Flow Regime Management for Riparian Restoration

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Flow Regime Management for Riparian Restoration




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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

Slide2

Development 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

Slide3

Case Studies

PG&E

Spring Gap-Stanislaus

Project

PCWA Middle Fork American River Project

PG&E Pit 3,4,5 Hydroelectric Project

Slide4

Considerations

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

Slide5

Considerations

Unimpaired Inflow Folsom Reservoir

Time

Series

Intra- and Inter-Annual VariabilityMultiple years with low precipitationInfrequent high magnitude eventsWet winters/springs & hot/dry summers

Slide6

Case Study No. 1

PCWA Middle Fork American River Project

Slide7

Riparian 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

Slide8

Case 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

Slide9

Magnitude

80 cfs

1,018 cfs

3,000 cfs

6,000 cfs

8,000 cfs

Scour

Riparian Vegetation

Case Study No. 1

Slide10

Case Study No. 1

Wetter years, often after high magnitude scouring events (re-setting flows)

Frequency

Slide11

Case 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

Slide12

Case Study No. 1

~8% in Stage

~ 2 inches per day on average

Recession Rate

Slide13

Case Study No. 2

PG&E Pit 3,4,5 Hydroelectric Project

Slide14

Riparian Management ObjectiveRemove encroaching vegetation (willows and torrent sedge)Promote cottonwood establishment on gravel bars, floodplains, and terraces

Case Study No. 2

Slide15

Case Study No. 2

Environmental Flow Schedule

Magnitude

Natural Hydrograph Shape

Slide16

Case 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

Slide17

Case Study No. 3

PG&E Spring Gap-Stanislaus Project

Slide18

Riparian Management ObjectivePromote cottonwood establishment Promote vegetation establishment on banks to improve bank stability

Case Study No. 3

Slide19

Case Study No. 3

Environmental Flow Schedule

Late Season Releases

Ramping

Rate

Slide20

Case 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

Slide21

A “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

Slide22

Case 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

Slide23

Questions?


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