Physical modelling of shrub-willow patches in prototype scale

Prototype-scale experiments using living plant material are useful in providing a more realistic representation of natural conditions compared to small-scale flume experiments with parts of plants. A major challenge associated with such experiments is the time and effort needed in collecting detailed, representative data on the plant properties. In this study, several alternative methods were tested under field conditions in a channel with two willow patches. Vertical structure of the vegetation in the foliated and unfoliated patches was determined using quartile-layer manual surveys. Photography and image analyses were applied to derive leaf dimensions, and subsequently, estimates for the leaf area index (LAI) and the leaf-to-stem area ratio (AL/AS) for the quartile layers. Terrestrial laser scanning (lidar) was tested to construct a 3D point cloud of the unfoliated patch to compare the results against the quartile-layer manual survey. In addition to the methodological outcomes for deriving vegetation properties, preliminary results on ADV (Acoustic Doppler Velocimeter) data analyses are reported on the vertical velocity distribution within the patches. Overall, it is expected that the observations reported herein are helpful for improved designs of large-scale experiments with natural vegetation.