University of Kashan Desert Ecosystem Engineering 2538-6336 11 35 2022 08 23 Investigation of the Impact of Bridge Structures on the River Route on the Hydraulic Behavior of the Flow (Case study: Velian River) Investigation of the Impact of Bridge Structures on the River Route on the Hydraulic Behavior of the Flow (Case study: Velian River) 59 72 113660 ‎10.22052/deej.2022.113660 FA Shabnam Vakili Alireza Moghaddamnia Journal Article 2022 04 18 Existence of constructions in the river route such as bridges, levee, nobles, etc. has changed the hydraulic behavior of the river flow and a change in this behavior may change the riverbed. In this research, the implementation of hydraulic model of Velian river and its results and the role of bridges (Chandar, Eskol Darreh, Ajin Dojin and Velian) in natural bed conditions have been investigated. For this purpose, HEC-RAS model has been used. The studied river was modeled in natural conditions and in the current situation for floods with different return periods of 2, 2.33, 5, 10, 25, 50, 100, 200, 500 and 1000. The results showed that the presence of bridges has the greatest impact on the flow cross-sectional area (11.6%) and the width of the free water surface (16.5%) and the least impact on the water level and energy gradient level (about zero percent). The froud number and flow velocities have decreased on all bridges except Valian Bridge. The height of the energy gradient has been variable. The least changes are related to water level, energy gradient and the most differences are related to water level width and area. According to the results obtained with a 25-year return period to make the necessary management decisions, it was suggested that School Darreh bridge be the first priority and Velian bridge be the last management priority due to the most changes in flow cross section and water level width. Existence of constructions in the river route such as bridges, levee, nobles, etc. has changed the hydraulic behavior of the river flow and a change in this behavior may change the riverbed. In this research, the implementation of hydraulic model of Velian river and its results and the role of bridges (Chandar, Eskol Darreh, Ajin Dojin and Velian) in natural bed conditions have been investigated. For this purpose, HEC-RAS model has been used. The studied river was modeled in natural conditions and in the current situation for floods with different return periods of 2, 2.33, 5, 10, 25, 50, 100, 200, 500 and 1000. The results showed that the presence of bridges has the greatest impact on the flow cross-sectional area (11.6%) and the width of the free water surface (16.5%) and the least impact on the water level and energy gradient level (about zero percent). The froud number and flow velocities have decreased on all bridges except Valian Bridge. The height of the energy gradient has been variable. The least changes are related to water level, energy gradient and the most differences are related to water level width and area. According to the results obtained with a 25-year return period to make the necessary management decisions, it was suggested that School Darreh bridge be the first priority and Velian bridge be the last management priority due to the most changes in flow cross section and water level width. https://deej.kashanu.ac.ir/article_113660_75731f356a9c266df1e66f511b950203.pdf