The Hydraulic Characteristics of Slope Flow

2012 ◽  
Vol 601 ◽  
pp. 123-127
Author(s):  
Zhen Zhou Shen ◽  
Wen Yi Yao ◽  
Zhan Bin Li ◽  
Pei Qing Xiao ◽  
Mian Li ◽  
...  
Keyword(s):  
Overland Flow ◽  
Infiltration Rate ◽  
Technology Support ◽  
Hydraulic Characteristics ◽  
Water Drainage ◽  
Erosion Model ◽  
Mechanism Research ◽  
Flow Hydraulics ◽  
Slope Flow ◽  
Important Branch

Slope hydrology is an important branch of Modern hydrology, it has a great significance to study the runoff and converge mechanism research of the basin. The characteristics study include of runoff velocity and infiltration rate etc al. the runoff velocity is an important physical quantity to describe overland flow hydraulics characterize. This paper study the effect of slope degrees and water drainage amount on the runoff velocity. The result shows: slope degree and water drainage both are the important factors to change the runoff velocity. The average runoff velocity were increased first and then reach steady-state fluctuations between 0.1-1m/s at different drainage amount, the time they got to the steady states was different. The results could provide some technology support to establishment slope erosion model.

Geo-informatics based Morphometric Analysis of a Reservoir Catchment in Shivalik Foothills of North-West India

2021 ◽  
Vol 58 (03) ◽  
pp. 286-299
Author(s):  
Mahesh Chand Singh ◽  
Rohit Singh ◽  
Abrar Yousuf ◽  
Vishnu Prasad
Keyword(s):  
Form Factor ◽  
Soil Erosion ◽  
Morphometric Analysis ◽  
Overland Flow ◽  
Infiltration Rate ◽  
Elongation Ratio ◽  
Alos Palsar ◽  
Bifurcation Ratio ◽  
Runoff Potential ◽  
Drainage Texture

The present study examined 35 morphometric parameters related to stream/drainage network, catchment geometry, and relief aspects for hydrological characterization of the Thana Dam catchment using geospatial tools and techniques. The dam catchment was delineated using the high-resolution Advanced Land Observing Satellite Phased Array type L-band Synthetic Aperture Radar (ALOS PALSAR) Digital Elevation Model (DEM) data in ArcGIS 10.4.1 software using the Arc Hydro tools. The catchment is comprised of 4th order stream, obtained using a stream threshold value of 100 m length. The lower values of elongation ratio (0.61), circularity ratio (0.22), and form factor (0.29) indicated higher soil erosion potential, mainly due to their inverse relationship with land erodibility. Moreover, the higher values of stream frequency (15.7), drainage density (>5.0), drainage texture (7.48 km-1), and mean bifurcation ratio (4.08-6.33) indicated higher runoff potential, which would intensify the soil erosion, mainly due to their direct relationship with erodibility. Bifurcation ratio, elongation ratio, circulatory ratio, form factor, altogether indicated an elongated shape of the catchment with a fine drainage texture. The higher values of bifurcation ratio and texture ratio of the catchment also indicated severe overland flow (low infiltration rate) with a limited scope for groundwater recharge in the area, which in turn might significantly encourage the soil erosion. Overall, it was concluded that the catchment has a huge runoff potential resulting in high soil erosion due to its fine texture, impermeable subsurface material, steep slope, low infiltration rate, limited vegetation, longer duration of overland flow, and higher surface runoff. The morphometric analysis was found to be suitable for identifying catchment shape and the factors affecting hydrologic conditions and erodibility of the catchment. Thus, Geo-informatics based morphometric analysis of a reservoir catchment can be useful to study the erosion potential in relation to hydrologic (rainfall-runoff relationship) and other related land characteristics (e.g., relief, slope, infiltration rate, etc.).

A hysteretic model for rainfall-runoff of a simplifed catchment 

2021 ◽  
Author(s):  
Denis Flynn ◽  
Warren Roche
Keyword(s):  
Overland Flow ◽  
Previous History ◽  
Infiltration Rate ◽  
Nonlinear Phenomenon ◽  
Hysteretic Model ◽  
Rainfall Runoff ◽  
Total Runoff ◽  
History Of ◽  
Preisach Operator ◽  
Rainfall Runoff Model

