For those who have taken the Technical Canyoneering Course you will remember our discussion Flash Floods and Meteorology and how the roles of the canyon and area topography relate to the potential for flash floods. As we have hit that time of year here on the Colorado Plateau for our flash flood awareness to be on heightened alert, a college from Zion Adventure Company in Springdale Utah, Dave Buckingham, wrote up an excellent piece on Flash Floods. Being right next to the Canyoneering hot spot, Zion National Park, Dave has surely witnessed what the power of a good rainstorm is. This article is an excellent reminder of the dangers posed to those venturing into the slot canyons. What are some of the things that we should consider before going, and what are some things to look at and think about when we find ourselves in imminent danger of being swept away:
I feel like surviving a flash flood comes down to 3 things:
1. realizing
that there is nothing any of us can do to eliminate the
risk
completely
2. preparing / learning / studying as much as you can in
advance to
help you manage the risks while you are in the canyon /
drainage
3. being highly aware of everything around you during the trip,
and
taking prompt action to escape floods
What is flood water like?
Imagine a torrent of water, loaded
with sediment, sticks and debris that
feels more like concrete, than
water. Flood waters easily move hundreds of
pounds of dead logs.
They have been known to move houses off foundations,
and carry cars
hundreds of yards, and even miles.
Trip
Planning:
1. How does flood risk change with respect to month, week, season
for your destination?
2. How many square miles, acres, etc. does the
canyon drain?
3. To what degree can precipitation be absorbed by the
watershed
area? (is the canyon rim made of rock? are there plants / grasses
that will absorb some of the falling rain)? In a canyon surrounded
only
by rocky, low-water-absorptionn terrain, there is often a
significant
problem with water running down the walls and the
complications this creates
by adding more volume to the flood water,
complicating escape routes, making
use of escape routes more
difficult, washing rocks in on top of hikers off
the rim.
4. To what degree has it rained there recently? In the sandstone
areas, a lack of rain in May, June and July causes the sandstone to
become baked like clay, and not able to absorb falling rain in the
summer like it does when precipitation falls more frequently, in
smaller
amounts in the winter.
5. How committing is the drainage? Is the whole
hike in the
canyon? Does the canyon have wider, open sections, or is it
narrow
and slotted the entire time? Where is the most committing, least
escapable section? Can you identify escape routes on the map? Can
you
determine if there are escape routes by reading guidebooks, or
talking to
people who have been before, can you get info from
internet canyon groups?
What are the logistics / skill sets
involved in these escapes? Can you and
your group pull them off, or
do they involve equipment and skills you do not
or will not have?
6. Make sure you allow an appropriate amount of time
for your group
to complete the trip. Building in extra time can be very
helpful.
Just because you read in a book that "the author completed the hike
in 7 hours" does not guarantee that you won't need 10 hours.
7.
Choose a starting time for your event that helps you best manage
rain risk
and being seriously committed. Often, in the Southwest
Desert, the period
between July 15-September 1 brings the
possibility of a heavy, isolated
thunderstorm each day. Starting
early, and finishing the trip by 2-3PM helps
hikers avoid being in
drainages during the time of day when the storm risk
is highest.
8. Learn how high the water does / can get in the
canyon/drainage
during a flood.
9. Consult experts, Gather
information, and set a personal threshold
for a forecast that you consider
"more dangerous" than acceptable in
advance. This helps you avoid minimizing
real risk, succumbing
financial, peer, or logistical pressure and convincing
yourself "i'm
sure it will be ok" when the forecast is truly marginal or
unfavorable. Prepare yourself and your group for the possibility
that
weather can cancel the event at any point.
10. Check the forecast as
close to departure as possible.
11. Understand signs of flooding. These
could be:
-thunderheads building
-rain falling
-water starting to
flow
-flowing water becoming discolored: red, brown, black, muddy as it
fills with sediment
-debris being washed down the drainage: trees, logs,
sticks, leaves,
other hikers
-sometimes folks hear a rumbling, thunderous
sound as flood water
approaches. I can tell you that people are often
unsettled when
they hear jet airplanes above them, while being in canyons,
as they
think this could be the sound of flood water.
While you are
in the canyon:
1. Continue to evaluate weather at all times.
2. Look
for signs of how high the water reached in past floods to
help you
understand how high you would need to climb to be above
flood water (wedged
logs, sticks, grasses and dead plants wrapped
around things in the direction
water travels).
3. Keep all group members informed. Discuss what you
might have to
do to escape a flood before you need to do it.
4. As
you travel, look for possible escape routes, store them in the
back of your
mind. Retreat back to a place you have been is
sometimes better, especially
if there is a known, useful escape.
Heading further into in the canyon into
territory you haven't seen
often brings no guarantees. If you travel past
major obstacles that
eliminate your ability to retreat back to an escape
route, keep this
in mind.
5. Look for signs of flooding described
above. Take action
promptly if you feel like a flood is developing. Avoid a
"well,
that is only one of many signs of flooding we are seeing, let's just
wait and see" approach. Work together with group members.
Sometimes
climbing a few feet makes a major difference.
6. Wait out the flood on
the high ground. This can take several
hours, and occasionally, even
days.
Hope this helps,
Take the Best of Care
Dave
Buckingham
Zion Adventure Company
Thanks to Dave for permission to re-post this article here.
