One thing leads to another, according to The Fixx. And in weather, it is frequently true. Take fires. They create burn scars. The bigger the scar, the more likely for flash flooding. Which can occur for up to a decade after the scar is made. And flash flooding, because of it’s movement, nature, and weight, can lead to landslides.
Why the landslide? And, can anything be done to mitigate it? Before those can be answered, one must understand how a landslide works.
We start with a healthy slope. Green trees, brush, grass. These retain fallen rainwater, and draw it into the soil. When a fire occurs,it burns…or chars…the landscape. This is actually a layer of carbon (and debris). Which is hydrophobic. Hydrophobic, literally, means to "fear water". But, in context here, means, to be water retardant. So, this carbon layer retards water from penetrating into the soil that is now well below the carbon/debris (hydrophobic) layer. So, the water has to go somewhere, and since water always finds its level, it of course, runs downhill. Fast. And trying to stop water on the move, is like trying to rip a phone book in half, with your hands. Good luck!
But, since it is raining all around you, you can be ignorant to the growing danger. Flood waters take time…there’s a delay…before they accumulate or run down. So now, we have a developing flash flood, heading downhill and into any streams in its path. The streams cannot possibly accommodate all this rainwater, so the stream both overflows its banks…and collects all kinds of debris…now creating a "debris flow." This can destroy anything in its path. Just as a tornado is nothing but wind and debris, the debris flow is nothing but water and debris..and it is frequently the debris that destroys and kills.
Let’s move forward in time now. Subsequent flash floods on this slope weaken the slope. The weight of the carbon layer itself, the lack of pliability, plus the weight of the running water…which gets heavier the further downhill it collects, can cause this hydrophobic layer to break free at a weak point. Now, we have a landslide. Which is truly unstoppable, until gravity neutrality is met.
Now, a few bullet points on this process:
-it only takes about a half an inch in an hour’s time, to create a flash flood on a burn scar area
-because flash floods take time for water to accumulate, the delay in danger can make one think there is no danger…until it is too late
-a burn scar can linger for up to a decade. (Regrowth takes time.)
Other than regrowth of foliage, there really is very little that can be done to mitigate this. You could plant, but the regrowth still takes time. Trying to remove the carbon (hydrophobic) layer on a mountain slope would be costly, time consuming, and dangerous in and of itself. Towns in it’s path could create permanent road blocks, but the water still has to flow somewhere. Realistically, the best solution…as difficult a choice as it may be, may be to move out of the burn scar area. Otherwise, you are literally putting your life in nature’s hands, for a decade, by simply "hoping for the best", every time it rains. And do you really want to live in fear, every time it rains? If the scar is significant, it’s simply not worth the risk.