- Mudslides can also be caused by very heavy rainfall, snowmelt or high levels of groundwater flowing through cracked bedrock.
- This may trigger a movement of soil or sediments in landslides that continue as mudflows.
Image: FILE
The Kenya Meteorological Department has warned that some parts of the country might experience mudslides due to the ongoing heavy rainfall.
Additionally, it has been confirmed that more than 900 residents have been affected by flash floods and mudslides in Suba South, Homa Bay.
The same has left four people dead.
In Mai Mahiu, an incident which caught the attention of the whole country on Monday dawn, more than 40 people were killed after mudslides in the area.
According to the Centers for Disease Control and Prevention (CDC), mudslides develop when water rapidly accumulates in the ground and results in a surge of water-saturated rock, earth, and debris.
They contain a significant proportion of clay.
They usually start on steep slopes and can be activated by natural disasters.
According to The Varnes classification of landslide types, an update, mudflows can move at speeds ranging from 3 meters/minute to 5 meters/second.
What causes mudslides?
Areas where wildfires or human modification of the land have destroyed vegetation on slopes are particularly vulnerable to landslides during and after heavy rains.
Mudslides can also be caused by very heavy rainfall, snowmelt or high levels of groundwater flowing through cracked bedrock.
This may trigger a movement of soil or sediments in landslides that continue as mudflows.
Mudslides have four named areas including the 'main scarp', in bigger mudflows the 'upper and lower shelves' and the 'toe'.
The main scarp will be the original area of incidence, the toe is the last affected area.
On the other hand, the upper and lower shelves are located wherever there is a large dip (due to a mountain or natural drop) in the mudflow's path.
A mudflow can have many shelves.
Cautions during heavy rains to avoid mudslides
It is advisable that during heavy rains and flash floods, one remains aware of any sudden increase or decrease in water level on a river that might indicate debris flow upstream.
CDC notes that a trickle of flowing mud may precede a larger flow.
People should also listen for rumbling sounds that might indicate an approaching mudflow.
"If landslide or debris flow danger is imminent, quickly move away from the path of the slide. Getting out of the path of a debris flow is your best protection. Move to the nearest high ground in a direction away from the path. If rocks and debris are approaching, run for the nearest shelter and take cover (if possible, under a desk, table, or other piece of sturdy furniture)," the Center states.
It is also important and safer to stay aware of a site of mudslides as flooding or additional slides may occur after.
How dangerous are mudslides?
Mudslides are fatal. At least 48 people died in the Mai Mahiu incident with scores still missing.
They also destroy and sweep away houses and vehicles.
They block roadways and railways. This can endanger motorists and disrupt transport and access to health care.
Disrupted roadways and railways can endanger motorists and disrupt transport and access to health care.
Overall, mudslides lead to trauma.
How can they be prevented?
Mudslides can be prevented by planting ground cover on slopes to stabilise the land, building retaining walls, and building channels or deflection walls to direct the flow around.
Additionally, constructing ditches in and/or around the slide area can help.
Sandbags are also a good temporary solution as they can slow the momentum of smaller mudslides.