Kenai Fjords National Park – Protection of Exit Glacier Road
The National Park Service (NPS) has taken interim and long-term measures to repair and reinforce a one-mile section of the access road to Exit Glacier, the most accessible and popular area of Kenai Fjords National Park, to address flooding damage exacerbated by climate impacts. While flooding is a recurring event in the glacial area, less predictable flow patterns and increased flood frequency due to climate change have destabilized drainage on the road. NPS worked with highway engineers to design an interim solution, using concrete barriers to keep flood waters off the road, while continuing to study long-term stabilization solutions. As a long-term solution, NPS has proposed to raise the road elevation five feet in the one-mile section, and install new box culverts to accommodate flow better.
Climate change has impacted the park’s resources significantly by increasing the frequency and degree of natural processes seen in weathering (breaking down of surface rocks), meteorological events, and the shrinking of Exit Glacier. Additionally, during the 2011-2012 season Exit Glacier received over 43 inches more snow than average, adding to the spring melt. Glacial melt predictably causes reoccurring flooding; however, the recent increased frequency and altered patterns of flooding have caused greater road deterioration and culvert inundation. The affected section of the access road, near the confluence of where the melting glacial ice joins the Resurrection River, is vulnerable to overflow, erosion, and damage from saturated mud.
To preserve safe visitor access and the road’s structural integrity, the Kenai Fjords Park is using science-based decision-making to develop a long-term flood mitigation effort as well as interim solutions to keep the road accessible. The Park performed an initial consultation with the Western Federal Lands Highway Division to develop an interim repair plan and a full design analysis. In September 2012, NPS contracted with Bristol Engineering Services of Anchorage, Alaska to perform the interim road repair and reinforcement project along the damaged one-mile section of the access road. In addition to road repairs, the project involved installation of 2200 feet of concrete barriers on the southern road shoulder to prevent water from overflowing the road surface. A 3-foot thick layer of riprap (rock armor) was placed on the roadway foreslope (the slope from the road shoulder to the ditch) to protect the road and prevent erosion, and 9 riprap barbs (protruding hard rock structures) were placed to direct water flow away from the road.
While developing and installing short-term solutions, NPS continued to study the flooding impacts of the dynamic glacial system through evaluation of hydrological data, and worked with FHWA to develop design alternatives for long term solutions which balance the protection of natural resources and the stabilization of the road. NPS noted in its summary of the Exit Glacier project that long term design solutions to the reoccurring flooding issue must address the future climate change impacts that Kenai Fjords Park is expected to face.
In July 2015, NPS released an Environmental Assessment and announced a preferred alternative for long-term flood mitigation. NPS plans to elevate the one-mile portion of the road that experiences recurring flooding, and replace pipe culverts with four new large box culverts to allow for higher flows under the road. NPS evaluated the alternative of raising the road and installing culverts against the existing conditions alternative, which would have kept the concrete barriers as the primary flood mitigation measure. As part of the preferred alternative, NPS will also remove the temporary flood mitigation structures that were installed, and will widen the road shoulder from one to three feet on each side to provide additional space for cyclists. NPS anticipates that the long-term solution selected will keep the road from being closed to vehicles during flood events, while the temporary flood mitigation measures would have still required closure of the road at six inches flood depth. Additionally, by elevating the road and installing larger culverts, the park can avoid further road damage from erosion which was previously occurring with each flood event. NPS anticipates construction will begin in 2016 and expects the project to cost $3.6 million for construction.
The National Parks transportation system is largely funded by the Federal Lands Transportation Program (FLTP), from which NPS currently receives approximately $250 million per year. The FLTP supports “transportation asset management” - work required to keep transportation assets like the access road to Exit Glacier in good condition.
This Adaptation Clearinghouse entry was prepared with support from the Federal Highway Administration. This entry was last updated on January 26, 2016.
Publication Date: September 2012
- Best practice
- Case study
- Air temperature
- Precipitation changes