Natural Hazard Control / Mitigation is essential. Any time of the year Rockfall can be a serious concern. In the winter snowslides are of prime concern. Springtime and early summer is when we see most of the mud, and rock avalanches, although the can occur any time of year.
The above is Cover photo from a piece I did for a Rocscience Newsletter, a publication put out by a computer program development organization in Toronto, ON, Canada. It is one of several computer programs I use when evaluating rockfall hazards. Computer simulation gives me thousands of variables, so I can plan, and determine more accurately what the “risk exposure” is?
The above 200 ton +/- some, a boulder that was position in such way it made sense to use our sequencing system to bring it down under controlled circumstances. Although, in some cases, I still use of explosives. When I do I use them I do so in a very controlled and careful way. Things like ignition rate, placement, and timing delays on multiple charges, make a big difference in the resultant.
Proactive Mitigation prevents accidents, saves lives, and money. Closing a major highway costs $$$$ not to mention the potential damage and threat to life.”
Natural Hazard Control is a tricky game. It is pretty hard to guesstimate exactly how mother nature will end up doing things. On top of that we must deal with physics and engineering principles. The first step is we do a hazard assessment and determine the Risk Exposure for the area of concern. It may be low enough nothing else needs to be done.
Shortly after returning from active duty in the military I began working at Timpanogos Cave National Monument as a National Park Ranger in Visitor Protection and Resource Management. Timpanogos Cave has a mile and a half trail (2.5 kilometers) that leads to the cave entrance and another short section that leads from the exit, back to the main trail.
The trail is located on a north-facing slope which means it has less natural rockfall than south-facing slope would. South-facing slopes are less steep (generally) because they experience many more freeze-thaw cycles than do north facing slopes.
Freeze-thaw cycles, or “Frost Wedging” break rocks loose. It is like having water in steel pipes, that freezes and breaks the pipe, except, in this case, the sun melts the snow and ice, then free water fills the cracks and freezes at night, breaking the rock to pieces.
As the sun hits them, or it warms up, these rocks are influenced by gravity and fall down to the canyon floor. If people happen to be in the way, well, it can be serious . . . Over the years, there have been a couple of serious incidents on the trail and one death. The NPS is quite proactive and designed a rockfall mitigation drape that was retractable, to go in the main chute above the cave trail, and a roof to go over the exit to protect visitors.
Back then I was fairly green, but I was a pretty fair rock climber and OK at the technical rescue. Since I was a climber I was asked to help the contractor install the Drape. My grandfather, an engineer for US Steel Corporation, taught me many engineering principles, but rockfall mitigation was not my specialty, I learned quite a bit. It was my first major project of this size.
So I went to work for the contractor, doing what I loved to do. Although, training the contractor’s personnel and trying to watch over things to prevent accidents was nerve-racking.
Anyway, that is where my natural hazard skills started to grow. I took these pictures years later after I had become an engineer and specialist in Rockfall and Avalanche Elimination and Mitigation. I took these pictures as our team installed the new rockfall fence at the exit, and I made sure the above system was working ok.
I n some cases, it is pretty straight forward, like this basic drape we installed near Eureka, on U.S. #6, but in most cases, it is a mixed approach. Over the years I have developed a system to establish the risk exposure for various areas of concern (AOC). A good example of the work we have done with the State of Utah. They have many AOC.
Quite a few years ago, we helped install the below special retractable hanging drape for the Department of the Interior, NPS.
Snow Avalanches change each year.
Paths are fairly common but the severity and frequency changes each year.
It was one of these spring snow avalanches that first made me think I was going to die for sure! We were hiking up the cave trail (early spring and the trail was closed to visitors) when we stopped for a break at a place called “dead dog” (I don’t know the full story, but a dog is supposed to be buried there.) While we were resting we heard a low rumble. It got louder and louder. I thought is was a jet was flying over, although I could not see it. It seemed really close to us.
Then the ground seemed to shake. I did not know what to think. I looked up above us and a monster avalanche hit the big rock buttress above us. I did not stop to watch I began to run for cover. As I was running I thought to myself: ” I always figured I would die, but not this way.” I did not watch the other two Park Rangers, as I ran and took cover behind the downside of a big boulder on the ridge we were resting on.
When things settled down I noticed the avalanche had actually split into two, when it hit the rock buttress above us. It buried the trail on the east side of us, and continued down the chute on the west side of us! Wow! Here’s a good habit for anyone who spends time in the mountain. Be conscious of “Objective Hazards- (things we do not have direct control over.) Stop in sheltered places. It has saved my life a number of times.
One of the Rangers had transferred to Timp Cave and was new to these mountains. He was my boss, Chief Ranger over our department, “Visitor Protection and Resource Management. He had transferred for White Sands National Park. Those type of experiences can be overwhelming. I think it was almost a month into summertime before he went back up the trail. With time we get used to it, but that was an abrupt introduction for him.
I had another interesting avalanche experience about a year later. We hunting deer on the face of 12,000 foot high Mt. Timpanogos. It had been snowing a fair amount (about 80% of all natural avalanches happen during or shortly after a snowstorm.) When we were coming back we found an avalanche had come down the North Face of Timp and had covered the dirt road. There we a couple of other trucks that were trapped on the west side. They were waiting for the forest service to come up and clear the road. They did not know that backcountry roads don’t usually have those kinds of services.
So we all grabbed our shovels and made a notch in the avalanche path, where the roadway was. I put some chains on my 4 x 4 and got a run at it. I hit the avalanche and the truck climbed up on top of it and I was partway across. Just as I hit the middle I started to sink. Wow! My heart sunk! “That’s all I needed to do is have my truck stuck in the middle of an avalanche path!” During a snowstorm, it is rather common to have slides run the same path, just a short time after previous ones.
Luck was with me, just as it seemed it was going to become hopelessly stuck, it grabbed something, or I got some divine help, either way, I did not argue. It continued to go up and over the avalanche debris to the other side. The others quickly followed.
A major avalanche at Bridal Veil Falls (a very rare 50-100 year cycle)
These hazards can be identified and evaluated so that we can eliminate them, or mitigate (lessen the potential for release and minimize the effects associated with the hazard. )
I, along with a great team of professionals, are looking forward to saving lives, preventing property damage, and much more. Please do feel free to contact us with any questions or concerns you might have.