In this study,SRTM DEM data and ASTER GDEM data were used as the basic topographic data,and Arc Hydro Tools was utilized for extension module so as to study on extracting digital drainage network of watershed based on...In this study,SRTM DEM data and ASTER GDEM data were used as the basic topographic data,and Arc Hydro Tools was utilized for extension module so as to study on extracting digital drainage network of watershed based on surface runoff model,as well as to compare the two extracted results.The result showed that through the introduction of drainage density parameter to determine the river drainage area threshold,the both extracted drainages showed the goodness-of-fit with the factual drainage network on 1∶250 000 scale topographic map,and the extracted digital river could be used in practical operation of the risk assessment model of mountain torrents disaster in Liaohe basin.展开更多
Geomorphological study of a basin is important for understanding theoverall basin characteristics which are helpful for the management of waterresources, construction along the river bank and natural hazard mitigation...Geomorphological study of a basin is important for understanding theoverall basin characteristics which are helpful for the management of waterresources, construction along the river bank and natural hazard mitigationwithin the area. The study was carried out in the Karra Khola Basin, oneof the prominent basins in the Eastern extreme of the Hetauda Dun Valley,Central Nepal, to investigate geomorphic characteristics of the mainstream of the basin, categorize them into various stream types and studybasin development through drainage basin’s morphometric parameters.Geographical Information System (GIS) and Remote sensing techniquesusing satellite images were used as a tool to make the morphometricanalysis of the basin along with its major 13 sub-basin and delineate streamclassification following the Rosgen’s Level I hierarchical inventory. Themain stream of the Karra Khola is characterized as A-, B- and C-typeand the tributaries segments as B- and F-type. The basin is structurallyunaffected and has the permeable surface area and elongated shape. Thehypsometric analysis indicates that the basin is mostly at the old stage ofgeomorphic development while four out of 13 sub-basin being at maturestage. The Karra Khola sub-basin have higher risk to flash flooding(Lg=0.1-0.16km). Drainage density value reveals that the basin is highlysusceptible to flooding, gully erosion, etc. Similarly, dissection index valueimplies that the north eastern region of the basin is highly vulnerable toerosion as it at the younger stage of geomorphic development. Since thestudy area is highly sensitive to future natural hazards, further study andappropriate measures should be followed for safeguarding against thefuture risk along the Karra Khola basin and its tributaries.展开更多
As Iran is located on one of the two earthquake-prone belts in the world, and existence of faults and earthquakes is normal in Iran tableland. The main reason of earthquake is Neotectonic movements which can be effect...As Iran is located on one of the two earthquake-prone belts in the world, and existence of faults and earthquakes is normal in Iran tableland. The main reason of earthquake is Neotectonic movements which can be effective in other natural disasters such as range movements. Due to the severe shortage of historical and seismic data and device in different parts of the world, particularly Iran, need for introducing more researchers and planners of Iran to tectonics and active tectonic areas is more visible. This study is an investigation of Neotectonic activities in Khafr basin area, Fars province. To achieve the aims of this study morphometric parameters were used. Investigations showed that severity and role of tectonic activities in different parts of the basin is different, results of geomorphic and tectonic assessments indicate these differences.Stream length-gradient index (SL) on the main stream is inactive and sub streams are semi active, the ratio of the basin (BS) is 2.27, drainage basin asymmetry index (AF) is in semi active class, the ratio of width to depth of Valley (VF) shows 0.78. Indicators mentioned are in class 3 based on Iat classification, that represents tectonic activity in the area is average. Other indicators are indicative of active tectonic in the basin such as drainage density index (D) with high density, river sinuosity (S) 1.25, reverse topography symmetry Factor (T) 0.3.Generally it can be considered as moderately active region in terms of tectonic activities.展开更多
