Alborz,as part of the Alpine-Himalayan orogeny belt,has been the result of the convergence of the Central Iranian and Eurasian plate since the late Triassic.The study area located in Central Alborz encompasses differe...Alborz,as part of the Alpine-Himalayan orogeny belt,has been the result of the convergence of the Central Iranian and Eurasian plate since the late Triassic.The study area located in Central Alborz encompasses different Quaternary faults.Thus,the present study aimed to evaluate the effect of faults on river landforms through morphotectonic indices and the causes of knickpoints and knickzones in the Bedrock Rivers in part of Central Alborz.To this end,six morphometric indices such as longitudinal gradient(SL),hierarchical anomaly(Δα),the bifurcation index(R),hypsometric integral and hypsometric curve(Hi-Hc),relative relief(Bh),and basin shape(Bs) were calculated and analyzed in38 sub-basins of the area.Finally,the area was divided into extremely high,high,medium,and low tectonic activity areas using the relative tectonic activity(IAT).Normalized steepness and concavity indices along with the longitudinal profiles of the streams were obtained using Matlab and Arc GIS software.Based on the findings,the existence of slope-break knickpoints at the mountain piedmont at the outlet of large rivers through active faults demonstrated that most of these landforms were created by movements along the main faults such as Khazar,Nusha,Soheil,Deylaman,Kashachal,representing high tectonic activity in the central and southern parts of the study area.However,the values of these indices were extremely low and indicated low tectonic activity in the northern parts located in the embayment part of the Caspian Sea.Finally,the findings revealed that these classes correspond well to the areas with landforms such as V-shaped and narrow valleys,gorges,deflected and offset streams,deformed Neogene,and Quaternary units that indicate the post-Neogene activity.展开更多
Initiation and recession of the knickpoints are significant boundary condition for processes of fluvial system. The distribution and recession rates of knickpoints contain information that provides a fundamental under...Initiation and recession of the knickpoints are significant boundary condition for processes of fluvial system. The distribution and recession rates of knickpoints contain information that provides a fundamental understanding of geomorphic processes. In the Yalu River-Wangtian＇e volcanic region of northeastern China, broadly distributed fiat lava terrain provides an ideal site to study the recession of fluvial knickpoints because knickpoints and waterfalls are well preserved here. Here we describe the distribution of knickpoints in the Yalu River-Wangtian＇e volcanic region by combining DEM analysis and numerical modeling Furthermore, we present a knickpoint celerity model, derived from stream-power incision model, to relate knickpoint recession rate to drainage area. We calibrate important empirical coefficients with our knickpoint celerity model; the best fit erosion coefficient （K） is 1.32×10^-8, and the best fit drainage area exponent （m） is 0.69. Error analysis indicates a close correspondence between synthetic and real knickpoints. Finally, we show that knickpoint recession rates in the Yalu River-Wangtian＇e volcanic region are -1-10 mm/a during the early stages of transient incision, and that the present rates are -1-6 mm/a. Our recession rate results are in good agreement with previous findings from the Aso Volcano and volcanoes near Boso Peninsula （Japan）, which have a similar geologic history to the Yalu River-Wangtian＇e volcanic region. Our present effort provides new insight into landscape evolution in the Yalu River-Wangtian＇e volcanic region in northeastern China.展开更多
堰塞坝会对山区河流的纵剖面产生强烈扰动,在某些情况下,堰塞坝造成的河流纵剖面变陡很容易与构造作用下基准面下降的迁移裂点混淆。然而,在何种程度下堰塞坝会影响基于地貌测量的构造分析还没有系统的研究。因此本文选取青藏高原东缘...堰塞坝会对山区河流的纵剖面产生强烈扰动,在某些情况下,堰塞坝造成的河流纵剖面变陡很容易与构造作用下基准面下降的迁移裂点混淆。然而,在何种程度下堰塞坝会影响基于地貌测量的构造分析还没有系统的研究。因此本文选取青藏高原东缘的雅砻江流域为研究对象,利用遥感影像解译,结合数字高程模型(DEM),来研究堰塞坝对河流纵剖面的影响。通过遥感影像解译和部分野外判识,在雅砻江流域共发现了34个堰塞坝;同时利用TopoToolbox工具包,选用30 m SRTM DEM提取了雅砻江流域河流纵剖面、河流裂点、河流陡峭指数等地貌参数。分析结果表明,有18个堰塞坝与河流裂点在空间上重叠,其中有8个堰塞坝形成高差>100 m的裂点,对河流纵剖面有显著的影响,并发现滑坡坝比泥石流坝对河流纵剖面的影响更大。进一步分析雅砻江主干流及其支流力丘河,发现堰塞坝所在的河段河流陡峭指数相对较大;在排除岩性和断层活动的影响后,发现堰塞作用也能够解释河流裂点的成因。本研究结果指示,在利用DEMs来提取和分析区域构造信息时,必须考虑由堰塞坝引起的河流裂点的影响。展开更多
