Conventional 2D electrical resistivity tomography (ERT) data were acquired along 16 parallel trav... more Conventional 2D electrical resistivity tomography (ERT) data were acquired along 16 parallel traverses spaced at 6.1 m (20 ft) intervals across a karst sinkhole site in Greene County Missouri. The acquired ERT data were processed as both 2D data and pseudo-3D data. Based on the correlation with the available core hole control, multichannel analysis of surface waves (MASW) data and field observations, it is concluded that the subsurface structure of the sinkhole is more reliably imaged on the pseudo-3D dataset than in the 2D dataset. The interpretation results of the pseudo-3D ERT indicated that the sinkhole developed at the intersection of three vertical solution-widened joint sets.
Sinkholes are inherent features of the karst terrain of Greene County, Missouri, that present haz... more Sinkholes are inherent features of the karst terrain of Greene County, Missouri, that present hazards and engineering challenges to construction/infrastructure development. Analysis of relationships between the spatial distribution of sinkholes and possible influencing factors can help in understanding the controls involved in the formation of sinkholes. The spatial analysis outlined herein can aid in the assessment of potential sinkhole hazards. In this research, Geographic Information System–based ordinary least squares regression (OLS) and geographically weighted regression (GWR) methods were used to determine and evaluate principal factors appearing to influence the formation and distribution of karst sinkholes. From the OLS result, seven out of 12 possible influencing factors were found to exert significant control on sinkhole formation processes in the study area. These factors are overburden thickness, depth to groundwater, slope of the ground surface, distance to the nearest...
A water resources development that is carried out on the basis of water budget information defini... more A water resources development that is carried out on the basis of water budget information definitely will minimize and/or avoid the water resources that are going to be exposed to risk and mismanagement, and hence led to a proper utilization of this precious ...
Conventional 2D electrical resistivity tomography (ERT) data were acquired along 16 parallel trav... more Conventional 2D electrical resistivity tomography (ERT) data were acquired along 16 parallel traverses spaced at 6.1 m (20 ft) intervals across a karst sinkhole site in Greene County Missouri. The acquired ERT data were processed as both 2D data and pseudo-3D data. Based on the correlation with the available core hole control, multichannel analysis of surface waves (MASW) data and field observations, it is concluded that the subsurface structure of the sinkhole is more reliably imaged on the pseudo-3D dataset than in the 2D dataset. The interpretation results of the pseudo-3D ERT indicated that the sinkhole developed at the intersection of three vertical solution-widened joint sets.
Investigating sinkhole morphology and formation mechanisms is key to understanding their long ter... more Investigating sinkhole morphology and formation mechanisms is key to understanding their long term impact and susceptibility to development, and aids in the design of effective mitigation measures. In this study, ERT (electrical resistivity tomography), MASW (multichannel analysis of surface waves) and borehole data were used to image the subsurface morphology of an active sinkhole in Greene County, Missouri. The study reveals that the sinkhole developed along a natural surface drainage pathway above a pervasively fractured limestone. The subsurface image of the sinkhole depicts a zone of near-vertical water seepage and soil piping. Based on the nature of the overburden material, and the morphology and current/past surface expression of the sinkhole, it is concluded that the sinkhole is predominantly a cover subsidence type of sinkhole. However, it is possible that minor cover collapse occurred locally and in an area slightly to the north of the current active sinkhole.
The paper presents results related to water balance of the May Nugus catchment, Tigray, Northern ... more The paper presents results related to water balance of the May Nugus catchment, Tigray, Northern Ethiopia. The catchment covering an area of 14.73 km 2 includes a small dam called May Nugus having an effective watershed area of 13.05km 2 with reservoir capacity of 23.82 x 10 6 m 3 and command area of about 1.24 sq. km. Hydrology of the area was characterized on the basis of land use, soil, slope, rainfall, temperature, evaporation, evapotranspiration, and runoff using meteorological data. Different methods like rainfall coefficient method is used to determine monthly distribution of rainfall including rainy and dry months; Penman method to calculate evaporation from the reservoir; Thornthwaite method and Thornthwaite water balance model to determine potential and actual evapotranspiration; and runoff coefficient method to estimate runoff. The catchment is characterized by one rainy season and two dry seasons during the year. The rainy season has five months duration and dry season seven months. The mean annual rainfall of the catchment is 737.57 mm, out of which rainy season accounts for 81.24 % and the dry season for 18.76 %. The total annual water loss by evaporation from the reservoir is 1404.4 mm. The mean annual actual evapotranspiration of the upper catchment and the command area is 613.33 mm and 569.84 mm, respectively. The mean annual runoff generated from the upper catchment and the command area is estimated to be 1.54 million m 3 and 0.146 million m 3 respectively. The amount of water that percolates into the ground in the upper catchment and command area as groundwater is estimated to be about 0.06 million m 3 and 0.22 million m 3 respectively, and the same at the reservoir site is 1.24 million m 3. The total amount of water which is actually available to recharge the groundwater within the catchment is 1.52 million m 3. In general, the command area of May Negus catchment has very good groundwater potential. If developed and utilized properly, it can be used conjunctively with dam water for multi purposes.