Debris flow can cause serious damages to roads, bridges, buildings and other infrastructures.Arranging several rows of deceleration baffles in the significant influence on the mobility and deposition characteristic of...Debris flow can cause serious damages to roads, bridges, buildings and other infrastructures.Arranging several rows of deceleration baffles in the significant influence on the mobility and deposition characteristic of debris flow. The deposit amount first increased then decreased when the flow density rises,flow path can reduce the flow velocity and ensure better protection of life and property. In debris flow prevention projects, deceleration baffles can effectively reduce the erosion of the debris flow and prolong the running time of the drainage channel.This study investigated the degree to which a 6 m long flume and three rows of deceleration baffles reduce the debris flow velocity and affect the energy dissipation characteristics. The influential variables include channel slope, debris flow density, and spacing between baffle rows. The experimental results demonstrated that the typical flow pattern was a sudden increase in flow depth and vertical proliferation when debris flow flows through the baffles. Strong turbulence between debris flow and baffles can contribute to energy dissipation and decrease the kinematic velocity considerably. The results showed that the reduction ratio of velocity increased with the increase in debris flow density,channel slope and spacing between rows. Tests phenomena also indicated that debris flow density hasand the deposit amount of debris flow density of 1500kg/m^3 reached the maximum when the experimental flume slope is 12°.展开更多
The Poni watershed,located in southwest Burkina Faso,is characterized by crystalline basement geological formations.The hydrogeology of the watershed is characterized by two types of aquifers:alterite aquifers and fis...The Poni watershed,located in southwest Burkina Faso,is characterized by crystalline basement geological formations.The hydrogeology of the watershed is characterized by two types of aquifers:alterite aquifers and fissured aquifers.Fissured aquifers are still the most widely used for drinking water supply.The general objective of the present work is to map the hydraulic potential of fissured aquifers in the Poni watershed,in order to identify areas with high hydraulic potential for sustainable and rational management of groundwater resources.Four methodological approaches were developed,the first three of which resulted in thematic maps of fracture density,drainage density and alteration thickness,using Landsat 8 and airborne geophysical images,Digital Terrain Model(DTM)data and borehole data.Next,four flow classes were defined according to the minimum flow required for the various types of drinking water supply works in Burkina Faso,followed by a study of their distribution on the various thematic maps produced for the definition of the coastlines.Finally,a weighting was made on the basis of coasts and coefficients assigned to each parameter for mapping the hydraulic potential of fissured aquifers.Field data(boreholes,structural measurements and hydrogeological indices)and previous studies were used to validate the mapping.Analysis of the distribution of borehole flow rates on the various thematic maps shows that borehole productivity is optimal for a fracture density of between 1.55 and 1.9 km/km^(2),a drainage density of between 0.28 and 0.35 km/km^(2)and an alteration thickness of less than 25 m.Hydraulic potential was mapped using the weighting method,based on the distribution of borehole flow rates on maps of weathering thickness,drainage network density and fracturing density,highlighting three hydrogeological domains:the low-productivity zone,occupying 24.40% of the basin's fissured aquifers,mainly found north of Gaoua,in the south-central and eastern parts of the basin around Gbomblora;the medium-productivity zone,occupying almost 31.57% of the fractured aquifers,is found mainly in the central-eastern part of the basin between Gaoua and Perigban,to the east of the commune of Gaoua,to the west of Kampti and to the west and northeast of Midebdo;and the good-productivity zone,representing 44,04% of the basin’s fissured aquifers,it is located mainly in the north-western part of the basin,north of Loropeni,east of Kampti,around Perigban and in the southeast,notably north-east of Batie.The high-productivity zones almost overlap with all the Water Production Centers(CPE)identified within the watershed during a hydrogeological study commissioned by COWI in 2019 on the search for high-productivity zones on the crystalline basement.This study constitutes a guide which will guide groundwater research and must be carried out before any land use project.展开更多
Al-Adhaim River is one of the main tributaries of the Tigris River,it has three main tributaries:Khassa Soo,Aq Soo,and Tuz Chia,all of which are seasonal streams.The course of Al-Adhaim River and its three tributaries...Al-Adhaim River is one of the main tributaries of the Tigris River,it has three main tributaries:Khassa Soo,Aq Soo,and Tuz Chia,all of which are seasonal streams.The course of Al-Adhaim River and its three tributaries flow in a very rugged topography,especially in the upper courses with high gradients.The exposed rocks in the catchment area are mainly soft claystone rocks with coarse conglomerate and sandstone,which are very easily eroded by the running water,especially during floods.We have used SRTM images of ground resolution of 3-arc-second(90 m)and a vertical resolution of approximately 10 m to divide the catchment area into 14 sub-basins using ArcGIS(Arc map).Moreover,many factors concerning soil erosion were calculated,such as drainage density,erosion intensity,erosion rates,and soil erodibility.We have found that the drainage density ranges between(0.26-0.39)km/km2 with class Poor,the Erosion Intensity ranges between(264-387)m/km2 with Very poor zone,the Erosion rates(Kk)ranges from(0.01-0.325),and the Erosion Coefficient ranges from(0.7-1.0).展开更多
