A Lake Minnetonka shoreline takes a beating: boat wake all summer, ice in winter, and water levels that rise and fall against the bank. There's more than one way to hold it, from native plants to rock riprap, and most of them involve a permit. This guide covers the options and the rules, with links to the agencies that write them. What a given shoreline needs, and what will be permitted, depends on the property and the project, so the agencies have the final word.
What wears a shoreline down
The DNR lists the usual causes on its riprap page: fluctuating water levels, increased wave action, ice pushes, loss of natural vegetation and human activity.
On Lake Minnetonka, boat wake is a big part of the wave action. Since January 1, 2023, the Lake Minnetonka Conservation District's wake rule limits all watercraft to 5 mph within 300 feet of shore, and the LMCD names the effect of wakes on the shoreline as one reason for the rule.
Ice does its damage in winter and early spring. Lake ice pushes against the bank and can leave a ridge of soil and rock along the shore, which state rules call an ice ridge.
Your options, from plants to rock
The Minnehaha Creek Watershed District's Shoreline and Streambank Stabilization Rule sorts stabilization into three kinds: biological, bioengineering and structural. Its stated policy is to limit disturbance to the natural shoreline and, where stabilization is needed, to promote bioengineering and similar naturalized methods.
Native plants
Native plants on the bank hold soil and slow runoff. Where it's appropriate, the DNR encourages natural alternatives to riprap to control erosion. Under the MCWD rule, planting vegetation doesn't need an MCWD permit as long as the bank isn't disturbed beyond ordinary planting.
Bioengineering
Bioengineering combines plants with natural materials. State rules name willow wattles, willow posts, brush mattressing, brush layering, fiber roll breakwaters, plant carpets and root wads among the techniques, and set conditions for using them without a DNR permit, including approval by the DNR commissioner and design or review by the soil and water conservation district or the watershed district (Minnesota Rules 6115.0215, subpart 4, item A).
Riprap
Riprap is natural rock placed along the shore to take the force of waves and ice. The DNR notes that it can reduce erosion but is expensive, puts a barrier between the land and the water, and "is not maintenance free and does not eliminate ice heaving." Plants set within the rocks help stabilize it and improve habitat. Riprap is allowed only where there is a demonstrated need to stop existing erosion or restore an eroded shoreline, not for landscaping or to replace a stable, naturally vegetated shore.
Walls at the water
The DNR says one or more rows of stacked boulders work as a retaining wall, not riprap, and need a DNR permit. Under the MCWD rule, a structural design at a 2:1 slope or steeper counts as a retaining wall, and a new one is allowed only under the district's Variances and Exceptions Rule, after showing there is no adequate alternative and with a structural analysis by a Minnesota-licensed professional engineer. For walls away from the water, see our retaining walls guide.
Which one fits
For most new stabilization other than planting, the MCWD asks for an erosion intensity calculation, and the result decides what's allowed: low erosion intensity must use a biological practice, medium may use biological or bioengineering, and high may use any of the three, riprap included.
How riprap is built: the official standards
These are the DNR's conditions for riprap that doesn't need a DNR permit (Minnesota Rules 6115.0215, subpart 4, item E):
- Natural rock averaging no less than 6 and no more than 30 inches in diameter, sized for the wave or current action and free of soil, debris and anything that could pollute the lake. No concrete.
- A filter of crushed rock, gravel or filter fabric underneath.
- No more than 6 feet waterward of the ordinary high water level.
- A finished slope no steeper than 3 to 1, measured on top of the rocks.
- No more than 200 feet of shoreline on a lake.
- Following the natural line of the shore, not covering emergent vegetation, and not blocking navigation or the flow of water.
The MCWD adds its own design standards. Riprap must be durable stone that meets MnDOT Class III or IV size and gradation, and it can't go higher than the top of the bank or 2 feet above the 100-year high water elevation, whichever is lower. Toe boulders can be up to 30 inches but must be at least half buried. A transitional granular filter goes between the native shoreline and the rock, with non-woven geotextile filter fabric beneath it. The slope can't be steeper than 3:1 unless site conditions make that impractical, lakeward encroachment should not exceed 5 feet and may not exceed 10, plantings should go between the boulders where feasible, and a floating sediment curtain is required while work below the top of the bank is underway.
Permits: who does what
The DNR
The DNR has jurisdiction below the ordinary high water level, and most projects there need a Public Waters Work Permit. Riprap that meets every condition above doesn't, but the installer still has to submit the DNR's landowner statement form either way (Minnesota Statutes section 103G.241).
