Geology of Precambrian rocks and isotope geochemistry of shear zones in the Big Narrows area, northern Front Range, Colorado

Abbott, Jeffrey T.

doi:10.3133/ofr701

Cited by 10 publications

(10 citation statements)

References 40 publications

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“…Straw and wood mulch were applied from helicopters in 2012 and 2013 to approximately 6 % and 18 % of the hillslopes in SG and HG, respectively. The underlying geology is primarily schist with scattered rock outcrops (Abbott, 1970(Abbott, , 1976Braddock et al, 1988), and the soils are predominantly Redfeather sandy loams (HPF BAER Report, 2012;Soil Survey Staff, 2018). Headwater reaches range from wide shallow swales to steep and confined channels; the middle reaches are generally steep and confined with scattered floodplain pockets; and the downstream reaches are wider with mostly continuous floodplains.…”

Section: Site Descriptionmentioning

confidence: 99%

Spatial and temporal patterns of sediment storage and erosion following a wildfire and extreme flood

2019

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Abstract. Post-wildfire landscapes are highly susceptible to rapid geomorphic changes, and the resulting downstream effects, at both the hillslope and watershed scales due to increases in hillslope runoff and erosion. Numerous studies have documented these changes at the hillslope scale, but relatively few studies have documented larger-scale post-fire geomorphic changes over time. In this study we used five airborne laser scanning (ALS) datasets collected over 4 years to quantify erosion and deposition throughout the channel network in two ∼15 km2 watersheds, Skin Gulch and Hill Gulch, in northern Colorado after a wildfire followed by a large, long-duration flood 15 months later. The objectives were to (1) quantify the volumes, spatial patterns, and temporal changes over time of erosion and deposition over a nearly 4-year period, and (2) evaluate the extent to which these spatially and temporally explicit changes are correlated to precipitation metrics, burn severity, and morphologic variables. The volumetric changes were calculated from a differencing of DEMs for 50 m long segments of the channel network and associated valley bottoms. The results showed net sediment accumulation after the wildfire in the valley bottoms of both watersheds, with greater accumulations in the wider and flatter valley bottoms in the first 2 years after burning. In contrast, the mesoscale flood caused large amounts of erosion, with higher erosion in those areas with more post-fire deposition. Only minor changes occurred over the 2 years following the mesoscale flood. Volume changes for the different time periods were weakly but significantly correlated to, in order of decreasing correlation, contributing area, channel width, percent burned at high and/or moderate severity, channel slope, confinement ratio, maximum 30 min precipitation, and total precipitation. These results suggest that morphometric characteristics, when combined with burn severity and a specified storm, can indicate the relative likelihood and locations for post-fire erosion and deposition. This information can help assess downstream risks and prioritize areas for post-fire hillslope rehabilitation treatments.

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Section: Site Descriptionmentioning

confidence: 99%

Spatial and temporal patterns of sediment storage and erosion following a wildfire and extreme flood

2019

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“…Only 13% of Skin Gulch and 18% of Hill Gulch remained unburned. Soils within both watersheds are mostly Redfeather sandy loams derived from Precambrian metasedimentary and metaigneous schists, gneisses, and plutonic igneous rocks (Abbott, 1970). Soils have 10-80% rock content by volume (BAER, 2012).…”

Section: Study Areamentioning

confidence: 99%

How do geomorphic effects of rainfall vary with storm type and spatial scale in a post-fire landscape?

