The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Rebecca Webb - One of the best experts on this subject based on the ideXlab platform.
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Changes in leaf inclination angle as an indicator of progression toward leaf surface storage during the rainfall interception process
Journal of Hydrology, 2020Co-Authors: Curtis D. Holder, Leal K. Lauderbaugh, Roser M. Ginebra-solanellas, Rebecca WebbAbstract:Abstract During rainfall events, rain and throughfall drops impact on individual leaves exerting a force that divides the drops into multiple droplets and produces momentary increases in the leaf inclination angle. A portion of the splash residue from the Raindrop impact accumulates on the leaf surface and adds mass to the lamina of leaf. This lab-based study examined changes in leaf inclination angle after the impact of a sequence of Raindrops of two different volumes (10 µl and 30 µl) on leaf surfaces of three different tree species (Acer saccharinum L., Ulmus pumila L., and Quercus gambelii Nutt.). Leaf inclination is measured as the angle between the lamina surface normal and the horizontal. The differences between the initial leaf inclination angle before Raindrop impacts and the steady-state leaf inclination angles after each Raindrop impact were examined to explore the hypothesis that rainsplash residue accumulated on leaves after Raindrop impact will incrementally increase the steady-state leaf inclination angle as the leaves approach leaf surface storage. The difference between the initial leaf inclination angle and the steady-state leaf inclination angle after two 10 µl Raindrops increased by 0.23° for Q. gambelii, 0.84° for A. saccharinum, and 1.29° for U. pumila. The difference between the initial leaf inclination angle and the steady-state leaf inclination angle after two 30 µl Raindrops increased by 0.56° for Q. gambelii, 1.45° for U. pumila, and 2.05° for A. saccharinum. For each species, the mass of the accumulated water incrementally increased the steady-state leaf inclination angle after each Raindrop impact. As expected, larger Raindrops produced more rainsplash residue on the leaf surface based on the incremental increase in steady-state leaf inclination angle after sequential Raindrop impacts. With repeated Raindrop impacts, leaves in the canopy accumulate more water (mass) as the maximum leaf surface storage is achieved. Observing changes in steady-state leaf inclination angles after Raindrop impact may serve as an indicator for rainfall interception totals during rainfall events.
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The influence of changes in leaf inclination angle and leaf traits during the rainfall interception process
Agricultural and Forest Meteorology, 2020Co-Authors: Roser M. Ginebra-solanellas, Curtis D. Holder, Leal K. Lauderbaugh, Rebecca WebbAbstract:Abstract Rainfall interception is a dynamic process where Raindrops exert a force on leaf surfaces causing splashing and changes in leaf inclination angles. Leaf biomechanical properties determine the resistance to changes in leaf inclination angle due to Raindrop impacts. The hydrophobicity of leaf surfaces may influence water movement off the leaf. A laboratory experiment incorporating a Raindrop generator and high-speed video camera was used to examine the relationships between Raindrop impact, leaf biomechanics, and water droplet retention of three tree species (Acer saccharinum, Ulmus pumila, and Quercus gambelii). Specifically, we explored if the impact of a falling Raindrop resulted in the maximum leaf inclination angle exceeding the water droplet retention angle, allowing for the leaf to shed the intercepted Raindrop. This study found that changes in leaf inclination angle after a single Raindrop impact could explain water movement off more than 6.7% of the leaf surfaces associated with the three tree species. The change in leaf inclination angle over time produced a decaying sinusoidal curve after Raindrop impact. The amplitude of the change in leaf inclination angle was greater with larger drops; however, this change varied with species. Quercus gambelii was least affected by drop impact compared with Acer saccharinum and Ulmus pumila. For species with stiff leaves, such as Quercus gambelii, the resistance of movement after Raindrop impact could be a factor in inhibiting the amount of precipitation shed from the canopy. The influence of Raindrop impact during rainfall events and leaf biomechanical properties may inform and enhance modeling of the dynamic process of rainfall interception.
Roser M. Ginebra-solanellas - One of the best experts on this subject based on the ideXlab platform.