Rangeland hillslopes provide much of the sediment supplied to channel systems and their lengths exert a fundamental constraint on hillslope diffusive processes.However,information regarding lengths of rangeland hillsl...Rangeland hillslopes provide much of the sediment supplied to channel systems and their lengths exert a fundamental constraint on hillslope diffusive processes.However,information regarding lengths of rangeland hillslopes,and how best to estimate them,is limited.In this study,three groups of watersheds(10 in total)were selected from the Walnut Gulch Experimental Watershed according to their geology,soil and vegetation characteristics.Group 1 watersheds were at lower elevations dominated by shrubs,Group 3 were at high elevations dominated by grass,and Group 2 were mixed shrub and grass.Their hillslope lengths were calculated from 1 m-resolution DEMs using three methods:a flow routing algorithm,slope-area relationships,and inverted relationship with drainage density.Parameters that characterize the current watersheds,including Hack's exponent and coefficient,watershed shape coefficient,channel concavity and steepness,and surface roughness,were quantified and related to hillslope lengths.Results shows:(1)estimated hillslope lengths were different for the three methods and between the three groups of watersheds;(2)hillslope lengths that measured from the flow routing algorithm for the ten selected watersheds primarily ranged from 30 to 100 m,with a median value of 63.0 m,which was 20%e50%greater than those derived from slope-area plots or drainage densities;(3)hillslope lengths estimated from the flow routing method were greater in Group 3 watersheds than in Group 2 and then in Group 1 watersheds.We attributed these differences in hillslope lengths to the historic epeirogenic pulses,watershed and drainage network morphology,and differences in vegetation characteristics;(4)measured hillslope lengths from the flow routing algorithm were best correlated with hillslope relief,then surface roughness,channel steepness and concavity.These results would benefit the applications of hydrological and erosion models in rangelands.展开更多
基金Supported by National Science and Technology Support Project(2008BAK49B07)~~
文摘In this study,SRTM DEM data and ASTER GDEM data were used as the basic topographic data,and Arc Hydro Tools was utilized for extension module so as to study on extracting digital drainage network of watershed based on surface runoff model,as well as to compare the two extracted results.The result showed that through the introduction of drainage density parameter to determine the river drainage area threshold,the both extracted drainages showed the goodness-of-fit with the factual drainage network on 1∶250 000 scale topographic map,and the extracted digital river could be used in practical operation of the risk assessment model of mountain torrents disaster in Liaohe basin.
文摘Geomorphological study of a basin is important for understanding theoverall basin characteristics which are helpful for the management of waterresources, construction along the river bank and natural hazard mitigationwithin the area. The study was carried out in the Karra Khola Basin, oneof the prominent basins in the Eastern extreme of the Hetauda Dun Valley,Central Nepal, to investigate geomorphic characteristics of the mainstream of the basin, categorize them into various stream types and studybasin development through drainage basin’s morphometric parameters.Geographical Information System (GIS) and Remote sensing techniquesusing satellite images were used as a tool to make the morphometricanalysis of the basin along with its major 13 sub-basin and delineate streamclassification following the Rosgen’s Level I hierarchical inventory. Themain stream of the Karra Khola is characterized as A-, B- and C-typeand the tributaries segments as B- and F-type. The basin is structurallyunaffected and has the permeable surface area and elongated shape. Thehypsometric analysis indicates that the basin is mostly at the old stage ofgeomorphic development while four out of 13 sub-basin being at maturestage. The Karra Khola sub-basin have higher risk to flash flooding(Lg=0.1-0.16km). Drainage density value reveals that the basin is highlysusceptible to flooding, gully erosion, etc. Similarly, dissection index valueimplies that the north eastern region of the basin is highly vulnerable toerosion as it at the younger stage of geomorphic development. Since thestudy area is highly sensitive to future natural hazards, further study andappropriate measures should be followed for safeguarding against thefuture risk along the Karra Khola basin and its tributaries.
