scholarly journals Identification of Debris‐Flow Channels Using High‐Resolution Topographic Data: A Case Study in the Quebrada del Toro, NW Argentina

2021 ◽  
Vol 126 (12) ◽  
Author(s):  
A. Mueting ◽  
B. Bookhagen ◽  
M. R. Strecker
Keyword(s):  
High Resolution ◽  
Debris Flow ◽  
Topographic Data ◽  
Flow Channels

scholarly journals Using kites for 3-D mapping of gullies at decimetre-resolution over several square kilometres: a case study on the Kamech catchment, Tunisia

2018 ◽  
Vol 18 (6) ◽  
pp. 1567-1582 ◽  
Author(s):  
Denis Feurer ◽  
Olivier Planchon ◽  
Mohamed Amine El Maaoui ◽  
Abir Ben Slimane ◽  
Mohamed Rached Boussema ◽  
...  
Keyword(s):  
High Resolution ◽  
Aerial Photography ◽  
Airborne Lidar ◽  
Data Set ◽  
Topographic Data ◽  
Independent Field ◽  
Wide Range ◽  
Laser Systems ◽  
High Level

Abstract. Monitoring agricultural areas threatened by soil erosion often requires decimetre topographic information over areas of several square kilometres. Airborne lidar and remotely piloted aircraft system (RPAS) imagery have the ability to provide repeated decimetre-resolution and -accuracy digital elevation models (DEMs) covering these extents, which is unrealistic with ground surveys. However, various factors hamper the dissemination of these technologies in a wide range of situations, including local regulations for RPAS and the cost for airborne laser systems and medium-format RPAS imagery. The goal of this study is to investigate the ability of low-tech kite aerial photography to obtain DEMs with decimetre resolution and accuracy that permit 3-D descriptions of active gullying in cultivated areas of several square kilometres. To this end, we developed and assessed a two-step workflow. First, we used both heuristic experimental approaches in field and numerical simulations to determine the conditions that make a photogrammetric flight possible and effective over several square kilometres with a kite and a consumer-grade camera. Second, we mapped and characterised the entire gully system of a test catchment in 3-D. We showed numerically and experimentally that using a thin and light line for the kite is key for a complete 3-D coverage over several square kilometres. We thus obtained a decimetre-resolution DEM covering 3.18 km2 with a mean error and standard deviation of the error of +7 and 22 cm respectively, hence achieving decimetre accuracy. With this data set, we showed that high-resolution topographic data permit both the detection and characterisation of an entire gully system with a high level of detail and an overall accuracy of 74 % compared to an independent field survey. Kite aerial photography with simple but appropriate equipment is hence an alternative tool that has been proven to be valuable for surveying gullies with sub-metric details in a square-kilometre-scale catchment. This case study suggests that access to high-resolution topographic data on these scales can be given to the community, which may help facilitate a better understanding of gullying processes within a broader spectrum of conditions.

Airborne Structure-from-Motion modelling for avalanche and debris flow paths in steep terrain with limited ground control

2020 ◽  
Author(s):  
Sean Salazar ◽  
Helge Smebye ◽  
Regula Frauenfelder ◽  
Frank Miller ◽  
Emil Solbakken ◽  
...  
Keyword(s):  
High Resolution ◽  
Debris Flow ◽  
Case Studies ◽  
Structure From Motion ◽  
Ground Control ◽  
Surface Model ◽  
Flight Plan ◽  
Surface Models ◽  
Steep Terrain

<p>The availability of consumer remotely piloted aircraft systems (RPAS) has enabled rapidly deployable airborne surveys for civilian applications. Combined with photogrammetric reconstruction techniques, such as Structure-from-Motion (SfM), it has become increasingly feasible to survey large areas with very high resolution, especially when compared with other airborne or spaceborne surveying techniques. A pair of case studies, using an RPAS-based field surveying technique for establishing baseline surface models in steep terrain, are presented for two different natural hazard applications.</p><p>The first case study involved a survey over the entire 1000-m length of a snow-free avalanche path on Sætreskarsfjellet in Stryn municipality in Norway. A terrain-aware, multi-battery flight plan was designed to ensure good photographic coverage over the entire avalanche path and 21 ground control points (GCP) were distributed evenly across the path and subsequently surveyed. More than 400 images were collected over a 0.5 km<sup>2</sup> area, which were processed using a commercial SfM software package. Two digital surface models were reconstructed, each utilizing a different ground control scenario: the first one with the full count of GCP, while the second used only a limited count of GCP, which is more feasible for a repeat survey when avalanche hazard is high. Comparison with data from a pre-existing, airborne LiDAR survey over the avalanche path revealed that the SfM-derived model that utilized only a limited number of GCP diverged significantly from the model that utilized all available GCP. Further differences between the SfM- and LiDAR-derived surface models were observed in areas with very steep slopes and vegetative cover. The same methodology can subsequently be applied during the winter season, after extensive snowfall and/or avalanche events, to deduce relevant avalanche parameters such as snow height, snow distribution and drift, opening of cracks in the snow surface (e.g. for glide avalanches), and avalanche outlines.</p><p>The second case study involved a survey over the entire 1000-m length of a debris flow path at Årnes in Jølster, Norway. The Årnes flow, which caused one fatality, was one of the largest of several tens of debris flows that occurred on July 30, 2019. The flows were triggered by an extreme precipitation event around the Jølstravatnet area. Like with the Sætreskarsfjellet avalanche path case study, a terrain-aware flight plan was established and 24 GCP were distributed and surveyed along the debris flow path. Over 400 images were collected over a 0.3 km<sup>2</sup> area, which were used to reconstruct a high-resolution surface model. Like with the avalanche case study, the SfM-derived model was compared with a pre-existing LiDAR survey-derived digital terrain model. Altitude and volume changes, due to the debris flow event, were calculated using GIS analysis tools.</p><p>The utility of the RPAS survey technique was demonstrated in both case studies, despite difficult accessibility for ground control. It is suggested that a real-time-kinematic (RTK)-enabled workflow may significantly reduce survey time and increase personnel safety by minimizing the number of required GCP.</p><p><strong>Keywords</strong>: Structure-from-Motion, photogrammetry, digital surface model, natural hazards, ground control.</p>

