Changes in Sediment Sources following Wildfire in Mountainous Terrain: A Paired–Catchment Approach, British Columbia, Canada

Owens, Philip N.; Blake, William H.; Petticrew, Ellen L.

doi:10.1007/s11267-006-9048-z

Cited by 25 publications

(13 citation statements)

References 7 publications

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“…As will be shown in this paper, neither peak fl ows nor sediment concentrations appear to have increased dramatically following the fi re (see also Owens et al, 2006;Petticrew et al, 2006), but the stream channel itself appears to have become unstable. The channel was initially a laterally stable plane-bed stream (after Montgomery and Buffi ngton, 1997), but since the fi re it has become laterally unstable, developing mid-channel bars and initiating several avulsions in the study reach.…”

Section: Introductionmentioning

confidence: 73%

Forest fire, bank strength and channel instability: the ‘unusual’ response of Fishtrap Creek, British Columbia

Eaton

Moore

Giles

2010

Earth Surf Processes Landf

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In August 2003, the McLure forest fi re burned 62% of the drainage basin of Fishtrap Creek. Streamfl ow has been measured there since the early 1970s, and suspended sediment concentration and channel morphology have been monitored since the fi re. Although the short post-fi re period (four years) limits our ability to draw fi rm conclusions about streamfl ow changes, there has been no obvious increase in peak fl ows since the fi re. However, the total runoff during the freshet period does appear to have increased and the onset of snowmelt appears to occur about two weeks earlier than it did prior to the fi re. Suspended sediment records from Fishtrap Creek and from an unburnt reference stream nearby are similar, suggesting that the burnt areas have remained relatively stable and that the sediment supply to Fishtrap Creek has not been dramatically altered. In contrast, the stream channel morphology has changed, widening by over 100% of the original width in some places and transforming from a laterally stable plane-bed morphology to a laterally active riffl e-pool morphology. The timing and magnitude of the observed morphologic changes are consistent with the predicted decline in bank strength due to root decay, implying that the observed changes are associated with an internal instability associated with changes to the stream boundaries, rather than with the more typically reported externally driven instabilities caused by changes in streamfl ow or sediment supply. This delayed response in the absence of large changes in streamfl ow or sediment supply, while 'unusual' in that it has not been documented in the previous literature, may be a common mode of response, particularly in wat'ersheds with nival fl ow regimes.

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Section: Introductionmentioning

confidence: 73%

Forest fire, bank strength and channel instability: the ‘unusual’ response of Fishtrap Creek, British Columbia

Eaton

Moore

Giles

2010

Earth Surf Processes Landf

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“…River discharge data are available for Fishtrap Creek at the WSC gauging station (WSC (2012), station ID 08LB024, see Eaton et al 2010a) of source materials (n027) was collected from Fishtrap and Jamieson watersheds soon after the 2003 wildfire in spring/ summer 2004 (for details see Owens et al 2006). A second set of source materials (n096) was collected in summer 2007.…”

Section: Study Sitementioning

confidence: 99%

Determining the effects of wildfire on sediment sources using 137Cs and unsupported 210Pb: the role of landscape disturbances and driving forces

et al. 2012

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Purpose Wildfires represent one of the major natural disturbances within forested landscapes and have potential implications for the quality and function of downstream aquatic ecosystems. This study aimed to determine if a wildfire in a mountainous, forested watershed in British Columbia, Canada, caused a change in the dominant sediment source in the immediate 1-2 years following the wildfire, and if the sediment sources changed over the medium term (3-7 years) as the landscape recovered. Materials and methods Source materials (surface soil, subsurface soil and channel bank material) and fluvial (suspended and channel bed) sediment samples were collected over the period 2004 to 2010 from a watershed burnt by a wildfire in 2003, and from an adjacent watershed that was not impacted (FRNs) caesium-137 ( 137 Cs) and unsupported lead-210 ( 210 Pb un ). An unmixing model was used to calculate the relative source contributions of the fluvial sediment samples. Results and discussion 137 Cs and 210 Pb un were concentrated in the upper layers of surface soils in both watersheds and were statistically different to concentrations in subsurface and channel bank material. In the burnt watershed, FRN concentrations were greatest in the ash layer. Sediment sources as determined by the unmixing model were 100% subsurface/channel bank material in the unburnt watershed, while in the burnt watershed 8.5±2.5% was derived from surface soils. In both watersheds, there were no major changes in the relative contributions from surface soil and from subsurface/channel bank material over the period 2004 to 2010. Thus, while the wildfire did cause a change in sediment sources, it was fairly subtle and did not conform to the effects following wildfire described for other studies in contrasting environments, which typically document a major increase in hillslope contributions relative to channel bank sources. Conclusions There was a limited response in terms of finegrained sediment sources (and also sediment fluxes) in the burnt watershed. The reason for this muted response to a severe wildfire is likely to be the lack of precipitation, especially winter precipitation and the associated snowmelt, in the first year following the wildfire. Thus while the landscape was primed for erosion and sediment transport, the lack of a driving force meant that there was a limited immediate postfire sediment response.Keywords Caesium-137 . Wildfire . Disturbance response . Fallout radionuclides . Sediment sources . Unsupported lead-210

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“…Burnt forested terrain presents additional challenges because of combustion of the litter layer and O-horizon. Recent work (Harden et al, 2004;Owens et al, 2006;Blake et al, 2006a) illustrates that the stable element content of surface soil can be enhanced due to mineralisation of canopy foliage and litter and the inclusion of derived ash into the soil matrix. There remain, however, unresolved issues regarding radionuclide partitioning between organic litter material and mineral soil and the fate of these radionuclides following wildfire.…”

Section: Introductionmentioning

confidence: 99%

Deriving hillslope sediment budgets in wildfire-affected forests using fallout radionuclide tracers

Blake¹,

Wallbrink²,

Wilkinson³

et al. 2009

Geomorphology

115

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Changes in Sediment Sources following Wildfire in Mountainous Terrain: A Paired–Catchment Approach, British Columbia, Canada

Cited by 25 publications

References 7 publications

Forest fire, bank strength and channel instability: the ‘unusual’ response of Fishtrap Creek, British Columbia

Forest fire, bank strength and channel instability: the ‘unusual’ response of Fishtrap Creek, British Columbia

Determining the effects of wildfire on sediment sources using 137Cs and unsupported 210Pb: the role of landscape disturbances and driving forces

Deriving hillslope sediment budgets in wildfire-affected forests using fallout radionuclide tracers

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