HR: 1340h
AN: H43B-0503    [Abstracts]
TI: Hydraulic Implications to Upper Basin Stream Systems From Changing Climatic Conditions in the Sierra Nevada
AU: * Cornwell, K
EM: cornwell@csus.edu
AF: Department of Geology California State University, Sacramento, 6000 J Street, Sacramento, CA 95819-6043
AU: Burns, R G
H43B-0503 AF: Department of Water Resources State of California, 1416 9th Street, Sacramento, CA 94236
AB: Projected climate changes in the Sierra Nevada of northern California may result in more variability in winter storm patterns and an increase in the frequency and magnitude of extreme precipitation events. Changing rain and snow patterns will alter the timing and amount of runoff in the streams that drain the west slope of the Sierra Nevada and will have bearing on water resource management strategies that rely on that runoff. These runoff changes will in turn challenge existing threshold conditions for channel stability, bank erosion, and hill slope stability. Increased sediment loads will impact existing water-routing infrastructure. Hydraulic conditions from several streams that drain the west slope of the Sierra Nevada in the American River drainage basin were measured to assess threshold changes in response to variable discharges. We reconstructed flow conditions from 1997 (early 1997 storms brought widespread flooding to the central and northern Sierra Nevada and peak flows at many gage sites in the region were the largest recorded during historical time) and 2005 in these channels (representing extreme and typical flow conditions) and then looked at changes to cross-sectional areas, flow velocities, channel shear stresses and sediment sizes since 1998 (earliest available sediment data). Initial insights suggest increases to runoff/discharge will likely produce pulses of mobilized coarser materials (resulting from greater channel shear stresses) that may take several years to transport through stream systems, and channel areas that are geologically weak (unconsolidated or weathered surface materials) may be susceptible to substantial erosion. These conditions will likely impact water-routing infrastructure in the upper basins (pipelines, pumps, and turbines) that manage water flow in the Sierra Nevada for much of northern California.
DE: 1807 Climate impacts
SC: Hydrology [H]
MN: Fall Meeting 2005