Figure 1. Map of Feather River Basin in northern California. (A) Region straddles the northwestern Sierra Nevada and Sacramento Valley. (B) Feather River Basin with Yuba and Bear subbasins. Most hydraulic mines were near 121 W longitude in Yuba and Bear basins.
Figure 2. Levee spacings with narrow Feather River floodway, wide Yuba R. floodway, and narrow constriction at Yuba mouth.
Figure 3. Levee cross-valley spacings in 1999 compared to 1909 (Feather River) and 1906 (Yuba River).
Figure 4. Widening of levee spacings from 1909 to 1999 on the lower Feather River. Levee spacings in 1909 were narrower. (A) 1909 levees on the east bank above and below Star Bend constricted channels to not much wider than low-water channel. By 1999 these constrictions were gone. 1909 west bank levees B were in essentially the same position as in 1999. (B) Levees positions on east bank of Feather River changed little from 1909 to 1999. A railroad embankment on the right bank constrained widths of moderate floods to less than 250 m. High floods flowed into Sutter Basin through crevasses. A Star Bend
Figure 5. Excerpt of rectified north half of Von Schmidt (1859) map of lower Feather River (flowing north to south) and Yuba River (flowing from upper right). Scale added.
Figure 6. 1906 longitudinal profile of lower Yuba River from The Narrows in the fan apex to Shanghai Bend below the Feather River confluence. Solid line is channel-bed elevation in 1906. The middle dashed and lower dotted lines are elevations of the pre-mining channel and bedrock, respectively. Numbers adjacent to thin vertical lines are depths of boreholes (meters) done in 1898 1899 that provide minimum depths of hydraulic mining sediment. Two thick vertical lines give depths to bedrock (17 and 15.9 m) based on bedrock exposed by dredging. (Source: CDC, 1906).
Figure 7. Excerpt from 1861 map of Yuba County showing two features not shown on 1859 map: (a) a channel southeast of the main channel around the area marked Linda. (b) a western chute cutting off the confluence. These conditions should represent pre-mining channels. (Source: Wescoatt, 1861)
Figure 8. Early positions of lower Yuba River based on Mendell s 1882 map. Undated paleochannels (light dotted) match 1859 pre-mining channels (dark dashed) (Von Schmidt, 1859; cf. Figure 5). A pre-1876 channel to the south (light dotted) matches the channel shown by Wescoatt (1861) and is interpreted as contemporary with the 1859 pre-mining channel to the north. A channel system along the south levee was labeled low-water channel in 1876. By 1880, much of the low-water Yuba channel had shifted two to three km northwest. Source: Mendell (1882) based on 1879 survey by Hall (1880).
Figure 9. Yuba River floodplain above Marysville in 1906. Lightly shaded channel is 1906 low-water channel. Dark channel is 2006 low-water channel. Heavy dashed line in southwest is 1859 channel (Von Schmidt, 1859). Heavy dotted line above and below center is 1879 channel (Mendell 1882). Other channels are 1906 high-water channels including former locations of main channel. Bordering lines along northwest and southeast floodplain margins are levees 4.1 km apart. Star is site of USGS stream gage and stratigraphic section. (Source: CDC, 1906, Sheet 2)
A C Historical B Figure. 10. Historical sediment at the US Geological Survey stream gauge on the Yuba River near Marysville is more than 6 m deep. A stump near the base of the section, rooted in pre-historic sediment, has two root crowns; indicating that the tree survived initial burial.
Figure 11. Excerpt from 1865 map of Yuba-Feather confluence showing three cutoffs from the lower Yuba southern meander bend in early stages of channel aggradation. The northern cutoff (NC) became an avulsion, abandoning the southern meander (SM) over which the Linda levee was later built (Figure 8). The southern cutoff (SC) apparently connected the Yuba River SM to the Feather River at Elisa Bend (EB). The western chute (WC) may be the same high-water channel shown in 1861 (Figure 7) which was later dredged. (Source: Pixley et al., 1865.) WC NC SM SC EB
X B X A Figure 12. Channelization around the Yuba-Feather confluence. A. A series of ditches were dredged south of Marysville by 1909. Two ditches connected with the Feather River at Elisa Bend and another turned the confluence south. Stratigraphic sections collected at the Xs are shown in Figures 13 and 15. (Source: CDC, 1912) B. These ditches are shown prominently in 1914. (Source: Crook, 1914)
Figure 13. Stratigraphic section on right bank of lower Yuba River at Marysville. Dark, massive silts at the base represent pre-mining alluvium. Historical sediment is highly stratified and at least 4.5 m thick; probably 5.5 m thick. BD is bulk density; T Hg is total elemental mercury concentration in sediment samples.
Fig. 14. Feather River channel changes at Elisa and Shanghai Bends. (A) In 1906, the Feather River in this area was beginning to experience changes in planform. Levees above the bend had shifted the channel eastward and altered the flow direction above the bend. The straight Dredge Canal to the south along the west levee initiated flows that bypassed Elisa Bend that ultimately resulted in an avulsion. (Source: CDC, 1912). (B) By 1909, much of the flow was passing south through the new dredged channel which was no longer straight but had begun a meander to the east. Elisa Bend was shifting south in a lower-amplitude wave. (C) The modern topography shows the configuration of upper Shanghai Bend and the channel scar that was Elisa Bend. Derived from 1999 LiDAR and sonar data. A EB
Figure 15. Stratigraphic sections of Feather River right bank exposures. (A) Above Shanghai Bend showing historical sediment ~5.5 m thick. Total mercury concentrations in sediment samples A through D were 0.18, 0.47, 0.35, and 0.05, respectively. (B) Below Shanghai Bend a distinct soil clearly marks premining surface ~3.3 m deep.
Figure 16. Sand sheets below the Bear River confluence are interpreted as a legacy of sediment from the hydraulic mining era. October, 1998. (Source of photo: California Department of Water Resources)
Figure 17. Lower Feather River at Sutter Bypass confluence. (A) 1909 CDC map: incipient cutoff of single channel. (B) Shaded relief map with oxbow lake largely filled in 1999. Derived from LiDAR DEM and SONAR channel bathymetry (Stonestreet and Lee, 2000).
Figure 18. Alternating longitudinal bars on lower Feather River from the beginning of Sutter Bypass to the Sacramento confluence. (A) Long wavelength bars on 1909 map (CDC, 1912). (B) Short wavelength bars on August 4 th, 1966 aerial photograph (EROS, 1966)
Figure 19. Crevasses through Southern Pacific Railroad embankment delivering water and sediment from lower Feather River to Sutter Basin. (Source: CDC, 1912)