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

Abstract

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 (Atot) of woody vegetation correlated linearly with the TLS-based voxel count, whereas the Atot 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 Atot and its vertical distribution. A new concept was proposed for deriving Atot for larger areas from the point cloud attributes of small sub-areas. The results indicated that the relationships between the TLS attributes and Atot of the sub-areas can be derived either by mm resolution TLS or by manual vegetation sampling. OPEN ACCESSWater 2015, 7 421

To Investigate the Flow Structure of Discontinuous Vegetation Patches of Two Vertically Different Layers in an Open Channel

“…Kamel et al [8] developed a k-epsilon (k-ε) model to predict the flow in meandering-type open channels. Jalonen et al [9] determined the characteristics of vegetation areas by flood plain flow modeling. Huai et al [10] analyzed the interaction of flows with rigid vegetation and investigated the effects of vegetation patches on flow by utilizing an LES model.…”

From 3D grassy vegetation point cloud to hydraulic resistance: Application to close‐range estimation of Manning coefficients for intermittent open channels

“…The leaf area index or the leaf‐to‐stem area ratio was introduced as a vegetation density measure of the blockage factor (Jalonen, Järvelä, & Aberle, ; Jalonen & Järvelä, ) for woody vegetation. Jalonen et al () characterized the mixed floodplain vegetation in order to derive metrics for hydraulic analyses. They found that mean heights of vegetation were best related to their frontal areas for herbaceous vegetation, whereas a complete view of their 3D structure was necessary for woody plants.…”

“…The recent spread of terrestrial laser scanner (TLS) offers possible vegetation size estimations from in‐field experiments for hydraulic applications (Jalonen et al ; Jalonen et al ; Boothroyd et al ). The TLS helped characterizing the height distribution and the volumetric blockage factor of plant communities at channel scale (Jalonen et al ; Jalonen et al ), or the complete morphology of single trees (Boothroyd et al ).…”

“…To our knowledge, although the empirical evidence of considering vegetation properties to infer flow transport (Vargas‐Luna et al ), and the potential of using TLS for predetermination of reach roughness parameters (Jalonen et al ), there is no empirical study linking vegetation point clouds derived from TLS scans to open‐channel roughness coefficients and especially for grassy plants that can be found in intermittent open channels of cultivated landscapes. Grassy plants have a small size and a large range of morphological variability and flexibiliy among species (Kattge et al ), ranging from the herbaceous ones, very flexible, to the sclerophyllous plants that had hard leaves and/or stems.…”

Advances in Remote Sensing of Flooding

“…Jalonen et al [9] used the terrestrial laser scanner technology and its data to determine the characteristics of vegetated areas. Thus, an improved accuracy level in the modeling of floodplain flow was achieved.…”