76 Alaska Business | June 2018 www.akbizmag.com
T I O N Transportation Road-Stream Crossings
Wildcards for Alaska’s transportation
infrastructure and fish
By Katrina Liebich
Putting a road across a stream in Alaska is a lot like going on an adventure. Survival of road and traveler alike hinges upon
careful planning and weighing the risks.
Plan for the 1 Percent
Rivers and streams are powerful and ever-changing. They carry rocks and logs and
heavy loads of silt and debris. They flood.
They carve out canyons. And when they encounter a road crossing not custom-built to
their unique characteristics, they find a way
around it. To avoid floods that overwhelm
roads, it’s necessary to design crossings that
give rivers and streams room to be their
dynamic selves—from their variable flows
down to their moving streambeds.
Case in point: in September 2012 a week-long storm generated severe flooding that overwhelmed the Matanuska-Susitna Borough’s
road system. Willow Creek rose three feet
and swelled to roughly ten times the volume
it carried the previous week. Montana Creek
ate away at Yoder Road and commandeered
Stream simulation culvert in Tyonek.
This site in Tyonek experienced washouts on an almost yearly basis. After this 3-foot diameter culvert
washed out in spring of 2012, it was finally replaced with an 8-foot embedded culvert and hasn’t
washed out since.