Mudflow: A natural disaster

1. DMMM
Natural Disaster
Mudflow
PILLAI HOC COLLEGE OF ENGINEERING AND TECHNOLOGY
By
Prof R. P. Narwade
Head of the Department
Civil Engineering Dept

2. Definition
 Rapid movement of debris containing
large amount of water
 Water get mixes with rock debris, soil or
regolith and forms a mud which flow
downward stream or mountain
 A MUDFLOW or MUDSLIDE occurs
when mud travels down a slope very
quickly.
 Mudflows, which are like giant moving
mud pies, happen when lots of water
mixes with soil and rock. The water makes
the slippery mass of mud flow quickly
down.
 Mudflows happen most
in mountainous places where a long dry
season is followed by heavy rains.
 Mudflow is of two types:
1. Lahar
2. Debris Flow
MUDFLOW
LANDSLIDE

3. Differentiation

4. Types of Mudflow
 Mudflows of volcanic eruptions are the most
dangerous, and are called lahars.
 A lahar is a type of mudflow or debris flow composed of
a slurry of ash, pyroclastic material, rocky debris,
and water.
 The material flows down from a volcano, typically along
a river valley.
 Lahars can move as quickly as 80km/h and are as thick
as Liquid Concrete .
 Lahar is an Indonesian term that describes a hot or cold
mixture of water and rock fragments that flows down the
slopes of a volcano and typically enters a river valley.
1. LAHAR
Lahar devastation after the eruption of Mount
Pinatubo, Philippines.
Lahars move rapidly down valleys like rivers of concrete

5. Lahar Video Demonstration

6. Types of Mudflow
2. DEBRIS FLOW
 Mixture of rocks debris or soil & water
 Moves as a viscous fluid
 Common after heavy rains
 Rapid movement – up to 50 km/hr, the more water
present the faster the rate of movement
 Common in semi-arid regions and along volcanoes
(lahars)
 Soil mass moving at a speed of few tens of meters to
a few hundred meters per hour is known as slump. It
is identified by rotational arc scars.
 A rapid snowmelt can also be a cause, where newly-
melted snow water is channeled over a steep valley
filled with debris that is loose enough to be
mobilized.
Debris Flow and Deposit at Arizona
Generally, it is not hazardous to life, but is threat to natural property

7. Debris Flow Video Demonstration

8. Causes
 Lahars have several possible causes:
 Snow and glaciers can be melted by lava or pyroclastic
flows during an eruption
 A flood caused by a glacier, lake breakout, or heavy rainfall
can release a lahar, also called glacier run
 Water from a crater lake, combined with volcanic material in
an eruption
 Lahars can occur without volcanic activity, if conditions are
right for the collapse and movement of mud from
existing volcanic ash deposits.
 Snow and glaciers can melt during periods of mild weather
 Earthquakes underneath or close to the volcano can shake
material loose and cause it to collapse triggering a lahar
avalanche.
 Rainfall or typhoons can cause slabs of solidified mud to come
rushing down the slopes, with devastating results.
1. LAHAR

9. Causes
2. DEBRIS FLOW
 Debris flows can be triggered in a number of ways.
 Typically, they result from sudden rainfall, where water
begins to wash material from a slope, or when water
removed material from a freshly burned stretch of land.
 A rapid snowmelt can also be a cause, where newly-melted
snow water is channeled over a steep valley filled with
debris that is loose enough to be mobilized.
 In either case, the rapidly moving water cascades down the
slopes and into the canyons and valleys below, picking up
speed and debris as it descends the valley walls.
 As the system gradually picks up speed, a feedback loop
ensues, where the faster the water flows, the more it can
pick up.

10. What to do BEFORE Mudflow ?
When it comes to mudslide safety, you need to have a plan beforehand so you know what to do in case of an
emergency. Here are the steps you should follow before a mudslide occurs to give you, your business, and your family
the best chance of surviving.
 Know your area’s mudslide history. Much like lightning, mudslides often strike the same place twice. Research past
events in your area to calculate your risk.
 Learn about local emergency response and evacuation plans. If you are told to evacuate it is good to know your
route ahead of time to minimize panic..
 Get your plans and kits together. Talk to everyone in your household or at your business about what they should
do if a mudslide occurs. Create and practice an emergency plan and know where your evacuation route is. Put
together an emergency kit.
 Get insurance. While landslide insurance isn’t typically available, you can get what is known as “debris flow
damage” coverage. Check with your insurance provider.