<div>The soil can be modelled as a porous medium in which the three phases of matter coexist and produce the emergent phenomenon of hysteresis.</div><div>Rate-independent hysteresis is a nonlinear phenomenon where the output depends not only on the current input but also the previous history of inputs to the system. In multiphase porous media such as soils, the hysteresis is in the relationship between the soil-moisture content, and the capillary pressure.</div><div>In this work, we develop a simplified hysteretic rainfall-runoff model consisting of the following subsystems that capture much of the physics of flow through a slab of soil:</div><div>1) A slab of soil where rainfall enters and if enough water is present in the soil, it will subsequently drain into the groundwater reservoir. This part of the model is represent by ODE with a Preisach operator.</div><div>2) A runoff component: If the rainfall exceeds the maximum infiltration rate of the soil, the excess will become surface runoff. This part of the model is represented by a series of two hysteretic reservoirs instead of the two linear reservoirs in the literature.</div><div>3) A ground water storage and outflow subsystem component: this is also modelled by a hysteretic reservoir. Finally, the outputs from the groundwater output and the overland flow are combined to give the total runoff. We will examine this model and compare it with non-hysteretic case both qualitatively and quantitively.</div>

Experimental study of sediment transport processes and size selectivity of eroded sediment on steep Pisha sandstone slopes

2020 ◽  
Author(s):  
Pan Zhang ◽  
Pingqing Xiao ◽  
Chunxia Yang
Keyword(s):  
Sediment Transport ◽  
Flow Velocity ◽  
Overland Flow ◽  
Yellow River ◽  
Transport Processes ◽  
The Yellow River ◽  
Size Selectivity ◽  
Coarse Sediment ◽  
Sediment Particles ◽  
Slope Flow

<p>The Pisha sandstone area on the Ordos Plateau of China is the primary source of coarse sediment of the Yellow River. Sediment size distribution and selectivity greatly affect sediment transport and deposition. Hence, sediment transport processes and size selectivity by overland flow on Pisha sandstone slopes were investigated in this study. Experiments were run with Pisha sandstone soil (bulk density of 1.35 g/cm<sup>3</sup>) under rainfall intensities of 87 and 133 mm/h with a 25° slope gradient, and the duration of simulated rainfall is 1 h. Sediment and runoff were sampled at 2-min intervals to examine the size distribution change of the eroded sediment. The particle composition, enrichment rate, fractal dimension, and time distribution characteristics of median grain size (d<sub>50</sub>) of eroded sediment were comprehensively analyzed. Statistical analyses showed that the erosion process of Pisha sandstone slope mainly transported coarse sediment. More than 40% of eroded sediment particles were coarse sediment, which will become the main sediment in the lower reaches of the Yellow River bed. The particle size of eroded sediment tended to gradually decrease with the continuous rainfall but remained larger than the background value of Pisha sandstone soil after refinement. The fractal dimension was positively correlated with the slope flow velocity, while the d<sub>50</sub> was negatively correlated with the slope flow velocity. Overall, these findings show a strong relationship between the sediment transport and flow velocity, which indicates that the selectivity and transportation of sediment particles on the Pisha sand slopes is mainly influenced by the hydrodynamic parameters of overland flow. This study provides a methodology and data references for studying the particle selectivity characteristics of eroded sediment and provides a scientific basis for revealing the mechanism of erosion and sediment yield in the Pisha sandstone area of China.</p>

"Partial area contribution" and "Overland flow discontinuity": from humid to arid hillslopes

2020 ◽  
Author(s):  
Hanoch Lavee
Keyword(s):  
Soil Moisture ◽  
Overland Flow ◽  
Infiltration Rate ◽  
Dead Sea ◽  
Livestock Grazing ◽  
Rainfall Simulation ◽  
Arid Areas ◽  
Shallow Subsurface ◽  
Partial Area ◽  
Semi Arid

