Threshold of critical power in streams

Bull, William B.

doi:10.1130/0016-7606(1979)90<453:tocpis>2.0.co;2

Cited by 404 publications

(262 citation statements)

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“…Regardless of how mean precipitation changes, increases in storm magnitude and/or decreases in surface resistance lead to sequential aggradation and erosion along the main valley network. The sequence of events observed in the model resembles the conceptual model of Bull [1979]. To explain an early Holocene episode of valley alluviation followed by downcutting in valleys in the southwestern United States, Bull proposed that the reduction of moisture at the Pleistocene-Holocene transition led to a reduction in vegetation cover.…”

Section: Discussionmentioning

confidence: 97%

Drainage basin responses to climate change

Tucker¹,

Slingerland²

1997

Water Resources Research

531

484

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Abstract. Recent investigations have shown that the extent of the channel network in some drainage basins is controlled by a threshold for overland flow erosion. The sensitivity of such basins to climate change is analyzed using a physically based model of drainage basin evolution. The GOLEM model simulates basin evolution under the action of weathering processes, hillslope transport, and fluvial bedrock erosion and sediment transport. Results from perturbation analyses reveal that the nature and timescale of basin response depends on the direction of change. An increase in runoff intensity (or a decrease in vegetation cover) will lead to a rapid expansion of the channel network, with the resulting increase in sediment supply initially generating aggradation along the main network, followed by downcutting as the sediment supply tapers off. By contrast, a decrease in runoff intensity (or an increase in the erosion threshold) will lead to a retraction of the active channel network and a much more gradual geomorphic response. Cyclic changes in runoff intensity are shown to produce aggradational-degradational cycles that resemble those observed in the field. Cyclic variations in runoff also lead to highly punctuated denudation rates, with denudation concentrated during periods of increasing runoff intensity and/or decreasing vegetation cover. The sediment yield from thresholddominated basins may therefore exhibit significant variability in response to relatively subtle environmental changes, a finding which underscores the need for caution in interpreting modern sediment-yield data.

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Section: Discussionmentioning

confidence: 97%

Drainage basin responses to climate change

Tucker¹,

Slingerland²

1997

Water Resources Research

531

484

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“…A river's incision history reflects local, regional, and often global changes in climate because such changes affect the river's stream power, base level, and sediment supply (e.g. Bull, 1979;Blum and Törnqvist, 2000). This history can be compared to independent climate records to assess the correlation between events in the river's history and, for example, glacial-interglacial cyclicity.…”

Section: Introductionmentioning

confidence: 99%

New constraints on the late Cenozoic incision history of the New River, Virginia

et al. 2005

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The New River crosses the core of the ancient, tectonically quiescent Appalachian orogen as it follows its course through North Carolina, Virginia, and West Virginia. It is ideally situated to record the changes in geomorphic process rates that occur in the Appalachians as a response to late Cenozoic climate variations. Active erosion features on resistant bedrock that floors the river at prominent knickpoints demonstrate that the river is currently incising toward base level. However, large packages of alluvial fill and fluvial terraces cut into this fill record an incision history for the river that includes several periods of stalled downcutting and aggradation. Cosmogenic 10 Be exposure dating, aided by mapping and sedimentological examination of terrace deposits, is used to constrain the timing of events in this history. Fill-cut and strath terraces at elevations 10, 20, and 50 m above the modern river yield cosmogenic exposure ages of approximately 130, 610, and 955 ka, respectively, but uncertainties on these ages are not well-constrained. This translates to a long-term average incision rate of 43 m/my, which is comparable to rates measured elsewhere in the Appalachians. During specific intervals over the last 1 Ma, however, the New River's incision rate reached 97 m/my. Fluctuations between aggradation and rapid incision appear to be related to late Cenozoic climate variations, though uncertainties in modeled ages preclude direct correlation of these fluctuations to specific climate change events. Erosion rates on higher alluvial deposits adjacent to the river are estimated from 10 Be concentrations; these rates are very low, about 2 m/my or less. This demonstrates a disequilibrium in the modern landscape, with river incision greatly outpacing erosion from nearby landforms.

