  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.
