Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on October 25, 2007) Vita. Includes bibliographical references.

High rates of runoff and soil loss occur in temperate areas in late winter and early spring. A low-intensity rainfall simulator and a snowmelt simulator were developed to study soil erosion by snowmelt and/or spring rainfall on a sandy loam soil of southern Quebec. Erosive agent, land slope, thaw depth of partly frozen soil, and intensity and duration of the event were studied in the laboratory using the simulators. All these factors had significant effects on soil erosion. Sediment concentration, soil loss rate, and total soil loss increased with increasing land slope, thaw depth, and intensity, duration, and impact energy of the erosive agent. Duration showed a significant interaction with each of the other factors. interaction between thaw depth and intensity of the event was significant under both snowmelt and rainfall simulation, whereas interaction between land slope and intensity was significant under rainfall simulation, but not under snowmelt simulation. Erosive agent also interacted with each of the other factors. All these interactions increased soil loss. The presence of a frozen sublayer interacted with the other factors and greatly increased runoff, sediment concentration and total soil loss. Rainfall caused more soil loss than did snowmelt under the same conditions.

Soil erosion is recognized as a global threat against the sustainability of the natural ecosystem and the environment because of its severe effects in agricultural productivity, damage to infrastructure and pollution of water bodies. Adverse impacts due to human activities resulting in accelerated soil erosion process have been well documented. Much more attention has been given to study the mechanisms associated with the process of soil erosion in the second half of the 20th century. Different mathematical models have been developed to simulate soil erosion processes and incorporate the result in different options of erosion controls. Modelling soil erosion is a complex process that involves numerous parameters. It is for this reason that even highly sophisticated and advanced erosion prediction models like Water Erosion Prediction Project (WEPP) do not incorporate all mechanisms of the soil erosion process. An obvious gap is the satisfactory explanation and incorporation of soil erosion mechanism associated with the initial portion of microchannels where both inter-rill and rill erosion exist. This study attempts to fill this gap through extension of knowledge in the area of soil erosion mechanism, specifically within the initial portions of rill where both splash erosion and erosion due to shear stress exist. Detachment of soil particles from the soil surface depends on the kinetic energy imparted by raindrops. Therefore, it is essential to estimate kinetic energy as accurately as possible to enable study of soil erosion and infiltration mechanisms. Rainfall simulation is widely used to generate rainfall of desired intensities and durations to study soil erosion, infiltration and other dynamic behaviours of soil. Kinetic energy of a rainfall event is often estimated from its intensity. The actual kinetic energy imparted on a soil surface is generally less than the total value of kinetic energy of a rainfall event. This is because of the cushioning effect of the overland flow. Therefore, there is a potential risk of over prediction of splash erosion by an erosion prediction model that does not account for this cushioning effect. In this study, experiments were carried out to estimate the kinetic energy of three different simulated rainfall events produced by three different combinations of pressures and nozzle sizes. The equipment consisted of a multipurpose hydraulic flume, 2m long and 1.4m wide. Five highly sensitive force transducers were mounted on the surface of the flume to measure the impact of raindrops. Different slopes were represented in the experiment by tilting the flume in four different angles from 0 to 15 degrees. Two tipping bucket rain gauges were used to measure rainfall intensity. The nozzles were placed at a height sufficient to produce terminal velocity by the falling rain drops before they hit the flume surface. Overland flow was generated by continuously supplying water to the inlet tank constructed at the upstream of the hydraulic flume. Responses received from the transducers (in the form of voltage) and from the tipping bucket (in the form of pulses) were recorded at regular intervals. Based on this experimental study, a logarithmic energy loss model that accounts for the depth of shallow overland flow, rainfall intensity and bed slope to estimate potential loss of kinetic energy is proposed. Analysis of the results from the study indicated a significant reduction in kinetic energy when the surface flow starts to build up. The analysis also indicated that a significant portion of the energy is lost even though the flow depth is small. This implies that while splash erosion initially contributes to the total amount of soil erosion, most of the erosion after the initial phase is due to the flow induced shear stress. Another important conclusion of this study is that steeper the slope, the lesser the expected overland flow depth and hence more potential for splash erosion and sheet erosion. The Nash Sutcliffe model efficiency statistic of 90% obtained from this study signifies that the model could be used as a useful predictive tool to estimate rainfall kinetic energy loss. The energy loss model developed as a result of this study can be incorporated in process-based soil erosion models to accurately estimate splash erosion and improve the predictive power of these models. In Addition, the model can be used to estimate the critical depth of overland flow when the kinetic energy approaching the soil surface is practically nil. This critical depth can be used to define the transition zone and explicitly define the term “Rill”. The multipurpose hydraulic flume designed and developed for this study can be used for further studies in area of hydraulic and soil erosion research. The methodology developed in this research will be helpful in carrying out further experiments and improve the proposed energy loss model. The potential Future improvements to the model include the followings: i) incorporating the effect of sediment concentration, ii) using wider ranges of intensities, and iii) using an actual soil bed. / Doctor of Philosopy (PhD)