et al. 2016

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In post-fire landscapes, increased runoff and soil erosion can cause rapid geomorphic change. We examined how different types of rainfall events in affected hillslope-scale erosion and watershed-scale channel change in two 14-16 km 2 watersheds within the 2012 High Park Fire burn area in northern Colorado, USA. The first set of rainfall events was a sequence of 12 short, spatially variable summer convective rain storms, and the second was a >200 mm week-long storm in September. We compared rainfall characteristics, hillslope sediment yield, stream stage, and channel geometry changes from the summer storms to those from the September storm. The summer storms had a wide range of rainfall intensities, and each storm produced erosion primarily in one study watershed. The September storm rainfall had less spatial variability, covered both watersheds, and its total rainfall depth was 1.5 to 2.5 times greater than the total summer rainfall. Because rainfall intensities were highest during some summer storms, average hillslope sediment yields were higher for summer storms (6 Mg ha-1) than for the September storm (3 Mg ha-1). Maximum storm rainfall intensities were good predictors of hillslope sediment yield, but sediment yield correlated most strongly with total depths of rainfall exceeding 10-30 mm h-1 intensity thresholds. The combined summer storms produced relatively small changes in mean channel bed elevation and cross section area, with no clear pattern of incision or aggradation. In contrast, the sustained rain across the entire study area during the September storm led to extensive upstream incision and downstream aggradation. Because of different spatial coverage of storms, summer storms produced more total hillslope erosion, whereas the September storm produced the greatest total channel changes. At both scales, high intensity rainfall above a threshold was responsible for inducing most of the geomorphic change.

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“…Straw and wood mulch were applied in 2012 and 2013 to approximately 6% and 18% of the hillslopes in SG and HG, respectively. The underlying geology is primarily schist with scattered rock outcrops (Abbott, 1970(Abbott, , 1976Braddock et al, 1988), and the soils are predominantly Redfeather sandy loams (HPF BAER Report, 2012;Soil Survey 5 Staff, 2018). Headwater reaches range from wide shallow swales to steep and confined; the middle reaches generally are steep and confined with scattered floodplain pockets; and the downstream reaches are wider with mostly continuous floodplains.…”

Section: Site Descriptionmentioning

confidence: 99%

Spatial and temporal patterns of sediment storage and erosion following a wildfire and extreme flood

Brogan¹,

Nelson²,

MacDonald³

2019

Preprint

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Abstract. Post-wildfire landscapes are highly susceptible to rapid geomorphic changes at both the hillslope and watershed scales due to increases in hillslope runoff and erosion, and the resulting downstream effects. Numerous studies have documented these changes at the hillslope scale, but relatively few studies have documented larger-scale post-fire geomorphic changes over time. In this study we used five airborne laser scanning (ALS) datasets collected over four years to quantify valley bottom changes in two ∼15 km2 watersheds, Skin Gulch and Hill Gulch, after the June 2012 High Park fire in northern Colorado and a large mesoscale flood 15 months later. The objectives were to: 1) quantify spatial and temporal patterns of erosion and deposition throughout the channel network following the wildfire and including the mesoscale flood; and 2) evaluate whether these changes are correlated to precipitation metrics, burn severity, or morphologic variables. Geomorphic changes were calculated using a DEMs of difference (DoD) approach for the channel network segmented into 50-m lengths. The results showed net sediment accumulation after the wildfire in the valley bottoms of both watersheds, with the greatest accumulations in the first two years after burning in wider and flatter valley bottoms. In contrast, the mesoscale flood caused large net erosion, with the greatest erosion in the areas with the greatest post-fire deposition. Volume changes for the different time periods were weakly but significantly correlated to, in order of decreasing correlation, contributing area, channel width, percent burned at high and/or moderate severity, channel slope, confinement ratio, maximum 30-minute rainfall, and total rainfall. These results suggest that morphometric characteristics, when combined with burn severity and a specified storm, can indicate the relative likelihood and locations for post-fire erosion and deposition. This information can help assess downstream risks and prioritize areas for post-fire hillslope rehabilitation treatments.

show abstract

Geology of Precambrian rocks and isotope geochemistry of shear zones in the Big Narrows area, northern Front Range, Colorado

Cited by 10 publications

References 40 publications

Spatial and temporal patterns of sediment storage and erosion following a wildfire and extreme flood

Spatial and temporal patterns of sediment storage and erosion following a wildfire and extreme flood

How do geomorphic effects of rainfall vary with storm type and spatial scale in a post-fire landscape?

Spatial and temporal patterns of sediment storage and erosion following a wildfire and extreme flood

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