streambank stabilization project

Streambank Stabilization Project

2005 2006

Streambank Stabilization Project

Nemaha County, Kansas

Located on the Nemaha River north of Seneca

Outline

I. Steep embankment and calculated soil loss

II. Excavation begins – Fall 2005

III. Flood requires re-sloping of banks

IV. Tree and native grass plantings

V. Finished Product – Spring 2006

VI. Other successful Streambank Stabilization Projects

Fall 2005

• Bank is eroding– reaching 30 foot drop off in places.

• Last couple rows of corn are unable to be harvested.

Approximately30 ft embankment

These air photographs show the dramatic difference in how the Nemaha river has changed courses over the years on this particular site.

2008 Much older air photograph of same area, year unknown.

Fall 2005 - Severity of Bank Cutting.

Average Calculated Weight Cubic Feet Soil Loss2.2 total acres @ 43,560 sq/ft/acre = 95,832 sq/ft95,832 sq/ft * 30 ft depth embankment = 2,874,960 cu/ft2,874,960 * 78lbs (average weight of 1 cubic foot of soil in Kansas)= 224,246,880 / 2000 lbs/ton= approximately 120 tons of total soil loss on this particular site

Average Tons of Soil Loss Calculations developed by comparing the two previous air photographs.

(Total area 2.2acres from where river moved - comparing pictures)

Spring 2005 before construction in Fall.

Site of Stabilization Project on West side of Nemaha River.

N

Starting Excavation - Fall 2005

• Dozers working to slope the steep embankment to an appropriate angle.

• 4:1 slope

Dozers and Backhoes working to slope the bank.State Conservation Commission provided funding for this project.

Shows bank angle achieved by dozer excavation.

• Shows right side (east bank) being pulled back from where the river had silted in - downstream is North on Nemaha River.

- This means that sediment had accumulated over time (right side of picture or east bank), had to be pulled away from the

stream channel, and then spread over a larger area.

East BankEast Bank

• High water event eroded bank. - Went back to site in early spring 2006 and site had eroded.(pictures from early spring after snowfall event)- Later in Spring 2006 had to reshape bank before rock weirs were put into place and before tree planting began.

Rock Weir Construction – Spring 2006

• Shows the angle at which rock weirs were placed to slow water velocity and reduce bank erosion.

• Total of 1,410 tons of shot rock (big boulders) added.

Tree Plantings

• 600 Willow Stakes were planted closest to the river.

• Sycamore trees were planted above the willow trees. Then American Plum and Fragrant Sumac were planted higher up the bank.

• Total of 2,066 bare rooted trees were planted.

• A 66 foot Native Grass buffer (CP-21)

was established above the tree

plantings.

Buffer Establishment

Project completed – Spring 2006

• Better than 90% survival of tree plantings .

• Streambank Stabilization project has already survived one major flood event.

Project Spring 2010

• Shows the tree plantings coming in nice on the bankside.

• The CP-21 buffer strip located above the tree plantings.

Another Streambank Stabilization Project on Nemaha River- established for 10 years, proven very successful!

- has survived several flood events

Rock Weirs and tree plantings in place Established Buffer Strip (CP-21)

This project from the previous slide was funded by the State Conservation Commission on the Nemaha River.

Picture is from Spring 2010.

- Project was completed in 2000.

Shows the success of many willow trees growing

along the river.

Thank You

Special Thanks To:

Nemaha County Conservation District Melvin Steinlage – Buffer Coordinator for Nemaha, Jackson, and Brown counties.

Pheasants Forever and Quail ForeverToni Larson – Farm Bill Wildlife Biologist

Nemaha County Natural Resources Conservation Service for technical assistance with the projects and PowerPoint.