Serving Brainerd Lakes & Southern Cass County Areas

Lakeshore Restoration

Protect and beautify your lakeshore.

Erosion control, bank stabilization, wetland restoration, water quality improvement, and habitat enhancement.

RIPRAP SHORE AND STREAMBANK PROTECTION

Check with local government to see if a permit is needed.

1. The riprap shall consist of natural rock only, measuring 12" diameter or larger.
2. The riprap shall conform to the natural alignment of the shore or streambank.
3. The minimum finished slope shall be no steeper than 3 feet horizontal to 1 foot vertical (3:1).
4. No materials shall be placed more than 5 feet waterward of the OHW, nor obstruct the flow of water.
5. The site is not along Lake Superior, on a designated trout stream, or a posted fish spawning area.

DEFINITION

Riprap is defined as coarse stones, boulders, or rock, loosely laid against an existing bank or shore for the purpose of preventing or controlling erosion. Only 12" diameter or larger natural rock riprap protection may be installed without a permit. The size of natural rock will reduce movement by natural forces. Riprap is generally placed to prevent erosion by wave action and currents; it is also useful in preventing burrowing animals (muskrat, beaver, etc.). Riprap does not prevent ice heaves.

LOCATION

The placement of riprap should be limited to the area subjected to erosion. This information sheet outlines guidelines for the placement of natural rock riprap without a permit. The installation of other types of riprap will require a permit.
Riprap shall be attempted only where site soils are capable of supporting riprap. Such soils may include various combinations of sand, silt and clay. Soils such as peat and muck are not capable of supporting riprap.

PLACEMENT

Dumped stone is the most flexible and will adjust itself to uneven bank settlement. In most cases, dumped stone is also the least costly. Hand-placed riprap should be roughly square or rectangular to facilitate placement by hand or derrick. Hand-placed riprap is easily disrupted by minor settling.

CONSTRUCTION

Riprap shall be installed with a minimum finished slope of 3:1. No riprap or filter materials shall be placed more than 5 feet waterward of the 0HW. A severely eroding bank may require filling in with a greater depth of natural rock before a stable slope may be achieved. Gently sloping banks are more stable for riprap and result in fewer failures. The extent of riprap into the water should be minimized since flow and wave action can cause stability problems.
A transitional layer of gravel, small stone, or fabric shall be placed between the fine material of an embankment and the riprap materials, The purposes of the filter are to:
(1) prevent fine embankment material from being pulled through the riprap materials
(2) distribute the weight of the overlying riprap to prevent settlement, and
(3) to provide relief to hydrostatic pressures inside the embankment.

MAINTENANCE REQUIREMENTS

All riprap requires maintenance. Proper filter blanket thickness, rock size, placement, and slope will prevent frequent maintenance. All riprap, however, will experience some displacement. The desired slope, thickness and rock surface should be restored when needed. All maintenance should be done in conformance with the above mentioned criteria.

Protect your shoreline using natural materials such as boulders and plantings. We service lakeshores throughout the Brainerd Lakes and Crow Wing County areas.

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