although this dynamic nature is often out of sight and mind, forgetting about it has led to many a historical catastrophe.
Recently, UC Santa Barbara geomorphologist Vamsi Ganti and his collaborators published a study finding that sea level rise will cause rivers to jump course, or avulse, more often on deltas than in the past. Now his team has discovered that a perfect storm of factors — including larger floods and finer sediment size — will enable these destructive events to occur farther and farther inland. Their results, which appear in Geophysical Research Letters, warn of major disasters poised to hit many urban centers that historically never had to worry about these issues.
On large, relatively flat rivers, avulsions tend to occur in the backwater region, Ganti explained. “This is the zone over which the river flow feels the effect of the sea level.” This region begins at the river mouth and can extend relatively far inland. For instance, the Mississippi River’s backwater reach stretches 500 kilometers from the coast.
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