Hillslope Morphology Drives Variability of Detrital <sup>10</sup>Be Erosion Rates in Steep Landscapes

DiBiase, Roman A.; Neely, Alexander B.; Whipple, Kelin X.; Heimsath, Arjun M.; Niemi, Nathan A.

doi:10.1029/2023gl104392

Cited by 2 publications

(3 citation statements)

References 58 publications

(126 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Hillslope gradients thus vary spatially depending on the exposure of underlying bare bedrock or the presence of vegetation (Moore et al, 2009;Neely et al, 2019;Schmidt et al, 2001). When examining morphodynamics of steep hillslopes, a problem emerges to describe the relative abundance of soil-mantled and bare-bedrock slopes and the threshold slopes of these hillslope types (DiBiase et al, 2023).…”

Section: Theoretical Frameworkmentioning

confidence: 99%

“…Conceptually, this patchwork develops as channel incision rates increase to balance rock uplift rates, and hillslopes steepen towards the stability angles of soil and rock (Burbank et al, 1996;DiBiase et al, 2023;Neely et al, 2019;Schmidt & Montgomery, 1995). In such settings, coarse sediment bypasses the hillslope weathering zone and can directly enter colluvial channels through landslides or rockfalls (Marc et al, 2021;Neely & DiBiase, 2020;Roda-Boluda et al, 2018).…”

Section: Sediment Supply From Soil-mantled and Barebedrock Hillslopes...mentioning

confidence: 99%

“…Of particular importance is the potential for dry ravel transport of fine-grained material following the incineration of vegetation on steep hillslopes Florsheim et al, 1991), soil erosion by rilling during storms (Alessio et al, 2021;Hyde et al, 2014;McGuire et al, 2017;Rengers et al, 2021), sediment production by fire-spallation on exposed bedrock (De Graff & Gallegos, 2012;Sarro et al, 2021), and prefire colluvial sediment stored within channel valleys (Morell et al, 2021;Nyman et al, 2020;Santi et al, 2008). Postfire dry ravel transport is characteristic of rapidly eroding transverse ranges of southern California (DiBiase & Lamb, 2020), where hillslopes are a patchwork of bare-bedrock cliffs and vegetated hillsides perched near slope-stability thresholds (Binnie et al, 2007;DiBiase et al, 2023).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The grain size of sediments delivered to steep debris‐flow prone channels prior to and following wildfire

Neely,

Moon,

DiBiase

et al. 2024

Earth Surf Processes Landf

Self Cite

View full text Add to dashboard Cite

Debris flows are powered by sediment supplied from steep hillslopes where soils are often patchy and interrupted by bare‐bedrock cliffs. The role of patchy soils and cliffs in supplying sediment to channels remains unclear, particularly surrounding wildfire disturbances that heighten debris‐flow hazards by increasing sediment supply to channels. Here, we examine how variation in soil cover on hillslopes affects sediment sizes in channels surrounding the 2020 El Dorado wildfire, which burned debris‐flow prone slopes in the San Bernardino Mountains, California. We focus on six headwater catchments (<0.1 km2) where hillslope sources ranged from a continuous soil mantle to 95% bare‐bedrock cliffs. At each site, we measured sediment grain size distributions at the same channel locations before and immediately following the wildfire. We compared results to a mixing model that accounts for three distinct hillslope sediment sources distinguished by local slope thresholds. We find that channel sediment in fully soil‐mantled catchments reflects hillslope soils (D50 = 0.1–0.2 cm) both before and after the wildfire. In steeper catchments with cliffs, channel sediment is consistently coarse prior to fire (D50 = 6–32 cm) and reflects bedrock fracture spacing, despite cliffs representing anywhere from 5% to 95% of the sediment source area. Following the fire, channel sediment size reduces most (5‐ to 20‐fold) in catchments where hillslope sources are predominantly soil covered but with patches of cliffs. The abrupt fining of channel sediment is thought to facilitate postfire debris‐flow initiation, and our results imply that this effect is greatest where bare‐bedrock cliffs are present but not dominant. A patchwork of bare‐bedrock cliffs is common in steeplands where hillslopes respond to channel incision by landsliding. We show how local slope thresholds applied to such terrain aid in estimating sediment supply conditions before two destructive debris flows that eventually nucleated in these study catchments in 2022.

