scholarly journals Correction to “Importance of a stochastic distribution of floods and erosion thresholds in the bedrock river incision problem”

2003 ◽  
Vol 108 (B8) ◽  
Author(s):  
Noah P. Snyder
Keyword(s):  
River Incision ◽  
Bedrock River Incision ◽  
Stochastic Distribution

scholarly journals Parameterization of river incision models requires accounting for environmental heterogeneity: insights from the tropical Andes

2020 ◽  
Vol 8 (2) ◽  
pp. 447-470 ◽  
Author(s):  
Benjamin Campforts ◽  
Veerle Vanacker ◽  
Frédéric Herman ◽  
Matthias Vanmaercke ◽  
Wolfgang Schwanghart ◽  
...  
Keyword(s):  
Spatial Patterns ◽  
Rainfall Variability ◽  
Nonlinear Relationship ◽  
Stream Power ◽  
Denudation Rates ◽  
River Incision ◽  
Power Models ◽  
Bedrock River Incision ◽  
Lithological Heterogeneity

Abstract. Landscape evolution models can be used to assess the impact of rainfall variability on bedrock river incision over millennial timescales. However, isolating the role of rainfall variability remains difficult in natural environments, in part because environmental controls on river incision such as lithological heterogeneity are poorly constrained. In this study, we explore spatial differences in the rate of bedrock river incision in the Ecuadorian Andes using three different stream power models. A pronounced rainfall gradient due to orographic precipitation and high lithological heterogeneity enable us to explore the relative roles of these controls. First, we use an area-based stream power model to scrutinize the role of lithological heterogeneity in river incision rates. We show that lithological heterogeneity is key to predicting the spatial patterns of incision rates. Accounting for lithological heterogeneity reveals a nonlinear relationship between river steepness, a proxy for river incision, and denudation rates derived from cosmogenic radionuclide (CRNs). Second, we explore this nonlinearity using runoff-based and stochastic-threshold stream power models, combined with a hydrological dataset, to calculate spatial and temporal runoff variability. Statistical modeling suggests that the nonlinear relationship between river steepness and denudation rates can be attributed to a spatial runoff gradient and incision thresholds. Our findings have two main implications for the overall interpretation of CRN-derived denudation rates and the use of river incision models: (i) applying sophisticated stream power models to explain denudation rates at the landscape scale is only relevant when accounting for the confounding role of environmental factors such as lithology, and (ii) spatial patterns in runoff due to orographic precipitation in combination with incision thresholds explain part of the nonlinearity between river steepness and CRN-derived denudation rates. Our methodology can be used as a framework to study the coupling between river incision, lithological heterogeneity and climate at regional to continental scales.

How rivers incise to survive periodic inputs of immobile landslide-derived boulders

2020 ◽  
Author(s):  
Noah Finnegan
Keyword(s):  
Drainage Area ◽  
Channel Width ◽  
Coast Range ◽  
Narrow Channels ◽  
River Incision ◽  
Eel River ◽  
Tectonically Active ◽  
Consistent Picture ◽  
Bedrock River Incision ◽  
Periodic Inputs

<p>Bedrock landsliding provides a strong negative feedback on bedrock river incision by causing long-lived burial events and hence hiatuses in downcutting.  Nevertheless, rivers in tectonically active settings carve deep canyons despite being periodically inundated with immobile boulders. How is this possible? In this contribution, we explore the processes through which rivers incise bedrock canyons within the Franciscan mélange in the actively uplifting California Coast Range. The Franciscan mélange is well known for its “melting ice cream topography” in which slow-moving landslides (“earthflows”) festoon the walls of river canyons and deliver car- to house-sized boulders to channels.  </p><p>Analysis of valley widths and river long profiles over ∼19  km of Alameda Creek (185  km<sup>2</sup> drainage area) and Arroyo Hondo (200  km<sup>2</sup> drainage area) in central California shows a very consistent picture in which earthflows that intersect these channels deposit immobile boulders that force tens of meters of gravel aggradation for kilometers upstream, leading to apparently long-lived sediment storage and channel burial at these sites. In contrast, over a ∼30  km section of the Eel River (5547  km<sup>2</sup> drainage area), there are no knickpoints or aggradation upstream of locations where earthflows impinge on its channel. Neither boulder supply nor transport capacity explains this difference. Rather, we find that the dramatically different sensitivity of the two locations to landslide blocking is linked to differences in channel width relative to typical seasonal displacements of landslides. The Eel River is ∼5 times wider than the largest annual seasonal displacement. In contrast, during wet winters, earthflows are capable of crossing and blocking the entire channel width of Arroyo Hondo and Alameda Creek. Hence, by virtue of having wide valley bottoms, larger rivers are more likely to simply flow around the toes of earthflows.  </p><p>For the smaller rivers in our study area that are chronically buried in landslide debris, our field observations provide evidence for two processes that may allow periodic bedrock river incision. Narrow channels in the Franciscan mélange that are buried in debris can incise epigenetic gorges around the margins of boulder jams during periods of earthflow dormancy when boulders are no longer input into channels.  Alternatively, during periods of earthflow dormancy, abrasion (and hence size reduction) of boulders in place from suspended sediment may ultimately render boulders mobile.  </p><p>Without explicit representation of these three processes, modeling the coupling of hillslope and channel evolution in this setting is not possible. </p><p><br><br></p>

scholarly journals Quantifying the competing influences of lithology and throw rate on bedrock river incision

