Streambank Stabilization Project

Transcription

1 Streambank Stabilization Project

2 Streambank Stabilization Project Nemaha County, Kansas Located on the Nemaha River north of Seneca

3 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

4 Fall 2005 Bank is eroding reaching 30 foot drop off in places. Last couple rows of corn are unable to be harvested. Approximately 30 ft embankment

5 These air photographs show the dramatic difference in how the Nemaha river has changed courses over the years on this particular site Much older air photograph of same area, year unknown.

6 Fall Severity of Bank Cutting. Average Tons of Soil Loss Calculations developed by comparing the two previous air photographs. (Total area 2.2acres from where river moved - comparing pictures) Average Calculated Weight Cubic Feet Soil Loss 2.2 total 43,560 sq/ft/acre = 95,832 sq/ft 95,832 sq/ft * 30 ft depth embankment = 2,874,960 cu/ft 2,874,960 * 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

7 Spring 2005 before construction in Fall. Site of Stabilization Project on West side of Nemaha River. N

8 Dozers working to slope the steep embankment to an appropriate angle. 4:1 slope Starting Excavation - Fall 2005

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

10 Shows bank angle achieved by dozer excavation.

11 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 Bank East Bank

12 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.

13 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.

14 600 Willow Stakes were planted closest to the river. Tree Plantings

15 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.

16 A 66 foot Native Grass buffer (CP-21) was established above the tree plantings. Buffer Establishment

17 Project completed Spring 2006 Better than 90% survival of tree plantings. Streambank Stabilization project has already survived one major flood event.

18 Project Spring 2010 Shows the tree plantings coming in nice on the bankside. The CP-21 buffer strip located above the tree plantings.

19 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)

20 This project from the previous slide was funded by the State Conservation Commission on the Nemaha River. Picture is from Spring Project was completed in Shows the success of many willow trees growing along the river.

21 Special Thanks To: Nemaha County Conservation District Melvin Steinlage Buffer Coordinator for Nemaha, Jackson, and Brown counties. Pheasants Forever and Quail Forever Toni Larson Farm Bill Wildlife Biologist Thank You Nemaha County Natural Resources Conservation Service for technical assistance with the projects and PowerPoint.