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