Mapping debris-flow channels in the southern Central Andes using high-resolution topographic data 

2021 ◽  
Author(s):  
Ariane Mueting ◽  
Bodo Bookhagen ◽  
Manfred R. Strecker
Keyword(s):  
High Resolution ◽  
Debris Flow ◽  
Central Andes ◽  
Transport Processes ◽  
Drainage Area ◽  
Flow Channels ◽  
Fluvial Transport ◽  
Stereo Photogrammetry ◽  
Southern Central ◽  
Flow Activity

<p>Resolving Earth’s surface at the meter scale is essential for an improved understanding of topographic signatures generated by debris-flow activity in high-relief mountainous terrains. Here, we explore the applicability and potential of digital elevation models (DEMs) derived from stereo-photogrammetry for debris-flow detection in the southern Central Andes of NW Argentina. Our analysis relies on a high-resolution (3 m) DEM created from SPOT-7 tri-stereo satellite data. We carefully validated DEM quality with ~5000 differential GPS points for an area of 245 km² in the Quebrada del Toro basin within the Eastern Cordillera.<span> </span></p><p>We build upon previous work that suggests that debris flows have a distinct signature in the drainage area and slope framework: debris-flow channels exhibit a nearly constant slope (no channel curvature), while channels dominated by fluvial transport processes show a negative power-law behavior in log-log space. Drainage-area approaches in geomorphic analysis are fast and efficient tools to distinguish signatures of debris-flow and fluvial transport processes, yet they might introduce an averaging bias because upstream areas are analyzed jointly.<span> </span></p><p>For a more precise localization and assessment of debris-flow activity, we evaluate topographic signatures of individual channels. We present a new approach that relies on connected components of similar slope that can be attributed to different transport regimes. Debris-flow activity reflects particularly steep segments of medium connected-component lengths in small drainage areas. The spatial occurrence and lengths of these segments are controlled by geologic and lithologic boundary conditions and we find that the highest debris-flow activity corresponds with steep slopes in areas documented Quaternary tectonic activity and the exposure of pervasively fractured bedrock. Comparing our results to topographic signatures of the corresponding catchments in log-log space, we show that individual channel approaches allow to better detect intra-catchment variability. These are imperative for understanding erosion and sediment-transport processes in the river channel. Since high-resolution data are needed to reliably resolve debris-flow channels, our meter-scale DEMs greatly improve the localization and prediction of debris-flow activity. Thus, for evaluations of recurring hazardous debris-flow activity in extensive, remote, and sparsely vegetated mountainous landscapes, stereo-photogrammetry presents a very suitable and cost-efficient alternative to airborne lidar data.<span> </span></p>

Comparing 1D and combined 1D/2D hydraulic simulations using high-resolution topographic data: a case study of the Koiliaris basin, Greece

2016 ◽  
Vol 62 (4) ◽  
pp. 642-656 ◽  
Author(s):  
Anthi-Eirini K. Vozinaki ◽  
Giasemi G. Morianou ◽  
Dimitrios D. Alexakis ◽  
Ioannis K. Tsanis
Keyword(s):  
High Resolution ◽  
Topographic Data

scholarly journals e-Navigating in highly-constrained waters: a case study of the Vistula Lagoon

2021 ◽  
pp. 1-10
Author(s):  
Adam Weintrit ◽  
Jacek Pietraszkiewicz ◽  
Wiesław Piotrzkowski ◽  
Wojciech Tycholiz
Keyword(s):  
High Resolution ◽  
Global Solution ◽  
Transition Process ◽  
Practical Implementation ◽  
Vistula Lagoon ◽  
Digital Era ◽  
High Resolution Bathymetry ◽  
Marine Navigation ◽  
The Vistula Lagoon

Abstract In recent years the transition of marine navigation to the digital era has been gaining momentum. Implementation of e-Navigation solutions varies from country to country in terms of their priorities, goals, levels and effects. Maritime authorities in Poland have been setting the pace in this transition process, not only in Poland but also in general as a global solution. The most recent example is the planned deployment of a variety of e-Navigation tools in the Vistula Lagoon: from GNSS-RTK Ground-Based Augmentation System, to virtual and synthetic aids to navigation, high-resolution bathymetry and advanced navigational software for piloting. The major objectives of this paper are, first, to summarise recent dynamics in the e-Navigation field, and second, to present a practical implementation of the e-Navigation concept in the Vistula Lagoon area.

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