show abstract

Section: Theoretical Frameworkmentioning

confidence: 99%

Section: Sediment Supply From Soil-mantled and Barebedrock Hillslopes...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The grain size of sediments delivered to steep debris‐flow prone channels prior to and following wildfire

Neely,

Moon,

DiBiase

et al. 2024

Earth Surf Processes Landf

Self Cite

View full text Add to dashboard Cite

show abstract

Fault activity in the San Gabriel Mountains, southern California, USA: Insights from landscape morphometrics, erosion rates, and fault-slip rates

Mere,

McPhillips

2024

Geological Society of America Bulletin

View full text Add to dashboard Cite

Many studies use landscape form to determine spatial patterns of tectonic deformation, and these are particularly effective when paired with independent measures of rock uplift and erosion. Here, we use morphometric analyses and 10Be catchment-averaged erosion rates, together with reverse slip rates from the Sierra Madre−Cucamonga fault zone, to reveal patterns in uplift, erosion, and fault activity in the range front of the San Gabriel Mountains in southern California, USA. Our analysis tests two prevailing hypotheses: (1) the range front of the San Gabriel Mountains is at steady state, in which rock uplift balances erosion and topographic elevations are stable throughout time, and (2) that west-to-east increases in elevation, relief, erosion rate, and stream-channel steepness across the interior of the massif reflect a parallel reverse-slip rate gradient on the range-bounding Sierra Madre−Cucamonga fault zone. We show that although deviations from steady state occur, the range-front hillslopes and stream channels are typically both well-connected and adjusted to patterns in Quaternary uplift driven by motion on the range-front fault network. Accordingly, landscape morphometrics, 10Be erosion rates, and model erosion rates effectively image spatial and temporal patterns in uplift. Interpreted jointly, these data reveal comparable peak slip rates on the Sierra Madre−Cucamonga fault zone and show that they do not monotonically increase from west to east. Thus, the eastward-increasing gradients developed within the interior of the massif are not solely related to reverse slip on the range-front faults. Evaluated on shorter length scales (<10 km), morphometric data corroborate earlier descriptions of the Sierra Madre−Cucamonga fault zone as multiple individual faults or fault sections, with slip rates tapering toward fault tips. We infer that these patterns imply the predominance of independent fault or fault section ruptures throughout the Quaternary, though data cannot rule out the possibility of large, connected Sierra Madre−Cucamonga fault zone ruptures. Deeper in the hanging wall of the Sierra Madre−Cucamonga fault zone, secondary faults accommodate range-front uplift. Motion on these faults may contribute to active uplift of the highest topography within the massif, in addition to partly reconciling differences between geologic and geodetic Sierra Madre−Cucamonga fault zone reverse-slip rates. This study provides a new, unified perspective on tectonics and landscape evolution in the San Gabriel Mountains.

show abstract

Hillslope Morphology Drives Variability of Detrital ¹⁰Be Erosion Rates in Steep Landscapes

Cited by 2 publications

References 58 publications

The grain size of sediments delivered to steep debris‐flow prone channels prior to and following wildfire

The grain size of sediments delivered to steep debris‐flow prone channels prior to and following wildfire

Fault activity in the San Gabriel Mountains, southern California, USA: Insights from landscape morphometrics, erosion rates, and fault-slip rates

Contact Info

Product

Resources

About

Hillslope Morphology Drives Variability of Detrital 10Be Erosion Rates in Steep Landscapes

Cited by 2 publications

References 58 publications

The grain size of sediments delivered to steep debris‐flow prone channels prior to and following wildfire

The grain size of sediments delivered to steep debris‐flow prone channels prior to and following wildfire

Fault activity in the San Gabriel Mountains, southern California, USA: Insights from landscape morphometrics, erosion rates, and fault-slip rates

Contact Info

Product

Resources

About

Hillslope Morphology Drives Variability of Detrital ¹⁰Be Erosion Rates in Steep Landscapes