文摘As Iran is located on one of the two earthquake-prone belts in the world, and existence of faults and earthquakes is normal in Iran tableland. The main reason of earthquake is Neotectonic movements which can be effective in other natural disasters such as range movements. Due to the severe shortage of historical and seismic data and device in different parts of the world, particularly Iran, need for introducing more researchers and planners of Iran to tectonics and active tectonic areas is more visible. This study is an investigation of Neotectonic activities in Khafr basin area, Fars province. To achieve the aims of this study morphometric parameters were used. Investigations showed that severity and role of tectonic activities in different parts of the basin is different, results of geomorphic and tectonic assessments indicate these differences.Stream length-gradient index (SL) on the main stream is inactive and sub streams are semi active, the ratio of the basin (BS) is 2.27, drainage basin asymmetry index (AF) is in semi active class, the ratio of width to depth of Valley (VF) shows 0.78. Indicators mentioned are in class 3 based on Iat classification, that represents tectonic activity in the area is average. Other indicators are indicative of active tectonic in the basin such as drainage density index (D) with high density, river sinuosity (S) 1.25, reverse topography symmetry Factor (T) 0.3.Generally it can be considered as moderately active region in terms of tectonic activities.
基金supported by the National Key Technology Research and Development Program of China (No. 2014BAL05B01)the Science and Technology Service Network Initiative of Chinese Academy of Sciences (No. KFJ-EW-STS-094)+1 种基金the National Science Foundation of China (No. 41302283)the West Light Foundation of Chinese Academy of Sciences
文摘Debris flow can cause serious damages to roads, bridges, buildings and other infrastructures.Arranging several rows of deceleration baffles in the significant influence on the mobility and deposition characteristic of debris flow. The deposit amount first increased then decreased when the flow density rises,flow path can reduce the flow velocity and ensure better protection of life and property. In debris flow prevention projects, deceleration baffles can effectively reduce the erosion of the debris flow and prolong the running time of the drainage channel.This study investigated the degree to which a 6 m long flume and three rows of deceleration baffles reduce the debris flow velocity and affect the energy dissipation characteristics. The influential variables include channel slope, debris flow density, and spacing between baffle rows. The experimental results demonstrated that the typical flow pattern was a sudden increase in flow depth and vertical proliferation when debris flow flows through the baffles. Strong turbulence between debris flow and baffles can contribute to energy dissipation and decrease the kinematic velocity considerably. The results showed that the reduction ratio of velocity increased with the increase in debris flow density,channel slope and spacing between rows. Tests phenomena also indicated that debris flow density hasand the deposit amount of debris flow density of 1500kg/m^3 reached the maximum when the experimental flume slope is 12°.
