Using a terrestrial laser scanner to characterize vegetation-induced flow resistance in a controlled channel

TL;DR

This study employs terrestrial laser scanning to accurately measure vegetation structure and water levels in a controlled channel, enhancing understanding of flow resistance caused by vegetation heterogeneity.

Contribution

It introduces a method using TLS to simultaneously characterize vegetation heterogeneity and water surface in situ in a controlled environment.

Findings

TLS effectively captures vegetation heterogeneity and water levels.

Vegetation blockage factors vary with plant spatial design.

Method enables rapid, detailed in situ measurements.

Abstract

Vegetation characteristics providing spatial heterogeneity at the channel reach scale can produce complex flow patterns and the relationship between plant patterns morphology and flow resistance is still an open question (Nepf 2012). Unlike experiments in laboratory, measuring the vegetation characteristics related to flow resistance on open channel in situ is difficult. Thanks to its high resolution and light weight, scanner lasers allow now to collect in situ 3D vegetation characteristics. In this study we used a 1064 nm usual Terrestrial Laser Scanner (TLS) located 5 meters at nadir above a 8 meters long equipped channel in order to both i) characterize the vegetation structure heterogeneity within the channel form a single scan (blockage factor, canopy height) and ii) to measure the 2D water level all over the channel during steady flow within a few seconds scan. This latter measuring system was possible thanks to an additive dispersive product sprinkled at the water surface. Vegetation characteristics and water surfaces during steady flows from 6 different plant spatial design on channel bottom for 4 plant species were thus measured. Vegetation blockage factors at channel scale were estimated from TLS points clouds and analyzed.