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Changes in leaf inclination angle as an indicator of progression toward leaf surface storage during the rainfall interception process
Journal of Hydrology, 2020Co-Authors: Curtis D. Holder, Leal K. Lauderbaugh, Roser M. Ginebra-solanellas, Rebecca WebbAbstract:Abstract During rainfall events, rain and throughfall drops impact on individual leaves exerting a force that divides the drops into multiple droplets and produces momentary increases in the leaf inclination angle. A portion of the splash residue from the Raindrop impact accumulates on the leaf surface and adds mass to the lamina of leaf. This lab-based study examined changes in leaf inclination angle after the impact of a sequence of Raindrops of two different volumes (10 µl and 30 µl) on leaf surfaces of three different tree species (Acer saccharinum L., Ulmus pumila L., and Quercus gambelii Nutt.). Leaf inclination is measured as the angle between the lamina surface normal and the horizontal. The differences between the initial leaf inclination angle before Raindrop impacts and the steady-state leaf inclination angles after each Raindrop impact were examined to explore the hypothesis that rainsplash residue accumulated on leaves after Raindrop impact will incrementally increase the steady-state leaf inclination angle as the leaves approach leaf surface storage. The difference between the initial leaf inclination angle and the steady-state leaf inclination angle after two 10 µl Raindrops increased by 0.23° for Q. gambelii, 0.84° for A. saccharinum, and 1.29° for U. pumila. The difference between the initial leaf inclination angle and the steady-state leaf inclination angle after two 30 µl Raindrops increased by 0.56° for Q. gambelii, 1.45° for U. pumila, and 2.05° for A. saccharinum. For each species, the mass of the accumulated water incrementally increased the steady-state leaf inclination angle after each Raindrop impact. As expected, larger Raindrops produced more rainsplash residue on the leaf surface based on the incremental increase in steady-state leaf inclination angle after sequential Raindrop impacts. With repeated Raindrop impacts, leaves in the canopy accumulate more water (mass) as the maximum leaf surface storage is achieved. Observing changes in steady-state leaf inclination angles after Raindrop impact may serve as an indicator for rainfall interception totals during rainfall events.
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The influence of changes in leaf inclination angle and leaf traits during the rainfall interception process
Agricultural and Forest Meteorology, 2020Co-Authors: Roser M. Ginebra-solanellas, Curtis D. Holder, Leal K. Lauderbaugh, Rebecca WebbAbstract:Abstract Rainfall interception is a dynamic process where Raindrops exert a force on leaf surfaces causing splashing and changes in leaf inclination angles. Leaf biomechanical properties determine the resistance to changes in leaf inclination angle due to Raindrop impacts. The hydrophobicity of leaf surfaces may influence water movement off the leaf. A laboratory experiment incorporating a Raindrop generator and high-speed video camera was used to examine the relationships between Raindrop impact, leaf biomechanics, and water droplet retention of three tree species (Acer saccharinum, Ulmus pumila, and Quercus gambelii). Specifically, we explored if the impact of a falling Raindrop resulted in the maximum leaf inclination angle exceeding the water droplet retention angle, allowing for the leaf to shed the intercepted Raindrop. This study found that changes in leaf inclination angle after a single Raindrop impact could explain water movement off more than 6.7% of the leaf surfaces associated with the three tree species. The change in leaf inclination angle over time produced a decaying sinusoidal curve after Raindrop impact. The amplitude of the change in leaf inclination angle was greater with larger drops; however, this change varied with species. Quercus gambelii was least affected by drop impact compared with Acer saccharinum and Ulmus pumila. For species with stiff leaves, such as Quercus gambelii, the resistance of movement after Raindrop impact could be a factor in inhibiting the amount of precipitation shed from the canopy. The influence of Raindrop impact during rainfall events and leaf biomechanical properties may inform and enhance modeling of the dynamic process of rainfall interception.
Curtis D. Holder - One of the best experts on this subject based on the ideXlab platform.
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Changes in leaf inclination angle as an indicator of progression toward leaf surface storage during the rainfall interception process
Journal of Hydrology, 2020Co-Authors: Curtis D. Holder, Leal K. Lauderbaugh, Roser M. Ginebra-solanellas, Rebecca WebbAbstract:Abstract During rainfall events, rain and throughfall drops impact on individual leaves exerting a force that divides the drops into multiple droplets and produces momentary increases in the leaf inclination angle. A portion of the splash residue from the Raindrop impact accumulates on the leaf surface and adds mass to the lamina of leaf. This lab-based study examined changes in leaf inclination angle after the impact of a sequence of Raindrops of two different volumes (10 µl and 30 µl) on leaf surfaces of three different tree species (Acer saccharinum L., Ulmus pumila L., and Quercus gambelii Nutt.). Leaf inclination is measured as the angle between the lamina surface normal and the horizontal. The differences between the initial leaf inclination angle before Raindrop impacts and the steady-state leaf inclination angles after each Raindrop impact were examined to explore the hypothesis that rainsplash residue accumulated on leaves after Raindrop impact will incrementally increase the steady-state leaf inclination angle as the leaves approach leaf surface storage. The difference between the initial leaf inclination angle and the steady-state leaf inclination angle after two 10 µl Raindrops increased by 0.23° for Q. gambelii, 0.84° for A. saccharinum, and 1.29° for U. pumila. The difference between the initial leaf inclination angle and the steady-state leaf inclination angle after two 30 µl Raindrops increased by 0.56° for Q. gambelii, 1.45° for U. pumila, and 2.05° for A. saccharinum. For each species, the mass of the accumulated water incrementally increased the steady-state leaf inclination angle after each Raindrop impact. As expected, larger Raindrops produced more rainsplash residue on the leaf surface based on the incremental increase in steady-state leaf inclination angle after sequential Raindrop impacts. With repeated Raindrop impacts, leaves in the canopy accumulate more water (mass) as the maximum leaf surface storage is achieved. Observing changes in steady-state leaf inclination angles after Raindrop impact may serve as an indicator for rainfall interception totals during rainfall events.
