Post-wildfire debris flows in southern British Columbia, Canada

2016 ◽  
Vol 25 (3) ◽  
pp. 322 ◽  
Author(s):  
Peter Jordan
Keyword(s):  
British Columbia ◽  
Debris Flows ◽  
Peak Flow ◽  
Mass Movement ◽  
Burned Areas ◽  
Low Intensity ◽  
High Severity ◽  
Wildfire Season ◽  
Spring Snowmelt ◽  
Debris Floods

Several post-wildfire debris flows and other landslides occurred after the extreme wildfire season of 2003 in the southern interior of British Columbia. Such events had not been previously reported in Canada, although they are common in lower latitudes. Severe wildfire seasons also were experienced in 2007 and 2009, and additional events were observed in four fires. Post-wildfire landslides have occurred in spring, summer and fall (autumn); events have been triggered by spring snowmelt, high-intensity summer rainstorms and low-intensity fall rainstorms. Of a total of 36 documented events, 23 were debris flows, and the most common initiating mechanism was high peak flow in channels. Most sediment in these events was derived from the channels, not from erosion in burned areas. Seven of the events were infiltration-triggered debris slides, and six events were debris floods. A variety of hydrologic changes can contribute to the prevalence of post-wildfire landslides and floods, including an increase in snowmelt rate. High-severity burn in catchment headwaters above steep channels is a topographic factor favouring debris flow occurrence. These observations demonstrate that the likelihood of debris flows and other mass-movement events in susceptible terrain is significantly increased following severe wildfire in this snow-dominated environment.

Mud and debris flows and associated earth dam failures in the Okanagan region of British Columbia

2013 ◽  
Vol 50 (8) ◽  
pp. 820-833 ◽  
Author(s):  
Dwayne D. Tannant ◽  
Nigel Skermer
Keyword(s):  
British Columbia ◽  
Debris Flows ◽  
Earth Dam ◽  
Loss Of Life ◽  
The Past ◽  
Dam Failures ◽  
Ground Conditions ◽  
Over The Top ◽  
Spring Snowmelt ◽  
Mud Flow

A review of debris and mud flows occurring over the past 100 years in the Okanagan region of British Columbia, Canada, reveals that most events have been associated with late spring snowmelt, spring rains occurring on the snowpack or intense localized convective rain storms in the summer. A troubling finding is that many of the most destructive debris and mud flows were triggered by failure of earth dams located high above the valley floor. The dam failures were caused by either seepage-related piping or water flowing over the top of the dam. Dam breaches can occur on hot sunny days in the spring, when snowmelt and saturated ground conditions occur in the headwaters of creeks flowing into the Okanagan valley. The record shows that there is a risk not only of property damage, but also of loss of life associated with these events. Comparison is made to similar mud flow events in western USA.

scholarly journals Forestry on fans: a problem analysis

2003 ◽  
Vol 79 (2) ◽  
pp. 291-296 ◽  
Author(s):  
David Wilford ◽  
Matt Sakals ◽  
John Innes
Keyword(s):  
British Columbia ◽  
Adverse Effects ◽  
Key Words ◽  
Debris Flows ◽  
High Volume ◽  
Problem Analysis ◽  
Stream Channels ◽  
Forestry Practices ◽  
Forest Practices ◽  
Debris Floods

Forested fans are often crossed by roads and their high-volume stands are attractive for harvesting. Gentle slopes of fans belie the fact that hydrogeomorphic hazards can be present. Fans can be the run out zones for debris flows and they can be subject to floods and debris floods. This study assessed the effect of natural hydrogeomorphic processes on forest practices that were undertaken on 55 fans in west central British Columbia. Forest practices aggravated these processes on 41 (74%) fans, leading to increased erosion and destabilization of fan surfaces and stream channels. Identification of hydrogeomorphic hazards is needed to avoid the adverse effects of forestry practices on fans. Key words: forested fans, forestry on fans, hydrogeomorphic processes, forest practices on fans, forest practices

scholarly journals Historical Landslide Fatalities in British Columbia, Canada: Trends and Implications for Risk Management

