Tuolumne River Report - U.S. Fish and Wildlife Service

GEOMORPHIC AND RIPARIAN INVESTIGATIONS3. FLUVIAL GEOMORPHIC AND RIPARIAN INVESTIGATIONSTo evaluate the extent that contemporary conditionson the Tuolumne River achieve the Attributesof Alluvial River Ecosystem Integrity(Attributes) presented in Chapter 2 requires somequantification of fluvial and riparian processes onthe Tuolumne River. Because this type of informationis limited or non-existent, we assessedmany of these processes during the developmentof this Restoration Plan. By comparing theactivities needed to achieve the Alluvial RiverAttributes, with constraints imposed by dams,human encroachment into the floodway, channeldegradation from past mining, etc., we can assesswhether management actions can restore theAttributes within existing constraints. Theseinstitutional constraints usually limit the ultimateextent of restoration, so a scaled-down river,combined with more intensive mechanicalmanagement to supplement this shortfall inAttributes (natural processes), may be required.The objective of this chapter is to quantify andevaluate several of the Attributes. Our evaluationof fluvial processes concentrated on the gravelbedded reach because most of the in-river factorslimiting salmon spawning, egg incubation, andrearing are in this reach. The riparian evaluationsextend throughout the 52 miles of river. Specificinvestigations included:Geomorphology and hydrology• Bedload impedance reaches• Bed mobility thresholds• Bedload transport at Basso Bridge• Fine sediment (sand) sources• Evolution of M.J. Ruddy 4-Pumps floodwayrestoration project and associated channeldesign considerations• Flood flow evaluationRiparian vegitation• Relate riparian vegetation series to hydrology/channel morphology• Corridor-wide riparian inventoryCHAPTER 377