A Field Investigation of Glacial Lake Outburst Potential in the Taiya River Watershed, Skagway, Alaska
On July 23, 2002, a lateral moraine of the West Creek Glacier liquefied, causing debris to slide into a glacial lake located in front of the glacier's terminus. The debris displaced a large volume of lake water into West Creek, generating a tremendous flood that poured into the Klondike Gold Rush National Historic Park (KLGO) and the community of Dyea, Alaska. This flood caused extensive damage to private property, bridges and roads, and forced the immediate evacuation of Dyea residents and approximately 50 campers from nearby campgrounds. This flood event surpassed the estimated 500-year flood for West Creek, producing a peak discharge of 16,209 cubic feet per second (cfs) (459 cubic meters per second) (Capps, 2004).
In reaction to this event, the KLGO funded a six-month investigation of geologic hazards conducted by a volunteer student geologist. This investigation identified a second lateral moraine, adjacent to West Creek Glacier Lake, which could replicate the results of the first lateral moraine slide. This same study identified a much larger potential threat at the Nourse Glacier, located within a tributary of the Taiya River. Nourse Lake has formed within the past 50years due to the retreat of its glacier. This lake has a surface area of approximately 170 acres (0.69 square kilometers) with a maximum depth of 95 feet (ft) (29 meters (m)). The lake has formed behind a 3944 (120 m) high terminal moraine. A catastrophic failure of this moraine may result in a peak discharge twice as large as the West Creek glacial flood (Capps, 2004).
On June 10, 2004, a multi-agency teleconference was held to discuss the potential threats of geohazards within the Taiya River watershed. This teleconference (Appendix A) was initiated by the KLGO in response to the July 2002 event and a reconnaissance study performed by a National Park Service (NPS) volunteer in 2003.
Both the West Creek Glacier (latitude -135.5105, longitude 59.5693) and the Nourse Glacier (-135.4250, 59.5693) (Figure 1) are on lands currently administered by the Bureau of Land Management (BLM), but are selected for conveyance by the State of Alaska under Section 6 of the Alaska Statehood Act PL85-508 (72 STAT 339) as amended.