Powerful alluvial rivers in the northern Alborz mountain ranges erode river banks due to having high slopes.Most of these rivers flow in forest areas.In this research,the rate of the river bank erosion was examined us...Powerful alluvial rivers in the northern Alborz mountain ranges erode river banks due to having high slopes.Most of these rivers flow in forest areas.In this research,the rate of the river bank erosion was examined using the exposed roots of the trees.For this purpose,8 reaches of Lavij Stream were investigated.To determine the first year of root exposure,two sets of macroscopic and microscopic indicators were utilized.Accordingly,the rate of the stream bank erosion was estimated.The results were analyzed by using statistical test,which showed insignificant differences between the two groups of indicators.Due to its more abundance(frequency)on the margins and easy detection of its root through the exposure(macroscopic and microscopic)indicators,Alnus glutinosa(black alder)species could be more easily and accurately analyzed as compared with any other tree species in the region.The mean erosion rate of the riverbank using the extruded roots was estimated to be 0.08 m/yr.The hydrological analyses of flood flows showed that 95%of Lavij Stream bank erosion was caused by the river bank full discharges with a return period of 1-3 years.展开更多
Assessing the contribution of sediments from different sources is essential to understand erosive processes and formulate further soil conservation strategies to address environmental problems.In this study,we combine...Assessing the contribution of sediments from different sources is essential to understand erosive processes and formulate further soil conservation strategies to address environmental problems.In this study,we combined the source fingerprinting approach with geochemistry,including comparison of potential sources,and distribution pattern of major elements,to estimate the different land-use relative contributions to streambed sediment in the Luowugou catchment(13.5 km^2)located on the Heishui River,the first branch of the Jinsha River,China.A total of 57 samples from stream bank,cropland,grassland,forest land,and sediments were collected,and then,15 elements were analyzed foreach sample.The fingerprinting results demonstrated that the stream bank(62.4%)had the greatest relative contribution to the bed sediment yield,while cropland,grassland,and forest land contributed 18.6%,14.9%,and 4.1%to the bed sediments,respectively.In comparison to the fingerprinting method,even though the results upon geochemistry only provide a qualitative assessment,the ranking of sediment contributions based on geochemistry was consistent with the sediment fingerprinting ranking,that is,stream bank>cropland>grassland>forest land.Our findings suggest that the focal point for sediment control practices should be the stream bank rather than cropland in the region.Geochemistry can result in an important means in validating the fingerprinting results.展开更多
In this work, we studied the dimensions of stream tube in the vertical as well as inclined bank conditions. Data were collected from both a physical model and a 3-D numerical model（SSIIM 2）. Equations for predicting...In this work, we studied the dimensions of stream tube in the vertical as well as inclined bank conditions. Data were collected from both a physical model and a 3-D numerical model（SSIIM 2）. Equations for predicting stream tube dimensions were presented and compared with existing formulae. In comparison with vertical bank, it is found that inclining bank causes the bottom stream tube width to be greater than at the surface. The strength of secondary current formed at the entrance of branch channel is reduced. These changes in flow pattern can reduce the amount of sediment delivery into the intake.展开更多
文摘Powerful alluvial rivers in the northern Alborz mountain ranges erode river banks due to having high slopes.Most of these rivers flow in forest areas.In this research,the rate of the river bank erosion was examined using the exposed roots of the trees.For this purpose,8 reaches of Lavij Stream were investigated.To determine the first year of root exposure,two sets of macroscopic and microscopic indicators were utilized.Accordingly,the rate of the stream bank erosion was estimated.The results were analyzed by using statistical test,which showed insignificant differences between the two groups of indicators.Due to its more abundance(frequency)on the margins and easy detection of its root through the exposure(macroscopic and microscopic)indicators,Alnus glutinosa(black alder)species could be more easily and accurately analyzed as compared with any other tree species in the region.The mean erosion rate of the riverbank using the extruded roots was estimated to be 0.08 m/yr.The hydrological analyses of flood flows showed that 95%of Lavij Stream bank erosion was caused by the river bank full discharges with a return period of 1-3 years.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA20020401)the Sichuan Science and Technology Program (2018JY0545)+1 种基金the National Basic Research Programme (973 Programme) of China (2015CB452704)the National Natural Science Foundation of China (No. 41571277)
文摘Assessing the contribution of sediments from different sources is essential to understand erosive processes and formulate further soil conservation strategies to address environmental problems.In this study,we combined the source fingerprinting approach with geochemistry,including comparison of potential sources,and distribution pattern of major elements,to estimate the different land-use relative contributions to streambed sediment in the Luowugou catchment(13.5 km^2)located on the Heishui River,the first branch of the Jinsha River,China.A total of 57 samples from stream bank,cropland,grassland,forest land,and sediments were collected,and then,15 elements were analyzed foreach sample.The fingerprinting results demonstrated that the stream bank(62.4%)had the greatest relative contribution to the bed sediment yield,while cropland,grassland,and forest land contributed 18.6%,14.9%,and 4.1%to the bed sediments,respectively.In comparison to the fingerprinting method,even though the results upon geochemistry only provide a qualitative assessment,the ranking of sediment contributions based on geochemistry was consistent with the sediment fingerprinting ranking,that is,stream bank>cropland>grassland>forest land.Our findings suggest that the focal point for sediment control practices should be the stream bank rather than cropland in the region.Geochemistry can result in an important means in validating the fingerprinting results.
文摘In this work, we studied the dimensions of stream tube in the vertical as well as inclined bank conditions. Data were collected from both a physical model and a 3-D numerical model（SSIIM 2）. Equations for predicting stream tube dimensions were presented and compared with existing formulae. In comparison with vertical bank, it is found that inclining bank causes the bottom stream tube width to be greater than at the surface. The strength of secondary current formed at the entrance of branch channel is reduced. These changes in flow pattern can reduce the amount of sediment delivery into the intake.
