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Project: Lower Prairie Creek Floodplain Restoration Design

Description: The project will increase the availability, timing, and quality of streamflow by: a. Reconnecting lower Prairie Creek to restored floodplains and backwater habitat, thereby allowing storm flows to reoccupy a broad area of floodplain, riparian, and wetland features. Restoring the incised channel will effectively increase the frequency with which streamflow will access the floodplain. b. Restoring the 10-foot incised channel of Prairie Creek will decrease the distance from floodplain to groundwater level and create an interconnected channel/floodplain system that will allow groundwater to reoccupy aquifer storage across 18 acres of restored floodplain. Along with this, groundwater infiltration will be increased by removing 16 acres of asphalt and constructing 9 acres of stormwater infiltration wetlands adjacent to the creek; creating significant long-duration inundated low-velocity areas in the restored floodplain and channel; lengthening the stream channel with meanders; and adding in-channel and floodplain complexity features that create backwater conditions. This new aquifer storage and infiltration will change the timing and the quality of streamflow for the better: downstream baseflows will increase via slow releases of cool streamflow that will persist longer into the dry season. Decreasing the distance from groundwater to the surface will create wetland conditions that help store and release cool water for a longer period in the dry season thereby sustaining cool-water conditions for salmon. Water temperatures in Redwood Creek, just upstream of the Prairie Creek confluence, are up to 10°F higher than in Prairie Creek, and are a limiting factor for pre smolt, smolts, summer rearing juveniles, and summer adult salmonids. c. Widening Prairie Creek’s incised channel and expanding the riparian corridor will provide area for sediment to move and be sorted into a natural pool bar riffle pattern. The restored system with large wood and complexity will allow for settling and transport of material and help maintain clear water conditions. d. Managing the active colonization of the creek by invasive reed canarygrass, which has a longer growth period than native vegetation that results in longer water withdrawal and can result in fish passage barriers and low dissolved oxygen conditions, will remove this demand on streamflow while improving habitat conditions for native species.

Reference Number: 36402020021

Implemented By: Save the Redwoods League

Objective:

Type: Water Management

Total Cost: $597,000.00

Project Status: Project Implementation

On Time?: Yes    Within Scope?: Yes    Within Budget?: Yes

Estimated Completion: 4/30/2024    Actual Completion:

Associated Counties: Humboldt

Project Benefits a Disadvantaged Community (or SDAC): Yes

Contribution SourcesContribution DateContribution Amount
  $597,000.00
Federal Contribution4/3/2020$55,000.00
Other State Funds4/3/2020$180,000.00
Private Contribution4/3/2020$30,000.00
Prop. 1, Stream Flow Enhancement4/3/2020$332,000.00


Project MetricMetric TopicQuantityUnit
Water ManagementWater Storage -- Conjunctive  
Water ManagementWatershed Protection  
Water ManagementOther  

Water Action Plan Target

    
Protect and Restore Important EcosystemsAction Description
Manage and Prepare for Dry PeriodsAction Description

Location

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