2003 Seattle Annual Meeting (November 25, 2003)
Paper No. 51-9
Presentation Time: 3:30 PM-3:45 PM

THE WEST CREEK GLACIAL OUTBURST FLOOD - KLONDIKE GOLD RUSH NATIONAL HISTORICAL PARK - SKAGWAY, ALASKA

CAPPS, Denny Lane, Klondike Gold Rush National Historical Park, National Park Service, P.O. Box 517, Skagway, AK 99840, denny_capps@partner.nps.gov.

On July 23, 2002, approximately 8 million cubic meters of lateral moraine and glacial outwash suddenly liquefied into a proglacial lake sending a surge of water down West Creek, a tributary of the Taiya River. The pre-failure moraine/outwash complex terminated abruptly at the shoreline of the proglacial lake and was perched approximately 150 meters above the water surface with an approximate average slope of 50. The moraine/outwash failure caused a large flood to sweep through Klondike Gold Rush National Historical Park (KLGO) lands, endangering human life and damaging cultural and natural resources and park infrastructure.

KLGO lies at the northernmost point of the Inside Passage of Southeast Alaska and contains the Chilkoot Trail, which parallels the Taiya River. The trail and nearby town site of Dyea were major hubs of activity during the Gold Rush of 1897-1898. The landscape is composed of steep glaciated valleys up to 1600 m deep that are connected to adjacent fjords. The underlying bedrock is primarily uniform granodiorite and the surficial geology includes glacial outwash, moraines, lacustrine deposits and alluvial fans. The Denali fault lies approximately 30 km west of the site, although no extraordinary seismic activity was detected around the time of the moraine/outwash complex failure event. Localities within Southeast Alaska have among the highest precipitation means in North America. However, the area encompassing KLGO averages only 66 cm/yr and there were no obvious weather-driven triggers to the event.

As part of a larger reconnaissance geohazards assessment of the 490 square kilometer Taiya River watershed, the West Creek flood event was studied along with two other known outburst events that have occurred since 1882. Tasks included: 1) reviewing and mapping the sources, mechanisms and affected areas of the event; 2) mapping other source and affected areas from all potential outburst floods in the watershed; 3) identifying and mapping other geohazards in the watershed and the areas that could be affected; and 4) determining the probability of a given type of geohazard occurring in the watershed. Work was done in consultation and under the supervision of KLGO and the National Park Service's Geologic Resources Division.

2003 Seattle Annual Meeting (November 25, 2003)
Session No. 51
Glaciers, Glacial Geology, and Glacial Ecosystems in the National Parks
Washington State Convention and Trade Center: 611/612
1:00 PM-3:45 PM, Sunday, November 2, 2003

Geological Society of America Abstracts with Programs, Vol. 35, No. 6, September 2003, p. 133

© Copyright 2003 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.