Measuring the migration of a river
Large river networks — such as those that funnel into the Colorado and Mississippi rivers — may seem to be permanent features of a landscape. In fact, many rivers define political boundaries that have been in place for centuries. But scientists have long suspected that river networks are not as static as they may appear, and have gathered geologic and biological evidence that suggest many rivers have been “rewired,” shifting and moving across a landscape over millions of years. Now researchers at MIT and the Swiss Federal Institute of Technology (ETH Zurich) have developed a mapping technique that measures how much a river network is changing, and in what direction it may be moving. Their results are published in this week’s issue of Science. The technique focuses on a river network’s drainage divides — ridgelines, such as along mountain ranges, that act as boundaries between two river basins. As rainwater...