Public Information Statement
Issued by NWS Alaska-Pacific RFC

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NOAK48 PACR 161634
PNSACR
AKZALL-171600-

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
ALASKA-PACIFIC RIVER FORECAST CENTER
800 AM AKDT WED APR 16 2014

... THIS IS FLOOD AWARENESS WEEK IN ALASKA...

THIS WEEK MARKS THE BEGINNING OF THE FLOOD SEASON FOR ALASKA.

EACH DAY OF FLOOD AWARENESS WEEK WILL FEATURE A UNIQUE TOPIC RELEVANT
TO EDUCATION AND PREPAREDNESS.

TODAY WE HIGHLIGHT GLACIER DAMMED LAKE RELEASES...

A GLACIER DAMMED LAKE FORMS WHEN WATER COLLECTS BEHIND, UNDER, OR
WITHIN GLACIERS. A GLACIER DAMMED LAKE RELEASE OCCURS WHEN THE LAKE
FILLS TO A LEVEL SUFFICIENT TO INITIATE DRAINING. SMALL GLACIER
DAMMED LAKES MAY FILL AND RELEASE MORE THAN ONCE PER YEAR, BUT LARGER
LAKES OFTEN TAKE ONE OR MORE YEARS TO FILL TO RELEASE LEVELS. LAKES
TYPICALLY DRAIN ALONG THE EDGE OF THE GLACIER OR THROUGH TUNNELS IN
THE GLACIAL ICE. RELEASES CAN HAPPEN OVER A TIME SPAN OF HOURS TO
WEEKS AND FLOWS IN RIVERS DOWNSTREAM CAN THREATEN LIVES, PROPERTY AND
INFRASTRUCTURE. WHILE SMALL LAKE RELEASES MAY ONLY CREATE SMALL RISES
IN FLOW DOWNSTREAM, LARGER LAKES CAN PRODUCE FLOODS MUCH GREATER THAN
FLOODS FROM ANY OTHER SOURCE ON THE AFFECTED RIVER. ALTHOUGH THE SIZE
OF GLACIER DAMMED LAKES VARIES SIGNIFICANTLY, LARGE QUANTITIES OF
WATER CAN BE STORED IN GLACIER DAMMED LAKES.  ALASKA HAS HUNDREDS OF
GLACIER DAMMED LAKES.

THE SKILAK GLACIER DAMMED LAKE TYPICALLY RELEASES IN THE LATE FALL
EVERY TWO YEARS, CAUSING A 1-4 FOOT RISE IN THE KENAI RIVER BELOW
SKILAK LAKE. WHEN THE LAKE RELEASES IN THE WINTER, THE RISE IN WATER
LEVELS CAN CAUSE BREAKUP OF THE LOWER KENAI ICE COVER AND RESULT IN
ICE JAMS AND LOCALIZED FLOODING IN THE SOLDOTNA AREA.

HUBBARD GLACIER, THE LONGEST TIDEWATER GLACIER IN AMERICA, IS AN
ADVANCING GLACIER THAT HAS CLOSED RUSSELL FJORD FROM DISENCHANTMENT
BAY, TEMPORARILY CREATING RUSSELL LAKE.  AS HUBBARD GLACIER CONTINUES
ITS ADVANCE, THE FJORD COULD BECOME PERMANENTLY BLOCKED, CAUSING
RUSSELL LAKE TO DRAIN INTO THE OLD SITUK CREEK CHANNEL AND THE LOWER
SITUK RIVER, ENDANGERING AN IMPORTANT FISHERY AND INUNDATING THE AREA
AROUND YAKUTAT AIRPORT.

SIMILARLY, TWEEDSMUIR GLACIER IN CANADA IS KNOWN TO PERIODICALLY
SURGE AND BLOCK THE ALSEK RIVER, CAUSING FORMATION OF A LARGE LAKE. A
FLOOD FROM TWEEDSMUIR LAKE WOULD TRAVEL DOWN THE ALSEK RIVER TO THE
GULF OF ALASKA, IN THE AREA OF DRY BAY.  SUCH AN EVENT WOULD THREATEN
THE SAFETY OF RIVER RAFTERS, COMMERCIAL FISHERMEN AND VISITORS, AND
POSE RISK TO PARK CONCESSIONERS, STAFF AND PROPERTY.

IN 2011.. A GLACIER DAMMED LAKE ON THE MENDENHALL GLACIER RELEASED
CAUSING FLOODING AND ONE OF THE HIGHEST CRESTS IN THE PERIOD OF
RECORD FOR THE MENDENHALL LAKE GAGE. THIS LAKE WAS PREVIOUSLY UNKNOWN
BUT APPEARS TO HAVE REACHED A POINT WHERE IT WILL CONTINUE TO FILL
AND RELEASE ON A REGULAR BASIS.

FOR MORE INFORMATION ON GLACIER DAMMED LAKE RELEASES IN
ALASKA...VISIT THE WEB SITE AT
http://aprfc.arh.noaa.gov/resources/gdl.php

TOMORROW WE WILL HIGHLIGHT RAINFALL FLOODING.

$$





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