Debris flows both occurs in mountainous areas and is
mainly formed by the effect of gravity and move downward at a certain slope.
So before the debris flow, that is, before the slopes
or retaining walls sliding down, we can find some special signs.
(1) If there are mudstones falling down on mountain roads or pedestrian paths,
you should think that a mudslide may occur. At this point,
be sure to avoid the place timely and take shelter in a safe place.
Similarly, if you find soil, rock, concrete, rock gobbets and uprooted plants
falling from slopes and retaining walls, you should also leave in time.
(2) If the slope, retaining wall or the surface of roads sink or appear
a new large crack, it is also an important sign of the arrival of debris flow
. In this case, you should evacuate quickly. If possible,
notify others in the neighborhood.
(3) If the water flowing out of slopes and retaining walls change color suddenly,
that is, from clear to muddy, it means that there might be a heavy rain
in the upstream. And heavy rains are the main reason of mudslides.
Therefore, seeing this situation, evacuate timely and do prevention work.
At the same time, if a large amount of rain flows on the slope and retaining
walls or if a large area of water seeps on the slope and retaining walls,
evacuate immediately, too.
In addition, we may encounter loosening of plaster or concrete slope protection,
or erosion signs and these are warnings of debris flows before they arrive.