2021 ◽  
Vol 9 ◽  
Author(s):  
Alex Strouth ◽  
Scott McDougall
Keyword(s):  
British Columbia ◽  
Risk Management ◽  
Debris Flows ◽  
Expert Judgment ◽  
Risk Tolerance ◽  
Economic Damage ◽  
Landslide Risk ◽  
Management Measures ◽  
Other World ◽  
Debris Floods

According to a Canadian government database, landslides are the most common type of disaster that occurs in the province of British Columbia. Recently there has been a trend in British Columbia toward using quantitative risk assessments to estimate life-loss risk at landslide hazard sites, and to compare these estimates with risk tolerance thresholds to determine the necessity for, and extent of, risk management measures. These risk estimates are most often calibrated by so-called ‘expert judgment’ because historical landslide fatality data are not readily available. This article addresses this gap by summarizing available historical data to better inform expert judgment. It shows that fatalities caused by landslides in British Columbia are rare (approximately one fatality per year in the last decade) and have decreased with time despite rapid population growth. Approximately half of these fatalities in the last decade are related to debris flows and debris floods that impact houses, whereas the other half are related to rockfalls, debris flows, and debris floods that impact highways. A comparison with other hazard types in the Canadian government’s disaster database suggests that, while not particularly deadly, landslides are still important because of the economic damage and service disruptions they cause. Although the data are specific to British Columbia, the methods for identifying and presenting landslide risk trends could be modified and adopted in other world regions where landslide fatality data are collected and quantitative risk management methods are utilized.

scholarly journals Influence of biopolymers on the rheological properties of seafloor sediments and the runout behavior of submarine debris flows

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jun Kameda ◽  
Hamada Yohei
Keyword(s):  
Rheological Properties ◽  
Debris Flows ◽  
Extracellular Polymeric Substances ◽  
Flow Behavior ◽  
Mass Movement ◽  
Rheological Parameters ◽  
Natural Environments ◽  
Natural Systems ◽  
Chemical Conditions ◽  
Seafloor Sediments

AbstractSubmarine debris flows are mass movement processes on the seafloor, and are geohazards for seafloor infrastructure such as pipelines, communication cables, and submarine structures. Understanding the generation and run-out behavior of submarine debris flows is thus critical for assessing the risk of such geohazards. The rheological properties of seafloor sediments are governed by factors including sediment composition, grain size, water content, and physico-chemical conditions. In addition, extracellular polymeric substances (EPS) generated by microorganisms can affect rheological properties in natural systems. Here we show that a small quantity of EPS (~ 0.1 wt%) can potentially increase slope stability and decrease the mobility of submarine debris flows by increasing the internal cohesion of seafloor sediment. Our experiments demonstrated that the flow behavior of sediment suspensions mixed with an analogue material of EPS (xanthan gum) can be described by a Herschel–Bulkley model, with the rheological parameters being modified progressively, but not monotonously, with increasing EPS content. Numerical modeling of debris flows demonstrated that the run-out distance markedly decreases if even 0.1 wt% of EPS is added. The addition of EPS can also enhance the resistivity of sediment to fluidization triggered by cyclic loading, by means of formation of an EPS network that binds sediment particles. These findings suggest that the presence of EPS in natural environments reduces the likelihood of submarine geohazards.

