Location: Snow River Railroad Trestle at Mile 14
Pull-off at turn off to trestle. Bus turnaround at bottom of hill.
Short Description: A jokulhlaup (pronounced yokel—lop) is a outburst of a glacially impinged lake. The watershed of the North Fork of the Snow River includes a large glacially impinged lake. Even though visual evidence is difficult to interpret; the concept of a jokulhlaup makes this stop worth while.
Required Equipment: None
Suggested Equipment: Before hand check out web site:
- http://water.weather.gov/ahps2/index.php?wfo=pafc (Explore information about Snow River)
- Aerial photos of the glacier and of North/South Forks for comparison
Safety Consideration: Parking is adjacent to river and Railroad Tracks.
Inquiry Prompts: What’s Going On Here?
Parking by the trestle provides a view of the Snow River drainage below the confluence of the North and South Forks. At first glance it seems typical of many valley streams in the area— heavily braided flowing through glacially deposited gravel. There seems to be a great deal of dead fall along the banks and piled into log jams. At first glance this tortured wide stream bed would provide testimony to flooding that happens in any stream… but alas… if one could see it from the air.
Looking at the provided aerial photo of the confluence we can see that there is a marked difference between the North and South Forks. What’s going on here?
But alas . . . the story.
The reason for the periodic and catastrophic flooding of the North Fork is because of the Snow River Glacier in the headwaters of the watershed. As the glacier moves forward, it blocks off the stream causing a large glacially impounded lake. This lake grows to the point that it begins to float the glacier, water begins to escape out from the bottom, it then erodes a larger exit and within a few days the entire lake rushes down the valley.
The Snow River jokulhlaup is neither an unusual nor rare event in Alaska. There are a number of examples throughout the state. However, since this (and the Skilak jokulhlaup ) drains into the Kenai drainage and into populated areas it is perhaps the most notorious and the most easily viewed. Every two or three years enough water has backed up behind the glacier to cause this devastating flooding event.
To learn more about the Snow River jokulhlaup explore the hydrological website provided to link to historic graphs and data.
In addition, check out the enclosed pamphlet that was created by USGS and published by the USFS.