Teesta river flood plain is one of the most significant landscapes in Bangladesh. The main theme of this research was to assess the present biogeomorphological state (biomass, herbaceous vegetation species, density of...Teesta river flood plain is one of the most significant landscapes in Bangladesh. The main theme of this research was to assess the present biogeomorphological state (biomass, herbaceous vegetation species, density of all vegetation species, flood plain extension mapping) of Teesta river flood plain under Gangachara upazila. The research work was conducted based on the objectives to prepare a map of Teesta river flood plain extension area, to estimate herbaceous vegetation (biomass, species types), and to find out the vegetation density to assess the present biogeomorphological state of study area. To present the flood plain area of Teesta river in the Gangachara upazila, base map has been used;herbaceous vegetation samples have been collected through quadrat method to estimate biomass (both in dry and before dry condition) using digital weight machine;vegetation density has been shown through NDVI of satellite image (Landsat-8) using red and NIR band in ArcGIS 10.1 software. From the results of this research, river flood plain area is found 68.5 sq. km;total 31 types of herbaceous species have been identified where Pouzolzia indica is the most dominated species covering 11.59% of the total area;maximum DNs value of NDVI is found +0.475242 which represents the highest vegetation density covering an area of 78 sq. km of the total area. The research may assist for the further study of river flood plain biogeomorphology throughout the country as well as in the world.展开更多
Downstream changes in channel morphology and flow over the ephemeral Dwarkeswar River in the western part of the Bengal Basin, eastren India were investigated. The river stretches from the Proterozoic Granite Gneiss C...Downstream changes in channel morphology and flow over the ephemeral Dwarkeswar River in the western part of the Bengal Basin, eastren India were investigated. The river stretches from the Proterozoic Granite Gneiss Complex to the recent Holocene alluvium, forming three distinctive geomorphological regions across the river basin: the pediplane and upper and lower alluvial areas. Sixty cross-sections from throughout the main trunk stream were surveyed and the bankfull width, depth, cross-sectional area, and maximum depth were measured. Sediment samples from each location were studied and the flow velocity, stream power, Manning’s roughness coefficient, and shear stress were estimated. The results show that the bankfull channel cross-section area, width, width-to-depth ratio, and channel capacity increased between the beginning and middle of the river. Thereafter, the size of the river started to decrease in the lower alluvial area. This was characterized by gentle gradients, cohesive bank materials with grass cover, and channel switching. Within the lower part of the river, the channel capacity was observed to diminish as the drainage area increased. This increased the bankfull flow frequency and accelerated large floodwater losses in the floodplain via overbank flows and floodways.展开更多
The Snake River in northwestern United States is 1735 km long, the largest tributary of the Columbia River and is the 13<sup>th</sup> longest river in the United States. The Snake River drainage basin incl...The Snake River in northwestern United States is 1735 km long, the largest tributary of the Columbia River and is the 13<sup>th</sup> longest river in the United States. The Snake River drainage basin includes parts of six U.S. states. The Snake River Plain was created by a volcanic hotspot that lies beneath Yellow-stone National Park. The previous Ice Age carved out canyons, cliffs and waterfalls along the middle and lower Snake River. The Missoula Flood was to the north and Bonneville Flood to the south altered the Snake River and surrounding landscape. The Snake River has a drainage basin of 282,000 km<sup>2</sup> in the states of Oregon, Washington, Utah, Nevada and Idaho. The Snake River drops from mountain elevations of 3000 m to its confluence with the Columbia River. The river is one of the most biologically diverse freshwater systems in the United States with trails designed to promote recreational tourism, increase use of the Snake River and create generations of people who care about the river and are willing to protect and provide environmental stewardship of the river watershed resources.展开更多
Taking the Songnen Plain as the research region and basing on the structural division of river water resources, the impounding models of flood water utilization are proposed. Considering the water requirement, potenti...Taking the Songnen Plain as the research region and basing on the structural division of river water resources, the impounding models of flood water utilization are proposed. Considering the water requirement, potential impoundage and the degree of risk, two modes of the flood water utilization are developed: full impounding and partial impounding. A risk assessment method is put forward according to variation of the flood storage capacity before and after impounding water. A representative hydrological year is taken as an example to analyze the application of the model at the downstream of the Nenjiang River. It is found that the model is very useful for the flood utilization and protection. For flood utilization, the spring drought can be relieved and the risk of impounding water is also acceptable. For flood protection, the river flood peak can be largely reduced and the impounding water can increase the river discharge at the low water period, at the same time the structure of river water resources can be improved as well.展开更多
Five deltaic deposit bodies, respectively belonging to five different stages, have been successively built on the Luan River since the Holocene. Although both the place where the river emptied itself into the sea and ...Five deltaic deposit bodies, respectively belonging to five different stages, have been successively built on the Luan River since the Holocene. Although both the place where the river emptied itself into the sea and the magnitude of these deposit bodies varied in different stages, the sediment processes of the delta were of the same model. 1. The Luan is a river carrying heavy sediment load to the north coast of the Bohai Bay. By actual measurements the mean discharge is 149 m^2/sec (the maximum discharge during flood peak being 34000m^3/sec); the mean annual silt discharge of the suspended load is 26.7×10~6 tons (maximum 87.9×10~6 tons), of which 63.5％ or more of the total takes place from June to August. During the flood period, the sudden rise-and-fall of the high sediment-loaded flow makes the river channel branched or changed easily and the deltaic plain consequently fans out toward the sea. 2. Because the Luan River has a low展开更多
文摘Teesta river flood plain is one of the most significant landscapes in Bangladesh. The main theme of this research was to assess the present biogeomorphological state (biomass, herbaceous vegetation species, density of all vegetation species, flood plain extension mapping) of Teesta river flood plain under Gangachara upazila. The research work was conducted based on the objectives to prepare a map of Teesta river flood plain extension area, to estimate herbaceous vegetation (biomass, species types), and to find out the vegetation density to assess the present biogeomorphological state of study area. To present the flood plain area of Teesta river in the Gangachara upazila, base map has been used;herbaceous vegetation samples have been collected through quadrat method to estimate biomass (both in dry and before dry condition) using digital weight machine;vegetation density has been shown through NDVI of satellite image (Landsat-8) using red and NIR band in ArcGIS 10.1 software. From the results of this research, river flood plain area is found 68.5 sq. km;total 31 types of herbaceous species have been identified where Pouzolzia indica is the most dominated species covering 11.59% of the total area;maximum DNs value of NDVI is found +0.475242 which represents the highest vegetation density covering an area of 78 sq. km of the total area. The research may assist for the further study of river flood plain biogeomorphology throughout the country as well as in the world.