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The influence of changes in leaf inclination angle and leaf traits during the rainfall interception process
Agricultural and Forest Meteorology, 2020Co-Authors: Roser M. Ginebra-solanellas, Curtis D. Holder, Leal K. Lauderbaugh, Rebecca WebbAbstract:Abstract Rainfall interception is a dynamic process where Raindrops exert a force on leaf surfaces causing splashing and changes in leaf inclination angles. Leaf biomechanical properties determine the resistance to changes in leaf inclination angle due to Raindrop impacts. The hydrophobicity of leaf surfaces may influence water movement off the leaf. A laboratory experiment incorporating a Raindrop generator and high-speed video camera was used to examine the relationships between Raindrop impact, leaf biomechanics, and water droplet retention of three tree species (Acer saccharinum, Ulmus pumila, and Quercus gambelii). Specifically, we explored if the impact of a falling Raindrop resulted in the maximum leaf inclination angle exceeding the water droplet retention angle, allowing for the leaf to shed the intercepted Raindrop. This study found that changes in leaf inclination angle after a single Raindrop impact could explain water movement off more than 6.7% of the leaf surfaces associated with the three tree species. The change in leaf inclination angle over time produced a decaying sinusoidal curve after Raindrop impact. The amplitude of the change in leaf inclination angle was greater with larger drops; however, this change varied with species. Quercus gambelii was least affected by drop impact compared with Acer saccharinum and Ulmus pumila. For species with stiff leaves, such as Quercus gambelii, the resistance of movement after Raindrop impact could be a factor in inhibiting the amount of precipitation shed from the canopy. The influence of Raindrop impact during rainfall events and leaf biomechanical properties may inform and enhance modeling of the dynamic process of rainfall interception.
Oloth Sengtaheuanghoung - One of the best experts on this subject based on the ideXlab platform.
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Experimental and modelling evidence of splash effects on manure borne Escherichia coli washoff
Environmental Science and Pollution Research, 2021Co-Authors: Claude Mugler, Olivier Ribolzi, Jeanlouis Janeau, Keooudone Latsachack, Chanthamousone Thammahacksa, Marion Viguier, Emilie Jarde, Thierry Henry-des-tureaux, Christian Valentin, Oloth SengtaheuanghoungAbstract:In tropical montane South-East Asia, recent changes in land use have induced increased runoff, soil erosion and in-stream suspended sediment loads. Land use change is also contributing to increased microbial pathogen dissemination and contamination of stream waters. Escherichia coli ( E . coli ) is frequently used as an indicator of faecal contamination. Field rain simulations were conducted to examine how E . coli is exported from the surface of upland, agricultural soils during runoff events. The objectives were to characterize the loss dynamics of this indicator from agricultural soils contaminated with livestock waste, and to identify the effect of splash on washoff. Experiments were performed on nine 1 m^2 plots, amended or not with pig or poultry manure. Each plot was divided into two 0.5 m^2 sub-plots. One of the two sub-plots was protected with a mosquito net for limiting the Raindrop impact effects. Runoff, soil detachment by Raindrop impact and its entrainment by runoff, and E . coli loads and discharge were measured for each sub-plot. The results show that Raindrop impact strongly enhances runoff generation, soil detachment and entrainment and E . coli export. When the impact of Raindrops was reduced with a mosquito net, total runoff was reduced by more than 50%, soil erosion was on average reduced by 90% and E . coli export from the amended soil surface was on average 3 to 8 times lower. A coupled physics-based approach was performed using the Cast3M platform for modelling the time evolutions of runoff, solid particles detachment and transfer and bacteria transport that were measured for one of the nine plots. After estimation of the saturated hydraulic conductivity, soil erodibility and attachment rate of bacteria, model outputs were consistent with measured runoff coefficients, suspended sediment and E . coli loads. This work therefore underlines the need to maintain adequate vegetation at the soil surface to avoid the erosion and export of soil borne potential pathogens towards downstream aquatic systems.
