investigation of the effect of bridge piers on sedimentation and erosion in karaj river

چکیده مقاله

Rivers each year carry million tons of solid and sedimentary materials from headwater to stuary . Whereas the happened damages by sedimentation by rivers to nature , agriculture , hydraulic structutre , is too large and harmful , therefore exact identification of this phenomenon and decreasing methods of these damages are the goals of hydraulic engineers . Also for selection of maning grittiness of river by using the given equation for estimating maning grittiness with the amount of materials , maning grittiness is estimated equal to 0.032 . This model is evaluated for 12 executive years and its results once for 4 years with bridge and without bridge . The result of study of floor profile shows that , in the primer 500.m of both in condition of with or without bridge the intensive erosion will be happened , and after this path , floor profile has 0. To 1.m. erosion , and it has been effected by bridge about 3000.m. from upstream of river . In without bridge Condition , after about 3 k.m., river had more erosion and it has sedimentation between Tehran – Karaj high –way bridge and Metro bridge . Using England – Henson sediment transport equation shows that , in general this method has more intensive erosion comparing to Ikerz and Wite equation

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