Presentations text content in Flow Regime Management for Riparian Restoration
Slide1
Flow Regime Management for Riparian Restoration
Katie Ross-Smith, PhD
SFS – 2016 Annual Meeting
Slide2Development of Environmental Flows for Riparian SystemsExample from a recent hydroelectric projectResponse of Riparian Systems to New FlowsExamples from two monitoring projectsPerspectives on Successful Communication of Technical Guidance
Talk Overview
Slide3Case Studies
PG&E
Spring Gap-Stanislaus
Project
PCWA Middle Fork American River Project
PG&E Pit 3,4,5 Hydroelectric Project
Slide4Considerations
When developing riparian environmental flows and interpreting potential of a riparian system“One-size-fits-all” approach is not appropriateSpeciesWatershed characteristics and physical processesHierarchy of characteristics and processes that vary in space and time and overlap to influence riparian systems
Sacramento River
Adapted from Goodwin et al 1997
Rubicon River
Willows
Cottonwood
Alder
Slide5Considerations
Unimpaired Inflow Folsom Reservoir
Time
Series
Intra- and Inter-Annual VariabilityMultiple years with low precipitationInfrequent high magnitude eventsWet winters/springs & hot/dry summers
Slide6Case Study No. 1
PCWA Middle Fork American River Project
Slide7Riparian Management ObjectiveMaintain/ enhance physical processes and conditions to support the riparian corridor By:Shaping annual flows to mimic shape and timing of unimpaired hydrograph
Case Study No. 1
Magnitude
Frequency
Timing
Recession Rate
Slide8Case Study No. 1
Geomorphic & Hydrologic StudiesChannel and floodplain topographic surveysStream and substrate classificationReach-specific stage-discharge relationships and flow modelingHistorical flow analysisRiparian StudiesMapping and quantitative data collection Cored and dated trees (179 trees) and tied to cross-sections
Slide9Magnitude
80 cfs
1,018 cfs
3,000 cfs
6,000 cfs
8,000 cfs
Scour
Riparian Vegetation
Case Study No. 1
Slide10Case Study No. 1
Wetter years, often after high magnitude scouring events (re-setting flows)
Frequency
Slide11Case Study No. 1
Successful recruitment occurred in years when: The snowmelt recession occurred during specific time periods that varied by elevationRecession rates were typically less than 2 inches per day
Timing and Recession Rate
Slide12Case Study No. 1
~8% in Stage
~ 2 inches per day on average
Recession Rate
Slide13Case Study No. 2
PG&E Pit 3,4,5 Hydroelectric Project
Slide14Riparian Management ObjectiveRemove encroaching vegetation (willows and torrent sedge)Promote cottonwood establishment on gravel bars, floodplains, and terraces
Case Study No. 2
Slide15Case Study No. 2
Environmental Flow Schedule
Magnitude
Natural Hydrograph Shape
Slide16Case Study No. 2
Monitored Change in Vegetation After 5 Years of New FlowsNo high magnitude scouring flows; freshet releasesRelatively small changes in inundation (4 to 10-inch increase in stage; 0 to 5-foot increase in wetted width)
Vegetation ResponseMinimal change in vegetation compositionLoss/reduction in in-channel torrent sedge tussocks in some locationsSmall shifts (including expansion) in some locationsChanges in width and depth have been insufficient to drown streamside encroaching vegetation
After 5 years
Slide17Case Study No. 3
PG&E Spring Gap-Stanislaus Project
Slide18Riparian Management ObjectivePromote cottonwood establishment Promote vegetation establishment on banks to improve bank stability
Case Study No. 3
Slide19Case Study No. 3
Environmental Flow Schedule
Late Season Releases
Ramping
Rate
Slide20Case Study No. 3
Monitored Vegetation Response 12 Years After Implementation of New FlowsOverbanking flows in 2 recent years; including 3rd highest in 76 year recordVegetation Response
53% increase in Riparian Forest Cover within 10 yearsRecent cottonwood and willow establishment after recent high flows
1998
2012
Slide21A “one-size-fits-all” approach to development of riparian flows is not appropriateWatershed characteristicsMorphodynamicsPlant species and life historyDetermine the factors limiting successful recruitment and/or establishment and clearly identify the riparian management objectiveFlows? And which component?And… other land uses?Use tools that link the site-specific characteristics, hydrology, and riparian vegetation
Perspectives on Successful Communication
Slide22Case Studies - Pacific Gas and Electric Company and Placer County Water Agency projectsNumerous people assisted with hydraulic modeling (J. Hammond; C. Addley; P. Graf) and field data collection
Acknowledgements
Slide23Questions?
Flow Regime Management for Riparian Restoration
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