Using polycyclic aromatic hydrocarbons to determine post-wildfire contamination and sediment sources in a large watershed in central British Columbia, Canada

2021 ◽  
Author(s):  
Kristen Kieta ◽  
Philip Owens ◽  
Ellen Petticrew
Keyword(s):  
British Columbia ◽  
Magnetic Susceptibility ◽  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
Large Scale ◽  
Sediment Samples ◽  
Burned Areas ◽  
Total Pahs ◽  
Polycyclic Aromatic ◽  
The Impact

<p>The Nechako River Basin (NRB) in central British Columbia is a large (52,000 km<sup>2</sup>), regulated basin that supports populations of sockeye and chinook salmon and the endangered Nechako white sturgeon. These important species are experiencing population declines and one potential cause of this decline is excess sediment, which can clog their spawning habitat and reduce juvenile success. This excess sediment is likely the product of a combination of factors, the most visible being the significant land cover changes that have occurred in the basin, which includes pressure from forestry and agriculture, the Mountain Pine Beetle epidemic, and large-scale wildfires in 2018. Focusing specifically on the impact of the 2018 wildfires on sediment transport from upland burned areas to adjacent waterways, this research aimed to determine the spatial and temporal contamination of tributaries and the mainstem of the Nechako River with polycyclic aromatic hydrocarbons (PAHs), which are produced during the combustion of organic matter and have been identified as toxic to aquatic organisms and to humans. Additionally, this study intended to determine if burned areas were a more significant contributor of sediment than unburned areas and better understand the utility of PAHs as a potential tracer. Source soil samples were collected in 2018 and 2020 from burned and unburned sites, and suspended sediment samples were collected throughout the ice-free period from 2018-2020 in three tributaries and three mainstem sites. All samples were analysed for PAHs, magnetic susceptibility, colour, and particle size. Results from the fall 2018 source samples show a significant difference in PAH concentrations between unburned and burned soils, and while concentrations of PAHs in source soils in 2020 were lower than in 2018, they were still elevated compared to unburned soils. Sediment samples showed that concentrations of total PAHs are higher in the mainstem sites than in the tributaries, with the greatest concentrations consistently found at the most downstream site on the mainstem of the Nechako River. Concentrations across sites were highest in samples taken during the spring snowmelt period in 2019, have decreased throughout the rest of the sampling period (2019-2020), and are well below sediment quality guidelines for total PAHs. In addition to determining the spatial and temporal extent of PAH contamination, this study also aims to use PAHs along with colour and measurements of magnetic susceptibility to trace sediments associated with the 2018 wildfires. The high cost of PAH analysis limits the number of samples that can be analysed and thus, these additional tracers will allow for the use of models such as MixSIAR that improve with a more robust number of samples. As large-scale megafires continue to burn across the globe, understanding their potential to contribute PAHs to local waterbodies and potentially be used as a tracer is as prescient as ever.</p>

Wildfire and Postfire Restoration Action Effects on Microclimate and Seedling Pine Tree Survivorship

2014 ◽  
Vol 5 (1) ◽  
pp. 174-182 ◽  
Author(s):  
Donald J. Brown ◽  
Ivana Mali ◽  
Michael R.J. Forstner
Keyword(s):  
Soil Moisture ◽  
Wind Speed ◽  
Soil Temperature ◽  
Air Temperature ◽  
Loblolly Pine ◽  
Absolute Humidity ◽  
Short Term ◽  
Burned Areas ◽  
High Severity ◽  
Postfire Management

Abstract Through modification of structural characteristics, ecological processes such as fire can affect microhabitat parameters, which in turn can influence community composition dynamics. The prevalence of high-severity forest fires is increasing in the southern and western United States, creating the necessity to better understand effects of high-severity fire, and subsequent postfire management actions, on forest ecosystems. In this study we used a recent high-severity wildfire in the Lost Pines ecoregion of Texas to assess effects of the wildfire and postfire clearcutting on six microclimate parameters: air temperature, absolute humidity, mean wind speed, maximum wind speed, soil temperature, and soil moisture. We also assessed differences between burned areas and burned and subsequently clearcut areas for short-term survivorship of loblolly pine Pinus taeda seedling trees. We found that during the summer months approximately 2 y after the wildfire, mean and maximum wind speed differed between unburned and burned areas, as well as burned and burned and subsequently clearcut areas. Our results indicated air temperature, absolute humidity, soil temperature, and soil moisture did not differ between unburned and burned areas, or burned and burned and subsequently clearcut areas, during the study period. We found that short-term survivorship of loblolly pine seedling trees was influenced primarily by soil type, but was also lower in clearcut habitat compared with habitat containing dead standing trees. Ultimately, however, the outcome of the reforestation initiative will likely depend primarily on whether or not the trees can survive drought conditions in the future, and this study indicates there is flexibility in postfire management options prior to reseeding. Further, concerns about negative wildfire effects on microclimate parameters important to the endangered Houston toad Bufo (Anaxyrus) houstonensis were not supported in this study.