2020 ◽  
Author(s):  
E. Kent ◽  
A.C. Whittaker ◽  
S.J. Boulton ◽  
M.C. Alçiçek
Keyword(s):  
Rock Type ◽  
Active Faults ◽  
Sedimentary Rocks ◽  
Normal Fault ◽  
Metamorphic Rocks ◽  
Stream Power ◽  
Western Turkey ◽  
River Incision ◽  
Bedrock River Incision

River incision in upland areas is controlled by prevailing climatic and tectonic regimes, which are increasingly well described, and the nature of the bedrock lithology, which is still poorly constrained. Here, we calculated downstream variations in stream power and bedrock strength for six rivers crossing a normal fault in western Turkey, to derive new constraints on bedrock erodibility as function of rock type. These rivers were selected because they exhibit knick zones representing a transient response to an increase in throw rate, driven by fault linkage. Field measures of rock mass strength showed that the metamorphic units (gneisses and schists) in the catchments are ∼2 times harder than the sedimentary lithologies. Stream power increases downstream in all rivers, reaching a maxima upstream of the fault within the metamorphic bedrock but declining markedly where softer sedimentary rocks are encountered. We demonstrate a positive correlation between throw rate and stream power in the metamorphic rocks, characteristic of rivers obeying a detachment-limited model of erosion. We estimated bedrock erodibility in the metamorphic rocks as kb = 2.2−6.3 × 10−14 ms2 kg−1; in contrast, bedrock erodibility values were 5−30 times larger in the sedimentary units, with kb = 1.2−15 × 10−13 ms2 kg−1. However, in the sedimentary units, stream power does not scale predictably with fault throw rate, and we evaluated the extent to which the friable nature of the outcropping clastic bedrock alters the long-term erosional dynamics of the rivers. This study places new constraints on bedrock erodibilities upstream of active faults and demonstrates that the strength and characteristics of underlying bedrock exert a fundamental influence on river behavior.

scholarly journals Chemical weathering as a mechanism for the climatic control of bedrock river incision

Nature ◽  
2016 ◽  
Vol 532 (7598) ◽  
pp. 223-227 ◽  
Author(s):  
Brendan P. Murphy ◽  
Joel P. L. Johnson ◽  
Nicole M. Gasparini ◽  
Leonard S. Sklar
Keyword(s):  
Chemical Weathering ◽  
River Incision ◽  
Climatic Control ◽  
Bedrock River Incision

scholarly journals Supplemental Material: Quantifying the competing influences of lithology and throw rate on bedrock river incision

2020 ◽  
Author(s):  
E. Kent ◽  
A.C. Whittaker ◽  
et al.
Keyword(s):  
River Incision ◽  
Bedrock River Incision

Methods; Tables S1–S15; and Figures S1–S4.

scholarly journals Lithology and orographic precipitation control river incision in the tropical Andes

2019 ◽  
Author(s):  
Benjamin Campforts ◽  
Veerle Vanacker ◽  
Frédéric Herman ◽  
Matthias Vanmaercke ◽  
Wolfgang Schwanghart ◽  
...  
Keyword(s):  
Amazon Basin ◽  
Rainfall Variability ◽  
Orographic Precipitation ◽  
Natural Environments ◽  
Relative Role ◽  
Tropical Andes ◽  
River Incision ◽  
Bedrock River Incision ◽  
The Impact

Abstract. Process-based geomorphic transport laws enable to assess the impact of rainfall variability on bedrock river incision over geological timescales. However, isolating the role of rainfall variability on erosion remains difficult in natural environments in part because the variability of rock strength and its resistance to incision are poorly constrained. Here, we explore spatial differences in the rate of bedrock river incision in the Tropical Andes. The Ecuadorian Andes are characterized by strong rainfall gradients due to orographic precipitation sourced in the Amazon basin. In addition, the tectonic configuration has generated a profound lithological heterogeneity. The relative role of either these controls in modulating river incision on millennial time scales, however, remains unclear. Using 10Be catchment-wide erosion rates, meteorological and hydrological data, as well as data on bedrock erodibility, we provide quantitative constraints on the importance of rainfall variability and lithological variations. Explicit incorporation of rock erodibility in river incision models predicated on the stream power equation enables us to identify a first order control of lithology on river incision rates. Rainfall variability based on a spatially and temporally explicit hydrological dataset and a stochastic-threshold river incision model explain regional differences in river incision that cannot be attributed to topographical and/or lithological variability.

scholarly journals Geologic constraints on bedrock river incision using the stream power law

1999 ◽  
Vol 104 (B3) ◽  
pp. 4983-4993 ◽  
Author(s):  
Jonathan D. Stock ◽  
David R. Montgomery
Keyword(s):  
Power Law ◽  
Stream Power ◽  
River Incision ◽  
Bedrock River Incision
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