Tillage erosion is a major contributor to the total soil erosion in cultivated topographically complex lands. No study has been carried out on tillage erosion associated with cereal-based production systems in the Canadian Prairies, and there is a need to examine tillage erosivity of secondary tillage and seeding implements and the effect of slope curvature on tillage translocation. With both tillage and water erosion occurring in a cultivated topographically complex landscape, it is valuable to investigate the relative contributions of and the possible linkage and interactions between these two erosion processes. Tillage translocation causes the mixture of subsoil into the till-layer, which may considerably affect soil properties and therefore the related biophysical processes. In this study, using plot tracers, we examined tillage translocation caused by four tillage implements: air-seeder, spring-tooth-harrow, light-cultivator and deep-tiller in southern Manitoba, Canada. We determined that secondary tillage and seeding implements could be as erosive as primary tillage implements in a cereal-based production system. In the majority of cases, tillage translocation could be explained by slope gradient alone; however, slope curvature also significantly affected tillage translocation. In two field sites in the North America Great Plains (NAGP), measured 137Cs inventories were converted into total soil erosion rates. Tillage and water erosion rates were estimated using models. The comparisons of the model estimates to 137Cs estimates showed that both tillage and water erosion significantly contributed to the total soil erosion in undulating slopes while tillage erosion was the predominant erosion process in hummocky hilltops. The contributions of and the linkage and interactions between water and tillage erosion showed predictable patterns in different landform elements, with the knowledge of which, landscape segmentation could be used to assess the potential of soil erosion. Further investigation of tillage translocation was demonstrated with four hypothetic landscapes: plane slope, symmetric hill, asymmetric hill and irregular hill, and is tested against field data. A Visual Basic coded program (TillTM) was developed to simulate the redistribution of soil constituents and soil mass. We determined that the pattern of soil mass redistribution was dependent on topography, while the pattern of soil constituent redistribution was affect by topographic features, tillage patterns and temporal scales. / February 2007

At present one of the challenges of soil erosion research in South Africa is the limited information on the location of gullies. This is because traditional techniques for mapping erosion which consists of the manual digitization of gullies from air photos or satellite imagery, is limited to expert knowledge and is very time consuming and costly at a regional scale (50-10000km²). Developing a robust, reliable and accurate means of mapping gullies is a current focus for the Institute for Soil, Climate and Water Conservation (ISCW) of the Agricultural Research Council (ARC) of South Africa. The following thesis attempted to answer the question whether “medium resolution multi-spectral satellite observations, such as Landsat TM, combined with information extraction techniques, such as Vegetation Indices and multispectral classification algorithms, can provide a semi-automatic method of mapping gullies and to what level of accuracy?”. More specifically, this thesis investigated the utility of three Landsat TM-derived Vegetation Index (VI) techniques and three classification techniques based on their level of accuracy compared to traditional gully mapping methods applied to SPOT 5 panchromatic imagery at selected scales. The chosen study area was located in the province of KwaZulu-Natal (KZN) South Africa, which is considered to be the province most vulnerable to considerable levels of water erosion, mainly gully erosion. Analysis of the vegetation indices found that Normalized Difference Vegetation Index (NDVI) produced the highest accuracy for mapping gullies at the sub-catchment level while Transformed Soil Adjusted Vegetation Index (TSAVI) was successful at mapping gullies at the continuous gully level. Mapping of gullies using classification algorithms highlighted the spectral complexity of gullies and the challenges faced when trying to identify them from the surrounding areas. The Support Vector Machine (SVM) classification algorithm produced the highest accuracy for mapping gullies in all the tested scales and was the recommended approach to gully mapping using remote sensing

At present one of the challenges of soil erosion research in South Africa is the limited information on the location of gullies. This is because traditional techniques for mapping erosion which consists of the manual digitization of gullies from air photos or satellite imagery, is limited to expert knowledge and is very time consuming and costly at a regional scale (50-10000km²). Developing a robust, reliable and accurate means of mapping gullies is a current focus for the Institute for Soil, Climate and Water Conservation (ISCW) of the Agricultural Research Council (ARC) of South Africa. The following thesis attempted to answer the question whether “medium resolution multi-spectral satellite observations, such as Landsat TM, combined with information extraction techniques, such as Vegetation Indices and multispectral classification algorithms, can provide a semi-automatic method of mapping gullies and to what level of accuracy?”. More specifically, this thesis investigated the utility of three Landsat TM-derived Vegetation Index (VI) techniques and three classification techniques based on their level of accuracy compared to traditional gully mapping methods applied to SPOT 5 panchromatic imagery at selected scales. The chosen study area was located in the province of KwaZulu-Natal (KZN) South Africa, which is considered to be the province most vulnerable to considerable levels of water erosion, mainly gully erosion. Analysis of the vegetation indices found that Normalized Difference Vegetation Index (NDVI) produced the highest accuracy for mapping gullies at the sub-catchment level while Transformed Soil Adjusted Vegetation Index (TSAVI) was successful at mapping gullies at the continuous gully level. Mapping of gullies using classification algorithms highlighted the spectral complexity of gullies and the challenges faced when trying to identify them from the surrounding areas. The Support Vector Machine (SVM) classification algorithm produced the highest accuracy for mapping gullies in all the tested scales and was the recommended approach to gully mapping using remote sensing

