Stream power

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

Relationships between soil detachment rate and runoff hydrodynamic indexes of purple soil slope and red soil slope

Abstract: Soil detachment process is one of the very important processes of erosion,transportation and deposition.Quantitative study of the soil detachment process is the basis of building the significant physical implication of soil erosion and prediction model.Taken the red soil and purple soil slopes respectively as the research fields,which was 3.0 long and 1.0 wide,a series of scouring experiments at 4 slope gradients(5°、 10°、15°、20°) and 5 water discharges(1.3l /min、3.0l /min、5.5l /min、6.5l /min、8.5l /min) were conducted.The relationships between soil detachment rate and runoff shear stress,unit stream power,stream power and cross-section specific energy are studied in this paper.The results show that the soil detachment rate increased with the increase in water discharge at the same slope gradient.Soil detachment rate increased at the beginning and then decreased,at last,the soil detachment rate became stable at the same water discharge.The time of soil detachment rate reaching its peak value became shorter along with the increase in water discharge.There exited a good linear relationship between the soil detachment rate and runoff shear stress,unit stream power,stream power and cross-section specific energy.All of these four indexes could be used for reflecting the soil detachment rate,but the stream power was better than the others.For the red soil the critical shear stress was about 1.25N /m2 and for the purple soil it was about 2.16N /m2.For the red soil the critical unit stream power was about 0.00014m /s and for the purple soil it was about 0.0018m /s.For the red soil the critical stream power was about 0.0083N /(m.s) and for the purple soil it was about 0.062 N /(m.s).For the red soil the critical cross-section specific energy was about 0.24cm and for the purple soil it was about 0.23 cm.

Flood Processes and Channel Responses in Typical Years of the Different Channel Patterns in Neimenggu Reaches of the Upper Yellow River

Abstract: The sedimentation on channel bed in the Neimenggu(Inner Mongolia) reach of the upper Yellow River has been relative severe since the last two decades.Some of researchers expect that artificial flood can erode the channel bed and lower the channel bed.In this work,the discharge-water level hydrographs of the maximal floods that occurred in the typical years have been revealed,and the shapes of the hydrographs include single line,clockwise loop,anticlockwise loop,and complex line plus anticlockwise loop,anticlockwise loop plus line,"8"-shape plus line,nested anticlockwise loop and cross lines.These relations can reflect whether the channel bed is eroded or deposited,when eroded or deposited,and whether the erosion and deposition are iterative.The responses of the Neimenggu channel of the upper Yellow River are different from those at the downstreams.The downward erosion and the depressed channel bed have a braiding channel pattern,the evident upward aggradation has a meandering pattern,and the slight upward aggradation or the balanced erosion-deposition has a straight pattern.This trend is adaptive to the stream power decrease downstreams.The decrease of concentration of suspended sediment downstream is the evidence.Artificial flood can not change the sedimentation trend on the meandering channel bed and can not help people to inhabit in the Hetao plain to avoid the flood hazard.

Uncertainty analysis of the HEC-RAS results in hydraulic simulation of Karoon River flow by Monte-Carlo approach

