Increasing tributary and in-Delta peak flows improves ecosystem health.

The Measure

Restoring to a healthier estuary using more natural functional flows - including in-Delta flows and tributary input flows - to support ecological floodplain processes: peak flows in the Sacramento River.

  • Expectations

    Large magnitude peak flows in the Sacramento River provide an important function in erosion and deposition processes that create healthy Delta habitats.

  • Performance Metrics

    • Frequency of 2-year return interval peak flows between November 1 and April 30, evaluated annually on a five-year rolling basis.

Number of days with peak flows 75,000 cfs or higher

Water years with flows 75,000 cfs or higher for at least 2 consecutive days meet the target. Blue bars indicate total number of days with flows 75,000 cfs or higher. Red bars indicate most consecutive days with flows 75,000 cfs or higher.

 

Target Met

Target: At least one peak flow greater than 75,000 cfs, lasting at least two days, every two years. 

Large magnitude peak flow in the spring (also referred to as “pulse” flow) is an important component of functional flows and has a wide-ranging positive effect on ecosystems. Spring peak flows are important for many native species in and along the Sacramento River, and within the Sacramento-San Joaquin Delta. Spring peak flows help inundate floodplains, thereby providing suitable habitat for many native migratory fish species. Periodic high flows also provide important channel forming functions including sediment transport and river bank erosion and deposition. Dynamic river channels create varied channel and riparian habitats supporting diverse riparian species communities. For example, channel bank erosion supports recruitment of Fremont cottonwood and creates habitat for bank swallow.

Each chapter of the Delta plan includes strategies to achieve the goals of the plan. These strategies are general guidance on achieving the objective laid out in the plan and in the Delta Reform Act of 2009. Associated with these strategies are recommendations. The recommendations describe more specific and implementable actions to support the achievement of Delta Plan strategies. Strategies and recommendations may also have associated performance measures. Delta Plan performance measures track progress in achieving desired outcomes for the Delta Plan. Below are the strategies and recommendations associated with this performance measure.

Delta Plan Strategy:
  • Create more natural functional flows
Delta Plan Recommendations:
  • Update Delta flow objectives
Metric:

Frequency of 2-year return interval peak flows between November 1 and April 30, evaluated annually on a five-year rolling basis, at Bend Bridge on the Sacramento River.

Baseline:

Hydrograph data for the Bend Bridge gage station (USGS gage 11377100) indicate that the magnitude of 14-day duration flows for pre-Shasta Dam (1891–1943) and post-Shasta dam (1960–2013) events are similar (approximately 20,000 cfs). However, the pre-Shasta Dam historical 1.5-year recurrence interval peak flow event (approximately 75,000 cfs) now occurs approximately every two years, and the pre-Shasta Dam 10-year recurrence interval flow (206,200 cfs) has been nearly halved (133,842 cfs).

Target:

By 2030, at least one peak flow greater than 75,000 cfs and lasting at least 48 hours in duration, every two years, at Bend Bridge on the Sacramento River.

Bend Bridge USGS daily gage data (USGS gage 11377100)

Recorded number of days with a daily average of at least 75,000 cfs 

Only used data from November 1 to April 30 for each water year

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