Stream Bank Stabilization Options and Techniques

Rob Cronauer

Watershed Specialist

January 22, 2016

Options• #1 Rip-rap

• #2 Rip-rap

• #3 Rip-rap

• #4 Rip-rap

• #5 Other

Rip-Rap

• The #1 used stream stabilization method…and for good reason…..it works!

• Choose proper size

• Install correctly

• There are some right and wrong ways to install

Not recommended to place rip-rap on layer of fabric

The fabric can “tent” allowing water behind it. Can be very strong such as a bed sheet catching a falling person.

Prevent erosion around and/or under rip-rap• Use large enough rock the stream can’t move

• “key” the rock into the stream bed

• “key” the rock into the upstream and downstream embankments, similar to bridge abutments

• Greatest stream velocity is at the toe of the slope

Mowing as close as possible to stream banks prevents woody vegetation and roots to stabilize the bank. The vertical bank on left will never become stabilized.

Would have preferred a more gentle slope but septic system was here

Place largest stone on the “face” of the rip-rap placement, where the greatest velocities are.

Chinking/choking in the voids between the angular stones helps “knit” them together. Use the largest size possible that will still find the voids in the rocks.

Jacobs Creek,

Laurellville

BEFORE

Jacobs Creek, LaurelvilleJacobs Creek,

Laurelville

1 year after

project

Jacobs Creek, Laurelville

R-7 keyed into the bank

“chocked with 2b”, and

trees planted on top of

slope, willow stakes on

slope

3 years AFTER

construction

No room to slope back bank because of the house

Stream won’t move this size rock. Rock keyed into stream bed. Rock above stream will stabilize entire bank. Stream will erode gravel bar. Rock sloped into creek to achieve maximum slope for stability.

Mowing as close as possible to stream banks prevents woody vegetation and roots to stabilize the bank. The vertical bank on left will never become stabilized.

Banks have been sloped back to establish vegetation on the banks and the rocks are at the toe, where the greatest velocities exists

Mowing as close as possible to stream banks prevents woody vegetation and roots to stabilize the bank. The vertical bank on right will never become stabilized.

Rock at toe of slope only needed on outside bend in the creek

Achieving vegetation on banks is crucial to stabilization, and should be a priority immediately after excavation. Erosion control matting can help in this process and can help prevent erosion if the stream should floodbefore grass can become established.

Shupe Run, Willows Park,

Mt.Pleasant

BEFORE

Shupe Run, Willows

Park, Mt. Pleasant

AFTER

Rock toe with fill and

live stakes

Gabion baskets

• don’t use

• If you have to use them, the greatest chance for failures are from erosion at the start of them, beginning of them, or at the bottom of them

• Must have them embedded into the stream bed and banks, to prevent velocity from getting behind or under them

The stream couldn’t move the rocks, but could erode out from under and around them

Rock deflectors installed to maintain velocity throughout channel to reduce sediment deposition

Dredging is a temporary solution to a permanent problem.Try to reduce the sediment loading from the source. If that can’t be accomplished increase channel capacity or modify flow.

Some other techniques rather than rip-rap• Stone structures, log structures, bank grading, etc…

• More pleasing to the eye with a more “natural” look

• Can often use on-site materials

• Design for fish habitat

• Should you desire, there are alternatives to rip-rap

Can be modified into a pond intake

Haymaker Run, Murrysville

Log cross vane, used for a

pond intake, see 4”pvc on

left downstream log

Mowing as close as possible to stream banks prevents woody vegetation and roots to stabilize the bank. The vertical bank on left will never become stabilized.

Notice the velocity “white water”

is at the ends of the logs and

well away from the bank

Mill Creek, Ligonier

BEFORE

Cut leaning trees

Mill Creek,

One year after construction

Mill Creek

AFTER

Multi-log deflectors

installed, one rootwad, and

live stakes on slopes, and

trees on top of slope

Mill Creek

Sediment deposits “building bank”

after first storm

Mill Creek, Ligonier

BEFORE

Mill Creek, Ligonier

Rootwads one year after

construction

Mill Creek

2 years AFTER

Rootwads installed

Many, many more options

• If your going to use rip-rap keep in mind a few keys. Use large enough rock, embed into banks and stream bed, consider choking with smaller rock. *use oversize rock in urban settings

• If your looking for an alternative to rip-rap, options are endless. I would be happy to help out.

THANK YOU!• Rob Cronauer (724) 837-5271