Abstract: Introduction The roughness parameter in hydraulic modelling of natural river and channel flows is not measurable easily and accurate point determination of roughness coefficient, its spatial and temporal variations includes several uncertainties that acts as the main source of error and uncertainties in hydraulic modeling. These drawbacks restricts the applicability of hydraulic modelling in river engineering projects, flood control and management, re-habitation and river restoration. Due to the uncertainties in rating curve, stage, top water width, stream power, shear stress, Froude number and velocity. Because of these drawbacks, in the current study uncertainty analysis by Monte-Carlo Simulation (MCS) combined with HEC-RAS model. Methodology In the current study uncertainty analysis, by Monte-Carlo Simulation (MCS) combined with HEC-RAS model is used to study a 105 km reach of Karoon River from Mollasani to Farsiat as shown in Fig. 1. The model is calibrated and verified using two year daily data of river flow and stage levels in Ahvaz station at the middle of the river reach. A computational control module is developed and combined with computational core of HEC-RAS to perform MCS automatically and the flowchart of modeling strategy and uncertainty analysis is presented in Fig.2. The MCS approach is coupled with computational core of HEC-RAS model by developing a subprogram that create and modifies the input files of HEC-RAS, run it automatically based on random samples of n Manning, and extracting the results of HEC-RAS model in each execution for further analysis in an automatic procedure. By using probability distribution of Manning roughness, 3000 simulations performed and graphical and quantitative indices used to evaluate the uncertainties of model results. In order to refine proper MCS from non-proper ones, the NSE>0.75 index is used to objectively sample n Manning from uncertainty analysis. The uncertainty analysis of proper MCS evaluated by 5 and 95% uncertainty bounds. The uncertainty analysis of model results are evaluated based on the six parameters of water surface elevation, top width of water, flow velocity, Froude number, stream power and shear stress in 3000 runs of peak flow and mean flow discharges respectively and quantified by two indices of 95PPU and d-factor. Results and Discussion The calibration and verification results of the HEC-RAS model in Figs 3-4 shows that in the calibration data set the R2 and RMSE of model in discharge are 0.94 and 21 (m3/s); and 093 and 0.6 (m) for water stage respectively. These values in the verification stage were 0.94 and 25.2(m3/s) for discharge; and 0.91 and 0.1(m) for water stage respectively. The results in 105 km length of Karoon River reveals high level of uncertainties with d-factor greater than 1 up to 11 in peak discharge of 3000 and mean daily discharge of 457 m3/s. These results revealed that using conditional evaluations based on NSE>0.75 reduced the uncertainty of d-factor in results of rating curve, stage, top water width, stream power, shear stress, Froude number and velocity. The d-factor of water stage reduced from 2 to 0.07 in peak discharge, and from 0.96 to 0.02 in average flows. These uncertainty reductions in top width of water were 2.5 to 0.19 in peak discharge and 1.3 to 0.078 in average flows of Karoon river. The highest uncertainty of HEC-RAS model results observed in water velocity and Froude number with di-factor 10.85 and 7.44 in peak discharge respectively. This trend of uncertainty reduction observed for water velocity, Froude number, stream power and shear stress along the river, as provided in Tables 1-3. The spectral responses of hydraulic parameters in model result that presented in Figs 5-10, indicate that although the HEC-RAS model produced high uncertainty values, especially in the complex domain of Karoon river, but these uncertainties dos not deviates the hydraulic patters of river flow in the study reach. The peak and maximum values and the zones of high vales of parameters, show high level of uncertainty than the small or moderate hydraulic situations. These indicates the inherent uncertainty in model results that causes high extents of spectral responses for model simulations. The provided findings necessitates the accurate determination of roughness coefficient according to its spatial and dynamic variations along the river reach. Conclusion The uncertainty results revealed high level of latent uncertainties in HEC-RAS model results and probabilistic analysis of models results is required for river re-habitation and management practices of large rivers such as Karoon River to provide certain and reliable results. The presented methodology and framer in the current study that uses automatic control and automation of HEC-RAS runs, strengths the modeling capability of one dimensional river flows for probabilistic analysis and automatic calibration of this mode.

Modelling Erosion Hazard: A Total Catchment Approach

Abstract: Physically based, computationally simple, analytical equations are derived for predicting erosion and deposition on complex slope geometries found in real three-dimensional terrain. Unit stream power theory provides the basis from which these relationships are developed. An example is given of predicted erosion and deposition on an experimental catchment at Wagga Wagga, Australia. Predicted zones of high erosion show good agreement with the observed locations of gullies and zones of severe sheet erosion.

Morphological controls on Hortonian surface runoff: An interpretation of steady-state energy patterns, maximum power states and dissipation regimes within a thermodynamic framework

Abstract: . Recent developments in hydrology have led to a new perspective on runoff processes, extending beyond the classical mass dynamics of water in a catchment. For instance, stream flow has been analysed in a thermodynamic framework, which allows the incorporation of two additional physical laws and enhances our understanding of catchments as open environmental systems. Related investigations suggested that energetic extremal principles might constrain hydrological processes, because the latter are associated with conversions and dissipation of free energy. Here we expand this thermodynamic perspective by exploring how hillslope structures at the macro- and microscale control the free energy balance of Hortonian overland flow. We put special emphasis on the transitions of surface runoff processes at the hillslope scale, as hillslopes energetically behave distinctly different in comparison to fluvial systems. To this end, we develop a general theory of surface runoff and of the related conversion of geopotential energy gradients into other forms of energy, particularly kinetic energy as the driver of erosion and sediment transport. We then use this framework at a macroscopic scale to analyse how combinations of typical hillslopes profiles and width distributions control the spatial patterns of steady-state stream power and energy dissipation along the flow path. At the microscale, we analyse flow concentration in rills and its influence on the distribution of energy and dissipation in space. Therefore, we develop a new numerical method for the Catflow model, which allows a dynamical separation of Hortonian surface runoff between a rill- and a sheet flow domain. We calibrated the new Catflow-Rill model to rainfall simulation experiments and observed overland flow in the Weiherbach catchment and found evidence that flow accumulation in rills serves as a means to redistribute energy gradients in space, therefore minimizing energy expenditure along the flow path, while also maximizing overall power of the system. Our results indicate that laminar sheet flow and turbulent rill flow on hillslopes develop to a dynamic equilibrium that corresponds to a maximum power state, and that the transition of flow from one domain into the other is marked by an energy maximum in space.