This study deals with the development of a Geographic Information System (GIS)-based geotechnical... more This study deals with the development of a Geographic Information System (GIS)-based geotechnical microzonation model/map using Analytic Hierarchy Process (AHP) for Shire-Endasilasie, a rapidly growing city in Tigray, northern Ethiopia. The influencing factors considered as inputs for the development of the model are (i) slope gradient, (ii) bed rock and soil type, (iii) swelling potential of soil and (iv) depth to groundwater level. The factors and the classes within each factor are assigned weight and rank values respectively. To avoid subjectivity, the assignment of weight and rank values and the analysis are done by the application of AHP method. From the weight and rank values of the layers, geotechnical suitability indices were calculated using a Weighted Linear Combination (WLC) model in GIS. These continuous numerical index values have been divided into different classes. The classification result implies that the less suitable zone represents the areas that require a detailed geotechnical investigation, the moderately suitable zone represents a provisional settlement area, and the suitable zone represents the areas that are best suitable for settlement.
Sinkholes are inherent features of the karst terrain of 1 Greene County, Missouri, that present h... more Sinkholes are inherent features of the karst terrain of 1 Greene County, Missouri, that present hazards and engineering challenges to construction/infrastructure development. Analysis of relationships between the spatial distribution of sinkholes and possible influencing factors can help in understanding the controls involved in the formation of sinkholes. The spatial analysis outlined herein can aid in the assessment of potential sinkhole hazards. In this research, Geographic Information System–based ordinary least squares regression (OLS) and geographically weighted regression (GWR) methods were used to determine and evaluate principal factors appearing to influence the formation and distribution of karst sinkholes. From the OLS result, seven out of 12 possible influencing factors were found to exert significant control on sinkhole formation processes in the study area. These factors are overburden thickness, depth to groundwater, slope of the ground surface, distance to the nearest surface drainage line, distance to the nearest geological structure (such as faults or folds), distance to the nearest road, and distance to the nearest spring. These factors were then used as independent variables in the GWR model. The GWR model examined the spatial non-stationarity among the various factors and demonstrated better performance over OLS. GWR model coefficient estimates for each variable were mapped. These maps provide spatial insights into the influence of the variables on sinkhole densities throughout the study area. GWR spatial analysis appears to be an effective approach to understand sinkhole-influencing factors. The results could be useful to provide an objec
Conventional 2D electrical resistivity tomography (ERT) data were acquired along 16 parallel trav... more Conventional 2D electrical resistivity tomography (ERT) data were acquired along 16 parallel traverses spaced at 6.1 m (20 ft) intervals across a karst sinkhole site in Greene County Missouri. The acquired ERT data were processed as both 2D data and pseudo-3D data. Based on the correlation with the available core hole control, multichannel analysis of surface waves (MASW) data and field observations, it is concluded that the subsurface structure of the sinkhole is more reliably imaged on the pseudo-3D dataset than in the 2D dataset. The interpretation results of the pseudo-3D ERT indicated that the sinkhole developed at the intersection of three vertical solution-widened joint sets.
Sinkholes are inherent features of the karst terrain of Greene County, Missouri, that present haz... more Sinkholes are inherent features of the karst terrain of Greene County, Missouri, that present hazards and engineering challenges to construction/infrastructure development. Analysis of relationships between the spatial distribution of sinkholes and possible influencing factors can help in understanding the controls involved in the formation of sinkholes. The spatial analysis outlined herein can aid in the assessment of potential sinkhole hazards. In this research, Geographic Information System–based ordinary least squares regression (OLS) and geographically weighted regression (GWR) methods were used to determine and evaluate principal factors appearing to influence the formation and distribution of karst sinkholes. From the OLS result, seven out of 12 possible influencing factors were found to exert significant control on sinkhole formation processes in the study area. These factors are overburden thickness, depth to groundwater, slope of the ground surface, distance to the nearest...
A water resources development that is carried out on the basis of water budget information defini... more A water resources development that is carried out on the basis of water budget information definitely will minimize and/or avoid the water resources that are going to be exposed to risk and mismanagement, and hence led to a proper utilization of this precious ...
Conventional 2D electrical resistivity tomography (ERT) data were acquired along 16 parallel trav... more Conventional 2D electrical resistivity tomography (ERT) data were acquired along 16 parallel traverses spaced at 6.1 m (20 ft) intervals across a karst sinkhole site in Greene County Missouri. The acquired ERT data were processed as both 2D data and pseudo-3D data. Based on the correlation with the available core hole control, multichannel analysis of surface waves (MASW) data and field observations, it is concluded that the subsurface structure of the sinkhole is more reliably imaged on the pseudo-3D dataset than in the 2D dataset. The interpretation results of the pseudo-3D ERT indicated that the sinkhole developed at the intersection of three vertical solution-widened joint sets.
