Landslide and Sinkhole

What is rainfall-induced landslides?

• These are common where the rock below the land surface is limestone, carbonate rock, salt beds, or rocks that can naturally be dissolved by groundwater circulating through them.

• Prolonged intense rainfall can often cause rainfall-induced landslides. The geological hazard occurs when water from rainfall seeps into the ground at a rate faster than the soil can drain it. As the spaces become filled up with water, the underlying ground material can no longer support the weight of the surface material, thereby resulting in a landslide.

• A form of mass wasting involving "very rapid to extremely rapid surging flow"^[a] of debris that has become partially or fully liquified by the addition of significant amounts of water to the source material.^[1]

  Mudflows contain a significant proportion of clay, which makes them more fluid than debris flows; thus, they are able to travel farther and across lower slope angles. Both types are generally mixtures of various kinds of materials of different sizes, which are typically sorted by size upon deposition.^[2]

• It is what happens when two blocks of the earth suddenly slip past one another.

The landslide movement is marked by high speed due to the fluidity and consistency of the material. One type is debris flow containing loose soil, rock, organic matter, air, and water. Another type is called mudflow, whose composition is at least 50% sand, silt, and clay. A combination of debris flow and mudflow is referred to as mudslide.

• Flow

• Topple

• Slump

• Slide

Free-falling of the materials that includes bouncing or rolling happens in this type of landslide movement. As a result, the rock and debris are heaped at the base of the slope.

• Creep

• Fall

• Slide

• Slump

• Flow

. Similar to a falling domino, the landslide movement is characterized by the tumbling over of a blocked unit or units due to gravity, the added force exerted by neighboring units, and water in the fissures.

• Flow

• Topple

• Slump

• Slide

• Creep

The unnoticeable gradual motion of materials characterizes the type of landslide movement. An area has to be monitored over a long period of time to detect its occurrence.

• Topple

• Slump

• Slide

• Creep

• Fall

The landslide movement happens along weak portions of the slope such as fault, joint, or bedding plane. The motion is usually parallel to the slope.

• Flow

• Topple

• Slump

• Fall

• Slide

The landslide movement is characteristic of the sliding mass movement of materials along an arched portion of the slope.

• Flow

• Topple

• Slump

• Slide

• Creep

What to do BEFORE a landslide?

• . Evacuate immediately when local authorities give the signal.

• Stay informed on the current news and warnings about the landslide.

• Assist if possible, in the rescue operation to search for casualties and missing people.

• Create and develop a household emergency plan for the family. Include the location of where to meet in case there is a need to leave the house immediately.

What to do BEFORE a landslide?

• Observe the conditions and monitor warning signs in the environment, which include unusual sounds from trees cracking or boulders knocking each other.

• . Stay in the part of the house that is farthest from the approaching landslide if caught indoors and take cover under a sturdy table or bench. Firmly hold on to the furniture until the tremors stop.

• Move quickly to a higher area when there is either a sudden increase or decrease of water flow, or a clear water turning murky.

• Assist if possible, in the rescue operation to search for casualties and missing people.

What to do AFTER a landslide?

• Keep clear of structures that may fall such as trees, power lines, and poles.

• Avoid immediately returning to the areas prone to landslides, unless the local authorities announce it is safe.

• Contact the local authorities to find out if there is a threat of a landslide in the area.

• Practice the evacuation plan with the family members.