Time of concentration of surface flow in complex hillslopes

Sabzevari, T.; Saghafian, Bahram; Talebi, Ali; Ardakanian, Reza

doi:10.2478/johh-2013-0034

Cited by 15 publications

(11 citation statements)

References 32 publications

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“…The proportions are similar as used for other larger watersheds. The interflow duration is directly related to the flow path of the water (Sabzevari et al 2013) and has been found to last between the 4 days for simulations of the small watersheds and the 70 days for the Blue Nile Basin at the Sudanese border (Tilahun et al 2013). Our value for the Gilgel Abay of 30 days is therefore reasonable.…”

Section: Physical Analysissupporting

confidence: 53%

Biohydrology of low flows in the humid Ethiopian highlands: The Gilgel Abay catchment

et al. 2014

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Abstract:In Ethiopia the population is rapidly expanding. As a consequence the landscape is rapidly changing. Eucalyptus plantations are increasing and irrigation projects are implemented. The hydrological effects of the changing landscape on river (low) flows have not been well documented and therefore the amount of water available in the future might be over optimistic. The objective of this paper is to establish how low flows have been impacted by new developments in irrigation and by landscape change. For this paper, we choose the Gilgel Abay in the headwaters of the upper Blue Nile basin, since it has both good quality discharge data and it is located in the Tana Beles growth corridor. Numerical and statistical means were used to analyze the 25 years of available low flow data. We found a statistically significant decreasing trend (P < 0.00001) of low flow in the Gilgel Abay. From 1980's to 1990's the low flow decreased by 25% and from 1990's to 2000's the low flow was reduced by 46%. The deterministic analysis with the Parameter Efficient Distributed (PED) model supported the statistical findings and indicated that in the middle of the nineteen nineties, after irrigation projects and eucalyptus plantations increased greatly, the low flows decreased more rapidly.

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Section: Physical Analysissupporting

confidence: 53%

Biohydrology of low flows in the humid Ethiopian highlands: The Gilgel Abay catchment

et al. 2014

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“…By solving the flow dynamic Equations (9)-(14), flow depth, velocity fields on the land surface and the flow discharge from the land surface can be obtained. The computed flow depth and velocity fields are, in turn, used for the erosion dynamics to predict the sediment concentration field on the et al, 2013 andTayfur, 2001 Soil detachability coefficient α kg/m 2 /mm 0.0006-0.0086 for high detachable soils and 0.00012-0.0017 for less detachable soils Foster, 1982;Sharma et al,1993 andTayfur, 2007 Soil erodibility coefficient 6 Foster, 1982;Sharma et al,1993 andTayfur, 2007 land surface and sediment discharge from the land surface (Tayfur, 2001).…”

Section: Solution Proceduresmentioning

confidence: 99%

“…By substituting Equation to this equation, overland flow depth obtains:

h_{x} ((), t) = {[\frac{n_{man} q ((), t) \emptyset_{p l} ((), x)}{\sqrt{s (x)}}]}^{1 true/ m}

where n man is the Manning roughness coefficient, s ( x ) is local slope, m is a parameter accounting for flow regimes ( m = 5/3 for turbulent flow, m = 2 for transition flow and m = 3 for laminar flow) (Sabzevari1 et al ., ). Now in order to obtain h x ( t ), the other variables in equation could be solved.…”

Section: Introductionmentioning

confidence: 99%

Physically based modelling of sheet erosion (detachment and deposition processes) in complex hillslopes

et al. 2016

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Abstract:A one-dimensional uncoupled model governed by this research is a physics-based modelling of the rainfall-runoff induced erosion process. The presented model is composed of three parts of a three-dimensional (3D) hillslope geometry, a nonlinear storage (kinematic wave) model for hillslope hydrological response, and an unsteady physically based surface erosion model. The 3D hillslope geometry model allows describing of the hillslope morphology by defining their plan shape and profile curvature. By changing these two topographic parameters, nine basic hillslope types are derived. The modelling of hillslope hydrological response is based on a flow continuity equation as the relation of discharge and flow depth is passed on kinematic wave approximation. The erosion model is based on a mass conservation equation for unsteady flow. The model assumes that suspended sediment does not affect flow dynamics. The model also accounts for the effect of flow depth plus loose soil depth on soil detachment. The presented model was run for two different precipitations, slope content, and length, and results were plotted for sediment detachment/deposition rate. Based on the obtained results, in hillslopes with convex and straight profile curvatures, sediment detachment only occurred in the whole length of the hillslope. However, in concave ones, sediment detachment and deposition only occurred together in hillslope. The hillslopes with straight profiles and convergent plans have the highest rate of detachment. Also, results show that most detachment rates occur in convex profile curvatures, which are about 15 times more than in straight profiles.

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“…At the pedon scale, soil erosion can be attributed to the separation of soil particles by raindrops and runoff during interrill erosion processes, so preventing this process is an important goal in the management of water and soil resources [6][7][8]. The amount of runoff is a function of navigation time, therefore the accurate estimation of the time of concentration and runoff threshold results in a more accurate hydrograph of flooding [9]. Designing methods and structures for soil water conservation requires accurate estimation of the amount and time of flood peak discharge and time of concentration.…”

Section: Introductionmentioning

confidence: 99%

“…A representative example of this kind of mixed and complex dynamic is the degraded soils of Iran. Since most soils in Iran have low permeability, precipitation exceeds infiltration, hence, surface runoff becomes dominant [9,13].…”

Section: Introductionmentioning

confidence: 99%

Effects of Roughness Coefficients and Complex Hillslope Morphology on Runoff Variables under Laboratory Conditions

Meshkat

Amanian

Talebi

et al. 2019

Water

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The geometry of hillslopes (plan and profile) affects soil erosion under rainfall-runoff processes. This issue comprises of several factors, which must be identified and assessed if efficient control measures are to be designed. The main aim of the current research was to investigate the impact of surface Roughness Coefficients (RCs) and Complex Hillslopes (CHs) on runoff variables viz. time of generation, time of concentration, and peak discharge value. A total of 81 experiments were conducted with a rainfall intensity of 7 L min−1 on three types of soils with different RCs (i.e., low = 0.015, medium = 0.016, and high = 0.018) and CHs (i.e., profile curvature and plan shape). An inclination of 20% was used for three replications. The results indicate a significant difference (p-value ≤ 0.001) in the above-mentioned runoff variables under different RCs and CHs. Our investigation of the combined effects of RCs and CHs on the runoff variables shows that the plan and profile impacts are consistent with a variation in RC. This can implicate that at low RC, the effect of the plan shape (i.e., convergent) on runoff variables increases but at high RC, the impact of the profile curvature overcomes the plan shapes and the profile curvature’s changes become the criteria for changing the behavior of the runoff variables. The lowest mean values of runoff generation and time of concentration were obtained in the convex-convergent and the convex-divergent at 1.15 min and 2.68 min, respectively, for the soil with an RC of 0.015. The highest mean of peak discharge was obtained in the concave-divergent CH in the soil with an RC of 0.018. We conclude that these results can be useful in order to design planned soil erosion control measures where the soil roughness and slope morphology play a key role in activating runoff generation.

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Time of concentration of surface flow in complex hillslopes

Cited by 15 publications

References 32 publications

Biohydrology of low flows in the humid Ethiopian highlands: The Gilgel Abay catchment

Biohydrology of low flows in the humid Ethiopian highlands: The Gilgel Abay catchment

Physically based modelling of sheet erosion (detachment and deposition processes) in complex hillslopes

Effects of Roughness Coefficients and Complex Hillslope Morphology on Runoff Variables under Laboratory Conditions

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