Landslides: warning signs from the USGS, and how Japan's leveled warnings work

Landslides kill people every year in steep, rainy places, from the Pacific Northwest to Japan. They are hard to predict, but both the U.S. Geological Survey (USGS) and Japan's land ministry describe warning signs, and Japan now issues landslide warnings with explicit levels. This article combines the two.

Warning signs (USGS)

The USGS cautions that some landslides give clues before they happen, while others happen suddenly without any warning signs. Clues it lists include:

• sounds of cracking or breaking wood, knocking boulders, groaning of the ground, or other unusual sounds, especially if they increase
• new cracks, bulges or other deformation in the ground, roads or other surfaces
• flowing water on a slope, or water ponding where it never has before
• leaning utility poles, deformed fences, or tilting trees on a hillside
• sticking windows or doors, and new cracks in walls, ceilings or foundations

Japan's Ministry of Land, Infrastructure, Transport and Tourism (MLIT) adds signs specific to debris flows, the fast-moving slurries that rush down valleys in heavy rain: a stream suddenly turning muddy or carrying driftwood, rumbling from the mountain, and a stream level dropping even though rain continues. MLIT says debris flows can move at 20 to 40 km per hour.

What to do

The USGS advice: leave the area immediately, but only if it is safe to do so. If you are in a building that is being hit by a landslide, it says it is best not to evacuate, and to go to the highest floor or climb onto a countertop until the landslide passes. That is advice for the moment of impact. The main lesson from Japan is to leave a landslide-risk zone early, before heavy rain peaks (our summary of the Japanese guidance below).

Japan's landslide warnings (since May 29, 2026)

Japan designates landslide warning zones; MLIT counts 721,014 of them nationwide as of June 30, 2026. The Japan Meteorological Agency (JMA) now names its warnings by level. In JMA's English naming: "Level 3 Warning (Landslide)," "Level 4 Urgent Warning (Landslide)" and "Level 5 Emergency Warning (Landslide)." JMA's English leaflet describes Level 4 as: "A disaster could happen at any time. Evacuate immediately from dangerous areas." Level 4 is the old "sediment disaster alert information," renamed.

JMA also shows landslide risk on a 1 km grid map called Kikikuru, and offers push notifications when risk rises. If you are staying in a valley or below a slope in Japan during heavy rain, check the hazard map portal (disaportal.gsi.go.jp) and move out of the zone by Level 4. See Japan's five alert levels explained.

Our Japanese edition has the detailed guide: 土砂災害の前ぶれと避難.