Land cover is a fundamental variable that links many facets of the natural environment and a key driver of global environmental change.Alterations in its status can have significant ramifications at local,regional and...Land cover is a fundamental variable that links many facets of the natural environment and a key driver of global environmental change.Alterations in its status can have significant ramifications at local,regional and global levels.Hence,it is imperative to map land cover at a range of spatial and temporal scales with a view to understanding the inherent patterns for effective characterization,prediction and management of the potential environmental impacts.This paper presents the results of an effort to map land cover patterns in Kinangop division,Kenya,using geospatial tools.This is a geographic locality that has experienced rapid land use transformations since Kenya's independence culminating in uncontrolled land cover changes and loss of biodiversity.The changes in land use/cover constrain the natural resource base and presuppose availability of quantitative and spatially explicit land cover data for understanding the inherent patterns and facilitating specific and multi-purpose land use planning and management.As such,the study had two objectives viz.(i) mapping the spatial patterns of land cover in Kinangop using remote sensing and GIS and;(ii) evaluating the quality of the resultant land cover map.ASTER satellite imagery acquired in January 23,2007 was procured and field data gathered between September l0 and October 16,2007.The latter were used for training the maximum likelihood classifier and validating the resultant land cover map.The land cover classification yielded 5 classes,overall accuracy of 83.5%and kappa statistic of 0.79,which conforms to the acceptable standards of land cover mapping. This qualifies its application in environmental decision-making and manifests the utility of geospatial techniques in mapping land resources.展开更多
The forecasting of the failure time of a slope remains a worldwide problem because of many different possibilities of geological conditions in combination with many varying external factors such as climate and vegetat...The forecasting of the failure time of a slope remains a worldwide problem because of many different possibilities of geological conditions in combination with many varying external factors such as climate and vegetation,and not well-defined or unknown time effects in deformation and failure models.The aim of this paper is to suggest a new method to carry out the phase division and to explore tangential angular features of the displacement-time curve of creep slopes as well as the acceleration characteristics in the process of slope deformation and the pre-warning criteria for critical failure.An imminent failure is pro-ceeded with usually three basic deformation phases,namely primary creep("decelerated") ,secondary creep("steadystate") and tertiary creep("accelerated") .Mostly,only during the accelerated phase the imminence of a possible slope failure is rec-ognized.The analysis of displacement data from a series of landslides allowed to recognize different evolutionary patterns of displacement.A quantitative approach was proposed to describe the tangential angle of the displacement-time curve and a new criterion based on the angle was put forward to divide the accelerated phase into three sub-phases:initial acceleration,medium acceleration,and the critical failure.A pre-warning criterion for critical failure is also proposed consequently. Changes of acceleration showed completely different characteristics from those of cumulative displacement and displacement in the process of slope deformation.The values of acceleration usually oscillate around 0 prior to the critical failure phase,whereas the acceleration increases abruptly when the deformation moves into the critical failure phase.This allows,therefore,for a method to forecast the time of the failure.So it is possible to define different alert acceleration threshold values to be used for emergency management.展开更多
The present study was an attempt to delineate potential groundwater zones in Kalikavu Panchayat of Malappuram district,Kerala,India.The geo-spatial database on geomorphology,landuse,geology,slope and drainage network ...The present study was an attempt to delineate potential groundwater zones in Kalikavu Panchayat of Malappuram district,Kerala,India.The geo-spatial database on geomorphology,landuse,geology,slope and drainage network was generated in a geographic information system(GIS)environment from satellite data,Survey of India topographic sheets and field observations.To understand the movement and occurrence of groundwater,the geology,geomorphology,structural set-up and recharging conditions have to be well understood.In the present study,the potential recharge areas are delineated in terms of geology,geomorphology,land use,slope,drainage pattern,etc.Various thematic data generated were integrated using a heuristic method in the GIS domain to generate maps showing potential groundwater zones.The composite output map scores were reclassified into different zones using a decision rule.The final output map shows different zones of groundwater prospect,viz.,very good(15.57%of the area),good(43.74%),moderate(28.38%)and poor(12.31%).Geomorphic units such as valley plains,valley fills and alluvial terraces were identified as good to excellent prospect zones,while the gently sloping lateritic uplands were identified as good to moderate zones.Steeply sloping hilly terrains underlain by hard rocks were identified as poor groundwater prospect zones.展开更多
基金Special thanks are due to the Water Resources Management Authority (WRMA) and Ministry of Livestock and Fisheries Development in Kenya, the International Institute for Geo-information Science and Earth Observation (ITC) in Netherlands and European Union for logistical and financial support.