基金the auspices of the University Grants Commission(No.21595/(NET-DEC.2013),F.15-6(DEC.2013))。
文摘Downstream changes in channel morphology and flow over the ephemeral Dwarkeswar River in the western part of the Bengal Basin, eastren India were investigated. The river stretches from the Proterozoic Granite Gneiss Complex to the recent Holocene alluvium, forming three distinctive geomorphological regions across the river basin: the pediplane and upper and lower alluvial areas. Sixty cross-sections from throughout the main trunk stream were surveyed and the bankfull width, depth, cross-sectional area, and maximum depth were measured. Sediment samples from each location were studied and the flow velocity, stream power, Manning’s roughness coefficient, and shear stress were estimated. The results show that the bankfull channel cross-section area, width, width-to-depth ratio, and channel capacity increased between the beginning and middle of the river. Thereafter, the size of the river started to decrease in the lower alluvial area. This was characterized by gentle gradients, cohesive bank materials with grass cover, and channel switching. Within the lower part of the river, the channel capacity was observed to diminish as the drainage area increased. This increased the bankfull flow frequency and accelerated large floodwater losses in the floodplain via overbank flows and floodways.
文摘The Snake River in northwestern United States is 1735 km long, the largest tributary of the Columbia River and is the 13<sup>th</sup> longest river in the United States. The Snake River drainage basin includes parts of six U.S. states. The Snake River Plain was created by a volcanic hotspot that lies beneath Yellow-stone National Park. The previous Ice Age carved out canyons, cliffs and waterfalls along the middle and lower Snake River. The Missoula Flood was to the north and Bonneville Flood to the south altered the Snake River and surrounding landscape. The Snake River has a drainage basin of 282,000 km<sup>2</sup> in the states of Oregon, Washington, Utah, Nevada and Idaho. The Snake River drops from mountain elevations of 3000 m to its confluence with the Columbia River. The river is one of the most biologically diverse freshwater systems in the United States with trails designed to promote recreational tourism, increase use of the Snake River and create generations of people who care about the river and are willing to protect and provide environmental stewardship of the river watershed resources.
基金the National Natural Science Foundation of China (Grant Nos. 50139020 and 50679012)
文摘Taking the Songnen Plain as the research region and basing on the structural division of river water resources, the impounding models of flood water utilization are proposed. Considering the water requirement, potential impoundage and the degree of risk, two modes of the flood water utilization are developed: full impounding and partial impounding. A risk assessment method is put forward according to variation of the flood storage capacity before and after impounding water. A representative hydrological year is taken as an example to analyze the application of the model at the downstream of the Nenjiang River. It is found that the model is very useful for the flood utilization and protection. For flood utilization, the spring drought can be relieved and the risk of impounding water is also acceptable. For flood protection, the river flood peak can be largely reduced and the impounding water can increase the river discharge at the low water period, at the same time the structure of river water resources can be improved as well.
文摘Five deltaic deposit bodies, respectively belonging to five different stages, have been successively built on the Luan River since the Holocene. Although both the place where the river emptied itself into the sea and the magnitude of these deposit bodies varied in different stages, the sediment processes of the delta were of the same model. 1. The Luan is a river carrying heavy sediment load to the north coast of the Bohai Bay. By actual measurements the mean discharge is 149 m^2/sec (the maximum discharge during flood peak being 34000m^3/sec); the mean annual silt discharge of the suspended load is 26.7×10~6 tons (maximum 87.9×10~6 tons), of which 63.5％ or more of the total takes place from June to August. During the flood period, the sudden rise-and-fall of the high sediment-loaded flow makes the river channel branched or changed easily and the deltaic plain consequently fans out toward the sea. 2. Because the Luan River has a low