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experimental and modelling evidence of short term effect of Raindrop impact on hydraulic conductivity and overland flow intensity
Journal of Hydrology, 2019Co-Authors: Claude Mugler, Olivier Ribolzi, Jeanlouis Janeau, Emma Rochellenewall, Keooudone Latsachack, Chanthamousone Thammahacksa, Marion Viguier, Emilie Jarde, Thierry Henridestureaux, Oloth SengtaheuanghoungAbstract:Tropical montane areas of Southeast Asia are exposed to high-intensity rainfall during the monsoon period. This is particularly problematic in areas where soils on steep slopes are cultivated as it can lead to heavy runoff, high soil erosion, and water pollution. The objective of this paper is to analyse the effect of the impact of Raindrops on the dynamics of runoff on such steep fields. Experiments under simulated rainfall were performed at the plot scale (1 m2) to quantify water export from the surface of upland agricultural soils during overland flow events. Four 1 m2 plots were divided in duplicated treatment groups: (a) control with no amendments, and (b) amended with pig manure. Each plot was divided into two 0.5 m2 rectangular subplots. One subplot was designated as a rain splash treatment; the other sub-plot was covered with a 2 mm grid size wire screen that was located 12 cm above the soil surface. The purpose of the screen was to break the Raindrops into fine droplets and to reduce fall height in order to drastically reduce their kinetic energy. Runoff was measured for each sub-plot. The results show that Raindrop impact drastically enhances runoff generation on both bare soils and on manure amended soils. When the impact of Raindrops was limited by screening, runoff was higher on amended soils than on bare soils. The temporal evolution of runoff was correctly modelled using a soil hydraulic conductivity that exponentially decreases over time of exposure to rainfall. Both experimental and modelling results showed that droplet energy induces a rapid evolution of the hydraulic properties of the soil surface due to crusting, resulting in a reduction of hydraulic conductivity and a concomitant increase in runoff rate.
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linking crop structure throughfall soil surface conditions runoff and soil detachment 10 land uses analyzed in northern laos
Science of The Total Environment, 2018Co-Authors: Guillaume Lacombe, Oloth Sengtaheuanghoung, Christian Valentin, Phabvilay Sounyafong, Anneke De Rouw, Bounsamai Soulileuth, Norbert Silvera, Alain Pierret, Olivier RibolziAbstract:In Montane Southeast Asia, deforestation and unsuitable combinations of crops and agricultural practices degrade soils at an unprecedented rate. Typically, smallholder farmers gain income from "available" land by replacing fallow or secondary forest by perennial crops. We aimed to understand how these practices increase or reduce soil erosion. Ten land uses were monitored in Northern Laos during the 2015 monsoon, using local farmers' fields. Experiments included plots of the conventional system (food crops and fallow), and land uses corresponding to new market opportunities (e.g. commercial tree plantations). Land uses were characterized by measuring plant cover and plant mean height per vegetation layer. Recorded meteorological variables included rainfall intensity, throughfall amount, throughfall kinetic energy (TKE), and Raindrop size. Runoff coefficient, soil loss, and the percentage areas of soil surface types (free aggregates and gravel; crusts; macro-faunal, vegetal and pedestal features; plant litter) were derived from observations and measurements in 1-m2 micro-plots. Relationships between these variables were explored with multiple regression analyses. Our results indicate that TKE induces soil crusting and soil loss. By reducing rainfall infiltration, crusted area enhances runoff, which removes and transports soil particles detached by splash over non-crusted areas. TKE is lower under land uses reducing the velocity of Raindrops and/or preventing an increase in their size. Optimal vegetation structures combine minimum height of the lowest layer (to reduce drop velocity at ground level) and maximum coverage (to intercept the largest amount of rainfall), as exemplified by broom grass (Thysanolaena latifolia). In contrast, high canopies with large leaves will increase TKE by enlarging Raindrops, as exemplified by teak trees (Tectona grandis), unless a protective understorey exists under the trees. Policies that ban the burning of multi-layered vegetation structure under tree plantations should be enforced. Shade-tolerant shrubs and grasses with potential economic return could be promoted as understorey.
Gunay Erpul - One of the best experts on this subject based on the ideXlab platform.
