Flooding and Landslide Events Northern British Columbia 1820-2006 _____________________________________________________________ D. Septer Province of British Columbia Ministry of Environment CONTENTS 1 Introduction 2 Scope 3 Information reliability 4 Organization of storm events 5 Community flooding and landslide archive 6 Chronological list of flooding and landslide events Appendices 1 Geographical index by rivers, creeks and lakes. 2 Geographical index by community. 3 Reported fatalities caused by slope failures and snow avalanches in northern British Columbia. Literature cited 2 1 Introduction Weather is one of the most common topics of conversation. Landslides, snow avalanches and flooding events may have devastating impacts on property and can result in the loss of human life. A clear understanding of the magnitude and frequency of landslides, flooding and storm events may help in project planning, emergency planning and risk assessment. Thus the importance of storms, which create such events, will be of interest to a wide audience ranging from emergency measure planners and foresters to engineers and historians. 2 Scope Historical information on weather events and their impacts is scattered throughout many different sources, including newspapers, technical reports and streamflow records. The intent of this report is to produce a chronological list of flooding and landslide events in the northern part of British Columbia. The area covered is north of a straight line running from Bella Bella in the west over Williams Lake and Blue River to the Rocky Mountains in the east. Some weather events causing fatalities in the adjacent Alaska panhandle have been included in the report. 3 Information reliability News coverage of extreme storm events and subsequent damage may vary considerably in detail and accuracy. Although an effort has been made to be as accurate and complete as possible, the chronological list of such events contained in this report is far from complete. In a report with a time span and geographic area like this, many storm and flood events will have been missed. Terminology used to describe mass wasting events often also varies widely in newspaper accounts. No effort has been made to confirm the correctness of the terms used in the original reports. Also as little as possible was changed in the original reporting. Eyewitness accounts and many reported cases of “worst flooding on record” are all in quotation marks by the author. Such information must be taken at face value. The historical detail contained in this report is strictly raw data without any analysis of the events. Consequently, this information is only as good as originally reported. Thus all the details and quotations must stand on their own merit, without benefit of the author’s analysis or comment. Unless stated otherwise, damage amounts are in dollar values of the time of the event. 4. Organization of storm events All damage causing events are organised chronologically starting with the ca. 1820 event and ending with a storm event on December 18-19, 2006. Some extreme wind and snow storm events have also been included even though they did not cause flooding or landslide damage. For information for a specific watercourse or community, refer to Appendix 1 and 2, respectively. A chronological list of some of the reported fatalities caused by slope failures and snow avalanches in northern British Columbia can be found in Appendix 3. 5. Community flooding and landslide archive Personal memories, diaries, newspaper articles all contain valuable information on historical storm and flood events. Many such events have been recorded while others only remain in the memories of those affected. This local knowledge may also make this report and thus flood warnings more accurate and help planners in future flood prevention measures. Additional information about any missed events can be send to the author’s address at P.O. Box 1000, Whaletown, BC - V0P 1Z0. 6. Chronological list of flooding and landslide events Ca. 1820 Event type: Rockslide. Precipitation: Not applicable. Source: Morice 1904; Evans (unpublished data) (p. 7). 3 Sometime around 1820, a large rockslide formed a blockage in the Bulkley River at Hagwilget Canyon, 1.5 km upstream from its confluence with the Skeena River. (Evans (unpublished data). Father Adrien Gabriel Morice, OMI describes the event as follows, “a large piece of rocky cliff overhanging the Bulkley (River) at a location now called Ackwilgate (Hagwilget)… having fallen across the stream, this barred it so completely that it formed a cataract of sufficient height to prevent the fish from getting up to the Moricetown fall. Threatened with starvation, the western Babines went in a body, armed cap-a-pie, and forcibly took the new terminus from its (Kitshkan) owners. In the course of time, the rock which was to give a name to the new place (Fallen Rock or Rocher