Gravel Rivers in Northeastern Italy
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Gravel Rivers in Northeastern Italy

December 14, 2010
In northeastern Italy, the Cellina, Meduna, and Tagliamento Rivers flow toward the Adriatic Sea. Fed by tributaries from nearby mountains, the rivers flow over a coastal floodplain that is densely packed with crops and settlements. Rain falls frequently in the mountainous region north of these rivers—some areas receive as much as 3,000 millimeters (120 inches) of rain a year—making it one of the wettest places in Italy. Because much of the rain occurs in heavy showers that erode the landscape, significant quantities of mud and debris flow into the rivers, and they are prone to flooding.

The Thematic Mapper on NASA's Landsat 5 satellite captured this natural-color image of northeastern Italy on September 21, 2010, showing parts of all three rivers. The gravel-coated riverbeds contrast sharply with the surrounding landscape, highlighting the river contours. The Cellina and Meduna Rivers converge in the south, forming a giant V shape.

When a river receives more sediment than it can move effectively, the river changes shape, often carving braided channels. Upstream from the Cellina, Meduna, and Tagliamento Rivers, the mountain basin is seismically active and prone to landslides. As a result, heavy sediment loads often reach these rivers, all three of which have braided channels.

Around the rivers, rectangular shapes of green, gold, and brown belong to cultivated fields. The crops mingle with settlements, some of them quite close to river channels. Some hydrologists have expressed concern about continued development on this floodplain because flood damage has occurred fairly frequently, just as the fertile soils have attracted farmers.

NASA image created by Robert Simmon, using data provided by the United States Geological Survey. Caption by Michon Scott.

Instrument: Landsat 5 - TM

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