Northern California Fremont Weir Floodway Fills • Earth.com

Last update: August 23rd, 2019 at 5:00 pm

Storms in mid-March 2016 brought some relief to drought-stricken northern California, as multiple days of rainfall replenished the area’s reservoirs. The water level of Lake Shasta, for example, returned to its historic average for mid-March.

The abundant rainfall also meant that flood protection systems were hard at work. The Shasta Dam spanning the Sacramento River is one point of flood control for the Sacramento Valley. Farther south along the rain-swollen river, water flowed into Yolo Bypass—a floodway between Davis and Sacramento—for the first time in three years.

Fremont Weir flood, March 17, 2016

Fremont Weir flood, March 17, 2016

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured these images of the river and floodway. The top image was acquired on March 18, 2015, when the area was relatively dry.The second image was acquired on March 17, 2016, after water topped the Fremont Weir and spilled into the bypass. Turn on the image comparison tool to see the difference.

The images are false color, composed from a combination of infrared and visible light (MODIS bands 7-2-1). Water in the river and bypass is dark blue; snow is light blue; vegetation is green; and bare ground is brown.

In the second image, the water level at Fremont Weir measured about 10.7 meters (35 feet)—still more than five feet below flood stage. The water level in the top image was about 4 meters (13.5 feet).

Yolo Bypass covers about 60,000 acres of private and public land, which has been irregularly inundated with water since construction of the concrete, water-diverting system in the 1920s. It last filled with water in 2012.

NASA

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