DeBoule) wore away to such an extent that the salmon could return to their former haunts up the river, but the Babines or Ackwilgates have since retained possession of both Fisheries.” ( Morice 1904). Ca. 1852 Event type: Glacial outburst flood. Precipitation: Not applicable. Source: deLagune 1972 (p. 276); Clague and Rampton 1982; Champagne-Aishihik Band 1988 (p. 6); Clarke 1989; Gabrielse and Yorath 1992; Evans (unpublished data) (p. 7). In the northwest part of the Cordillera, the oral traditions of the Southern Tuchone people record a disastrous outburst flood in the St. Elias Mountains caused by the draining of Lake Alsek formed by the damming of Alsek River by Lowell Glacier (Clague and Rampton 1982; Champagne-Aishihik Band 1988). *1) In Neoglacial times, Lake Alsek filled and emptied several times. Its actual size depended primarily on the geometry of the Lowell Glacier ice dam (Clague and Rampton 1982). In its last phase, about 1850, the pool elevation of Lake Alsek was approximately 595 m above sea level (a.s.l.). At this level, the lake was almost 200 m deep and 100 km long, extending into the Kaskawulsh and Dezadesh River valleys flooding the present site of Haines Junction (588 m a.s.l) (Clague and Rampton 1982; Champagne-Aishihik Band 1988). Around 1852, the glacier dam broke (deLagune 1972) suddenly releasing the water of Lake Alsek into the Alsek River. The glacial outburst flood, involving an approximate volume of 4,700 million m3 (Clarke 1989), “destroyed several Indian villages and killed countless people” (Champagne-Aishihik Band 1988) downstream of Lowell Glacier, including a settlement at the confluence of the Alsek and Tatshenshini rivers (Evans (unpublished data). ----------------------------- *1) Gabrielse and Yorath (1992) define the Canadian Cordillera as, “extending from the base of the Continental slope in the west to the western limit of undeformed strata underlying the Interior Plains, and from the Beaufort Sea in the north to the international boundary in the south.” May 16, 1866 Event type: Landslide. Precipitation: Not applicable. Source: Cariboo Sentinel, May 17, 1866; Evans (unpublished data) (p. 5) Case History 1. On May 16 around 3 p.m., a landslide came down near Barkerville. The event was described in the Cariboo Sentinel, making it the first located newspaper report of a damaging landslide in the Cordillera. (Evans (unpublished data). “…. the denizens of Barkerville were startled at hearing a very unusual noise…. it was observed that a large portion of the earth on the Western hill side (sic) behind town was on the move carrying everything before it, until it was obstructed by the Hibernia Co.’s shaft house… water and mud forced an entrance through the back door of (Messrs. Floyd and Co.’s store) and swept right through it into the street destroying a great deal of goods. Messrs. Floyd and Co.’s loss will amount to $500. (Cariboo Sentinel, May 17, 1866). June 17, 1866 Event type: Debris flow. Precipitation: Not available. Source: Evans (unpublished data). On June 17, a debris flow occurred at Van Winkle, near Quesnel. The water and debris flooded houses and buried a street. The debris flow was released by the breach of a landslide dam in Van Winkle Creek. July 1875 Event type: Spring runoff flooding. Precipitation: Not applicable. Source: British Columbian, July 11, 1875. The Fraser River at Queslnemouth (Quesnel) rose 4 ft. (1.2 m) higher than was ever known before. It reached 33 ft. (9.9 m) above the low water mark, flooding several warehouses and other buildings. July 5-7, 1891 Event type: Landslide dam failure and fatal slides. 4 Precipitation: Port Simpson (198.4 mm/3 days), July 5-7, 1891. Source: The Daily Columbian, July 8 and 13, 1891; Victoria Daily Colonist, July 14, 1891; The Metlakahtlan, December 1891; B.C. Ministry of Energy, Mines and Petroleum Resources. 1993; Walbran 1909. In early July, a freak summer rainstorm hit the area around present-day Prince Rupert. Though during the early summer of 1891 the weather had been warm and dry for some time, a sudden change took place on July 4 around midnight. During the three days of steady rain between July 5-7, Port Simpson, at the time the only location where weather records were kept, rainfall measured 194.8 mm in 72 hours. Possibly an even larger amount of rain may have fallen in the Inverness Channel area, southwest of Prince Rupert. According to one account, some 12 in. (over 300 mm) of rain fell in the 24 hours alone. The three days of steady rain caused debris slides along the Inverness Channel. The North Pacific and Inverness salmon canneries, two of the 19 such canneries operating at the mouth of the Skeena River, were hit by mud and debris slides. Though the reports on fatalities differ, as many as 50 people may have perished as a result of these slides. On July 6, at about 1 a.m., a large debris slide came down heading straight for the Inverness Cannery.