Flood is any flow of water, which overflows the natural or artificial banks of a body of water. Flooding is one of the fundamental environmental challenges that results from interaction between man and his environment...Flood is any flow of water, which overflows the natural or artificial banks of a body of water. Flooding is one of the fundamental environmental challenges that results from interaction between man and his environment. In Nigeria, Flooding is one of the most common environmental hazards and there is increasing vulnerability of populations and infrastructure to flooding and flood related hazards. This study used GIS as a tool to analyze the cause and the impact of flooding in the study area. The study used both primary and secondary data, through a questionnaire, geographic information system and remote sensing. The result showed that the nature of the basin in the study area resulted to the high volume of water in the major river (River Osun) during raining season, which resulted to overflow across its bank. Fieldwork shows that the river overflows its bank at 500 meters to the north and the south and the GIS analysis shows that over 1000 houses get affected at any point of flooding occurrences, hence the width of the river is less than 8 meters and the depth on the average in less than 10 meter over the bridge of the River Osun. The study recommends methods by which flooding could be controlled in the study area through regular dredging, effective waste management and drainage control.展开更多
The homogeneous hidden Markov model(HMM), a statistical pattern recognition method, is introduced in this paper. Based on the HMM, a 53-yr record of daily precipitation during the flood season(April-September) at 389 ...The homogeneous hidden Markov model(HMM), a statistical pattern recognition method, is introduced in this paper. Based on the HMM, a 53-yr record of daily precipitation during the flood season(April-September) at 389 stations in East China during 1961-2013 is classified into six patterns: the South China(SC) pattern, the southern Yangtze River(SY) pattern, the Yangtze-Huai River(YH) pattern, the North China(NC) pattern, the overall wetter(OW) pattern, and the overall drier(OD) pattern. Features of the transition probability matrix of the first four patterns reveal that 1) the NC pattern is the most persistent, followed by the YH, and the SY is the least one; and 2) there exists a SY-SC-SY-YH-NC propagation process for the rain belt over East China during the flood season. The intraseasonal variability in the occurrence frequency of each pattern determines its start and end time. Furthermore,analysis of interdecadal variability in the occurrence frequency of each pattern in recent six decades has identified three obvious interdecadal variations for the SC, YH, and NC patterns in the mid-late 1970 s, the early 1990 s, and the late 1990 s. After 2000, the patterns concentrated in the southern region play a dominant role, and thus there maintains a "flooding in the south and drought in the north" rainfall distribution in eastern China. In summary, the HMM provides a unique approach for us to obtain both spatial distribution and temporal variation features of flood-season rainfall.展开更多
文摘Flood is any flow of water, which overflows the natural or artificial banks of a body of water. Flooding is one of the fundamental environmental challenges that results from interaction between man and his environment. In Nigeria, Flooding is one of the most common environmental hazards and there is increasing vulnerability of populations and infrastructure to flooding and flood related hazards. This study used GIS as a tool to analyze the cause and the impact of flooding in the study area. The study used both primary and secondary data, through a questionnaire, geographic information system and remote sensing. The result showed that the nature of the basin in the study area resulted to the high volume of water in the major river (River Osun) during raining season, which resulted to overflow across its bank. Fieldwork shows that the river overflows its bank at 500 meters to the north and the south and the GIS analysis shows that over 1000 houses get affected at any point of flooding occurrences, hence the width of the river is less than 8 meters and the depth on the average in less than 10 meter over the bridge of the River Osun. The study recommends methods by which flooding could be controlled in the study area through regular dredging, effective waste management and drainage control.
基金Supported by the National Natural Science Foundation of China(41675081)National Key Research and Development Program of China(2017YFA0603804)
文摘The homogeneous hidden Markov model(HMM), a statistical pattern recognition method, is introduced in this paper. Based on the HMM, a 53-yr record of daily precipitation during the flood season(April-September) at 389 stations in East China during 1961-2013 is classified into six patterns: the South China(SC) pattern, the southern Yangtze River(SY) pattern, the Yangtze-Huai River(YH) pattern, the North China(NC) pattern, the overall wetter(OW) pattern, and the overall drier(OD) pattern. Features of the transition probability matrix of the first four patterns reveal that 1) the NC pattern is the most persistent, followed by the YH, and the SY is the least one; and 2) there exists a SY-SC-SY-YH-NC propagation process for the rain belt over East China during the flood season. The intraseasonal variability in the occurrence frequency of each pattern determines its start and end time. Furthermore,analysis of interdecadal variability in the occurrence frequency of each pattern in recent six decades has identified three obvious interdecadal variations for the SC, YH, and NC patterns in the mid-late 1970 s, the early 1990 s, and the late 1990 s. After 2000, the patterns concentrated in the southern region play a dominant role, and thus there maintains a "flooding in the south and drought in the north" rainfall distribution in eastern China. In summary, the HMM provides a unique approach for us to obtain both spatial distribution and temporal variation features of flood-season rainfall.
