10
community
december13
2011
DIY Flood Forecasting
With more information you will know if there is real danger for flooding
By Bill Langmaid
If you’ve lived in Vernonia for
any time at all, chances are you know
someone that was affected by a flood.
We had one in 1996, and then another
in 2007. Other events have occurred as
well, but they were much more local-
ized than either of those 500 year flood
events. As winter approaches, people
look fearfully at the rivers, certain that
the floods will happen again.
At some point they will, but it
takes a very specific set of circumstances
for a flood to occur. It’s not just when
we get a lot of rain, or just when there is
snow on the ground, or when the folks
on the Portland news stations are casting
about for another sensational story and
want to speculate on a recurrence of high
water.
Now, I am no expert in any of
the fields which are typically associated
with flood forecasting, but I did pay at-
tention to the available data and made
some key observations of the data’s be-
havior during the flood events. Hope-
fully you’ll gain some knowledge from
this article so that you’ll be able to rec-
ognize when there is a danger and when
there isn’t one. But, if something does
happen, even if you aren’t expecting it,
make sure to be prepared by following
official recommendations as they are is-
sued.
The two key floods in our re-
cent history were similar in components,
even if they acted differently. In 1996 the
flood hit in the middle of winter, when
we had had very cold weather followed
by snow. This did two things. It made the
ground impermeable, like a parking lot,
and the snow provided water storage.
The amount of water in 1 cubic foot of
powdery snow is considerably less than
that in 1 cubic foot of slushy snow.
In 1996 the Pineapple Express
headed right up the Willamette Val-
ley, and the combination of very warm
weather and heavy rains over a few days
melted all that slushy snow. But the
ground stayed frozen, and the melted
snow and rain just ran to the valley bot-
toms and into the rivers. So, 1996 was
frozen ground, a decent snowpack, lots
of rain, and warm air.
The 2007 flood was caused by
hurricane like conditions. There was
a super-saturated weather system that
moved quickly to the coast and then
stalled as it climbed the Oregon Coast
Range. As it stalled, the western edge
of the system was still over the ocean,
picking up water, which it then dumped
over the land. A total of 11” fell in the
Vernonia area, at a prolonged rate of .4”
per hour.
The rain volume alone would
have caused some flooding, but the real
kicker was that the rain was being ab-
sorbed into the upland snow. The hur-
ricane also brought warm air, and that
warm air increased the temperature from
32 to 50o F in 24 hours, and melted all
the snow in fewer than 8 hours. That
meant there was an effective rainfall rate
of over 1” every hour.
The river rose at a rate of 7”
per hour on the Clear Creek gauge, and
when those waters ran into the flow from
Rock Creek, it was too much. Both riv-
ers slowed down and backed up, dump-
ing water over their banks and into the
town. The events leading up to the flood-
Disaster Supplies Kit
• Water—three gallons for each person who would use the kit and an additional four
gallons per person or pet for use if you are confined to your home.
• Food—at least a three-day supply in the kit, consider stocking a two-week supply of
food and water in your home.
• Items for infants, seniors, disabled persons or anyone with serious allergies—
including special foods, denture items, extra eyeglasses, hearing aid batteries,
prescription and non-prescription medications that are regularly used, inhalers and
other essential equipment.
• Non-electric kitchen accessories—a manual can opener; mess kits or disposable
cups, plates and utensils; utility knife; sugar and salt; aluminum foil and plastic wrap;
re-sealable plastic bags.
• A portable, battery-powered radio or television and extra, fresh batteries
• Several flashlights and extra, fresh batteries
• A first aid kit
• One complete change of clothing and footwear for each person—including sturdy
work shoes or boots, raingear and other items adjusted for the season, such as hats and
gloves, thermal underwear, sunglasses, dust masks.
• Blankets or a sleeping bag for each person
• Sanitation and hygiene items—shampoo, deodorant, toothpaste, toothbrushes,
comb and brush, lip balm, sunscreen, contact lenses and supplies and any medications
regularly used, toilet paper, towelettes, soap, hand sanitizer, liquid detergent, feminine
supplies, plastic garbage bags (heavy-duty) and ties (for personal sanitation uses),
medium-sized plastic bucket with tight lid, disinfectant, household chlorine bleach.
• Other essential items—paper, pencil, needles, thread, small A-B-C-type fire
extinguisher, medicine dropper, whistle, emergency preparedness manual.
• Entertainment—including games and books, favorite dolls and stuffed animals for
small children.
• A map of the area marked with places you could go and their telephone
numbers. • An extra set of keys and IDs—including keys for cars and any properties
owned and copies of driver’s licenses, passports and work identification badges.
• Cash and coins and copies of credit cards
• Copies of medical prescriptions
• Matches in a waterproof container.
• A small tent, compass and shovel
Pack the items in easy-to-carry containers, label the containers clearly and store them
where they would be easily accessible.
NOTE: Always keep a shut-off valve wrench near the gas and water shut-off valves in
your home.
