Modelling velocity distribution for vegetated flows using Entropy theory considering stiffness variation along plant length

Aquatic plants in rivers modify the flow structure by exerting resistance to the flow, which impacts the flood mitigation and river management. The resistance of a plant depends on its flexural rigidity (EI), which varies along a plant length (L), but was considered constant throughout its length, in the previous velocity distribution models. In this study, the samples of three aquatic plants – Water chestnut, Lily, and Lotus, are collected, which was not yet explored till date to determine the EI. Further, using the own-weight cantilever method, their EI along the stem is determined in the laboratory. The measured EI is further utilized to establish a relationship between EI and the plant’s morphological characteristics, enabling the easy estimation of EI on-field. Subsequently, an entropic velocity distribution is proposed for flows with submerged flexible vegetation, employing the EI variation along plant stem. The laboratory experiments are conducted to measure velocity profile at the downstream of the aquatic plants, which is utilized to validate the proposed velocity distribution. Moreover, the proposed velocity distribution is also compared with the previous velocity model, which considered the constant EI along the plant length. The results showed that the proposed velocity distribution with the inclusion of EI variation along plant length, improved prediction and outperformed the previous model, with Nash–Sutcliffe Efficiency (NSE) > 0.7, Coefficient of Determination (R2) > 0.75, and Absolute Relative Error (ARE) < 0.25. Thus, the proposed model can be utilized to predict the velocity profile at river sites with submerged aquatic plants.