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Severe Flooding in Alaska’s Denali National Park

By: Christopher C. Burt, 6:43 PM GMT on June 27, 2014

Severe Flooding in Alaska’s Denali National Park

Severe flooding has affected portions of Denali National Park and Preserve in interior Alaska. A large area of rain impacted most of mainland and southeast Alaska on Wednesday and Thursday June 25-26 with some historical accumulations. This is a guest blog courtesy of Brian Brettschneider of Borealis Scientific, LLC in Anchorage, Alaska.

The three most prominent NWS stations in Alaska (Anchorage, Juneau, and Fairbanks) all received greater than 3/4” precipitation for the first time on record for a same single day of the year. The highest intensity precipitation occurred over the 6,000,000-acre Denali National Park and Preserve. Many areas in the Park saw between 2.00” and 3.00” of rainfall. The table below shows maximum 24-hour precipitation totals. All of these stations are part of the Remote Automatic Weather Stations (RAWS) network (with the exception of the Kantishna site).



Maximum 24-hour precipitation totals in and around Denali National Park and Preserve obtained from the University of Utah Mesowest site and the Fairbanks Newsminer.

According to the Fairbanks Newsminer, the Denali Park Road (the only road that traverses the Park) is impassable with water and debris along several portions between the Eielson Visitor’s Center and Kantishna. The Alaska Dispatch has reported that water was crossing the road in three places and that significant debris was flowing over the road. Over 100 staff and guests at several lodges between Wonder Lake and Kantishna are stranded and can only be evacuated by helicopter due to water covering the airstrip in Kantishna. A photo near a flooded lodge taken near Kantishna, Alaska, at the end of the Denali Park Road, is shown below.



Flooding near Kantishna on June 26th. Image credit: Christina Blakey, AP

While the precipitation totals in the table above would not be all that impressive for most places in the U.S., they are highly anomalous for interior Alaska. Many of the 24-hour rainfall totals are greater than the 10-year recurrence interval and in some case approach the 25-year recurrence interval according to the NOAA Precipitation Frequency Atlas for Alaska (e.g., the 24-hour total at Wonder Lake is slightly less than the 25-year recurrence interval). The map below shows the location of each station listed in the precipitation table, along with the location of the Park Road and the location where the road is flooded and covered with debris.



Maximum 24-hour precipitation totals for all stations in, and near, Denali National Park and Preserve on June 25 and June 26, 2014. Map credit: Brian Brettschneider.

The map above shows the greatest single 24-hour precipitation total. Eight stations reported more than 1.50” in 24 hours, four reported more than 2.00”, and Wonder Lake reported 3.29”. In some cases, slightly more rain fell over a period of time greater than 24 hours but in most instances the heavy rain occurred did, in fact, fall within a 24-hour period.

All of the major rivers throughout the Park originate in the glaciers of the Alaska Range. They typically are braided channels with very wide floodplains to accommodate massive amounts of spring and summer snowmelt and summer glacial melt. The photos below show the Toklat River after the recent heavy rains compared to normal flow conditions. Notice the wide, shallow valley with multiple braided channels. Even after this recent significant precipitation event, the channel easily contains the runoff.



Toklat River in Denali National Park and Preserve. The photo orientations are slightly different. Upper photo image credit: Daniel A. Leifheit via National Park Service. Lower panel photo credit: Brian Brettschneider.

It appears that the rivers causing the most problems during this event are not the large ones like the Toklat River or the McKinley River, but some of the smaller tributary rivers whose flow is largely influenced by spring snowmelt and summer rain. These channels are much more V-shaped and respond more quickly to high rates of precipitation.

None of the streams or rivers within the Park is gauged by the Alaska Pacific River Forecast Center or any other river monitoring organization, so only a post-storm analysis will reveal how much water actually flowed through these channels. Thankfully, no injuries have been reported as a result of the storm so far in the Park (as of this writing on the morning of June 27th). Nevertheless, many tourists travel from far and wide to visit Denali NP (at great expense) and their once-in-a-lifetime trip has been significantly impacted.

At least they will leave Alaska with an exciting story to relate!

KUDOS: Dr. Brian Brettschneider, Climate Scientist, Borealis Scientific, LLC, Anchorage, Alaska for this blog.

Christopher C. Burt
Weather Historian

Extreme Weather Flood

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

Quoting 462. Brian Brettschneider:

The three most prominent NWS stations in Alaska (Anchorage, Juneau, and Fairbanks) all received greater than 3/4%u201D precipitation for the first time on record for a same single day of the year.


