The bright spot among the flood systems tested in 1997 was, ironically, the American River. Despite having the largest 3-day vloume of runoff ever, the existing facilities handled storm flows without any major problems.
The success of Sacramento’s flood system wasn’t a matter of luck; the storm intensity and subsequent runoff in the American River watershed was the equivalent of that occurring in other watersheds to the north and the south, including the Feather, Tuolumne and San Joaquin. Instead the lack of flooding in Sacramento resulted from prudent operation at Folsom Dam and relatively reliable levees the result of nearly a decade of pressure on engineers and managing agencies to do something besides just demanding yet another dam on the American River.
Poor operation at Folsom Dam during the 1986 storms led to embarrassing criticism, especially from a prestigious National Research Council report released in 1994. In addition, over the last ten years, federal, state, and local governments have made major investments in Sacramento’s levee system. As a result of careful scrutiny and more investment, dam operators in 1997 made sure they promptly made required flood releases and maintained plenty of empty space in the reservoir for the seasons major storm events.
However, the American River does not represent an ideal opportunity for restoration / floodplain management. Developed areas along the river cannot provide greater floodplain storage or levee set backs. Like other parts of the state, suburban Sacramento has encroached along the rivers historic floodway to such a degree that many residents have backyard gardens planted along the toes of levees, making levee set back options extremely expensive and politically impractical.
But public safety can be improved by fixing the existing American River flood system: Folsom Dam and downstream levees. Fixing the existing flood system can be done in two principle ways: (1) stabilizing and improving levees with internal, concrete- like slurry walls, and increasing their size and resistance to erosion; (2) structurally modifying the dam at Folsom by lowering spillways and enlarging its outlet works. Those improvements, combined with earlier and more aggressive flood releases from the dam, can provide Sacramento with protection from any foreseeable floods along the American River.