Landslides risk in Delaware

You're standing in the backyard of a house in Wilmington, looking at a steep bank that drops down to the Brandywine. The seller says it's been stable for decades. Probably true. Delaware doesn't have many landslides — the statewide risk rating is 1 out of 5. But 'not many' isn't 'none.' If you're buying on a slope, or if you own a home near a river bluff or the coast, you should know what you're looking at.

Why Delaware looks like this

Delaware is flat. Most of the state sits on the Atlantic Coastal Plain, a gentle terrain of sand, silt, and clay that doesn't produce the kind of dramatic slides you see in California or West Virginia. The highest point in the state is only a few hundred feet above sea level, near the Pennsylvania line in New Castle County. So why would a landslide ever happen here?

It happens on the edges. The steep banks of the Brandywine Creek and Christina River in New Castle County can slump after heavy rain. The bluffs along the Delaware Bay and the Atlantic coast — from Cape Henlopen down through Rehoboth Beach, Bethany Beach, and Fenwick Island — are made of loose sand and gravel. Those bluffs erode constantly. When a storm hits, whole sections can collapse, especially after a nor'easter or a hurricane. That's not a classic landslide, but it's the same process: gravity moving soil downhill. The difference is that in Delaware it usually happens slowly, a few feet at a time, or in small slumps after a wet winter.

Kent County and Sussex County have fewer steep slopes, but you still see problems along the St. Jones River, the Murderkill River, and man-made ponds and drainage ditches. Construction sites with unsecured fill can also fail. The state's rating of 1 of 5 reflects that most homes never see this. But if you're on a bluff or a riverbank, your risk is higher than the statewide average.

Insurance gaps people miss

Here's the hard truth: your standard homeowners policy in Delaware does not cover landslide. It doesn't cover mudslide, either. Most policies exclude 'earth movement' — that includes earthquakes, sinkholes, and landslides. You might think flood insurance would help. It won't. The National Flood Insurance Program (NFIP) covers mudflow, which is a river of liquid mud, but not a landslide that moves as a solid block of earth. That distinction matters after a storm when you're trying to file a claim.

What about hurricane coverage? In Delaware, wind damage from a hurricane is typically covered, but flooding is not unless you have separate flood insurance. Landslide is a third category, and it's usually excluded from both. The only way to get landslide coverage is a difference in conditions (DIC) policy or a specialized earthquake policy that explicitly includes landslide. Those are rare in Delaware, and most agents won't even quote them. So for most homeowners, the practical answer is: you're self-insured for landslide. That's a reason to focus on prevention and on knowing your slope.

If you're buying a house on a bluff in Sussex County or along the Delaware River, ask the seller for any geotechnical reports. Ask your insurance agent to show you the exclusion in writing. Don't assume your policy covers it.

A practical weekend plan

You don't need to spend a lot of money to reduce your landslide risk in Delaware. The main driver is water. Water in the soil makes it heavy and slippery. So your first job is to get water away from your foundation and away from any slopes.

Start with your gutters and downspouts. If they dump water at the top of a slope, you're asking for trouble. Extend them at least 5 to 10 feet away from the house, and make sure they discharge onto flat ground, not down a hill. Check for cracks in your driveway, patio, or foundation. Small cracks let water in. If you see new cracks after a storm, that's a sign the ground is moving.

If you live on a bluff, look for leaning trees or poles. Trees that tilt downhill can indicate soil creep. Also look for exposed roots or soil pulled away from foundations. On the coast, watch for signs of erosion at the edge of the bluff. You can't stop erosion, but you can avoid building too close to the edge.

If you only do three things this weekend: clean your gutters, extend your downspouts, and walk your property looking for new cracks or tilting. That's about 90% of what you can control. A geotechnical engineer is worth calling if you see something that worries you, but for most homes in Delaware, that's overkill.

Questions we get

Does Delaware actually have landslides?

Yes, but they're small and localized. Most are slumps or soil creep on riverbanks and coastal bluffs. You won't see a mountain slide, but you might see a section of your yard drop a foot after a wet winter. The state's official risk rating is low, but if you're on a steep slope, your personal risk is higher.

What should I do if I live on a bluff in Sussex County?

First, don't panic. Bluffs erode slowly. But do keep an eye on the edge. If you're within 20 feet of the bluff edge, consider having a geotechnical engineer look at it. You can also check with the Delaware Department of Natural Resources and Environmental Control (DNREC) about coastal construction rules. They regulate building near the coast. And remember that your insurance likely won't cover a landslide, so prevention is your best protection.

Is landslide covered by my Delaware homeowners policy?

Almost never. Standard policies exclude earth movement. Flood insurance doesn't cover it either. You'd need a special rider or a DIC policy, and those are hard to find in Delaware. So assume you're on your own. That's another reason to keep water away from slopes and to document the condition of your property with photos.

Official maps and agencies

For more information, check these official sources:

• Delaware Emergency Management Agency — state agency for emergency preparedness and response.
• USGS Landslide Hazards Program — national research and maps.
• Ready.gov – Landslides — federal preparedness guidance.

You can also look at FEMA's National Risk Index for Delaware, which shows the low overall risk. But remember that risk is local. A house on a flat lot in Dover is not the same as a house on a bluff in Bethany Beach.