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“…The identification of terraces has predominantly been for the purposes of studying valley aggradation phases (i.e., terrace production), with much less attention directed toward the erosional processes that influence terrace preservation (Lewin and The factors that influence terrace preservation can be represented using the concept of force and resistance (Bull, 1979). Using this concept, fluvial response (i.e., terrace removal) can be considered to reflect the balance between driving factors that promote their erosion (e.g., stream power) or resistance (e.g., boundary material resistance).…”

Section: Introductionmentioning

confidence: 99%

“…Following channel incision, time-dependant weathering processes lead to the development of pedogenic constituents such as clay and iron minerals, and thus soil characteristics are useful for broadly differentiating the ages of terraces (Walker, 1962;Harden and Taylor, 1983;Tsai et al, 2007). In this way, the degree of soil development can help overcome issues associated with terraces in areas of subdued topographic relief where differences in surface elevations can be unclear (Warner, 1972;Cohen and Nanson, 2008).The identification of terraces has predominantly been for the purposes of studying valley aggradation phases (i.e., terrace production), with much less attention directed toward the erosional processes that influence terrace preservation (Lewin and The factors that influence terrace preservation can be represented using the concept of force and resistance (Bull, 1979). Using this concept, fluvial response (i.e., terrace removal) can be considered to reflect the balance between driving factors that promote their erosion (e.g., stream power) or resistance (e.g., boundary material resistance).…”

mentioning

confidence: 99%

“…Using this concept, fluvial response (i.e., terrace removal) can be considered to reflect the balance between driving factors that promote their erosion (e.g., stream power) or resistance (e.g., boundary material resistance). While Bull (1979) suggested the use of the specific variables of stream power to represent force and critical power to represent the resistance, a broader, catchment-scale focus may encompass other factors such as catchment area, drainage density, slope, lithology, stream power, valley width, or alluvial material properties that are relevant to processes operating over timescales of terrace evolution.The main aim of this paper is a spatial classification of terraces across five catchments in the Wet Tropics region of northeast Australia for the purposes of examining terrace preservation and catchment factors associated with their removal.In this paper we undertake desktop mapping of terraces based on terrain, elevation, and soil type and validation using ground truthing and independent chronostratographic data. We assess catchment terrace preservation using metrics for spatial preservation and remnant configuration.…”

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confidence: 99%

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Alluvial terrace preservation in the Wet Tropics, northeast Queensland, Australia

et al. 2015

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Alluvial terraces provide a record of aggradation and incision and are studied to understand river response to changes in climate, tectonic activity, sea level, and factors internal to the river system. Terraces form in all climatic regions and in a range of geomorphic settings; however, relatively few studies have been undertaken in tectonically stable settings in the tropics. The preservation of alluvial terraces in a valley is driven by lateral channel adjustments, vertical incision, aggradation, and channel stability, processes that can be further understood through examining catchment force-resistance frameworks. This study maps and classifies terraces using soil type, surface elevation, sedimentology, and optically stimulated luminescence dating across five tropical catchments in northeast Queensland, Australia. This allowed for the identification of two terraces across the study catchments (T1, T2).The T1 terrace was abandoned ~13.9 ka with its subsequent removal occurring until ~7.4 ka. Abandonment of the T2 terrace occurred ~4.9 ka with removal occurring until ~1.2 ka. Differences in the spatial preservation of these terraces were described using an index of terrace preservation (TPI). Assessments of terrace remnant configuration highlighted three main types of terraces: paired, unpaired, and disconnected, indicating the importance of different processes driving preservation.Regional-scale variability in TPI was not strongly correlated with catchment-scale surrogate variables for drivers of terrace erosion and resistance. However, catchmentspecific relationships between TPI and erosion-resistance variables were evident and are used here to explain the dominant processes driving preservation in these tropical settings. This study provides an important insight into terrace preservation in the tectonically stable, humid tropics and provides a framework for future research linking the timing of fluvial response to palaeoclimate change. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT IntroductionAlluvial terraces are topographic landforms that result from floodplain abandonment when a river incises, therefore providing records of river aggradation and incision (Leopold et al., 1964). Terraces have formed in all global regions and are commonly studied to understand how rivers have responded to the combined effects of changes in external controls including climate, tectonics, and sea level (Merritts et al., 1994;Macklin et al., 2002;Bridgland and Westaway, 2008) and in internal controls, such as catchment morphology (Coulthard et al., 2005) and reach-specific conditions (Houben, 2003).Terraces are generally identified in the landscape using a range of techniques including soil properties (see reviews in Birkeland, 1990;Huggett, 1998), topographic data (Pazzaglia and Gardner, 1993;Jones et al., 2007), aerial and satellite imagery (Litchfield and Berryman, 2005), with correlations further aided by sedimentology and dating (Stokes et al., 2012). The use of soil characteristics to classify terrace...

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Threshold of critical power in streams

Cited by 404 publications

References 0 publications

Drainage basin responses to climate change

Drainage basin responses to climate change

New constraints on the late Cenozoic incision history of the New River, Virginia

Alluvial terrace preservation in the Wet Tropics, northeast Queensland, Australia

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