Determining Characteristic Vegetation Areas by Terrestrial Laser Scanning for Floodplain Flow Modeling

Detailed modeling of floodplain flows and associated processes requires data on mixed, heterogeneous vegetation at river reach scale, though the collection of vegetation data is typically limited in resolution or lack spatial information. This study investigates physically-based characterization of mixed floodplain vegetation by means of terrestrial laser scanning (TLS). The work aimed at developing an approach for deriving the characteristic reference areas of herbaceous and foliated woody vegetation, and estimating the vertical distribution of woody vegetation. Detailed experimental data on vegetation properties were gathered both in a floodplain site for herbaceous vegetation, and under laboratory conditions for 2-3 m tall trees. The total plant area (A(tot)) of woody vegetation correlated linearly with the TLS-based voxel count, whereas the A(tot) of herbaceous vegetation showed a linear correlation with TLS-based vegetation mean height. For woody vegetation, 1 cm voxel size was found suitable for estimating both the A(tot) and its vertical distribution. A new concept was proposed for deriving A(tot) for larger areas from the point cloud attributes of small sub-areas. The results indicated that the relationships between the TLS attributes and A(tot) of the sub-areas can be derived either by mm resolution TLS or by manual vegetation sampling.