LiDAR derived ecological integrity indicators for riparian zones: Application to the Houille river in Southern Belgium/Northern France

Abstract

a b s t r a c tRiparian zones are central landscape features providing several ecosystem services and are exceptionally rich in biodiversity. Despite their relatively low area coverage, riparian zones consequently represent a major concern for land and water resource managers confirmed within several European directives. These directives involve effective multi-scale monitoring to assess their conditions and their ability to carry out their functions. The objective of this research was to develop automated tools to provide from a single aerial LiDAR dataset new mapping tools and keystone riparian zone attributes assessing the ecological integrity of the riparian zone at a network scale (24 km).Different metrics were extracted from the original LiDAR point cloud, notably the Digital Terrain Model and Canopy Height Model rasters, allowing the extraction of riparian zones attributes such as the wetted channel (0.89 m; mean residual) and floodplain extents (6.02 m; mean residual). Different riparian forest characteristics were directly extracted from these layers (patch extent, overhanging character, longitudinal continuity, relative water level, mean and relative standard deviation of tree height). Within the riparian forest, the coniferous stands were distinguished from deciduous and isolated trees, with high accuracy (87.3%, Kappa index).Going further the mapping of the indicators, our study proposed an original approach to study the riparian zone attributes within different buffer width, from local scale (50 m long channel axis reach) to a network scale (ca. 2 km long reaches), using a disaggregation/re-agraggation process. This novel approach, combined to graphical presentations of the results allow natural resource managers to visualise the variation of upstream-downstream attributes and to identify priority action areas.In the case study, results showed a general decrease of the riparian forests when the river crosses built-up areas. They also highlighted the lower flooding frequency of riparian forest patches in habitats areas.Those results showed that LiDAR data can be used to extract indicators of ecological integrity of riparian zones in temperate climate zone. They will enable the assessment of the ecological integrity of riparian zones to be undertaken at the regional scale (13,000 km, completely covered by an aerial LIDAR survey in 2014).

Classification of riparian forest species and health condition using multi-temporal and hyperspatial imagery from unmanned aerial system

“…Because of the typical linear and narrow shape of the riparian zones, fieldbased monitoring involves sampling, high labor costs, and time-consuming travels (Debruxelles et al 2009;Myers 1989). The continuous improvement of the spatial resolution of remote sensing data combined with more powerful computer capacity and new geomatic procedures to extract information make the remote sensing approach more competitive (Alber and Piégay 2011;Carbonneau and Piégay 2012;Johansen et al 2010;Michez et al 2013;Roux et al 2014). The use of this very-high-resolution (VHR) imagery in a multitemporal approach is an emerging topic (Ardila et al 2012;Champion 2012;Lasaponara et al 2014).…”

Regional hydromorphological characterization with continuous and automated remote sensing analysis based on VHR imagery and low‐resolution LiDAR data

“…Stout and Belmont () and Michez et al . (, 2014) focused primarily on floodplain features and did not fully characterize in‐channel riverscape units, while neither Piégay et al . (), Bertrand et al .…”

“…Michez et al . (, ) used LiDAR and photogrammetric digital surface models for the characterization of the riparian zones from local to regional scales in Wallonia (Belgium). Stout and Belmont () developed a semi‐automated selection of fluvial terraces and floodplain features from LiDAR data.…”

The use of remote sensing to characterise hydromorphological properties of European rivers

“…Riparian corridor features (Johansen et al 2010a, b;Michez et al 2013) LiDAR and High resolution multi-spectral Large wood and organic debris…”

“…Moreover they found that SPOT-5 data were not useful for mapping most of the riparian attributes because of its coarse spatial resolution (pixel size = 10 m). More recently, Michez et al (2013) developed automated tools to quantify key riparian zone attributes for the assessment of the ecological integrity of the riparian zone at a network scale from a single aerial LiDAR dataset (Houille River, Belgium). This type of analysis offers the possibility of expanding the assessment of riparian zone vegetation to the entire Flanders region, which was completely mapped in 2014 with aerial LIDAR (13.000 km).…”