文摘Land cover is a fundamental variable that links many facets of the natural environment and a key driver of global environmental change.Alterations in its status can have significant ramifications at local,regional and global levels.Hence,it is imperative to map land cover at a range of spatial and temporal scales with a view to understanding the inherent patterns for effective characterization,prediction and management of the potential environmental impacts.This paper presents the results of an effort to map land cover patterns in Kinangop division,Kenya,using geospatial tools.This is a geographic locality that has experienced rapid land use transformations since Kenya's independence culminating in uncontrolled land cover changes and loss of biodiversity.The changes in land use/cover constrain the natural resource base and presuppose availability of quantitative and spatially explicit land cover data for understanding the inherent patterns and facilitating specific and multi-purpose land use planning and management.As such,the study had two objectives viz.(i) mapping the spatial patterns of land cover in Kinangop using remote sensing and GIS and;(ii) evaluating the quality of the resultant land cover map.ASTER satellite imagery acquired in January 23,2007 was procured and field data gathered between September l0 and October 16,2007.The latter were used for training the maximum likelihood classifier and validating the resultant land cover map.The land cover classification yielded 5 classes,overall accuracy of 83.5%and kappa statistic of 0.79,which conforms to the acceptable standards of land cover mapping. This qualifies its application in environmental decision-making and manifests the utility of geospatial techniques in mapping land resources.
基金supported by Ya-lung River Joint Research Foundation of National Natural Science Foundation of China and ErTan Hydropower Development Company Ltd.(Grants No.50579099)the National Basic Research Program"973"+2 种基金Project of the Ministry of Science and Technology of the People’s Republic of China(Grant No.2008CB425801)the Creative Team Program of the Ministry of Education in China(Grant No. IRT0812)the Major Cultivation Project in University Scientific and Technological Innovation Program of the Ministry of Education,the Development of Monitoring and Forecast System for Geohazards Based on WEB
文摘The forecasting of the failure time of a slope remains a worldwide problem because of many different possibilities of geological conditions in combination with many varying external factors such as climate and vegetation,and not well-defined or unknown time effects in deformation and failure models.The aim of this paper is to suggest a new method to carry out the phase division and to explore tangential angular features of the displacement-time curve of creep slopes as well as the acceleration characteristics in the process of slope deformation and the pre-warning criteria for critical failure.An imminent failure is pro-ceeded with usually three basic deformation phases,namely primary creep("decelerated") ,secondary creep("steadystate") and tertiary creep("accelerated") .Mostly,only during the accelerated phase the imminence of a possible slope failure is rec-ognized.The analysis of displacement data from a series of landslides allowed to recognize different evolutionary patterns of displacement.A quantitative approach was proposed to describe the tangential angle of the displacement-time curve and a new criterion based on the angle was put forward to divide the accelerated phase into three sub-phases:initial acceleration,medium acceleration,and the critical failure.A pre-warning criterion for critical failure is also proposed consequently. Changes of acceleration showed completely different characteristics from those of cumulative displacement and displacement in the process of slope deformation.The values of acceleration usually oscillate around 0 prior to the critical failure phase,whereas the acceleration increases abruptly when the deformation moves into the critical failure phase.This allows,therefore,for a method to forecast the time of the failure.So it is possible to define different alert acceleration threshold values to be used for emergency management.
文摘The present study was an attempt to delineate potential groundwater zones in Kalikavu Panchayat of Malappuram district,Kerala,India.The geo-spatial database on geomorphology,landuse,geology,slope and drainage network was generated in a geographic information system(GIS)environment from satellite data,Survey of India topographic sheets and field observations.To understand the movement and occurrence of groundwater,the geology,geomorphology,structural set-up and recharging conditions have to be well understood.In the present study,the potential recharge areas are delineated in terms of geology,geomorphology,land use,slope,drainage pattern,etc.Various thematic data generated were integrated using a heuristic method in the GIS domain to generate maps showing potential groundwater zones.The composite output map scores were reclassified into different zones using a decision rule.The final output map shows different zones of groundwater prospect,viz.,very good(15.57%of the area),good(43.74%),moderate(28.38%)and poor(12.31%).Geomorphic units such as valley plains,valley fills and alluvial terraces were identified as good to excellent prospect zones,while the gently sloping lateritic uplands were identified as good to moderate zones.Steeply sloping hilly terrains underlain by hard rocks were identified as poor groundwater prospect zones.
