minnehaha creek – reach 14 streambank improvement project

Minnehaha Creek – Reach 14Streambank Improvement

Project

Design Concept 1 – From the Creek

• Is this a “fun” stream to paddle?

• The allure of a journey, what’s around the next bend?– Viewing wildlife– Viewing architecture– Hearing the sounds– Connecting with the water

Design Concept 1 – From the Creek

Is Natural Buffer Strong Enough?

• Project feasibility study included hydraulic modeling– Average bankfull

shear stress = 0.43 lb/ft2

– Max, 100 yr shear stress at France Ave. weir = 1.2 lb/ft2

• By the numbers, in general nothing larger than 6” rock is required.

• Homeowner observations?

Design Concept 2 – From the Home

• Different desires in ownership– Viewing wildlife– Viewing the stream– Hearing the sounds– Access to the water– Separation from

neighbors

Is this the “best” stream to live on?

• Different aesthetic preferences– Neat & orderly– Manicured– Natural & organic

What Could It Look Like?

Before After

Variable Site Conditions

• Sun exposure (Full sun to full shade)• Slope• Existing rip rap (rock) or retaining wall• Variable water levels• Existing structure or gardens

Sun Exposure

Full Sun to Full Shade – There are natives for that

Images courtesy of Prairie Moon Nursery

Slope

Existing Turf Grass – Remove & Re-Vegetate with Native Buffer• Rely on the strength of the deep growing

roots.

Existing Rip Rap – Cover w Soil & Re-Vegetate with Native Buffer

Minneapolis AvenueMinnetrista, MN

Existing Rip Rap – Live Stake or Joint Planting

Existing Retaining Wall – Replace with Vegetated Rock Wall• Retaining walls offer no habitat

• But retaining walls are usually installed for specific reasons– Hydraulic protection of bridges and culverts– Maximize real estate

• Vegetated Rock Wall– Space between the stones provide edge habitat– Reduces the need to regrade the banks– Overhanging vegetation can reduce thermal

loading of the stream

• Reflective flow

Existing Retaining Wall – Replace with Vegetated Rock Wall

Existing Retaining Wall – Replace with ‘Terraced Pocket’ Boulder Wall

Variable Water Levels

Excerpts from Shaw, D. and Schmidt, R. 2003, Plants for Stormwater Design

Work with Existing Structures & Gardens

Concept Plan

In Stream Habitat Improvements

• Root Wads– Provide wood debris and cover– Protect the bank from erosion

In Stream Habitat Improvements

• Vegetated Brush Mattress– Build up eroded areas by trapping

sediment

In Stream Habitat Improvements

• In-Stream Boulders– Provide small scour pools & current

breaks

In Stream Habitat Improvements

• Stream Barbs– Diverts flow from eroding banks– Capture sediment

In Stream Habitat Improvements

• Coir Logs– Capture sediment during high water

levels

Visit Wenck’s Similar Projects• Shingle Creek Drive & Hampshire Ave.,

Brooklyn Park, MN– Stabilize Shingle Creek streambanks, install

native buffer and add in-stream habitat for an entire reach

• 26th Ave & Sycamore Ln Plymouth, MN– Stabilize Plymouth Creek streambanks,

install native buffer and add in-stream habitat for an entire reach

• Minneapolis Ave & Crest Ridge Ct., Minnetrista, MN– Recreate a waterway out of an eroded gully

that can handle urban runoff.– Example of vegetated riprap

Preparation for the Site Visit• Review your sun condition (sun,

part sun or shade).• Review the seed list that

matches your sun condition.• Review the plant list the matched

your sun condition and select the one you think will complement the seed list and your landscaping.

• Review the concept plan and make edits, write down your thoughts and be prepared to discuss.