We are on the south bank of the Yuba River, standing atop a gigantic pile of gravel in the midst of a landscape so strange and devoid of life that it calls up images of the moon. The water below us seems to bear no relationship to any real river. It’s oddly blue, very clear, and is confined to a channel between near-vertical gravel walls that, in some places, rise as high as 100 feet on both banks. So eerie is this scene that I can’t actually see the river flowing; it seems frozen in place. Turning to look downstream in the direction of Marysville, I see a vast gray stony field with odd-shaped mounds extending to the horizon, with only here and there a bush or a tree.

This alien yet oddly beautiful place is called the Goldfields. It’s a 10,000-acre wasteland left behind by the Gold Rush in the middle reach of the Lower Yuba River, about 20 miles west of Nevada City. I’m with Derek Hitchcock, an ecologist working with the South Yuba River Citizens League (SYRCL) to restore salmon habitat here. “Ironically,” he says, “the magnitude of the destruction wreaked upon the Yuba watershed in the 19th and 20th centuries has created a unique river system that presents unique restoration opportunities in the 21st century.”

After gold was discovered in the American River in 1848 and before a court largely stopped the practice in 1884, hydraulic mining blasted away entire hillsides and sluiced 1.5 billion cubic feet of debris down the tributaries of major Sierra rivers flowing into the Central Valley. Almost half of that came out of the Yuba watershed. Vast amounts of gravel, mud, uprooted plants, and other debris traveled down into the Feather River, on into the Sacramento River, and as far as San Francisco Bay--which helps to explain why the Bay is so shallow; its average depth is only eight feet.

Much of the heavier debris landed along a six-mile stretch of the Lower Yuba, where it slows as it enters the flat Central Valley, and where, in the past, it used to spread, becoming a braided valley river. Piling up, the debris raised the riverbed, causing floods that drowned hundreds of square miles of farmland in a mixture of mud and gravel. In 1893, the State set up the California Debris Commission to build dams that would capture mining debris that was still coming down rivers, to keep it out of the Valley.

On the Yuba, Daguerre Point Dam was constructed at the downstream end of the enormous gravel deposit, and about 16 miles of “training walls” were erected to channelize the river by piling gravel on both the north and south banks, as well as down the center of the river in some places to create two channels. The effect was to keep the river from spreading in its floodplain and to turn this stretch of the Yuba into a conveyance channel that speeds water downstream to serve agricultural and municipal users.

By the turn of the century, a switch from mercury to cyanide for gold extraction made it profitable to mine the Lower Yuba again, for gold that came down with the debris. In cooperation with State water supply engineers, miners used bucketline dredges, and piled gravel still higher on the banks. They gouged into the riverbed and flood basin, leaving steep ravines and deep holes that filled with water and became ponds. They turned over earth and gravel again and again and threw it onto piles, building odd-shaped mounds. Today gravel mining is the major extractive industry in the Goldfields. The aggregate here has high commercial value for construction.