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Sediment Pours into Lake Pontchartrain

Sediment Pours into Lake Pontchartrain

Days of intense rainfall in August 2016 led to widespread flooding in southern Louisiana. Rivers swelled high above their banks, and many crested at record-high levels.

When the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this image on August 17, 2016, brown sediment (bits of mud, rock, and minerals) was pouring from Lake Maurepas into Lake Pontchartrain through Pass Manchac.

Floods transport huge amounts of sediment as fast-moving rivers and streams can pick up and move larger particles more easily than slow-moving waters. They also collect runoff from lands that are usually above the water line.

The multi-day rainfall accumulations that hit southern Louisiana (more than 20 inches in some places) stemmed from an unusual storm pattern similar to a tropical depression, except that surface winds were light. The system was extremely slow moving, dropping 600 percent of normal rain over a seven-day period, according to the Lower Mississippi River Forecast Center of the U.S National Weather Service.

NASA image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response. Caption and image cropping by Adam Voiland.

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