Stream power

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

Combining SfM Photogrammetry and Terrestrial Laser Scanning to Assess Event-Scale Sediment Budgets along a Gravel-Bed Ephemeral Stream

Abstract: Stream power represents the rate of energy expenditure along a stream reach and can be calculated using topographic data acquired via structure-from-motion (SfM) photogrammetry and terrestrial laser scanning (TLS). This study sought to quantitatively relate morphological adjustments in the Azohia Rambla, a gravel-bed ephemeral stream in southeastern Spain, to stream power (ω), critical power (ωc), and energy gradients (∂ω/∂s), along different reference channel reaches of 200 to 300 m in length. High-resolution digital terrain models (HRDTMs), combined with ortophotographs and point clouds from 2018, 2019, and 2020, and ground-based surveys, were used to estimate the spatial variability of morphological sediment budgets and to assess channel bed mobility during the study period at different spatial scales: reference channel reaches (RCRs), pilot bed survey areas (PBSAs), and representative geomorphic units (RGUs). The optimized complementary role of the SfM technique and terrestrial laser scanning allowed the generation of accurate and reliable HRDTMs, upon which a 1-D hydrodynamic model was calibrated and sediment budgets calculated. The resulting high-resolution maps allowed a spatially explicit analysis of stream power and transport efficiency in relation to volumes of erosion and deposition in the RCR and PBSA. In addition, net incision or downcutting and vertical sedimentary accretion were monitored for each flood event in relation to bedforms and hydraulic variables. Sediment sources and sinks and bed armoring processes showed different trends according to the critical energy and stream power gradient, which were verified from field observations. During flows exceeding bankfull discharges (between 18 and 24 m3 s−1 according to channel reach), significant variations in ∂ω/∂s values and ω/ωc ratios (e.g., −15 2 for a peak discharge of 31 m3 s−1) were associated with a large amount of bedload mobilized upstream and vertical accretion along the middle reach (average rise height of 0.20 to 0.35 m for the same event). By contrast, more moderate peak flows (≤10 m3 s−1) only produced minor changes resulting in surface washing, selective transport, and local bed scouring.

Some morphological and hydraulic characteristics of river-patterns in the Zaire Basin

Abstract: Summary A survey of the main rivers of the Zaire Basin (Equatorial Africa), carried out on aerial photographs, has resulted in the establishment of several relationships between the physiographic regions of Zaire and a number of selected river types. It was found that the river stability depends on its regime and on the stability of its banks. Clayey forested banks are the most stable ones. The degree of complexity of the rivers, proportional to the number of islands and sand bars per unit length, increases with the abundance of sand in their basins. Larger rivers tend to be more complex but stable ones tend to a single talweg. A detailed sampling of bed-sediments from selected rivers in the Bandundu area (the Kwango, the Kwilu and the Kasai rivers) revealed that three morphologically different rivers carry the same 280 mu — sands which have an almost identical good sorting. The differences in shear stress or stream power between the three rivers are matced by a different transport rate and by an unequal repartition of the finer and the coarser sediments on the bed, but not by any difference in the average composition of the bed-load since this is provided by the same Kalahari sands.

Self-adjustment mechanism of bed structures under hydrology and sediment regimes.

Abstract: Bed structures develop in many coarse gravel-bed rivers, and the distribution of bed structures is obviously impacted by the environment conditions, especially hydrology and sediment regimes. This study carried out field investigations in natural tributaries of the Yangtze River to study the sizes of bed structures, their distribution in the basin, as well as their connections with local hydrology and sediment regimes. A field experiment was also conducted to study the evolution and functions of bed structures. Results of both the investigations and experiment indicated that under the conditions of low bedload, the structure intensity is in a positive correlation with the unit-width stream power, which is consumed by bed structures when the river is in a dynamic equilibrium. If the structures are not able to dissipate the whole energy, the river status turns into disequilibrium and the riverbed would be eroded by excess energy, and the river system would move to a stable position on the structure-power equilibrium line. The fluvial morphology of coarse-grained riverbeds is controlled by this mechanism to some extent. Sometimes excess energy can be consumed by bedload transport even with insufficient structure intensity, thus a unified power consumption model including bedload is also discussed.