That's a pretty amazing statistic, especially given the geographical distance between those stations; that's a little like, say, Atlanta, Kansas City, and Minneapolis all experiencing abnormally large amounts of rain on a single day, and from the same system.

This isn't the Alaska I grew up with...
Neapolitan, here is a graphic I put together regarding the precipitation at Fairbanks, Anchorage, and Juneau on the same day:
Dr. Brian B,
"Many of the 24-hour rainfall totals are greater than the 10-year recurrence interval and in some case approach the 25-year recurrence interval according to the NOAA Precipitation Frequency Atlas for Alaska (e.g., the 24-hour total at Wonder Lake is slightly less than the 25-year recurrence interval)."

Then some of the rainfall amounts in your graphic happen somewhere between every 10 to 25 years, and some happen more often than every ten years, if I understand what you are saying. The average level on the page you linked goes out to 1000 years. I am curious how this is extrapolated. Do you know how far back the actual rainfall data goes? How does the snow depth/melt in the Alaska Range this Spring/Summer compare to the average?

Last question is because I think one important aspect of the heavy rainfall might be how the streams and rivers respond r/t potential effect on salmon runs.

Gosh, Neo. did you spend your childhood in Alaska?
I spent many years all over Alaska and have family in southcentral, so I've kept an eye on Alaska weather and other goings-on for about four decades.

I'm confused as to which handle belongs to Brian Brettschneider of Borealis Scientific, LLC in Anchorage, Alaska. The handle quoted from elsewhere - Brian Brettschneider, or DrBrianB. I'm also not clear on significance of your circles rainfall graphic, and really don't understand what you think is significant about heavier than average rainfall in Juneau, Anchorage and Fairbanks all on the same day?

And, please, sir, what is your background?

TIA
Quoting 2. DrBrianB:

Neapolitan, here is a graphic I put together regarding the precipitation at Fairbanks, Anchorage, and Juneau on the same day:

Thanks. I think that Venn diagram (the "circle rainfall graphic") is a clear and very clever way to show the historical significance of the recent Alaskan precipitation event. The fact that Alaska's three most prominent weather stations have never before experienced a day with simultaneous 1/2" rainfall events--much less simultaneous 3/4" rainfall events--in the previous 28,000-plus days of recordkeeping is, in my opinion, further evidence that the climate isn't what it used to be.
Quoting 3. Barefootontherocks:

Dr. Brian B,
Do you know how far back the actual rainfall data goes? How does the snow depth/melt in the Alaska Range this Spring/Summer compare to the average?

Last question is because I think one important aspect of the heavy rainfall might be how the streams and rivers respond r/t potential effect on salmon runs.

I'm also not clear on significance of your circles rainfall graphic, and really don't understand what you think is significant about heavier than average rainfall in Juneau, Anchorage and Fairbanks all on the same day?

And, please, sir, what is your background?

TIA

Those are a lot of questions. I'll try to answer them quickly.

1) There has been intermittent data collection at Wonder Lake for decades. Also, the Eielson Visitor's Center has a good data record. The other stations have much more limited data (10-20 years). That being said, NOAA does a pretty good job with developing recurrence intervals.

2) Salmon do not have a problem with rain swollen rivers. That being said, they prefer shallower, clearer water for spawning. The glacial rivers in the Park are probably far to silty for salmon to spawn but that is just a guess.

3) The circles on the rainfall graphic represent the annual frequency of precipitation thresholds for the three largest cities in Alaska. Each city has a vastly different precipitation regime. The fact that it took 28,422 days of concurrent record keeping for all three stations to record over 0.50" of precipitation on the same say is quite remarkable in my opinion.

4) As for my background, I have a Ph.D. in Environmental Geography with a specialization in climatology. My dissertation was on tropical climatology (see http://journals.ametsoc.org/doi/pdf/10.1175/2007J AMC1711.1 ) but since moving to Alaska about 10 years ago my research in focused on all things Alaska as well as climate visualizations. Here is a sample visualization I put together last week showing the progression of normal temperatures throughout the year: https://www.youtube.com/watch?v=D9Eyl5tYcSU
More than 200 millimetres of rain fell over a 48-hour period in parts of a region that already experienced a spring so wet many farmers did not have a chance to seed crops. The normal average rainfall for the entire month of June in the area is about 92 millimetres. A rainfall warning continued Sunday night and into Monday, with 20 to 40 millimetres expected.

Flooding leads to state of emergency in southern Prairies
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