If you own lakeshore property in the Detroit Lakes area, shoreline erosion is not a hypothetical problem — it is something you can see happening season after season. Wave action, boat wakes, ice heave, and spring snowmelt runoff are relentless forces working against your bank. Riprap is one of the most effective and time-tested tools available for stopping that erosion and protecting both your property and the water quality of the lake.

Here is what you need to know about riprap — what it is, why it works, and why maintaining it matters as much as installing it correctly in the first place.

What Is Riprap?

Riprap is a layer of large natural rock — typically ranging from 6 to 30 inches in diameter — placed along a shoreline to absorb and deflect the energy of moving water. Unlike a retaining wall, which is a rigid vertical structure, riprap works by distributing the force of wave action across a sloped surface of interlocking stones. Water loses its energy as it moves through and around the rocks rather than hitting a hard surface and rebounding.

When installed correctly, riprap sits on a bed of filter fabric, crushed rock, or gravel that prevents the fine soil underneath from washing out through the gaps. The stone layer above protects the bank. The filter layer below protects the stone. Both layers working together is what gives a properly installed riprap shoreline its longevity.

Why Becker County Lakeshores Need It

Shoreline erosion in the Detroit Lakes area is driven by several forces that compound on each other throughout the year.

Summer boat traffic and wave action are the most visible culprits. The lakes around Detroit Lakes see heavy recreational use from May through September. Every passing boat generates wake that hits the shore repeatedly over a full season. Without protection, that constant wave energy gradually undercuts the bank, destabilizes vegetation, and moves soil into the lake.

Ice heave in winter is a force that does not get enough attention. As lake ice expands and contracts through freeze-thaw cycles, it can push against unprotected shoreline banks with significant force — slowly lifting and displacing soil season after season. Riprap's mass and interlocking structure resists this movement in a way that soft banks simply cannot.

Spring snowmelt runoff concentrates water flow along the bank just as the soil is at its most saturated and vulnerable. Properties with any grade running toward the shore are particularly susceptible to significant soil loss during the melt period each year.

Left unaddressed, shoreline erosion does not just affect the appearance of your property. It contributes sediment and nutrients to the lake, degrades fish and wildlife habitat, and over time undermines the structural integrity of anything built near the water's edge.

The Advantages of Riprap for Lakeshore Protection

Long-term durability. A properly installed riprap shoreline with a correct filter layer underneath will last decades with minimal intervention. It does not rot, rust, or require repainting.

Natural appearance. Riprap blends into a lakeshore environment far more naturally than a concrete wall or steel sheet pile. With native vegetation planted between and behind the rocks, a well-done riprap shoreline can be both functional and genuinely attractive.

Flexibility. Unlike rigid structures, riprap can shift slightly with the natural movement of the shoreline and still maintain its protective function. Minor settling does not cause structural failure the way it can with hard-wall installations.

Property value protection. An eroding lakeshore is a liability. A stable, well-maintained riprap shoreline protects the land you have and maintains the value of what is often a significant investment.

The Minnesota DNR provides clear guidance on when and how riprap is appropriate for lakeshore properties throughout our state: Minnesota DNR — Shoreline Alteration: Riprap

What Proper Installation Looks Like — and Why It Matters

Not all riprap installations are equal. A shoreline lined with rock that was simply dumped against the bank without proper bed preparation will not hold. The filter layer underneath is not optional — it is what prevents the soil from migrating out through the gaps in the stone over time, which causes the rock to settle and the bank to fail.

Proper installation requires the right stone size for the wave energy at that specific location, the correct slope, a filter bed underneath, and rock placed in a way that interlocks and holds rather than shifting independently.

The Minnesota DNR specifies that natural rock riprap must be between 6 and 30 inches in diameter, placed on a proper filter of crushed rock, gravel, or filter fabric, and installed at a slope no steeper than 3 horizontal to 1 vertical. Concrete is not permitted: Minnesota DNR — Shoreland Information for Property Owners

If you are considering a riprap installation, working with a professional who understands both the installation requirements and Minnesota DNR permitting guidelines protects your investment and keeps you on the right side of state regulations.

The Importance of Riprap Maintenance

This is the step most property owners skip — and it is where a lot of Becker County shorelines start to fail.

Riprap requires periodic inspection and maintenance to continue performing as intended. Here is what to watch for:

Gaps and settlement. Over time, individual rocks can shift, sink, or be displaced by ice. Gaps in the stone layer expose the filter bed and underlying soil to wave energy. Left unaddressed, a small gap becomes a progressively larger failure.

Undermining at the waterward edge. The toe of the riprap — the bottom edge closest to the water — is under the most stress. If it begins to settle or undercut, the entire slope above it becomes unstable. This is the most common and most serious maintenance issue we see.

Vegetation growing through the rock. Shallow-rooted vegetation in the rock is not necessarily a problem — in fact it can help stabilize the slope. Deep-rooted invasive plants, however, can displace rocks and create pathways for soil loss over time.

Ice damage after hard winters. After a particularly hard freeze and thaw season, a walk along your riprap in early spring to check for displaced stone is time well spent.

Addressing small problems early — resetting displaced rocks, filling gaps, reinforcing the toe — is significantly less expensive than allowing a section to fail completely and requiring a full reinstallation.

Protecting your shoreline starts with the right installation and the right maintenance plan.

At Miller Yard Care & Construction, we work with lakeshore properties throughout the Detroit Lakes area and Becker County. Whether you are dealing with active erosion, a failing existing shoreline, or looking to protect a stable bank before problems develop, we can assess your property and recommend the right approach.

Learn more about our Landscaping and Shoreline Services here.

(218) 849-9794

Frequently Asked Questions

Q: Do I need a permit to install riprap on my Becker County lakeshore? A: It depends on the project. Minnesota DNR does not require a Public Waters Work Permit for riprap installations that meet all state standards — including stone size, slope, filter layer, and shoreline length limits. However, local permits may still be required. We recommend consulting with the DNR and your county before beginning any shoreline work.

Q: How long does riprap last? A: A properly installed riprap shoreline with a correct filter layer can last 20 to 40 years or more with routine maintenance. The filter bed and the integrity of the toe are the two most critical factors in long-term performance.

Q: Can I just add more rock on top of existing riprap that is settling? A: Sometimes, but not always. If the settlement is caused by a failing filter layer or undermining at the toe, adding rock on top addresses the symptom rather than the cause. A proper assessment of why the rock is settling is the right first step.

Q: Is riprap the only option for shoreline erosion on my Detroit Lakes property? A: No. The Minnesota DNR strongly encourages native vegetation for shoreline stabilization where conditions allow, and it is often a more cost-effective first option. For steep slopes, significant wave exposure, or areas with active erosion, riprap is frequently the most practical and durable solution. We assess each property individually.