Using Digital Surface Models from UAS Imagery of Fire Damaged Sphagnum Peatlands for Monitoring and Hydrological Restoration

Abstract

The sub-alpine and alpine Sphagnum peatlands in Australia are geographically constrained to poorly drained areas c. 1000 m a.s.l. Sphagnum is an important contributor to the resilience of peatlands; however, it is also very sensitive to fire and often shows slow recovery after being damaged. Recovery is largely dependent on a sufficient water supply and impeded drainage. Monitoring the fragmented areas of Australia’s peatlands can be achieved by capturing ultra-high spatial resolution imagery from an unmanned aerial systems (UAS). High resolution digital surface models (DSMs) can be created from UAS imagery, from which hydrological models can be derived to monitor hydrological changes and assist with rehabilitation of damaged peatlands. One of the constraints of the use of UAS is the intensive fieldwork required. The need to distribute ground control points (GCPs) adds to fieldwork complexity. GCPs are often used for georeferencing of the UAS imagery, as well as for removal of artificial tilting and doming of the photogrammetric model created by camera distortions. In this study, Tasmania’s northern peatlands were mapped to test the viability of creating hydrological models. The case study was further used to test three different GCP scenarios to assess the effect on DSM quality. From the five scenarios, three required the use of all (16–20) GCPs to create accurate DSMs, whereas the two other sites provided accurate DSMs when only using four GCPs. Hydrological maps produced with the TauDEM tools software package showed high visual accuracy and a good potential for rehabilitation guidance, when using ground- controlled DSMs.

Unoccupied Aircraft Systems (UAS) for Marine Ecosystem Restoration

“…From both lidar and SfM, 3D point clouds ( Figure 2B and Supplementary Video S1) can be used to create digital surface models, and digital elevation models ( Figure 2C) when data are georectified within a vertical datum. UAS-derived 3D modeling has been conducted in a variety of environments including shorelines (Gonçalves and Henriques, 2015;Seymour et al, 2018;Lowe et al, 2019;Seymour et al, 2019;Casella et al, 2020), several shallow-water/tidal habitats (Long et al, 2016;Ventura et al, 2016;Casella et al, 2017;Kalacska et al, 2018;Windle et al, 2019), and to study hydrological dynamics in wetlands (Capolupo et al, 2015;de Roos et al, 2018;Harvey et al, 2019).…”

Unmanned Aircraft System (UAS) Structure-From-Motion (SfM) for Monitoring the Changed Flow Paths and Wetness in Minerotrophic Peatland Restoration

“…The flow paths in peatlands after restoration can be visible on-site, but usually only during the high-water seasons. However, the flow paths can also be simulated by analyzing a digital elevation model (DEM) (e.g., [21]). The highly detailed digital surface model (DSM) and its ground-filtered derivative, digital terrain model (DTM), can be produced using airborne remote sensing [22].…”

“…Many methods [28][29][30][31][32] are restricted to two-dimensional products, such as orthomosaic pictures for the classification of vegetation coverage. However, there are also examples of UAS-SfM-based topographical analysis [21,33,34].…”

“…For catchments including peat cover, topography has been studied for predicting wetland distribution [40][41][42][43], optimizing hydrotopographic methodologies [37,44,45] and revealing correlations not only with hydrological variables, such as groundwater level and soil moisture [37,43,46], but also other environmental variables, such as plant species richness and soil pH [47]. De Roos et al ( 2018) used an SfMbased DSM to model the hydrological one-instant flow accumulation and wetness of a temperate, fire-damaged peatland restoration site [21]. Furthermore, Dale et al (2020) used multi-temporal SfM data to detect elevation and flow accumulation changes in tidal wetland restoration [19].…”

Taking a closer look at invasive alien plant research: A review of the current state, opportunities, and future directions for UAVs

“…The favourable properties of UAV‐borne remote sensing systems mean that they have been successfully, and repeatedly, used for data collection (Manfreda et al, ; Pajares, ) for a wide range of applications (Baena, Boyd, & Moat, ; Dandois & Ellis, ; Dash, Watt, Pearse, Heaphy, & Dungey, ; Goodbody, Coops, Tompalski, Crawford, & Day, ; Kachamba, Ørka, Gobakken, Eid, & Mwase, ; Morley et al, ; Puliti, Ørka, Gobakken, & Næsset, ; Wallace, Lucieer, Watson, & Turner, ). Several reviews have summarized aspects of UAV research in a range of contexts including environmental monitoring (Manfreda et al, ), forestry (Torresan et al, ), ecology (Anderson & Gaston, ) and other domains (De Roos, Turner, Lucieer, & Bowman, ; Singh & Frazier, ). However, no review has yet addressed the application of UAV data to support IAP research even though these data are well suited to this application.…”