Abstract
Estimating the main hydrodynamic features of real vegetated water bodies is crucial to assure a balance between their hydraulic conveyance and environmental quality. Riparian vegetation stands have a high impact on vegetated channels. The present work has the aim to integrate riparian vegetation’s reflectance indices and hydrodynamics of real vegetated water flows to assess the impact of riparian vegetation morphometry on bulk drag coefficients distribution along an abandoned vegetated drainage channel fully covered by 9–10 m high Arundo donax (commonly known as giant reed) stands, starting from flow average velocities measurements at 30 cross-sections identified along the channel. A map of riparian vegetation cover was obtained through digital processing of Unnamed Aerial Vehicle (UAV)-acquired multispectral images, which represent a fast way to observe riparian plants’ traits in hardly accessible areas such as vegetated water bodies in natural conditions. In this study, the portion of riparian plants effectively interacting with flow was expressed in terms of ground-based Leaf Area Index measurements (LAI), which easily related to UAV-based Normalized Difference Vegetation Index (NDVI). The comparative analysis between Arundo donax stands NDVI and LAI map enabled the analysis of the impact of UAV-acquired multispectral imagery on bulk drag predictions along the vegetated drainage channel.
Highlights
IntroductionThe identification of the riparian vegetation traits affecting flow resistance is one of the most relevant topics of both modeling and experimental analyses in ecohydraulics [4,5]
The outcomes of this study showed a good correlation between ground-based Leaf Area Index (LAI) measurements and Normalized Difference Vegetation Index (NDVI) derived by digital processing of Unnamed Aerial Vehicle (UAV)-acquired multispectral images
Bulk drag coefficients CD associated with a real vegetated drainage channel fully covered by 9–10 m high Arundo donax stands were predicted and validated here, based on the LAI map derived by NDVI assessments obtained through digital processing of UAV-acquired multispectral images of the riparian vegetation cover
Summary
The identification of the riparian vegetation traits affecting flow resistance is one of the most relevant topics of both modeling and experimental analyses in ecohydraulics [4,5]. Riparian plants behave differently depending on their bio-mechanical and morphometric traits, and on their submergence. According to Västilä and Järvelä [4], when flexural rigidity of riparian plant’s stems is very far from negligible, flow resistance associated with weed riparian vegetation species can be computed by exploiting Leaf Area Index (LAI). The implications of the interaction between flow and vegetation in vegetated water bodies on their main fluid dynamic features have been largely investigated in many experimental and numerical analyses by schematizing riparian plants as naturallike elements [8,9,10,11]
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