تازه های تحقیق
عنوان مقاله [English]
Alluvial floodplains, and in particular those associated with the world's largest rivers, have a complex relief that is produced by recurring erosional, and depositional events.The magnitude, heterogeneity, spatial distribution, and connectivity of this relief controls river floodwater routing and storage, sediment dispersal, and biogeochemical cyclingChannel Lateral movement and course changes are main causes for floodplain extend ,bank erosion and soil loss due to cut bank .Aras river that located in NW of Iran(from 45°E to 48°E), have many curvatures on course and due to this reason Aras is made high rate movement yearly .Aras is a boarder river and for this reason is very important that direction is determined .
In this article for determining the rate of lateral movement is used landsats 5,2 (Mss) landsat5™landsat 7(ETM+) and landsats(OLI) with 30 and 15 resoulation in 1985 to 2015 epoch. In this study is used Rm, R and MI for rate and degree movement and rate of river course curvature .
In order to determining of power flow against instability of mater in this article is used MI idex:
And for determining of rate of displacement of channel, is used of Rm index:
Investigation on the curvature radial Aras channel show that average rate of radial is 509.62 m. In other site this rate is 515.71 m. The study also show that changes in Aras river course is vary .When wide is high ,channel migration is excess .In recent time this changes is high ,but rate of migration in Iran site and other site is decrease to compare of past time .The average of channel migration to Iran site is 27,21m in 2010 and other site rate is 28,32 m.
Sum all area that located at other site due to displacement are 1410255 m3 (1985-2015).Area in site of Iran is 2230869 m3 (1985-2015).That is to say ,difference is 820614 m3.This has meaning that our land and soil is placed other site due to channel movement .Yearly average displacement of channel Aras river is 475 m at Iran site and 353 m at other site .So ,displacement at two site is vary .Over the past three decades, the fluvial dynamics of meander bends, including processes related to outer bank erosion, have been the focus of numerous scientific investigations. Despite this effort,a comprehensive understanding of the hydraulic processes of outer bank erosion—especially the role of flow turbulence—remains elusive.Because natural river flows are fully turbulent, the erosive stresses acting on the banks of meandering rivers should be related to turbulent stresses. Current models of outer bank erosion, however, rely on simple parameterization of the flow via excess velocity, excess shear stress at the bank toe, or excess flow depth .
Aras River is very dynamic .This river make curvature in its curse and cut bank .When river make meander in flow curse ,cut power of flow is increase .This high power is energy for bank cut and movement .Soil lost is other result for cut bank .This story is happened in northern border of Iran .