Aggradation of the Yuba River EarthCache

This location can be accessed by a short walk along the southern levee of Marysville. Stairs to access the levee are near the south end of D Street behind the Tao Temple.

At the founding of Marysville, the bed of the Yuba River was 20 to 25 feet below the streets of Marysville. At the time, the river was a clear stream with sand and gravel lining its bed and had clearly defined riverbanks.

Steam ships traveled up the Feather River to a landing south just east of here. This location made Marysville one of the largest settlements in California at the beginning of the Gold Rush. However, the Gold Rush also caused the town much damage.

Hydrologic mining was developed to extract gold from ancient placer gold deposits. The largest hydraulic mine, the Malakoff Diggins mine (Malakoff Diggins Earthcache) is located up the Yuba River from Marysville.

All of the mining debris from this and other mines entered the Yuba River and was transported down into the Central Valley. During that time, the Yuba Rive became a muddy and the channel crooked and narrow. So much sediment filled the channel that the river bottom rose above the streets of Marysville. This process of depositing material in a stream is called aggradation.

Marysville was at the end of the sediment that was deposited. Sediment was deposited in a fan shape starting about 14 miles upstream from Marysville with a width of 1 to 3 miles. It is estimated that up to 600,000,000 cubic yards of mining debris was deposited in this fan.

In order to protect the city from the rising river, levees were constructed all the way around the city effectively limiting any growth. The aggradtion of the river bottom also made it so that riverboats could no longer navigate the river cutting off cheap easy transportation to the city. Effects of the mining debris were noticed all the way down into San Francisco Bay.

In 1884 a series of court rulings stopped the dumping of mining debris into rivers. This effectively stopped hydraulic mining, but interestingly hydraulic mining has never been outlawed. These court rulings have been described as the first environmental protection rulings in the country.

Immediately after hydraulic mining ended, the Yuba and other rivers affected by hydraulic mining debris began eroding back down to their pre-mining levels. Many of these rivers have relatively steep sides and with terraces of sand and gravel.

Logging requirements:
Send me a note with :

1. The text "GC1CXXJ Aggradation of the Yuba River" on the first line
2. The number of people in your group.
3. Look across the river to the southeast see if you can identify a terrace of sand and gravel above the river, are there any deposits on the Marysville side of the river?
4. Does that terrace look to be above the street level in Marysville?
5. How does the level of the river compare to the street level in Marysville?

The following sources were used to generate this cache:

• Carolyn Merchant Green Versus Gold: Sources in California's Environmental History Published 1998
• Dick Meehan, Dams, Levees, King Cong, the Viet Cong, and the Problem of Underground Seepage Control. http://www.stanford.edu/~meehan/flood/cnn.html

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