Author(s): Giuseppe Francesco Cesare Lama; Mariano Crimaldi

Linked Author(s): Giuseppe Francesco Cesare Lama

Keywords: Ecohydraulics, Vegetated drainage channels, Thermography, Bulk drag coefficient, UAV

Abstract: The assessment of the key hydrodynamic properties induced by riverine and aquatic vegetation on vegetated watercourses at field scale is the main objective of Ecohydraulics. The purpose of this study is the possibility to predict the real-scale values of bulk drag coefficients along an abandoned vegetated drainage channel colonized by 9–10 m high Arundo donax L. (most commonly known as giant reed) stands, starting from the employment of a portable thermographic camera mounted on a commercial Unnamed Aerial Vehicle (UAV). The thermographic camera (or thermal imager) is a portable device capable of creating an image by employing the infrared (IR) radiation acquired by its sensors, like a common HD camera that returns an image using visible light. The sensor is defined as a “bolometer”, which is a device employed for measuring the power of incident electromagnetic radiation via the heating of the monitored objects. Once known the flow average velocity at thirty instrumented cross-sections, and a map of the riparian vegetation’s Normalized Difference Vegetation Index (NDVI) obtained through digital processing of UAV-based multispectral acquisitions, it was possible to obtain a correlation between NDVI-based Leaf Area Index (LAI) of the giant reed stands analyzed here and their thermal properties. The direct comparison between giant reed stands’ bulk drag obtained through mapped LAI values and those obtained from the processing of the thermal imager acquisitions enabled the analysis of the impact of these techniques on the predictions of the main hydrodynamic features associated with the examined vegetated drainage channel. The potential of the outcomes of this study is extremely useful in cases of hardly accessible territories such as vegetated drainage channels characterized by the massive presence of riparian stands at natural phenological and morphometric conditions.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022SS9

Year: 2022