This list is provided courtesy of the Centers for Disease Control, Atlanta GA
http://emergency.cdc.gov/preparedness/kit/disasters/
ing were eerily similar, and allow us to
predict our future actions with some ac-
curacy. Rapidly increasing temperatures,
saturated snowpack, and heavy rains
from a stalled storm front were shared
characteristics. The main difference was
that the 1996 rain event lasted several
days, and the 2007 event lasted one day.
That is what happened, and
here are some tools to help you moni-
tor the river. By looking at the USGS
website (http://waterdata.usgs.gov/nwis/
uv?14299800) that shows the Clear
Creek gauge, anyone can check the rate
of increase in the river height. Since the
river is a modified vee shape, meaning
the bankful width is greater than the
bed’s width, it takes more water to in-
crease height as it gets higher. For ex-
ample, at 5’ of depth, the river is moving
270 cubic feet per second (cfs). At 10’,
still under flood stage, it has increased
twelve-fold, to 3,270 cfs. It more than
doubles again to reach 15’ (it peaked at
18.6’ in 2007) flowing at 8,640 cfs.
When I am monitoring the river
because of my interest in evacuating the
Vernonia Cares Food Bank, I am only
interested in height increasing after it
hits 9 feet. This is an important number
because there is already a significant,
but not dangerous, volume of water at
that level. I then look at the shape of in-
crease, and if it looks like a very steep
line, with an increase of over .4 feet per
hour, then it is important for me to look
at other indicators, like snowpack, tem-
perature, and duration of rain forecast.
The Snotel-Seine Creek re-
cording station information is also
available on the web, but isn’t as
user friendly. The site is located at
http://www.wcc.nrcs.usda.gov/nwcc/
site?sitenum=743&state=or but the data
is obscured by some links. The easiest
one to use to get the information is the
Snow Water Equivalent (SWE) hourly
chart for the last 7 days, selected by the
relevant report features and clicking on
the yellow [View Current] button. For
SWE, the important factor is the total
available liquid. With .5” of falling rain,
and .5” of snowmelt, that results in 1” of
water available to enter the river.
If we have 1” of rain or snow-
melt in Vernonia over the course of a
day, the Nehalem will experience a two
foot rise at Sword’s bridge. Likewise,
a rain/melt volume of 1” per day at the
Clear Creek gauge will result in an 18”/
day rise in the river there. Snowmelt is
hard to gauge without knowing the SWE
of the snowpack, but if the situation war-
rants this information will be publicized.
The final site I watch is the north
coast National Weather Service (NWS)
forecast report at http://forecast.weather.
gov/MapClick.php?zoneid=ORZ003.
This is a forecast for a pretty general
area, but the important indicators are
warnings about unusual amounts of rain,
and rapidly warming temperatures.
The floods of ‘96 and ‘07 were
learning experiences for the NWS, and
now they broadcast those warnings in
conjunction with any flood warnings.
Keeping these sites bookmarked in your
browser can be helpful. There are more
resources out there, but these are the
ones that I use. The links above, plus
more, are available at our city website,
www.vernonia-or.gov.
Be Prepared to “Shelter in Place”
By Bill Langmaid
“Shelter in place” is a concept
that calls for citizens to manage their
own survival needs during a disaster, at
least in the short term. It gives emergen-
cy management services time to assess
damages, prepare a response, and begin
delivering services to those most in dan-
ger.
Vernonia has had its share of re-
cent disasters, and experience has taught
us that transportation can quickly be-
come difficult or impossible. This means
it is even more important to be prepared
before a storm hits. Several companies
have capitalized on the “shelter in place”
concept by offering kits of one kind or
another. Since these are usually fairly
expensive, a lot of households skip this
step.
But many of the items found in
these kits are already available in your
house. Please see the sidebar for a listing
of these items. The Vernonia Cares Food
Bank has graciously offered to help fam-
ilies that already receive assistance with
the creation of a kit. All a person has to
do is request those extra items, and the
good folks down at the Food Bank will
help out.
The items in the list are those
that ensure survival during the 2-5 day
window when otherwise healthy people
are unable to get more supplies. These
include adequate water (1 gallon/day/
person), adequate food (>1200 calories/
day/person when not exercising, other-
wise >2000 calories/day), and shelter.
Shelter may seem like a “given” since
we are talking about “shelter in place”,
but it is a word that includes warmth and
comfort.
If the power is out and your
house is heated with electric baseboards,
you have no heat. What is the alterna-
tive? There are a number of them, in-
cluding wood stoves, kerosene heaters,
and propane heaters. All should be used
cautiously, as improper use can cause
death. The ultimate protection is a gen-
erator, which can either be gasoline or
natural gas/propane powered. This al-
lows continued use of our regular heat
sources.
Other items to include should
be a camp stove for cooking, candles
for light, books, games, and items which
occupy children. Have several changes
of clothing for each person, and warm
blankets or a sleeping bag. If a person in
your household has special needs which
cannot be met without power, notify the
authorities before the emergency. Dis-
cuss plans with neighbors and friends,
and develop a network of self-suffi-
ciency. Waiting for help to arrive can be
stressful, but good preparation can put
you back in control of the situation.
Some other resources to inves-
tigate include web pages for the Red
Cross, the City of Vernonia, and Moun-
tain House--an Oregon business which
sells freeze dried foods.