scholarly journals 2D Runout Modelling of Hillslope Debris Flows, Based on Well-Documented Events in Switzerland

Geosciences ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 70 ◽  
Author(s):  
Florian Zimmermann ◽  
Brian W. McArdell ◽  
Christian Rickli ◽  
Christian Scheidl
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Mass Movement ◽  
Clay Content ◽  
Systematic Evaluation ◽  
Mountain Areas ◽  
Flow Processes ◽  
Friction Parameters ◽  
Cohesive Interaction ◽  
Hillslope Debris Flow

In mountain areas, mass movements, such as hillslope debris flows, pose a serious threat to people and infrastructure, although size and runout distances are often smaller than those of debris avalanches or in-channel-based processes like debris floods or debris flows. Hillslope debris-flow events can be regarded as a unique process that generally can be observed at steep slopes. The delimitation of endangered areas and the implementation of protective measures are therefore an important instrument within the framework of a risk analysis, especially in the densely populated area of the alpine region. Here, two-dimensional runout prediction methods are helpful tools in estimating possible travel lengths and affected areas. However, not many studies focus on 2D runout estimations specifically for hillslope debris-flow processes. Based on data from 19 well-documented hillslope debris-flow events in Switzerland, we performed a systematic evaluation of runout simulations conducted with the software Rapid Mass Movement Simulation: Debris Flow (RAMMS DF)—a program originally developed for runout estimation of debris flows and snow avalanches. RAMMS offers the possibility to use a conventional Voellmy-type shear stress approach to describe the flow resistance as well as to consider cohesive interaction as it occurs in the core of dense flows with low shear rates, like we also expect for hillslope debris-flow processes. The results of our study show a correlation between the back-calculated dry Coulomb friction parameters and the percentage of clay content of the mobilised soils. Considering cohesive interaction, the performance of all simulations was improved in terms of reducing the overestimation of the observed deposition areas. However, the results also indicate that the parameter which accounts for cohesive interaction can neither be related to soil physical properties nor to different saturation conditions.

A debris flow triggered by the breaching of a moraine-dammed lake, Klattasine Creek, British Columbia

1985 ◽  
Vol 22 (10) ◽  
pp. 1492-1502 ◽  
Author(s):  
John J. Clague ◽  
S. G. Evans ◽  
Iain G. Blown
Keyword(s):  
British Columbia ◽  
Debris Flow ◽  
Debris Flows ◽  
Southern Coast ◽  
Coast Mountains ◽  
Debris Avalanches ◽  
Unconsolidated Sediment ◽  
Sudden Release ◽  
Dammed Lake ◽  
Unusual Origin

A very large debris flow of unusual origin occurred in the basin of Klattasine Creek (southern Coast Mountains, British Columbia) between June 1971 and September 1973. The flow was triggered by the sudden release of up to 1.7 × 106 m3 of water from a moraine-dammed lake at the head of a tributary of Klattasine Creek. Water escaping from the lake mobilized large quantities of unconsolidated sediment in the valley below and thus produced a debris flow that travelled in one or, more likely, several surges 8 km downvalley on an average gradient of 10° to the mouth of the stream. Here, the flow deposited a sheet of coarse bouldery debris up to about 20 m thick, which temporarily blocked Homathko River. Slumps, slides, and debris avalanches occurred on the walls of the valley both during and in years following the debris flow. Several secondary debris flows of relatively small size have swept down Klattasine Creek in the 12–14 years since Klattasine Lake drained.

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