مدلسازي عددي الگوي فرسايش و رسوبگذاري در رودخانه هاي آبرفتي (مطالعه موردي: رودخانه قره سو در استان كرمانشاه)

Numerical Modeling of Erosion and Sedimentation Patterns in Alluvial River (Case Study: Gharasoo River in Kermanshah province

رونديابي درازمدت رسوب و تعيين محل هاي فرسايش و رسوبگذاري در رودخانه ها اطلاعات مفيدي براي ﻃﺮاﺣﯽ ﺳﺎزهﻫﺎي ﻫﯿﺪروﻟﯿﮑﯽ و ﻣﺪﯾﺮﯾﺖ رودﺧﺎﻧﻪ در اﺧﺘﯿﺎر ﻣﻬﻨﺪﺳﺎن ﻗﺮار ﻣﯽدﻫﺪ. از اﯾﻦرو در اﯾﻦ ﺗﺤﻘﯿﻖ ﻣﺪﻟﯽ ﮐﺎﻣﭙﯿﻮﺗﺮي ﺑﺮاي روﻧﺪﯾﺎﺑﯽ رﺳﻮب در رودﺧﺎﻧﻪ ﺗﻬﯿﻪ ﺷﺪ ﮐﻪ در آن ﭘﺲ از ﻣﺤﺎﺳﺒﻪ ﭘﺮوﻓﯿﻞ ﺟﺮﯾﺎن در ﻫﺮ ﮔﺎم زﻣﺎﻧﯽ ﺑﺎ ﺣﻞ ﻣﻌﺎدﻟﻪ ﭘﯿﻮﺳﺘﮕﯽ رﺳﻮب ﺗﻐﯿﯿﺮات ﭘﺮوﻓﯿﻞ ﺑﺴﺘﺮ ﺑﺮاي ﻫﻤﺎن ﮔﺎم زﻣﺎﻧﯽ ﻣﺤﺎﺳﺒﻪ ﻣﯽﺷﻮد. ﭘﺲ از ﺻﺤﺖﺳﻨﺠﯽ ﻣﺪل، ﺗﻐﯿﯿﺮات ﻓﺮﺳﺎﯾﺶ و رﺳﻮبﮔﺬاري در ﺑﺎزهاي ﺑﻪ ﻃﻮل 18/5 ﮐﯿﻠﻮﻣﺘﺮ ﺑﺮاي ﻣﺪت زﻣﺎن 5 و10 ﺳﺎل ﺑﺎ اﺳﺘﻔﺎده از رواﺑﻂ ﻣﯿﺮ، ﭘﺎرﮐﺮ و وﯾﻠﺴﻮن )ﺑﺎر ﺑﺴﺘﺮ( ﻣﺤﺎﺳﺒﻪ ﺷﺪ. در اداﻣﻪ ﺑﺎ ﺣﻞ ﻋﺪدي ﻣﻌﺎدﻟﻪ دﯾﻔﺮاﻧﺴﯿﻞ ﻣﺘﻮﺳﻂﮔﯿﺮي ﺷﺪه در ﻋﻤﻖ اﺛﺮ ﺑﺎر ﻣﻌﻠﻖ ﺑﺮ ﭘﺮوﻓﯿﻞ ﻓﺮﺳﺎﯾﺶ و رﺳﻮبﮔﺬاري، ﺑﺮاي ﻣﺪت 5 ﺳﺎل ﺑﺮرﺳﯽ ﮔﺮدﯾﺪ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ ﻓﺮآﯾﻨﺪ ﻏﺎﻟﺐ در ﺑﺎزه ﻣﻮرد ﻣﻄﺎﻟﻌﻪ، ﻓﺮﺳﺎﯾﺶ اﺳﺖ. از ﻃﺮﻓﯽ ﻣﯿﺰان ﻓﺮﺳﺎﯾﺶ و رﺳﻮبﮔﺬاري ﮐﻪ از راﺑﻄﻪ وﯾﻠﺴﻮن ﺑﻪدﺳﺖ ﻣﯽآﯾﺪ ﻧﺴﺒﺖ ﺑﻪ رواﺑﻂ دﯾﮕﺮ ﺑﯿﺸﺘﺮ اﺳﺖ. ﻫﻤﭽﻨﯿﻦ ﺑﺎ درﻧﻈﺮ ﮔﺮﻓﺘﻦ ﺑﺎر ﻣﻌﻠﻖ، ﺗﻐﯿﯿﺮات ﻓﺮﺳﺎﯾﺶ و رﺳﻮبﮔﺬاري ﺑﯿﺸﺘﺮي ﺑﻪدﺳﺖ آﻣﺪ و ﺑﻪﻋﺒﺎرﺗﯽ ﺣﺬف اﺛﺮ ﺑﺎر ﻣﻌﻠﻖ ﺧﻄﺎي زﯾﺎدي را در ﭘﯿﺶﺑﯿﻨﯽﻫﺎي ﻓﺮﺳﺎﯾﺶ و رﺳﻮبﮔﺬاري در رودﺧﺎﻧﻪ ﻣﺬﮐﻮر اﯾﺠﺎد ﺧﻮاﻫﺪ ﮐﺮد.

Longtime sediment routing and determining the location of sedimentation and erosion in rivers provide useful information for engineers to design hydraulic structures and river management. Therefore, in the present research a computer model was developed to simulate sediment movement in a river, in which after flow calculation at each time step, sediment continuity equation was solved numerically to predict bed change at the same time step. After model verification, using Meyer, Parker and Wilson equations for bed load prediction, bed variation of the river with 18.5 km length for 5 and 10 years was calculated. Also by numerical solution of 1-D depth average differential equation to calculate suspended load concentration the effect of suspended load on sedimentation and erosion pattern during 5-year simulation was investigated. The results showed that the erosion phenomenon was dominate pattern at the river reach. Also calculated volumes of sedimentation and erosion using the Wilson equation were more than those from the other relations. In addition the result showed with considering the effect of suspended load, variations and amounts of sedimentation and erosion were increased. Therefore, significant mistake would occur in prediction of sedimentation and erosion pattern in the mentioned river reach if the effect of suspended load was not considered