Landslides risk in New Hampshire

Landslide characteristics in New Hampshire

New Hampshire is rated level 2 out of 5 for landslide risk on FEMA's National Risk Index, which means the statewide probability of landslides is relatively low but not negligible. The state's rugged landscape, especially the White Mountains, the Monadnock area, and other hilly regions, contains steep slopes that can fail under the right conditions. Glacial soils, weathered rock, and joints in granite ledges all contribute to a slow but real hazard.

Most landslides in New Hampshire are shallow and small, such as debris slides, soil slumps, and rockfalls. They are often triggered by heavy rainfall, especially during summer thunderstorms or Nor'easters, and by the rapid melting of deep snowpack in the spring. These events can happen with little warning. Developed hillsides, road cuts, and home sites carved into slopes are particularly exposed, as the alteration of natural ground can weaken the soil or change drainage patterns.

Although large catastrophic landslides are rare in the state, even small slides can damage property and disrupt access. The official state emergency management agency, New Hampshire Homeland Security and Emergency Management (HSEM), works with local officials and the U.S. Geological Survey to monitor hazards and provide public safety guidance. If you live near a steep slope, riverbank, or in a mountainous area, it is worth understanding the signs of ground movement.

How it affects homes

Landslide damage can range from cosmetic cracks to catastrophic destruction. In New Hampshire, the most common effects on homes are cracked foundations, bowed or leaning retaining walls, broken driveways, damaged utility lines, and blocked doors or windows. In more severe cases, a slide can push a house off its foundation or completely bury the lower level. Even a minor slide can undermine a septic system or cause water to pool, leading to additional problems.

Insurance is a critical concern. Standard homeowners insurance policies in New Hampshire do not cover landslide or earth movement damage. Flood insurance through the National Flood Insurance Program also excludes landslides because they are not caused by rising floodwaters. For coverage, you would need a separate landslide or earth movement endorsement, which is often sold through specialty providers. Availability can be limited, and premiums may be high if your home is in a known hazard zone. Contact your insurance agent to ask about your options, and if you are buying a home on a slope, consider a geotechnical evaluation before closing.

If a landslide occurs near your home, the first priority is safety. Stay away from the affected area, because additional slides can happen. Then report the damage to your local emergency manager and to the New Hampshire HSEM for guidance on recovery resources.

How to prepare your home

Preparing for landslide risk in New Hampshire is mostly about managing water and recognizing early warning signs. Here are practical steps you can take:

• Inspect your property for cracks in driveways, sidewalks, and foundation walls. Cracks that widen or appear suddenly can indicate ground movement.
• Manage drainage around your home. Keep gutters and downspouts clear and direct water far from your foundation. Do not let water pool on or near slopes.
• Avoid placing fill or heavy structures on the upper part of a natural slope, as extra weight can increase stress on the ground.
• Plant deep-rooted native vegetation on slopes to help stabilize soil. Avoid overwatering lawns on steep areas, as excessive moisture can reduce soil strength.
• Build or maintain retaining walls with proper drainage (e.g., weep holes or gravel backfill) so water pressure does not build up behind them.
• Watch for leaning trees, tilted poles, or visible soil movement on your lot or neighboring slopes. These are red flags.
• Contact a licensed geotechnical engineer if your home is very close to a steep slope or if you have any concerns. They can recommend site-specific solutions.
• Have an emergency plan that includes evacuation routes and a meeting place, in case local authorities order an evacuation due to imminent danger.

These steps are covered in more detail in the Ready.gov guide to landslides and debris flow, which also advises to listen to local weather forecasts and heed landslide warnings.

Frequently asked questions

What causes landslides in New Hampshire?

Most landslides in New Hampshire are caused by a combination of steep slopes, soil saturation, and disturbance. Heavy rainfall, rapid snowmelt, or a pipe leak can quickly saturate the ground, reducing friction between soil particles. When gravity overcomes friction, the slope can give way. Vegetation removal, excavation, and construction on slopes can also weaken the natural stability.

Are there any warning signs of a landslide I should look for?

Yes. Important warning signs include new cracks in plaster, tiles, floors, or foundations; sticking doors or windows; continuous soil movement or visible depressions; tilted trees or fence posts; and unusual water flow, like a wet spot on a dry slope or water seeping from the ground. If you see these signs, contact your local emergency manager or a geotechnical engineer for an assessment.

What should I do during heavy rain if I live on a slope?

Stay alert and listen to local weather alerts on NOAA Weather Radio or from New Hampshire HSEM. If you see or hear signs of a landslide, such as loud rumblings, cracking sounds, or sudden earth movement, evacuate immediately. Move to higher ground and call 911 if you suspect a landslide is starting. Do not return until officials say it is safe, as multiple slides can occur in the same area.

Official resources

• New Hampshire Homeland Security and Emergency Management
• USGS Landslide Hazards Program
• Ready.gov – Landslides and Debris Flow