Effects of Vegetation Arrangement and Floodplain-main Channel Interaction on the Longitudinal Dispersion Coefficient in Compound Channels

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 K /U*iHi is greater for the staggered arrangement rather than tandem arrangement.