<p>In humid temperate areas, where infiltration rate and soil moisture are high the hillslopes are draining mainly via shallow subsurface flow. Overland flow is seldom generated on the very low parts of hillslopes when the soil is saturated up to the surface. This spatial pattern is known as “partial area contribution”.</p><p>In contrary, in arid areas, where the soil moisture is hygroscopic most of the time, overland flow is generated not because of soil saturation conditions but only when rainfall intensity is higher than the infiltration rate.  </p><p>Nevertheless, we found a “partial area contribution” pattern in several arid and semi-arid areas due other controlling factors:</p><ol><li>In eastern Sinai, under rainfall simulation experiments on scree slopes, due to high spatial differences in the soil texture, runoff coefficient in the gullies was almost 100% while in the very permeable interfluves runoff wasn’t generated at all. Overland flow was generated, therefore, only in the gullies (Lavee ,1973; Yair & Lavee ,1976).</li> <li>In an instrumented experimental watershed in the Northern Negev, the specific overland flow yield from long plots ,extending from the divide to the slope base (around 60m in length), was consistently lower than the combined specific overland flow yield from the adjacent two short plots (around 30m in length), draining the upper and the lower sections of the hillslope, respectively. This means that the overland flow is discontinuous and at least part of the overland flow that was generated at the upper part of the hillslope infiltrated, in most overland flow events, into the soil, before reaching the slope base. In other words, only the lower part of the hillslope contributes, in most cases, overland flow to the channel. Such overland flow discontinuity is controlled by: 1. The typical short duration of rain showers in arid areas. As more than 80% of the rain showers last for less than 15 minutes, the total flow duration is usually shorter than the concentration time. 2. The spatial distribution of infiltration rate. In this case it was mainly the relatively high infiltration rate in the colluvial cover at the lower part of the hillslopes in part of the study area that absorbed large amount of the water flowing from the upper part of the hillslopes (Lavee, 1982; Yair & Lavee, 1985; Lavee & Yair, 1990).</li> <li>In an experimental project along a climatological transect, running from the Mediterranean climate near Jerusalem to the extreme arid climate near the Dead Sea, the main reason for the overland flow discontinuity, especially in the semi-arid area, was the mosaic pattern of “source patches”, on which overland flow was generated, and “sink patches”, in which at least part of the direct rain and the incoming overland flow infiltrated. This pattern is produced by different processes, mainly via the effect of vegetation, but also due to the effects of micro-topography, big stones, especially if they are partly embedded in the soil, and livestock grazing (Lavee & Poesen, 1991; Lavee et al., 1998; Stavi et al., 2008).</li> </ol>

scholarly journals An efficient semi-distributed hillslope erosion model for the sub humid Ethiopian Highlands

2012 ◽  
Vol 9 (2) ◽  
pp. 2121-2155 ◽  
Author(s):  
S. A. Tilahun ◽  
C. D. Guzman ◽  
A. D. Zegeye ◽  
T. A. Engda ◽  
A. S. Collick ◽  
...  
Keyword(s):  
Surface Runoff ◽  
Overland Flow ◽  
Sediment Concentration ◽  
Base Flow ◽  
Nile Basin ◽  
Erosion Model ◽  
Blue Nile ◽  
Ethiopian Highlands ◽  
Source Areas ◽  
Blue Nile Basin

Abstract. During the last two decades, saturated excess runoff has become accepted as the main source for overland flow in humid regions. Erosion modeling has generally not kept up with this new reality and predictions are often not based on landscape topographic position, which is a main variable in saturation excess runoff. In addition, predicting sediment loss in Africa has been hampered by using models that have been developed in western countries and do not perform as well in the monsoon climate prevailing in most of the continent. The objective of this paper is to develop a simple erosion model that can be used in the Ethiopian highlands in Africa. We base our sediment prediction on a simple distributed saturated excess hydrology model that predicts surface runoff from severely degraded lands and from bottom lands that become saturated during the rainy season and estimates interflow and base flow from the remaining portions of the landscape. By developing an equation that relates surface runoff to sediment concentration generated from runoff source areas, assuming that base flow and interflow are sediment free, we were able to predict daily sediment concentrations from the Anjeni Watershed and Blue Nile Basin with a Nash Sutcliffe efficiency ranging from 0.64 to 0.77 using only two calibrated sediment parameters. Anjeni is a 113 ha watershed in the 17.4 million ha Blue Nile Basin in the Ethiopian Highlands. The daily flows were predicted with Nash Sutcliffe efficiency values ranging from 0.80 to 0.93 if degraded areas were assumed the major sediment source areas and covered 14% of the Anjeni watershed and 20% of the Blue Nile basin. The analysis suggests that identifying the runoff source areas and predicting the surface runoff correctly is an important step in predicting the sediment concentration.

scholarly journals Using Wastewater in Irrigation: The Effects on Infiltration Process in a Clayey Soil

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 968 ◽  
Author(s):  
Ammar A. Albalasmeh ◽  
Mamoun A. Gharaibeh ◽  
Ma’in Z. Alghzawi ◽  
Renato Morbidelli ◽  
Carla Saltalippi ◽  
...  
Keyword(s):  
Soil Water ◽  
Hydraulic Properties ◽  
Field Experiments ◽  
Overland Flow ◽  
Clayey Soil ◽  
Water Infiltration ◽  
Treated Wastewater ◽  
Water Drainage ◽  
Infiltration Process ◽  
Relevant Effect