文摘Alborz,as part of the Alpine-Himalayan orogeny belt,has been the result of the convergence of the Central Iranian and Eurasian plate since the late Triassic.The study area located in Central Alborz encompasses different Quaternary faults.Thus,the present study aimed to evaluate the effect of faults on river landforms through morphotectonic indices and the causes of knickpoints and knickzones in the Bedrock Rivers in part of Central Alborz.To this end,six morphometric indices such as longitudinal gradient(SL),hierarchical anomaly(Δα),the bifurcation index(R),hypsometric integral and hypsometric curve(Hi-Hc),relative relief(Bh),and basin shape(Bs) were calculated and analyzed in38 sub-basins of the area.Finally,the area was divided into extremely high,high,medium,and low tectonic activity areas using the relative tectonic activity(IAT).Normalized steepness and concavity indices along with the longitudinal profiles of the streams were obtained using Matlab and Arc GIS software.Based on the findings,the existence of slope-break knickpoints at the mountain piedmont at the outlet of large rivers through active faults demonstrated that most of these landforms were created by movements along the main faults such as Khazar,Nusha,Soheil,Deylaman,Kashachal,representing high tectonic activity in the central and southern parts of the study area.However,the values of these indices were extremely low and indicated low tectonic activity in the northern parts located in the embayment part of the Caspian Sea.Finally,the findings revealed that these classes correspond well to the areas with landforms such as V-shaped and narrow valleys,gorges,deflected and offset streams,deformed Neogene,and Quaternary units that indicate the post-Neogene activity.
基金supported jointly by National Science Foundation of China (Grant Nos. 40702028, 41030317)State Key Laboratory of Earthquake Dynamics (Grant Nos. LED2009A06,LED2008A02)Zhang Huiping was also supported as a visiting professor to CU by China Scholarship Council (Grant No. 2007106279)
文摘Initiation and recession of the knickpoints are significant boundary condition for processes of fluvial system. The distribution and recession rates of knickpoints contain information that provides a fundamental understanding of geomorphic processes. In the Yalu River-Wangtian＇e volcanic region of northeastern China, broadly distributed fiat lava terrain provides an ideal site to study the recession of fluvial knickpoints because knickpoints and waterfalls are well preserved here. Here we describe the distribution of knickpoints in the Yalu River-Wangtian＇e volcanic region by combining DEM analysis and numerical modeling Furthermore, we present a knickpoint celerity model, derived from stream-power incision model, to relate knickpoint recession rate to drainage area. We calibrate important empirical coefficients with our knickpoint celerity model; the best fit erosion coefficient （K） is 1.32×10^-8, and the best fit drainage area exponent （m） is 0.69. Error analysis indicates a close correspondence between synthetic and real knickpoints. Finally, we show that knickpoint recession rates in the Yalu River-Wangtian＇e volcanic region are -1-10 mm/a during the early stages of transient incision, and that the present rates are -1-6 mm/a. Our recession rate results are in good agreement with previous findings from the Aso Volcano and volcanoes near Boso Peninsula （Japan）, which have a similar geologic history to the Yalu River-Wangtian＇e volcanic region. Our present effort provides new insight into landscape evolution in the Yalu River-Wangtian＇e volcanic region in northeastern China.
文摘堰塞坝会对山区河流的纵剖面产生强烈扰动,在某些情况下,堰塞坝造成的河流纵剖面变陡很容易与构造作用下基准面下降的迁移裂点混淆。然而,在何种程度下堰塞坝会影响基于地貌测量的构造分析还没有系统的研究。因此本文选取青藏高原东缘的雅砻江流域为研究对象,利用遥感影像解译,结合数字高程模型(DEM),来研究堰塞坝对河流纵剖面的影响。通过遥感影像解译和部分野外判识,在雅砻江流域共发现了34个堰塞坝;同时利用TopoToolbox工具包,选用30 m SRTM DEM提取了雅砻江流域河流纵剖面、河流裂点、河流陡峭指数等地貌参数。分析结果表明,有18个堰塞坝与河流裂点在空间上重叠,其中有8个堰塞坝形成高差>100 m的裂点,对河流纵剖面有显著的影响,并发现滑坡坝比泥石流坝对河流纵剖面的影响更大。进一步分析雅砻江主干流及其支流力丘河,发现堰塞坝所在的河段河流陡峭指数相对较大;在排除岩性和断层活动的影响后,发现堰塞作用也能够解释河流裂点的成因。本研究结果指示,在利用DEMs来提取和分析区域构造信息时,必须考虑由堰塞坝引起的河流裂点的影响。