Investigating sinkhole morphology and formation mechanisms is key to understanding their long ter... more Investigating sinkhole morphology and formation mechanisms is key to understanding their long term impact and susceptibility to development, and aids in the design of effective mitigation measures. In this study, ERT (electrical resistivity tomography), MASW (multichannel analysis of surface waves) and borehole data were used to image the subsurface morphology of an active sinkhole in Greene County, Missouri. The study reveals that the sinkhole developed along a natural surface drainage pathway above a pervasively fractured limestone. The subsurface image of the sinkhole depicts a zone of near-vertical water seepage and soil piping. Based on the nature of the overburden material, and the morphology and current/past surface expression of the sinkhole, it is concluded that the sinkhole is predominantly a cover subsidence type of sinkhole. However, it is possible that minor cover collapse occurred locally and in an area slightly to the north of the current active sinkhole.
The paper presents results related to water balance of the May Nugus catchment, Tigray, Northern ... more The paper presents results related to water balance of the May Nugus catchment, Tigray, Northern Ethiopia. The catchment covering an area of 14.73 km 2 includes a small dam called May Nugus having an effective watershed area of 13.05km 2 with reservoir capacity of 23.82 x 10 6 m 3 and command area of about 1.24 sq. km. Hydrology of the area was characterized on the basis of land use, soil, slope, rainfall, temperature, evaporation, evapotranspiration, and runoff using meteorological data. Different methods like rainfall coefficient method is used to determine monthly distribution of rainfall including rainy and dry months; Penman method to calculate evaporation from the reservoir; Thornthwaite method and Thornthwaite water balance model to determine potential and actual evapotranspiration; and runoff coefficient method to estimate runoff. The catchment is characterized by one rainy season and two dry seasons during the year. The rainy season has five months duration and dry season seven months. The mean annual rainfall of the catchment is 737.57 mm, out of which rainy season accounts for 81.24 % and the dry season for 18.76 %. The total annual water loss by evaporation from the reservoir is 1404.4 mm. The mean annual actual evapotranspiration of the upper catchment and the command area is 613.33 mm and 569.84 mm, respectively. The mean annual runoff generated from the upper catchment and the command area is estimated to be 1.54 million m 3 and 0.146 million m 3 respectively. The amount of water that percolates into the ground in the upper catchment and command area as groundwater is estimated to be about 0.06 million m 3 and 0.22 million m 3 respectively, and the same at the reservoir site is 1.24 million m 3. The total amount of water which is actually available to recharge the groundwater within the catchment is 1.52 million m 3. In general, the command area of May Negus catchment has very good groundwater potential. If developed and utilized properly, it can be used conjunctively with dam water for multi purposes.
This study deals with the development of a Geographic Information System (GIS)-based geotechnical... more This study deals with the development of a Geographic Information System (GIS)-based geotechnical microzonation model/map using Analytic Hierarchy Process (AHP) for Shire-Endasilasie, a rapidly growing city in Tigray, northern Ethiopia. The influencing factors considered as inputs for the development of the model are (i) slope gradient, (ii) bed rock and soil type, (iii) swelling potential of soil and (iv) depth to groundwater level. The factors and the classes within each factor are assigned weight and rank values respectively. To avoid subjectivity, the assignment of weight and rank values and the analysis are done by the application of AHP method. From the weight and rank values of the layers, geotechnical suitability indices were calculated using a Weighted Linear Combination (WLC) model in GIS. These continuous numerical index values have been divided into different classes. The classification result implies that the less suitable zone represents the areas that require a detailed geotechnical investigation, the moderately suitable zone represents a provisional settlement area, and the suitable zone represents the areas that are best suitable for settlement.
Sinkholes are inherent features of the karst terrain of 1 Greene County, Missouri, that present h... more Sinkholes are inherent features of the karst terrain of 1 Greene County, Missouri, that present hazards and engineering challenges to construction/infrastructure development. Analysis of relationships between the spatial distribution of sinkholes and possible influencing factors can help in understanding the controls involved in the formation of sinkholes. The spatial analysis outlined herein can aid in the assessment of potential sinkhole hazards. In this research, Geographic Information System–based ordinary least squares regression (OLS) and geographically weighted regression (GWR) methods were used to determine and evaluate principal factors appearing to influence the formation and distribution of karst sinkholes. From the OLS result, seven out of 12 possible influencing factors were found to exert significant control on sinkhole formation processes in the study area. These factors are overburden thickness, depth to groundwater, slope of the ground surface, distance to the nearest surface drainage line, distance to the nearest geological structure (such as faults or folds), distance to the nearest road, and distance to the nearest spring. These factors were then used as independent variables in the GWR model. The GWR model examined the spatial non-stationarity among the various factors and demonstrated better performance over OLS. GWR model coefficient estimates for each variable were mapped. These maps provide spatial insights into the influence of the variables on sinkhole densities throughout the study area. GWR spatial analysis appears to be an effective approach to understand sinkhole-influencing factors. The results could be useful to provide an objec
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