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Raindrop and flow interactions for interrill erosion with wind driven rain
Journal of Hydraulic Research, 2013Co-Authors: Gunay Erpul, Donald Gabriels Emeritus, Saskia Visser ResearcherAbstract:Wind-driven rain (WDR) experiments were conducted to evaluate the interrill component of the Water Erosion Prediction Project model with a two-dimensional experimental set-up in a wind tunnel. Synchronized wind and rain simulations were applied to soil surfaces on windward and leeward slopes of 7, 15 and 20%. Since WDR fall trajectory varied with horizontal wind velocities of 6, 10, and 14 m s−1, magnitude of Raindrop normal and lateral stresses on flow at the impact-flow boundary also changed and differentially directed lateral jets of Raindrop splashes with respect to downward flows occurred. To account for interactions between Raindrop impact and interrill shallow flow, a vector approach with kinetic energy fluxes of both Raindrop splashes and flow were used and this resulted in greater correlations in predicting sediment delivery rates.
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mechanics of interrill erosion with wind driven rain
Earth Surface Processes and Landforms, 2013Co-Authors: Gunay Erpul, Chi Hua Huang, Donald Gabriëls, Dennis C Flanagan, Darrell L Norton, S M VisserAbstract:The vector physics of wind-driven rain (WDR) differs from that of wind-free rain, and the interrill soil detachment equations in the Water Erosion Prediction Project (WEPP) model were not originally developed to deal with this phenomenon. This article provides an evaluation of the performance of the interrill component of the WEPP model for WDR events. The interrill delivery rates were measured in the wind tunnel facility of the International Center for Eremology (ICE), Ghent University, Belgium with an experimental setup to study different Raindrop impact velocity vectors. Synchronized wind and rain simulations with wind velocities of 6, 10 and 14 m s–1 were applied to a test surface placed on windward and leeward slopes of 7, 15 and 20%. Since both rainfall intensity and Raindrop impact velocity varied greatly depending on differences in the horizontal wind velocity under WDRs, the resultant kinetic energy flux (KEr, in J m–2 s–1) was initially used in place of the WEPP model intensity term in order to incorporate the effect of wind on impact velocity and frequency of Raindrops. However, our results showed only minor improvement in the model predictions. For all research data, the model Coefficients of Determination (r2) were 0·63 and 0·71, when using the WEPP and the KEr approaches, respectively. Alternately, integrating the angle of rain incidence into the model by vectorally partitioning normal kinetic energy flux (KErn, in J m–2 s–1) from the KEr greatly improved the model's ability to estimate the interrill sediment delivery rates (r2?=?0·91). This finding suggested that along with the fall trajectory of wind-driven Raindrops with a given frequency, Raindrop velocity and direction at the point of impact onto the soil surface provided sufficient physical information to improve WEPP sediment delivery rate predictions under WDR
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Sand transport under increased lateral jetting of Raindrops induced by wind
Geomorphology, 2008Co-Authors: Gunay Erpul, Donald Gabriëls, Wim Cornelis, H Samray, T GuzelorduAbstract:Abstract Wind tunnel experiments for ‘Raindrop Detachment and Wind-Driven Transport’ (RD–WDT) process were conducted under improved lateral jetting induced by wind velocities of 6.4, 10, and 12 m s− 1 at nozzle operating pressures of 75, 100, and 150 kPa. Wind-driven rainfalls were also incident on the windward and leeward slopes of 4° and 9° to have a broad variation in the angle of incidence. The objective of this experimental set-up was to distinguish the roles of both impact components of obliquely striking wind-driven Raindrops on RD and wind on WDT. Raindrop impact components and reference horizontal wind were quantified by normal (Etz) and horizontal (Etx) kinetic energy fluxes and wind shear velocity (u⁎), respectively, to physically model the process of RD–WDT. The results showed, at each level of u⁎, differential sand transport rates by RD–WDT (qm(RD–WDT)) occurred depending on the magnitude of Raindrop impact components, and qm(RD–WDT) increased as the relative contribution of Etz increased. Although Etx was more correlated with qm(RD–WDT) than Etz, the extreme increases in Etx at the expense of Etz brought about no increases but decreases in qm(RD–WDT). An RD–WDT model was built under the process of examining the discrete effects of Etz and Etx on RD together with u⁎ and resulted in a better coefficient of determination (R2 = 0.89) than only total kinetic energy (Et) did alone with u⁎ (R2 = 0.84). In this study, Etx was strongly related to u⁎ and not to Etz, which was the principal difference from the previous rainsplash studies, which relied on the compensatory lateral jet development by the compressive pressure build-up at the Raindrop–soil interface. Including Etx in the RD–WDT model both separated the distinct role of each Raindrop impact component in RD and improved the performance of u⁎ in WDT by better distinguishing its interaction with Etx, which was not explicitly separated in previous models of RD–WDT.
