University of Tehran Press Iranian Journal of Soil and Water Research 2008-479X 51 2 2020 04 20 Effects of Vegetation Arrangement and Floodplain-main Channel Interaction on the Longitudinal Dispersion Coefficient in Compound Channels Effects of Vegetation Arrangement and Floodplain-main Channel Interaction on the Longitudinal Dispersion Coefficient in Compound Channels 479 488 72924 10.22059/ijswr.2019.285507.668263 FA Hossein Hamidifar Water Engineering Department, College of Agriculture, Shiraz University, Shiraz, Iran Mohammad Hossein Omid Department of Irrigation and Reclamation Eng., Campus of Agriculture and Natural Resources, College of Agricultural Engineering and Technology, University of Tehran, Karaj, Iran. Journal Article 2019 07 30 Several factors affecting pollutant transport in rivers. Among those, vegetation is less studied by researchers. Due to the appropriate conditions in floodplains, such as adequate moisture and fertile sediments, it is possible to develop and grow different types of vegetation in these areas. Depending on the type of vegetation, their effect on the flow and subsequently on mass transfer is different. In this paper, the effects of flow depth, vegetation arrangement, and the interaction between the floodplain and the main channel on the longitudinal dispersion coefficient, K, in a compound channel has been studied. The results show that K is greater in the main channel rather than the floodplain. In addition, the interaction of the main channel and floodplain increases the K values up to 30 and 88% for non-vegetated and vegetated conditions, respectively, which are statistically significant. Similarly, the effect of vegetation arrangement on the K values are statistically significant, and <em>K</em> /<em>U</em>_*i<em>H</em>_i is greater for the staggered arrangement rather than tandem arrangement. Several factors affecting pollutant transport in rivers. Among those, vegetation is less studied by researchers. Due to the appropriate conditions in floodplains, such as adequate moisture and fertile sediments, it is possible to develop and grow different types of vegetation in these areas. Depending on the type of vegetation, their effect on the flow and subsequently on mass transfer is different. In this paper, the effects of flow depth, vegetation arrangement, and the interaction between the floodplain and the main channel on the longitudinal dispersion coefficient, K, in a compound channel has been studied. The results show that K is greater in the main channel rather than the floodplain. In addition, the interaction of the main channel and floodplain increases the K values up to 30 and 88% for non-vegetated and vegetated conditions, respectively, which are statistically significant. Similarly, the effect of vegetation arrangement on the K values are statistically significant, and <em>K</em> /<em>U</em>_*i<em>H</em>_i is greater for the staggered arrangement rather than tandem arrangement. https://ijswr.ut.ac.ir/article_72924_0fbb709493da906608470aeed807afd1.pdf