A landslide is the mass movement of rock, earth, or debris down a slope. This phenomenon occurs when the downward force of gravity exceeds the internal strength and friction holding the slope materials together. Landslides are most frequently triggered by external factors such as prolonged heavy rainfall, which saturates the ground and increases the material’s weight, or by seismic activity like earthquakes. Human activities, including poor land-use practices or altering drainage patterns, can also increase the risk. Understanding how to identify risk and take proactive measures is the most effective way the public can protect themselves and their property from this hazard.
Understanding Local Risk and Warning Signs
Assessing your local environment for landslide susceptibility is the first step in personal safety planning, especially if you live near steep slopes, existing slide areas, or natural drainage paths. Monitoring weather forecasts for prolonged periods of intense rainfall or rapid snowmelt is crucial, as these common triggers saturate the ground and compromise stability.
The earth often provides clear warning signs that movement is occurring, which can manifest over days or even years. Look for new or unusual cracks appearing in the ground, pavement, sidewalks, or building foundations. Doors and windows that suddenly stick or jam can indicate that the building’s frame is shifting due to ground movement.
Observe the landscape for subtle changes, such as leaning utility poles, fences, or trees. Bulging ground at the base of a slope is a strong indicator of pressure buildup. Pay attention to changes in water flow, like new springs, seeps, or saturated ground where the area was typically dry. A sudden increase or decrease in creek water levels, or a shift from clear to muddy water, can signal debris movement upstream.
Structural Mitigation for Your Property
Long-term property safety depends heavily on controlling water. Implementing robust drainage control measures is an effective preventative action for homeowners on or near slopes. This includes ensuring that gutters and downspouts divert water well away from slopes and foundations, channeling runoff into a safe area like a storm drain or street.
Subsurface drainage, often using French drains or trenches filled with gravel and perforated pipes, helps lower the groundwater level in the soil. Lowering the saturation level directly improves the slope’s stability by reducing the weight and internal pressure of the soil mass. Homeowners should also promptly repair any leaking water lines, pools, or septic systems that could introduce excess moisture into the ground.
Slope stabilization can involve engineering solutions like building retaining walls, which are designed to hold back soil and debris. Retaining walls must be properly engineered with adequate drainage features, such as drain pipes and clean granular backfill, to prevent water pressure from building up behind them. For any major structural changes, consult a geotechnical engineer to assess the land’s specific conditions and design the appropriate solution.
Planting deep-rooted vegetation is a natural way to stabilize soil, as the roots bind the earth together and reduce erosion. Conversely, removing existing vegetation from a slope can significantly increase the risk, as the soil loses that natural reinforcement. Choose plants known for their strong root systems to maintain the integrity of the slope’s surface.
Immediate Survival Actions During a Slide
If you hear unusual sounds like a faint rumbling that increases in volume, or the cracking of trees and knocking of boulders, these are signals of immediate danger. Upon recognizing these sounds or visible movement, evacuate immediately and quickly move away from the path of the slide. Move toward the nearest high ground in a direction perpendicular to the flow, avoiding river valleys and low-lying areas.
If you are indoors and escape is impossible, seek immediate shelter under a sturdy piece of furniture. Position yourself in the part of the building furthest from the approaching landslide and hold on firmly until all movement has completely stopped. If you are caught outdoors and cannot escape the path, curl into a tight ball, protecting your head and neck with your hands.
Never attempt to cross a road or bridge if water or mud is flowing over it, as the flow can accelerate rapidly and carry away vehicles. If you are driving and your vehicle stalls or is caught in the flow, abandon the car and move to the highest ground possible without delay. During a severe storm, remaining alert and awake is advisable, as many landslide fatalities occur when people are sleeping.
Safety Measures After the Event
Once the initial movement has stopped, stay away from the slide area due to the high risk of secondary landslides or continued earth movement. Listen to local radio or television for emergency updates and instructions from authorities, who will advise when it is safe to return. Flooding often follows a landslide, so remain vigilant for rising water levels.
If it is safe to do so without entering the direct slide path, check for injured or trapped neighbors and direct professional rescuers to their location. Do not move seriously injured people unless they are in immediate danger of further harm. When authorities permit you to return, inspect your home for structural damage, looking for cracks in walls, foundations, and chimneys.
Check all utilities. If you smell gas or suspect damaged gas, water, or electrical lines, leave the building immediately and report the hazard to the appropriate authorities. Avoid walking through the debris, as it can contain sharp objects, contaminated materials, and unstable ground. Before re-occupying a damaged building, have a qualified professional assess the structural integrity and stability of the surrounding land.