FLOODS
It's not surprising that Juneau has flood-prone areas; all that water has to go somewhere! Land around rivers is known as floodplain; the area that is covered by water when the river rises enough to overcome the boundaries of its banks. Flooding is a natural event that causes loss and damage when human development encroaches on floodplains.
Runoff flooding is the most common type of flood in the Juneau area. This type of flooding typically occurs due to weather systems that bring prolonged rainfall. Runoff floods can also occur as water is shed from mountainsides as ice and snow melts. Heavy rains can also saturate soils and lead to landslides.
Juneau Areas At Risk of Flooding
Mendenhall River
The large Mendenhall River runs seven miles from Mendenhall Lake through
the Mendenhall Valley. There is significant development in the
Mendenhall Valley that could be affected by flood waters. Minor
flood stage of the Mendenhall River is 12 feet, which was last reached in
October of 1998. Because o
f
the flood control measures in place along the Mendenhall River drainage, it
would take a flood stage of 14 feet or more to cause extensive flood
problems along the floodplain of the Mendenhall River. When minor flood
stage occurs on the Mendenhall, however, more extensive flooding will occur
on Montana and Jordan Creeks.
High water on Mendenhall Lake will result in flooding on the edges of the lake, including the campground and Skater's Cabin.
Montana Creek
Montana Creek, in the back of the Mendenhall Valley, experiences some form
of flooding roughly every three years. This flooding is usually associated
with heavy rain events in late summer or fall. Official flood stage
(17 feet) on Montana Creek is usually reached by a combination of heavy rains
and runoff from the melting snow pack. 
The low-lying back portion of Montana Creek Road sees minor flooding when the creek rises to its bank-full stage of 15 feet. When the creek reaches 16 feet, the Mendenhall Campground and Skater's Cabin see minor flooding, water pools on the back portion of Montana Creek Road to a depth of approximately one inch, and nearby residents experience flooding in yards and driveways.
At official flood stage of 17 feet, flood waters cross Back Loop Road. Residents of parts of Montana Creek Road would experience flood damages to their homes and property.
The record high water mark on the Montana Creek gage near the Back Loop Road Bridge was 17. 3 feet, on October 20, 1998.
Jordan Creek
The headwaters of Jordan Creek, which is located in the southeast portion
of the Mendenhall Valley, originate at the base of Thunder Mountain.
A USGS river gage was recently installed about 200 yards upstream of the Trout
Street Bridge.
Based on comparisons, the new USGS gage shows minor flooding at 7.3 feet,
moderate flooding at 8 feet, and major flooding at 9 feet. Moderate
and worse flooding can affect the Jordan Creek subdivision area, as well as
the businesses along the creek between Egan Drive and the airport.
Jordan Creek flooded in 1972 (picture at right).
Lemon Creek
Immediately northwest of downtown Juneau is Lemon Creek, which flows out of the Tongass National Forest. Some development in the Lemon Creek area could be affected by moderate flooding. Downstream, the creek runs under the Egan Expressway.
Thane Road
Snowslide Creek, Cross Bay Creek, and Sheep Creek all usually contain very little water, but can flood Thane Road during heavy rains.
Flood Monitoring
The National Weather Service Forecast Office in Juneau monitors for flooding in Southeast Alaska. The staff coordinates hydrological forecasts and warnings with the River Forecast Center in Anchorage. Flood watches and warnings are issued when conditions warrant. The National Weather Service works with local emergency managers to ensure that the appropriate actions are taken once a flood watch or warning is disseminated.
What You Can Do
- Be aware of your home's proximity to floodplains. If you live in a floodplain, evaluate your home and determine what you can do to reduce flood damages.
- Make sure that you have flood insurance for your home if you live in an area vulnerable to floods. Floods can damage everything in your home, and insurance makes it possible to recover some of your financial losses.
- During heavy rain, keep an eye on streams and rivers. Be prepared to head to higher ground if floodwaters threaten.
- Never drive or walk over flooded areas. Flood waters of only 6 inches can be powerful enough to sweep a human off his or her feet, and it only takes 18 inches of water to float a vehicle. Don't take the risk - find another way to get to your destination!
- Do not let children play in flooded areas.
- Stay away from downed power lines.
- Monitor NOAA Weather Radio or your local radio stations for updates on the flood situation.
- Do not use fresh food that has come in contact with flood waters.
- Boil drinking water before using.
- After a flood, wells should be pumped out and the water tested for purity before drinking.
- Wash canned goods that come in contact with flood waters with soap and hot water.
- Do not handle live electrical equipment in wet areas; electrical equipment should be checked and dried before returning to service.
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