Ri River erbend bend Levee ee Se Setb tback k and nd - - PowerPoint PPT Presentation

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Ri River erbend bend Levee ee Se Setb tback k and nd Floodplain odplain Res estora toration tion Jon Hansen, Project Manager March 28, 2017 Department of Natural Resources and Parks Water and Land Resources Division River and

SLIDE 1

Ri River erbend bend Levee ee Se Setb tback k and nd Floodplain

dplain Res

estora toration tion

Jon Hansen, Project Manager

March 28, 2017

Department of Natural Resources and Parks Water and Land Resources Division River and Floodplain Management Section

SLIDE 2

Elliott Reach Restoration and Mitigation Design Update

May 2014

Riverbend Levee Setback and Floodplain Restoration Riverbend

SLIDE 3

Site and Reach Overview

SLIDE 4

Neighborhood Flooding January 8, 2009 7870 cfs @ Landsburg

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Project Goals

Improve quality, quantity and sustainability of

salmonid spawning and rearing habitat

Reduce flood and erosion risks to people, property

and infrastructure

Accommodate public use consistent with future

ecological conditions on site

Balance flood and ecological benefits and other
bjectives with project costs

SLIDE 6

Potential Project Elements

Levee Removal Existing Levee New Setback Floodplain Excavation Fill Placement New Channel (Perm, seasonal, ephem)

SLIDE 7

Alternatives Considered

Six Alternatives with combination of elements
Alternative 1 most aggressive

– Full removal and setback of left bank levees and Herzman – Largest benefit for flood and habitat – Would require NEW right bank protection – High Cost and not feasible in near term

Alternative 6 Smallest scale

– Limited to former Mobile Home Site – Very limited habitat, but some flood hazard reduction benefits – Easiest to implement, but not attractive to grant agencies

SLIDE 8

Alternative 6

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Evaluation Process

Compare Alternatives

– Benefits, Costs, Risks and fit with long term – Aided by modeling, studies and analysis

Based on Goals

– Refined by objectives with metrics for each – Specific enough to differentiate – Provides enough info to make informed decision – BUT there is still uncertainty with natural processes

Selection made via “Gate” process

SLIDE 10

Evaluation Matrix

SLIDE 11

Evaluation Matrix

SLIDE 12

Evaluation Matrix

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Preferred Alternative

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Alternative 4 – Simple Overview

SLIDE 15

Schedule

June 2015 – Project Initiation
July 2015 – Data Collection and Analysis

begins

Winter 2016 – Alternative Analysis
March 2017 – Preliminary design

milestone/RCO

Fall 2018 – Final Plan complete
Summer 2019 – construction target

SLIDE 16

Potential Pond Modification

SLIDE 17