Thesis (M.S.)--Montana State University--Bozeman, 2004. / Typescript. Chairperson, Graduate Committee: Douglas J. Dollhopf. Includes bibliographical references (leaves 85-88).

No description available.

No description available.

No description available.

A grid type portable rainfall simulator, developed at Virginia Tech from support by the Office of Surface Mining, Department of Interior under Grant NO. G5114009, was used to apply 2.3 inch per hour “storms” to three replicated plots to determine surface mine soil erodibility factors for two distinctly different soils in southern West Virginia. Other variables included in the study were detailed soil descriptions for each site, initial and final soil moistures, plot rainfall distributions and the particle size distributions of the eroded materials. The soil erodibility indexes for the silt silt-loam and sandy respectively. loam soils averaged 0.408 and 0.735. Erodibility indexes for the silt silt-loam decreased, while indexes for the sandy loam soil remained constant for repeated rainfall applications. Using statistical analysis, rainfall distributions were shown to be uniform across plots for most rainfall applications. From a particle size distribution analysis of the eroded soil material, the percentage of silt and clay decreased, while the percentage of sand increased at each site with repeated rainfall applications. A rock mulching effect was present at the end of each testing sequence. / Master of Science

From the Proceedings of the 1971 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 22-23, 1971, Tempe, Arizona / The rotadisk rainulator is a recently developed rainfall simulator utilizing a full-cone-spray type nozzle. Its unique feature is the rotation of disks of various size openings that makes it possible to produce intensities from close to zero up to full nozzle capacity. Disks may be quickly changed, making it possible to study the effects of various intensities on infiltration rates, such as occur in natural storms. For all intensities above 1.0 in/hr, the instrument comes closer to duplicating kinetic energies and momenta of natural rainfall than any other type of rainfall simulator. Little rainfall-runoff data are available on most of the Lower Gila watersheds. Infiltration rates were therefore determined using the rotadisk rainulator on recompacted soil samples from the watershed. The results permitted a ranking of the watersheds on the basis of infiltration rates, which supports an independent flood frequency analysis indicating that the flood threat from subwatersheds along the Gila is much lower than had previously been projected. When the instrument is taken into the field, it should be possible to directly determine the infiltration rates of different soil and vegetation types, which will be of more use to hydrologists than data from recompacted samples

From the Proceedings of the 1973 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - May 4-5, 1973, Tucson, Arizona / An infiltrometer was designed to more closely simulate natural storm characteristics and still maintain sufficient portability to be used in various test sites in the field. In addition to portability, a relatively large test plot can be used over a relatively long duration. The instrument is designed to produce rainfall intensities of 2 to 6 inches per hour which are comparable to natural storm intensities found in northern Arizona. Capillary tubes produce water drops of equivalent kinetic energy at impact to natural raindrops. Errors due to lateral flow are minimized through peripheral wetting. Mounting the infiltrometer on a four-wheel drive vehicle allows nearly the portability of a hand carried unit with a greater water carrying capacity and allows the equipment to be large enough to test a representative plot.