文摘The Poni watershed,located in southwest Burkina Faso,is characterized by crystalline basement geological formations.The hydrogeology of the watershed is characterized by two types of aquifers:alterite aquifers and fissured aquifers.Fissured aquifers are still the most widely used for drinking water supply.The general objective of the present work is to map the hydraulic potential of fissured aquifers in the Poni watershed,in order to identify areas with high hydraulic potential for sustainable and rational management of groundwater resources.Four methodological approaches were developed,the first three of which resulted in thematic maps of fracture density,drainage density and alteration thickness,using Landsat 8 and airborne geophysical images,Digital Terrain Model(DTM)data and borehole data.Next,four flow classes were defined according to the minimum flow required for the various types of drinking water supply works in Burkina Faso,followed by a study of their distribution on the various thematic maps produced for the definition of the coastlines.Finally,a weighting was made on the basis of coasts and coefficients assigned to each parameter for mapping the hydraulic potential of fissured aquifers.Field data(boreholes,structural measurements and hydrogeological indices)and previous studies were used to validate the mapping.Analysis of the distribution of borehole flow rates on the various thematic maps shows that borehole productivity is optimal for a fracture density of between 1.55 and 1.9 km/km^(2),a drainage density of between 0.28 and 0.35 km/km^(2)and an alteration thickness of less than 25 m.Hydraulic potential was mapped using the weighting method,based on the distribution of borehole flow rates on maps of weathering thickness,drainage network density and fracturing density,highlighting three hydrogeological domains:the low-productivity zone,occupying 24.40% of the basin's fissured aquifers,mainly found north of Gaoua,in the south-central and eastern parts of the basin around Gbomblora;the medium-productivity zone,occupying almost 31.57% of the fractured aquifers,is found mainly in the central-eastern part of the basin between Gaoua and Perigban,to the east of the commune of Gaoua,to the west of Kampti and to the west and northeast of Midebdo;and the good-productivity zone,representing 44,04% of the basin’s fissured aquifers,it is located mainly in the north-western part of the basin,north of Loropeni,east of Kampti,around Perigban and in the southeast,notably north-east of Batie.The high-productivity zones almost overlap with all the Water Production Centers(CPE)identified within the watershed during a hydrogeological study commissioned by COWI in 2019 on the search for high-productivity zones on the crystalline basement.This study constitutes a guide which will guide groundwater research and must be carried out before any land use project.
文摘Al-Adhaim River is one of the main tributaries of the Tigris River,it has three main tributaries:Khassa Soo,Aq Soo,and Tuz Chia,all of which are seasonal streams.The course of Al-Adhaim River and its three tributaries flow in a very rugged topography,especially in the upper courses with high gradients.The exposed rocks in the catchment area are mainly soft claystone rocks with coarse conglomerate and sandstone,which are very easily eroded by the running water,especially during floods.We have used SRTM images of ground resolution of 3-arc-second(90 m)and a vertical resolution of approximately 10 m to divide the catchment area into 14 sub-basins using ArcGIS(Arc map).Moreover,many factors concerning soil erosion were calculated,such as drainage density,erosion intensity,erosion rates,and soil erodibility.We have found that the drainage density ranges between(0.26-0.39)km/km2 with class Poor,the Erosion Intensity ranges between(264-387)m/km2 with Very poor zone,the Erosion rates(Kk)ranges from(0.01-0.325),and the Erosion Coefficient ranges from(0.7-1.0).
文摘Rangeland hillslopes provide much of the sediment supplied to channel systems and their lengths exert a fundamental constraint on hillslope diffusive processes.However,information regarding lengths of rangeland hillslopes,and how best to estimate them,is limited.In this study,three groups of watersheds(10 in total)were selected from the Walnut Gulch Experimental Watershed according to their geology,soil and vegetation characteristics.Group 1 watersheds were at lower elevations dominated by shrubs,Group 3 were at high elevations dominated by grass,and Group 2 were mixed shrub and grass.Their hillslope lengths were calculated from 1 m-resolution DEMs using three methods:a flow routing algorithm,slope-area relationships,and inverted relationship with drainage density.Parameters that characterize the current watersheds,including Hack's exponent and coefficient,watershed shape coefficient,channel concavity and steepness,and surface roughness,were quantified and related to hillslope lengths.Results shows:(1)estimated hillslope lengths were different for the three methods and between the three groups of watersheds;(2)hillslope lengths that measured from the flow routing algorithm for the ten selected watersheds primarily ranged from 30 to 100 m,with a median value of 63.0 m,which was 20%e50%greater than those derived from slope-area plots or drainage densities;(3)hillslope lengths estimated from the flow routing method were greater in Group 3 watersheds than in Group 2 and then in Group 1 watersheds.We attributed these differences in hillslope lengths to the historic epeirogenic pulses,watershed and drainage network morphology,and differences in vegetation characteristics;(4)measured hillslope lengths from the flow routing algorithm were best correlated with hillslope relief,then surface roughness,channel steepness and concavity.These results would benefit the applications of hydrological and erosion models in rangelands.
