Stream power

About: Stream power is a research topic. Over the lifetime, 1135 publications have been published within this topic receiving 51324 citations.

Erosional response of an actively uplifting mountain belt to cyclic rainfall variations

Abstract: . We present an approximate analytical solution to the stream power equation describing the erosion of bedrock in an actively uplifting mountain range subject to periodic variations in precipitation rate. It predicts a time lag between the climate forcing and the erosional response of the system that increases with the forcing period. The predicted variations in the sedimentary flux coming out of the mountain are also scaled with respect to the imposed rainfall variations in a direct proportion to the discharge exponent, m, in the stream power law expression. These findings are confirmed by 1-D and 2-D numerical solutions. We also show that the response of a river channel is independent of its length and thus the size of its catchment area, implying that all actively eroding streams in a mountain belt will constructively contribute to the integrated signal in the sedimentary record. We show that rainfall variability at Milankovitch periods should affect the erosional response of fast uplifting mountain belts such as the Himalayas, Taiwan or the South Island, New Zealand, and predict 1000 to 10 000-year offsets between forcing and response. We suggest that this theoretical prediction could be used to independently constrain the value of the poorly defined stream power law exponents, and provide an example of how this could be done, using geochemical proxy signals from an ODP borehole in the Bengal Fan.

Sedimentation in the ice‐contact environment, with examples from shropshire (england)

Abstract: Glacial sedimentation is assigned to two environments, the pro-glacial and the ice-contact. This paper is concerned with sedimentation in the ice-contact environment. The sub-drift topography of the area of study and the direction of ice movement are shown to be conducive to ice stagnation which is necessary for widespread ice-contact sedimentation. Ridges of glacigenic sediment show faulted, collapsed margins and lateral kettle holes characteristic of ice-contact landforms. The internal structure of these ridges is analysed in terms of primary and secondary sedimentary structure and texture. The spatial distribution of sedimentary structure and texture is shown to be similar to the fluvial models of Allen (1964) and Visher (1965). The absence of lateral extension of the fluvial members is interpreted as being due to stream training by ice walls preventing lateral migration. Large thicknesses of horizontal stratification and strongly unimodal palaeocurrent estimates are believed to be a result of this low sinuosity. Primary sedimentary structure and texture are used to designate facies. The distribution of the facies is thought to be diagnostic of the ice-contact environment. Downstream facies migration is thought to have occurred as a result of changes in the ratio of sediment supply to stream power.

Evaluating a multiclass net deposition equation in overland flow conditions

Abstract: [1] The movement of sediment and related pollutants in overland flow from the point of erosion to a stream normally occurs through a series of deposition zones. Here we present the evaluation of a new multiclass model of sediment transport through these zones. This model simulates size-selective net deposition as a result of simultaneous deposition by settling and nonselective reentrainment of previously deposited sediment [Hairsine et al., 2002; Sander et al., 2002]. Multiclass sediment deposition models provide a useful basis for simulating off-site effects of soil erosion, but information on the grain-size composition of deposited and exported sediment is crucial for calibrating and evaluating such models. Therefore the multiclass sediment deposition model was tested using detailed experimental data. Information on the amount of sediment deposition, on the grain-size distribution of the deposited and exported sediment, and on the spatial pattern of the deposits was collected during sediment deposition experiments. Calibration of the multiclass model, using one part of these data, was performed by adjusting the fraction of stream power available for sediment reentrainment by minimizing errors between both simulated and observed total outflow sediment concentration and grain-size distribution of the exported sediment. Evaluation was conducted, using the other part of the data, over a wide range of conditions. The evaluation shows that the deposition equation is capable of reasonably simulating the observed size selectivity of the deposition process. However, the model is not capable of simulating correctly the spatial pattern of the deposited sediment because of simplifications used in the hydraulic model.