Morphodynamics and morphological evolution characteristics of blowouts dunefields:A case study in Haitan Island,Fujian
Blowouts,developed over the dunefield,as a type of coastal aeolian landforms,have been the focus of aeolian geomorphology research.Meanwhile,the core issue of studying blowout is the model of development and evolution of blowout and feedback mechanism between blowout aerodynamic and morphodynamics.Choosing the typical area of blowouts developing in Haitan Island,we investigated the morphodynamics and aerodynamics of the saucer,half-bowl and trough blowouts by conducting field monitoring.Real Time Kinematic GPS was used to topography survey and 2D ultrasound anemometers were to explore wind flow dynamics."Space for time substitution"has been used to explore the evolution models of blowouts and feedback mechanism between aeolian process and blowouts morphological development.The results show that:(1)The trailing edge of saucer blowout enlarges and erosional basin gets steeper till a scarp occurs along prevailing wind direction.The entrance tends to recede as wind flow approaching.Half-bowl blowout expands and is deepened and the erosional wall is broken into the outlet.The erosional basin of trough blowout enlarges into deflation zone,the east-hand erosional wall is broken and extends the trailing edge.(2)The airflow distribution pattern within the blowout is influenced by wind direction and blowout topography,and the flow velocity fluctuation within blowout determine the erosion and deposition at different spots.(3)The evolution model for blowout can be concluded that erosion notches are initiated,and developed into a saucer blowout,till enlarged into the half-bowl shape blowout,turn into the trough blowout and die out.The vegetation cover plays an important role in the entire evolution cycles,especially the half-bowl shape blowout transfers into trough blowout,and trough blowout enlarges until it dies out,as a result of topography influence and depth limits.Therefore,by analyzing and exploring the morphological changes,morphology and dynamics mechanisms,and evolution patterns of blowouts in the degenerated area of Haitan Island,this study will provide an in-depth understanding of the morphology-dynamics feedback mechanisms,and evolution patterns in the degradation process of coastal blowouts,and will be conducive to providing better scientific guidance for the prevention and treatment of coastal blowouts,so as to better cope with global climate change in terms of the destruction of coastal littoral habitats,erosion of foredunes and shoreline retreat,and the human properties lost,which is of great scientific significance and application value.
万方数据
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