Beaches and barrier islands are vulnerable to extreme storm events, such as hurricanes, that can cause severe erosion and overwash to the system. Having dunes and a wide beach in front of coastal infrastructure can provide protection during a storm, but the influence that nearshore bathymetric features have in protecting the beach and barrier island system is not completely understood. The spatial variation in nearshore features, such as sand bars and beach cusps, can alter nearshore hydrodynamics, including wave setup and runup. The influence of bathymetric features on long-wave runup can be used in evaluating the vulnerability of coastal regions to erosion and dune overtopping, evaluating the changing morphology, and implementing plans to protect infrastructure. In this thesis, long-wave runup variation due to changing bathymetric features as determined with the numerical model XBeach is quantified (eXtreme Beach behavior model). Wave heights are analyzed to determine the energy through the surfzone. XBeach assumes that coastal erosion at the land-sea interface is dominated by bound long-wave processes. Several hydrodynamic conditions are used to force the numerical model. The XBeach simulation results suggest that bathymetric irregularity induces significant changes in the extreme long-wave runup at the beach and the energy indicator through the surfzone.

Abstract In this study, a static electric contact tester with a vacuum system and gas supply system is used to investigate the effects of experimental parameters, such as inert gas kind, supply voltage, and the gap between the contacts, on the electric-arc characteristics and the erosion type for the electric contacts of silver. The experimental results show that chargeable threshold voltage in helium is higher than that in argon or air. In addition, the erosion surface of anode is observed, and the erosion area and volume are calculated and analyzed. Results show that the erosion area and volume in helium are smaller than that in argon or air. According to the observation of SEM photomicrographs, metal sputtering of the erosion hole in helium is smaller than that in argon or air. It is expected to provide the domestic electrical contact manufacturer in improving the research and development technique of the electrical contacts, and the design reference related to ultra-precision machining using a clean room.

No description available.

No description available.

We present channel length and stream order for possible fluvial channels present in Cassini Synthetic Aperture Radar (SAR) data from Ta to T19. These features are present at most latitudes observed, with the bulk of the channels located in near-equatorial latitudes. Many of them are also organized into four branching channel networks, three of third order and one of fourth order, similar to river systems on Earth and Mars. These networks appear well integrated, with few streams that are not incorporated into the higher order branches. The median channel length for all channels on Titan is 29 km, with the longest channels all being incorporated into the channel networks. Estimates of channel width and depth of 1 km and 100m respectively result in a channel volume of 1012 m3 which, when extrapolated to the entire surface of Titan results in 1013 m3 of sediment.

The service life of rigid sewer pipes is often controlled by joint integrity. Leaking joints can cause ingress of water and develop voids where surrounding soil has eroded. The influence of soil voids on the stability of buried rigid pipes is investigated, considering the effects of void size, void location and void shape. A series of simplified void geometries are defined, and their influence on bending moments in the rigid sewer is studied through finite element analysis. Elastic analysis indicates that the bending moments from expanding voids at the springline will increase slowly, accelerating once the void spans a 45 degree arc, approximately doubling at 90 degrees, and tripling if the loosened backfill is modeled for shear failure. This preliminary study suggests that the growth of erosion voids should be stopped before they reach 45 degrees, but validation through physical testing is necessary. Elastic-plastic finite element analysis is used to calculate the deformation of rigid fractured pipe with different thicknesses, considering both bonded and full-slip interface conditions. The analysis confirms that bonded idealized flexible pipe theory is very effective for calculation of increases in horizontal diameter of the fractured pipe. Furthermore, decreases in vertical diameter can be simply related to increase in horizontal diameter using (1-2t/OD) obtained from fractured pipe kinematics. Both elastic and elastic-plastic finite element analyses used to study the deformations of fractured rigid pipe reveal that contact angle appears to be the dominant factor affecting fractured pipe deformations. Deformation of the damaged rigid pipe increases dramatically with void growth and accelerates when erosion void contacts with the outer surface of the pipe over an arc greater than 45 degrees. Computational analyses examine the behavior of centrifuge model tests which examine soil load transfer to flexible sewer liners after fracture and erosion voids form nearby. The magnitude of deformation changes for finite element models is found to be comparable to observations when voids are formed at springline. However the development patterns are dramatically different as voids located under the invert, and it appears that the laboratory test featured physical characteristics that are not modeled in the analysis. / Thesis (Master, Civil Engineering) -- Queen's University, 2007-09-24 20:33:29.689

The Mfolozi, the second largest catchment in KwaZulu Natal, is already severely degraded over substantial areas. Its mean annual sediment load is extremely high and deposits on its floodplain have caused very serious financial losses. Previous studies in the catchment have attributed its soil loss to poor land use practices by peasant farmers. There is a concern that this production will be substantially increased by land use changes incumbent on the land reform programme. In order to ensure that this programme does not lead to increased degradation and exacerbate associated environmental and socio-economic problems, this study identified both subcatchments and land types that are highly susceptible to erosion and already highly eroded. An unpublished map showing the location of 19 categories of erosional forms and three categories of extreme relief features was available for use. The density (and areal extent in the case of badlands) of each of these forms within each of the 16 possible land types within each of the 43 subcatchments, was obtained and related to their dominant physiographic variables. The findings revealed that the catchment is not as severely or extensively eroded as suggested by previous studies. A substantial portion of the former Natal areas, mostly targeted for reallocation, have however, been shown to be unsuitable for this purpose. / Thesis (M.A.)-University of Durban-Westville, 1996.