Meteorological antecedents to debris flow in southwestern British Columbia; Some case studies

Church, Michael; Miles, Michael J.

doi:10.1130/reg7-p63

Cited by 76 publications

(45 citation statements)

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“…Conductivity has not been determined at this site, but visual inspection suggests it may exceed the average value of 7 x 10" 2 m s" 1 reported above. Several authors, notably VanDine (1985) and Church & Miles (1987), have noted that many debris torrents are triggered during storms of less than five-year return period. It has been suggested, though not yet proven satisfactorily, that localized cells of intense precipitation, in zones of strong orographic forcing, may be embedded within otherwise non-extreme storm events.…”

Section: Discussionmentioning

confidence: 99%

“…Annual totals at sea level are about 1800 mm, but orographic enhancement results in a 100% increase at elevations over 1000 m. Church & Miles (1987) provide a detailed discussion of the regional climate and its influence on debris torrent activity.…”

Section: Study Areamentioning

confidence: 99%

“…Winter storms are far more important than spring snowmelt in producing debris torrents in this area since 16 of the 18 known events since 1960 have occurred in the period October-February (Thurber Consultants, 1983;Church & Miles, 1987).…”

Section: Study Areamentioning

confidence: 99%

“…A preliminary statement concerning debris supply processes within selected catchments in the Howe Sound area is provided by Bovis & Dagg (1987). In Western Canada, as in Japan, many debris torrents are triggered by orographically enhanced rainfall, though a variety of other meteorological antecedents, including snowmelt and rain-on-snow, have recently been identified for southwest British Columbia by Church & Miles (1987). Whatever their causes, water inputs of the order 50-100 mm per day are capable of triggering debris torrents either directly, by the critical discharge mechanism described by Takahashi (1981), or indirectly, by a variety of hillslope instability events which provide surcharge shear stress to potentially unstable debris stored along steep channels.…”

Section: Introductionmentioning

confidence: 99%

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A model for debris accumulation and mobilization in steep mountain streams

Bovis

Dagg

1988

Hydrological Sciences Journal

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Section: Discussionmentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A model for debris accumulation and mobilization in steep mountain streams

Bovis

Dagg

1988

Hydrological Sciences Journal

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“…Similarly, snowmelt, often combined with rainfall ("rain-on-snow"), is recognized as a common triggering factor of debris 30 flows (Church and Miles, 1987) and shallow landslides (which may subsequently transform into debris flows) (Bíl et al, 2015). In spite of this general understanding, there is little systematic effort to quantify its influence and its role may often be under-estimated (Decaulne et al, 2005).…”

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confidence: 99%

The temporally varying roles of rainfall, snowmelt and soil moisture for debris flow initiation in a snow dominated system: the compound trigger concept

Mostbauer

Kaitna

Prenner

et al. 2017

Preprint

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Abstract. Debris flows represent a severe hazard in mountain regions. Though significant effort has been made to predict such events, the trigger conditions as well as the hydrologic disposition of a watershed at the time of debris flow occurrence are not well understood. Traditional intensity-duration threshold techniques to establish trigger conditions generally do not 10 account for distinct influences of rainfall, snowmelt, and antecedent moisture. To improve our knowledge on the connection between debris flow initiation and the hydrologic system and to overcome the above limitations, this study explores the use of a semi-distributed conceptual rainfall-runoff model, linking different system variables such as soil moisture, snowmelt, or runoff with documented debris flow events in the inner Pitztal watershed, western Austria. The model was run on a daily basis between 1953 and 2012. Analyzing a range of modelled system state and flux variables at days on which debris flows 15 occurred, three distinct dominant trigger mechanisms could be clearly identified. While the results suggest that for 68% (17 out of 25) of the observed debris flow events during the study period high-intensity rainfall was the dominant trigger, snowmelt was identified as dominant trigger for 24% (6 out of 25) of the observed debris flow events. In addition, 8% (2 out of 25) of the debris flow events could be attributed to the combined effects of low-intensity, long-lasting rainfall and transient storage of this water, causing elevated antecedent soil moisture conditions. The results also suggest a relatively 20 clear temporal separation between the distinct trigger mechanisms, with high-intensity rainfall as trigger being limited to mid-and late summer. The dominant trigger in late spring/early summer is snowmelt. Based on the discrimination between different modelled system states and fluxes and more specifically, their temporally varying importance relative to each other, rather than their absolute values, this exploratory study demonstrates that already the use of a relatively simple hydrological model can prove useful to gain some more insight into the importance of distinct debris flow trigger mechanisms in a 25 compound trigger concept, highlighting in particular the relevance of snowmelt contributions and the switch between mechanisms in early-to mid-summer in snow dominated systems.

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The role of debris supply conditions in predicting debris flow activity

Bovis

Jakob²

1999

Earth Surf. Process. Landforms

335

212

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Debris flow frequency and magnitude were determined for 33 basins in southwest British Columbia. Basins were first classified as either weathering-limited or transport-limited using a discriminant function based on debris-contributing area, an area-weighted terrain stability number, and drainage density. Multiple regression was used to predict magnitude, peak discharge, frequency and activity (frequency times magnitude) within each group of basins. Model performance was improved by stratifying the total sample of debris flow basins into weathering-and transport-limited groups. Explained variance increased by an average of 15 per cent in the transport-limited sample, indicating that sediment supply conditions in the more active basins are fundamental in predicting debris flow activity. An independent test of the regression models with 11 basins yielded generally good results for debris flow magnitude and peak discharge. Prediction of debris flow frequency proved problematical in weathering-limited basins. The methods developed here provide estimates of debris flow attributes in basins for which few data on past events are available.

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Meteorological antecedents to debris flow in southwestern British Columbia; Some case studies

Cited by 76 publications

References 0 publications

A model for debris accumulation and mobilization in steep mountain streams

A model for debris accumulation and mobilization in steep mountain streams

The temporally varying roles of rainfall, snowmelt and soil moisture for debris flow initiation in a snow dominated system: the compound trigger concept

The role of debris supply conditions in predicting debris flow activity

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