Landslides risk in North Dakota

Landslide risk in North Dakota: what makes this state different

North Dakota has one of the lowest landslide hazards in the country. FEMA's National Risk Index rates the state 1 out of 5 for this hazard, and that low rating comes down to terrain: the great majority of North Dakota is flat to gently rolling glaciated prairie — the Red River Valley in the east, the Drift Prairie in the center, and broad, level benches of the Missouri Plateau in the west. Landslides need two things that flat ground rarely provides at once: a steep slope and enough water to weaken it.

Where those two conditions do come together, landslides are possible. The most exposed areas tend to be:

• Missouri River valley bluffs — steep, clay-rich slopes along the river corridor, including developed areas near Bismarck and Mandan where homes sit on or below the bluffs.
• Reservoir shorelines — the banks of Lake Sakakawea and Lake Oahe, where wave action, changing water levels, and saturated soils can trigger slumps and shoreline collapse.
• The North Dakota Badlands — the rugged breaks along the Little Missouri River and its tributaries, where soft sandstone, siltstone, and clay layers produce rockfalls, topples, and slumps.
• Steep river and coulee banks — the Pembina Gorge and other deeply cut valleys in the northeast, plus cut banks along rivers and streams statewide.
• Engineered slopes — highway cuts, dam embankments, and building sites where fill has been placed on a slope or the toe of a slope has been excavated.

The types of movement seen here are usually not the fast, catastrophic landslides of mountainous states. More often they are slumps and earthflows in glacial till and clay — slow, creeping movements that crack foundations and tilt fence posts over months or years — along with rockfalls in the Badlands and bank slumping along reservoirs and rivers.

Timing follows the weather. Most slope failures in North Dakota happen in spring, when rapid snowmelt and spring rain saturate the ground, or after heavy summer thunderstorms. Repeated freeze-thaw cycles also loosen soil and rock on exposed slopes. Prolonged wet periods, and human changes such as leaking pipes, concentrated roof drainage, or irrigation on a hillside, can push a marginal slope over the edge at any time of year.

How it affects homes

Because the state's landslides are usually small and slow, damage to homes tends to be gradual rather than dramatic. Typical problems include:

• Cracks in foundations, basement walls, slabs, and interior drywall
• Doors and windows that suddenly stick, or floors that feel uneven and sloped
• Separation between a house and its attached garage, deck, porch, or steps
• Broken water, sewer, gas, or septic lines as the ground shifts
• Failed retaining walls, cracked driveways, sidewalks, and patios
• Loss of yard, trees, or part of the building lot where a bluff or bank gives way

Even movement of a few inches can mean costly structural repairs, and damage often gets worse over time if the water source feeding the slope is not fixed. Homes built at the top of a steep bluff, at the toe of a slope, or on older landslide deposits are the most vulnerable.

Insurance is the part homeowners most often get wrong. Standard homeowners policies generally exclude damage from earth movement, including landslides, and the National Flood Insurance Program does not cover landslide or earth movement damage either. Some carriers offer a separate difference in conditions (DIC) policy that can add earth movement coverage; availability and cost vary widely, so it is worth asking your agent directly. If a slope failure is caused by a neighbor's leaking pipe or a contractor's excavation, there may be liability considerations — in that case, document everything and talk with your insurer and, if needed, an attorney. Keep photos, repair receipts, and a written record of when cracks first appeared.

How to prepare your home

Even in a low-risk state, a few practical steps reduce the chance that your home is affected.

1. Manage water around the house. Keep gutters and downspouts clean, and discharge roof water well away from slopes and foundations — never onto a hillside. Grade soil so surface water drains away from the house, and consider professional drainage or a French drain on wet slopes.
2. Do not load the top or cut the toe of a slope. Adding fill, a large deck, a pool, or a shed at the crest of a bluff adds weight that can trigger movement. Excavating at the bottom removes support.
3. Keep deep-rooted vegetation in place. Native grasses, shrubs, and trees help hold soil, though large trees on a steep bluff also add weight and wind leverage — get advice before clearing or planting.
4. Inspect regularly. Walk your property each spring and after heavy rain. Look for new cracks in the ground, tilted trees or fence posts, bulging soil at the base of a slope, new springs or seeps, and doors or windows that no longer close properly.
5. Maintain retaining walls and drainage structures. Weep holes, drains behind walls, and outlet pipes need to keep working; a clogged drain can saturate the soil behind a wall.
6. Get a professional opinion before you buy or build. On or near a bluff, bank, or steep slope, hire a licensed geotechnical engineer or engineering geologist to evaluate the site. This is also wise before major additions or regrading.
7. Review your insurance. Confirm in writing what your policy does and does not cover, and ask about DIC or excess coverage for earth movement.
8. Plan for evacuation. Know the warning signs — sudden muddy water, rumbling or cracking sounds, ground that looks or feels like it is moving. If you see them, leave immediately and call 911, then contact your local emergency manager. Your county emergency management office and the North Dakota Department of Emergency Services can advise on local plans.
9. Keep documents safe. Store insurance policies, photos, and important papers somewhere other than the threatened part of the home.

Frequently asked questions

Are landslides common in North Dakota?

No. North Dakota is rated 1 out of 5 for landslide risk in FEMA's National Risk Index, and because most of the state is flat prairie, the hazard is limited to relatively few places with steep slopes. Landslides do occur, mostly as slow slumps and earthflows along river bluffs, reservoir shorelines, and the Badlands, and they are usually triggered by spring snowmelt, heavy rain, or erosion.

Does homeowners insurance cover landslide damage in North Dakota?

Usually not. Most standard homeowners policies exclude earth movement, which includes landslides, and flood insurance through the NFIP also does not cover landslide damage. If you own property on or near a steep slope, ask your insurance agent whether a difference in conditions (DIC) policy or another endorsement is available, and confirm the answer in writing.

Which parts of North Dakota have the highest landslide risk?

The steepest terrain carries the most risk: the Missouri River valley bluffs and adjacent slopes, the shorelines of Lake Sakakawea and Lake Oahe, the Badlands along the Little Missouri River and its tributaries, the Pembina Gorge, and steep cut banks along rivers and streams. Homes on or at the base of these slopes — and on older landslide deposits — face the greatest exposure. USGS maintains nationwide landslide information at usgs.gov/programs/landslide-hazards.

Official resources

• North Dakota Department of Emergency Services — state emergency preparedness, response, and recovery information.
• USGS Landslide Hazards Program — science, maps, and research on landslides nationwide.
• Ready.gov – Landslides and Debris Flow — federal guidance on warning signs, evacuation, and safety.