Again, I really should stay out of this debate, as I see landslides
every single day after a rain, and I've never ever seen one related
to fire damage - so I should have stayed out of the conversation
because, while I have years of experience with the non-fire related
landslides, I have absolutely zero experience with the fire related
But, to just answer the "why" I was saying that, is that I don't
believe mudslides are, in general, caused by the lack of vegetation
that results from the lack of vegetation maintenance after a fire,
which, in itself, is natural, but which we (the government) strive
to prevent (which is debatable, I agree, whether that is sound
land management policy).
The geology out here is a geology of landslides. Period. With or
without man, the landslides will continue forever (until the land
is flattened into a muddy plain).
So, I'll try to gracefully beg out, after having explained my gut
feeling - but - in the same breath - saying very clearly that I have
never researched the subject of fire-related landslides - so - I had
opined merely my internal feelings based only on gut feeling and zero
research into fire-related deforestation effects on landslide clustering
and/or intensity in California.
PS: I saw a dozen (or more) small landslides just this week, here
in the mountains above the Silicon Valley, and there hasn't been a
major fire in these parts since the 1980's. Landslides are normal
and natural out here. I see them every single day. The trucks
park along the side of the road, scraping them away every single
time it rains.
Danny D. wrote, on Sat, 13 Dec 2014 16:06:03 +0000:
Here is a picture of the roadcrew trucks, parked overnight, where
they perform periodic maintenance on the road just before and during
the rainy season:
They keep pulling that bucket loader off the line to scrape some
landslide off a road here and there all over the place.
If I get a chance, I'll snap some pictures of (small) landslides that
happened just yesterday in the rain as there must be a half dozen
of them (small, of course) in my commute into town, as I recall.
I agree. The hills are made of dried mud and when enough rain gets to the
innards, they slide. It's not just the surface, it's the whole damn hill
that "melts" away. At best ground vegetation creates a thin surface skin on
the top of these mud piles that resists light rain erosion but when you get
enough water into the mix it's "there she blows!"
<<Mudslides occur after water rapidly saturates the ground on a slope, such
as during a heavy rainfall. According to O'Connor, it doesn't take high
relief in the topography to create a slide. Rather, it just takes a pull of
gravity strong enough to bring down material that is made fluid enough by
water. - Strategies to decrease the risk of mudslides include draining water
off hillsides, armoring the bases of hills so they are not undercut by
rivers, and "loading the toe," says O'Connor. In the case of "loading the
toe," engineers put heavy mass, such as large rocks, at the base of a hill
to try to anchor the slope and prevent it from coming loose.>>
They note that one sign of an impending mudslide is trees tilting. If a
huge tree's root system can't stabilize a hillside, it's pretty doubtful
that ground cover of any sort is really going to stop a huge mudslide.
The problem with your theory is it helps a bit but does not/can not
stop the slides. Vegetation can stabilize the top1 to 5 feet over a
period of 5 to 100 years. It takes a LONG time to get the roots down
over a foot.
The bigger problem is there is virtually NO bedrock in those hills.
They are essentially "silt dunes", sitting on a slanted table. When
they get saturated to below the root web they just turn to soup and
start to ooze. Eventually the ooze turns into a full-scale slip and
the relatively stable root-web turns into a "magic carpet" and slides
down the hill, taking everyting in it, on it, and in front of it,
along for the ride towards the Pacific.
On Sat, 13 Dec 2014 08:36:36 +0000 (UTC), "Danny D."
You are right in that generally the regrowth comes from the root
system remaining below the ground after the fire, along with seeds
released by the heat of the fire (certain pines, and I believe
redwoods, cannot reseed without fire).
The biggest problem in California is people are building homes where
no person in their right mind would consider building anything due to
the instability of the geological formations underlying the whole
area. Matthew 7:24-27 repeats what was even back then considered to be
solid well-known knowledge:
Yes, kudzu can become a nuisance. Yet, planting
would go a long way towards stabilizing the land.
If the residents took to keeping goats as pets
that might slow down the kudzu from taking over
the world. Besides kudzu can be used as a food
and fiber source for human use.
Danny D. wrote, on Sat, 13 Dec 2014 00:57:18 +0000:
Here's are a few references for the mountains in NJ/NY/PA being
*taller* than the Himalayas, if anyone cares:
The highest point in all of NJ is now about 1,800 feet, so erosion
took off miles of height (which is why the continental shelf pile of mud
is so large, even 60 miles out from the east coast of the United States).
Think about it this way.
a) Asia is huge, India is pretty big.
b) When they crash, you get big mountains.
A) North America is huge, Africa is huge.
B) When they crash, you get even bigger mountains.
It's my understanding that the driving record of Arizona (which used to
be nearer to the edge of the continent) is as bad as that of the east coast.
Erosion occurs without man's intervention, where *miles* of sediments
are washed down the mountains into the oceans or onto the desert plains.
If man puts a house on top of a cliff, that house is doomed,
just as much as every lake every dammed is doomed to silt up unless
I had forgotten about this request, so, to update you, here is
a (very) small mudslide on the side of the road (which is common):
These slides are countless, all along the roadsides, after every
The road crews drive up and down all day, clearing them up. Here
is a representative picture of what I mean when I say the entire
mountain is just a 3,000 foot tall hill of mud, with a road
carved out on top, and houses dotting the sides ...
I agree. These metal and concrete "screens" are all over the place.
But mainly on the major roads.
These "side" roads have 10 to 40 foot tall "walls of mud" on the
uphill side, and it would cost far more than anyone is willing to
pay to put the screens everywhere.
So, we just deal with the mudslides. Every single time it rains.
Or even when it doesn't rain.
My main point was that, when you put a house on a hill that is
essentially 3,000 feet of mud, there is nothing man is going to
do to prevent landslides.
Fire or not. Landscaping or not. There will be landslides.
Entire towns are built on landslides out here.
It's part of the topography.
Danny D. wrote, on Thu, 18 Dec 2014 11:27:34 +0000:
For example, what's the chance of saving this tree right at
the edge of a bend in the road on this mountain of mud?
That picture was taken from my car as I was driving, where
the road curves to the right just under that tree.
Everything here on the mountain is destined to be washed into
the San Francisco Bay, over time. It's natural. Fire or not.
Landscaping or not. Re-vegetation or not.
CA is destined to burn/drought/rain/flood, over and over again.
That's its natural state. That our species thinks it can control
these forces w/o consequence will eventually lead to our demise.
In a funny way, that's not actually true.
Remember, the Salinian Block is actually a huge piece of rock
which has moved about 300 or so miles, from around Los Angeles,
up along the coast, toward northern California (and it's still on
its journey to the Aleutians), at a rate of about two
inches per year along the San Andreas Fault.
So, it can happen. But it will be a few hundred million years
when/if it does... :)
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