The MCWD
The MCWD requires a permit to disturb the bank below the ordinary high water level to stabilize it or to add an amenity, which covers riprap, bioengineering, retaining walls, boat ramps and sand blankets. No MCWD permit is needed to maintain a working practice when no material is added and the bank isn't disturbed, or to plant vegetation. Projects that meet the rule's design standards may qualify for a Fast Track permit.
One permit for both
Inside the MCWD, DNR General Permit 2001-6009 covers riprap, bioengineering, ice ridge removal, retaining walls and similar shoreline work for property owners who have an MCWD permit for it, with no separate DNR authorization needed. The current general permit runs through March 16, 2027, and other agencies' rules, including the city's, still apply.
Ice ridges
State rules let an ice ridge be removed or graded without a DNR permit when, among other conditions, the ridge formed within the last year, no more than 200 feet of shoreline is affected, local permits are in place or not required, exposed ground is stabilized right away, and local zoning officials, the watershed district and the soil and water conservation district get seven days' notice (Minnesota Rules 6115.0215, subpart 4, item B).
The LMCD
The LMCD sets rules for using Lake Minnetonka itself, including the wake rule above. Check with the LMCD about any part of a project that reaches out onto the lake.
The city
Cities have jurisdiction above the ordinary high water level, and the DNR notes that a local permit may be required, especially if more than 10 cubic yards of material are moved, removed or added, riprap included. City shoreland rules also cover hardcover. Minnetonka Beach, for example, doesn't count riprap as hardcover when it's consistent with what the lot needs to protect its shoreline. Our hardcover guide covers those limits.
Every one of these depends on the property and the project, and the agencies make the final call.
What it costs and how we help
Shoreline riprap starts at $10,000, and the price rises with the length of shoreline, access to it, and what the permit calls for. We handle MCWD-DNR shoreline permitting in-house, from the application to coordinating with the agencies, and build the project the permit approves. Our shoreline restoration page covers the work itself.
Shoreline and riprap FAQ
Do I need a permit for riprap on Lake Minnetonka?
Usually. Lake Minnetonka is in the Minnehaha Creek Watershed District, where disturbing the bank below the ordinary high water level for riprap needs an MCWD permit, and that permit also covers the DNR side under the DNR's general permit for the district. The city may need its own permit for work above the ordinary high water level. Requirements depend on the property and the project.
Is riprap or a natural shoreline better?
It depends on how hard the shore is eroding. The DNR encourages natural alternatives where they're appropriate, and the MCWD's rule generally allows rock only where erosion intensity is high. Riprap reduces erosion, but the DNR notes it is expensive, isn't maintenance free and doesn't eliminate ice heaving. Plants in and above the rock help it hold.
Does the MCWD require a permit for shoreline work?
For most of it. A permit is needed to disturb the bank below the ordinary high water level for riprap, bioengineering, retaining walls, boat ramps or sand blankets. Planting, and maintaining a working practice without adding material or disturbing the bank, don't need one.
If I have an MCWD permit, do I also need a DNR permit?
For the shoreline work it covers, usually not. DNR General Permit 2001-6009 lets property owners in the district who hold an MCWD permit do riprap, bioengineering, ice ridge removal and similar work without a separate DNR authorization. It runs through March 16, 2027, and other agencies' rules still apply.
Can I build a retaining wall at the water's edge?
Only in limited cases. The DNR treats stacked boulders as a retaining wall that needs a DNR permit, and the MCWD allows a new shoreline wall only under its variance rule, after showing there is no adequate alternative and with a structural analysis by a licensed professional engineer.
What can I do about an ice ridge?
State rules allow an ice ridge to be removed or graded without a DNR permit if it formed within the last year, covers no more than 200 feet of shoreline, local permits are in place or not needed, and local zoning officials, the watershed district and the soil and water conservation district get seven days' notice, among other conditions.
Does riprap stop ice damage?
Not entirely. The DNR says riprap is not maintenance free and does not eliminate ice heaving. The MCWD requires shoreline designs to follow engineering principles for wave energy and ice pressure, and plantings between and above the rock help hold it.
How does the LMCD wake rule help shorelines?
Since January 1, 2023, every boat on Lake Minnetonka has to stay at 5 mph or less within 300 feet of shore. The LMCD adopted the rule partly because of the effect large wakes have on the shoreline, docks and private property.
How much does shoreline riprap cost?
With us, shoreline riprap starts at $10,000. The final price depends on the length of shoreline, access to it, and what the permit calls for.
Can you handle the permits?
Yes. We handle MCWD-DNR shoreline permitting in-house, and we coordinate with the city when its permits apply. Approval is up to the agencies, and what they require depends on the property and the project.