Soil water infiltration is a critical process in the soil water cycle and agricultural practices, especially when wastewater is used for irrigation. Although research has been conducted to evaluate the changes in the physical and chemical characteristics of soils irrigated by treated wastewater, a quantitative analysis of the effects produced on the infiltration process is still lacking. The objective of this study is to address this issue. Field experiments previously conducted on three adjacent field plots characterized by the same clayey soil but subjected to three different irrigation treatments have been used. The three irrigation conditions were: non-irrigated (natural conditions) plot, irrigated plot with treated wastewater for two years, and irrigated plot with treated wastewater for five years. Infiltration measurements performed by the Hood infiltrometer have been used to estimate soil hydraulic properties useful to calibrate a simplified infiltration model widely used under ponding conditions, that were existing during the irrigation stage. Our simulations highlight the relevant effect of wastewater usage as an irrigation source in reducing cumulative infiltration and increasing overland flow as a result of modified hydraulic properties of soils characterized by a lower capacity of water drainage. These outcomes can provide important insights for the optimization of irrigation techniques in arid areas where the use of wastewater is often required due to the chronic shortage of freshwater.

Effects of sheep grazing episodes on sediment and nutrient loss in overland flow

Soil Research ◽  
2004 ◽  
Vol 42 (2) ◽  
pp. 213 ◽  
Author(s):  
A. H. Elliott ◽  
W. T. Carlson
Keyword(s):  
Overland Flow ◽  
Infiltration Rate ◽  
Nutrient Loss ◽  
Late Winter ◽  
Nutrient Loads ◽  
Sheep Grazing ◽  
Bare Ground ◽  
Nitrogen And Phosphorus ◽  
Particulate Nutrients ◽  
Grass Growth

The effect of sheep grazing on the loss of sediment and nutrients in overland flow was investigated on a hill-country farm in the Waikato, New Zealand. The losses were measured in runoff produced artificially with small (0.5 m2) and large (1050 m2) rainfall simulators. Immediately after intensive winter grazing, rainfall applied at high intensity increased concentrations by a factor of 13–16 for sediment and particulate nutrients, 33–76 for dissolved reactive phosphorus and ammonium-nitrogen, and 5–7 for dissolved organic nitrogen and phosphorus. During summer, when there was less removal of vegetative cover, there was a smaller effect of grazing. The concentrations of sediment and particulate nutrients in overland flow were strongly correlated with the percentage of bare ground. The concentrations returned to background levels within 6 weeks after grazing, and the infiltration rate and ground cover also recovered from grazing in this time. The small rainfall simulator experiments showed that the infiltration rate decreases with grazing, which results in greater runoff after grazing. The greater runoff combines with the increased concentrations to give higher loads after grazing. In late winter, the infiltration rates were approximately half the summer values and the soil erodibility was approximately double, so the risk of high sediment and nutrient loads is greatest in winter, especially considering the higher rainfall and lower grass growth. The management implications are that exposure of bare ground associated with intensive grazing should be avoided, especially in winter.

scholarly journals Effects of Simulated Gravel on Hydraulic Characteristics of Overland Flow Under Varying Flow Discharges, Slope Gradients and Gravel Coverage Degrees

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Xiaona Liu ◽  
Dengxing Fan ◽  
Xinxiao Yu ◽  
Ziqiang Liu ◽  
Jiamei Sun
Keyword(s):  
Water Conservation ◽  
Flow Resistance ◽  
Overland Flow ◽  
Hydraulic Parameters ◽  
Flow Depth ◽  
Hydraulic Characteristics ◽  
Power Functions ◽  
Laboratory Flume ◽  
Ecological Construction ◽  
Soil And Water

AbstractTo quantify the hydraulic characteristics of overland flow on gravel-covered slopes, eight flow discharges (Q) (8.44–122 L/min), five slope gradients (J) (2°–10°) and four gravel coverage degrees (Cr) (0–30%) were examined via a laboratory flume. The results showed that (1) gravel changed flow regime. Gravel increased the Reynolds number (Re) by 2.94–33.03%. Re were less affected by J and positively correlated with Cr and Q. Gravel decreased the Froude number (Fr) by 6.83–77.31%. Fr was positively correlated with Q and J and negatively correlated with Cr. (2) Gravel delayed the flow velocity (u) and increased the flow depth (h) and flow resistance (f). Gravel reduced u by 1.20–58.95%. u was positively correlated with Q and J and negatively correlated with Cr. Gravel increased h by 0.12–2.41 times. h was positively correlated with Q and Cr and negatively correlated with J. Gravel increased f by 0.15–18.42 times. f were less affected by J, positively correlated with Cr and negatively correlated with Q. (3) The relationships between hydraulic parameters and Q, J and Cr identified good power functions. Hydraulic parameters were mainly affected by Cr. These results can guide the ecological construction of soil and water conservation.

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