11. What to do DURING Mudflow ?
Here’s what you should do if a mudslide occurs or if you know one is likely to occur.
 Evacuate immediately. Inform affected neighbors and businesses if you can. Take any pets or livestock with you if
possible.
 Contact your police or fire department or your local public works to inform them as well.
 Listen for unusual sounds. These are sounds that may indicate moving debris, such as trees cracking or boulders
knocking together. Mudslides make a rumbling sound so listen for that too!
 If you are near a stream or channel, be alert for any sudden increase or decrease in water flow. Muddy water is
another sign that debris could be moving from upstream. Be prepared to move quickly.
 Look for tilted trees, telephones poles, fences, or walls as well as new holes or bare spots on hillsides.
 Stay awake. If you live in an area prone to mudslides make sure you stay awake during severe storms and when
wildfires are affecting your area.
 Be alert when driving as well. Roads may become blocked by debris.

12. If you’ve safely evacuated you could come home to a lot of damage. Here’s what you should do after a mudslide
occurs at your home or business.
 Stay away from the site until local officials tell you it’s safe. Flooding or addition landslides could still occur so
it’s best to wait for the official “OK.”
 Listen to the radio or TV for updates on weather conditions, mudslides, and evacuation orders.
 Check for injured or trapped people and animals near the slide without entering the slide area.
 Help people who need special assistance first like infants, the elderly, and those with disabilities.
 Look for and report broken utility lines. If you smell gas or suspect a leak call 101.
 Check your home and/or business’ foundation, chimney, and surrounding land for any cracks or damage.
 Replant damaged ground as soon as possible to prevent more mudslides from occurring. Lack of ground cover
can also cause flash flooding.
 Be alert to potential health conditions. Rashes, trench foot, wound infections, and GI illnesses are all common
after mudslides and cleanup. Go to the doctor immediately if you think you are suffering from a disaster-related
illness.
What to do AFTER Mudflow ?

13. Past Relevant Disastrous Events

14. Effects
Land
Mudslides move at more than 20
mph and contain not just mud,
but rocks, trees and other debris.
This means they can rip land to
pieces, leaving deep gullies and
large mud deposits. Mudslides
can devastate agricultural land:
all crops will be destroyed. It is
not all bad news as mudslides
also bring rich nutrients down to
lower ground, so once the
mudslide passes the ground can
be more productive.
Property
Due to the pace mudslides move
at, even buildings are not entirely
safe. Concrete and brick buildings
in cities and towns are normally
safe due to solid foundations and
the probability of the slide
stopping beforehand. Outbuildings
-- watersheds, stables, anything not
attached to a main house -- and
farm structures are much more at
risk as they may not be as strong
and will bear the full force of the
slide.
Infrastructure
In the same way that they destroy
property and land, mudslides can
also destroy infrastructure in the
area. This can include ripping up
roads, damaging pipes and
bringing down power and
communication lines. Electric
pylons and communication lines
are particularly vulnerable as they
have little or no foundation.
Roads being destroyed may also
hamper relief efforts.

15. Effects
People
According to the California
Geological Survey, between 1978
and 2003 more than 100 people
were killed in the state as a result
of mudslides. These people were
directly in the path of the slide or
those living in rooms below
ground level.
Rivers
Eventually, mudslides tend to reach
an area where they cannot cross,
such as rivers. In this situation, the
mud and rock flow into the river
and flow out to the ocean. This can
cause large silt deposits on the river
bed -- harmful to marine plants
and animals, animals relying on the
water and local human populations.
The eventual upside is that the
nutrients brought down by the
slide will improve the quality of
plant growth in the water.
Cleanup
All of this destruction has to be
cleaned up after the slide has
subsided. Cleanup costs time and
money. Disaster relief funds are
normally set up when these
events occur. Specialists are
brought in to help, and the U.S.,
like other developed nations, has
a strong system in place to help
affected areas get back to
normal. As with other natural
disasters, like earthquakes and
tsunamis, it is developing nations
that suffer the most as there are
fewer plans in place.

16. Thank You
By
Professor Raju Narwade
Head of the Department
Civil Engineering Dept