scholarly journals Multiscale Very-High Resolution Topographic Models in Alpine Ecology: Pros and Cons of Airborne LiDAR and Drone-Based Stereo-Photogrammetry Technologies

2021 ◽  
Author(s):  
Annie S. Guillaume ◽  
Kevin Leempoel ◽  
Estelle Rochat ◽  
Aude Rogivue ◽  
Michel Kasser ◽  
...  
Keyword(s):  
Species Distribution Modelling ◽  
Airborne Lidar ◽  
Swiss Alps ◽  
The Arctic ◽  
Site Characteristics ◽  
Digital Elevation ◽  
Stereo Photogrammetry ◽  
Arabis Alpina ◽  
Western Swiss Alps ◽  
Very High

The vulnerability of alpine environments to climate change presses an urgent need to accurately model and understand these ecosystems. Popularity in use of digital elevation models (DEMs) to derive proxy environmental variables has increased over the past decade, particularly as DEMs are relatively cheaply acquired at very high resolutions (VHR; <1m spatial resolution). Here, we implement a multiscale framework and compare DEM-derived variables produced by Light Detection and Ranging (LiDAR) and stereo-photogrammetry (PHOTO) methods, with the aims of assessing their relevance and utility in species distribution modelling (SDM). Using a case study on the arctic-alpine plant Arabis alpina in two valleys in the western Swiss Alps, we show that both LiDAR and PHOTO technologies can be relevant for producing DEM-derived variables for use in SDMs. We demonstrate that PHOTO DEMs rivalled the accuracy of LiDAR, putting the current paradigm of LiDAR being the more accurate of the two methods into question. We obtained DEMs at spatial resolutions of 6.25cm-8m for PHOTO and 50cm-32m for LiDAR, where we determined that the optimal spatial resolutions of DEM-derived variables in SDM were between 1 and 32m, depending on the variable and site characteristics. We found that the reduced extent of PHOTO DEMs altered the calculations of all derived variables, which had particular consequences on their relevance at the site with heterogenous terrain. However, for the homogenous site, we found that SDMs based on PHOTO-derived variables generally had higher predictive powers than those derived from LiDAR at matching resolutions. From our results, we recommend carefully considering the required DEM extent to produce relevant derived variables. We also advocate implementing a multiscale framework to appropriately assess the ecological relevance of derived variables, where we caution against the use of VHR-DEMs finer than 50cm in such studies.

scholarly journals Multiscale Very High Resolution Topographic Models in Alpine Ecology: Pros and Cons of Airborne LiDAR and Drone-Based Stereo-Photogrammetry Technologies

2021 ◽  
Vol 13 (8) ◽  
pp. 1588
Author(s):  
Annie S. Guillaume ◽  
Kevin Leempoel ◽  
Estelle Rochat ◽  
Aude Rogivue ◽  
Michel Kasser ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Species Distribution Modelling ◽  
Airborne Lidar ◽  
Swiss Alps ◽  
The Arctic ◽  
Site Characteristics ◽  
Digital Elevation ◽  
Stereo Photogrammetry ◽  
Study Sites ◽  
Very High

The vulnerability of alpine environments to climate change presses an urgent need to accurately model and understand these ecosystems. Popularity in the use of digital elevation models (DEMs) to derive proxy environmental variables has increased over the past decade, particularly as DEMs are relatively cheaply acquired at very high resolutions (VHR; <1 m spatial resolution). Here, we implement a multiscale framework and compare DEM-derived variables produced by Light Detection and Ranging (LiDAR) and stereo-photogrammetry (PHOTO) methods, with the aim of assessing their relevance and utility in species distribution modelling (SDM). Using a case study on the arctic-alpine plant, Arabis alpina, in two valleys in the western Swiss Alps, we show that both LiDAR and PHOTO technologies can be relevant for producing DEM-derived variables for use in SDMs. We demonstrate that PHOTO DEMs, up to a spatial resolution of at least 1 m, rivalled the accuracy of LiDAR DEMs, largely owing to the customizability of PHOTO DEMs to the study sites compared to commercially available LiDAR DEMs. We obtained DEMs at spatial resolutions of 6.25 cm–8 m for PHOTO and 50 cm–32 m for LiDAR, where we determined that the optimal spatial resolutions of DEM-derived variables in SDM were between 1 and 32 m, depending on the variable and site characteristics. We found that the reduced extent of PHOTO DEMs altered the calculations of all derived variables, which had particular consequences on their relevance at the site with heterogenous terrain. However, for the homogenous site, SDMs based on PHOTO-derived variables generally had higher predictive powers than those derived from LiDAR at matching resolutions. From our results, we recommend carefully considering the required DEM extent to produce relevant derived variables. We also advocate implementing a multiscale framework to appropriately assess the ecological relevance of derived variables, where we caution against the use of VHR-DEMs finer than 50 cm in such studies.

scholarly journals Flood vulnerability assessment in the Accra Metropolis, southeastern Ghana

2021 ◽  
Vol 11 (7) ◽  
Author(s):  
Benjamin Wullobayi Dekongmen ◽  
Amos Tiereyangn Kabo-bah ◽  
Martin Kyereh Domfeh ◽  
Emmanuel Daanoba Sunkari ◽  
Yihun Taddele Dile ◽  
...  
Keyword(s):  
Drainage Density ◽  
Geological Structures ◽  
Flood Vulnerability ◽  
Rock Types ◽  
Digital Elevation ◽  
Annual Population ◽  
Density Values ◽  
High Runoff ◽  
Elevation Model ◽  
Very High

AbstractFloods in Ghana have become a perennial challenge in the major cities and communities located in low-lying areas. Therefore, cities and communities located in these areas have been classified as potential or natural flood-prone zones. In this study, the Digital Elevation Model (DEM) of the Accra Metropolis was used to assess the drainage density and elevation patterns of the area. The annual population estimation data and flood damages were assessed to understand the damages and population trend. This research focused primarily on the elevation patterns, slope patterns, and drainage density of the Accra Metropolis. Very high drainage density values, which range between 149 and 1117 m/m2, showed very high runoff converging areas. High drainage density was also found to be in the range of 1117–1702 m/m2, which defined the area as a high runoff converging point. The medium and low converging points of runoff were also found to be ranging between 1702–2563 m/m2 and 2563–4070 m/m2, respectively. About 32% of the study area is covered by natural flood-prone zones, whereas flood-prone zones also covered 33% and frequent flood zones represent 25%. Areas in the Accra Metropolis that fall in the Accraian and Togo series rock types experience high floods. However, the lineament networks (geological structures) that dominate the Dahomeyan series imply that the geological structures in the Dahomeyan series also channel the runoffs into the low-lying areas, thereby contributing to the perennial flooding in the Accra Metropolis.

Very high resolution environmental predictors in species distribution models

2013 ◽  
Vol 38 (1) ◽  
pp. 79-96 ◽  
Author(s):  
Jean-Nicolas Pradervand ◽  
Anne Dubuis ◽  
Loïc Pellissier ◽  
Antoine Guisan ◽  
Christophe Randin
Keyword(s):  
High Resolution ◽  
Species Distribution ◽  
Species Distribution Models ◽  
Environmental Data ◽  
Swiss Alps ◽  
Fine Scale ◽  
Distribution Models ◽  
Model Quality ◽  
Vegetation Height ◽  
Very High

Recent advances in remote sensing technologies have facilitated the generation of very high resolution (VHR) environmental data. Exploratory studies suggested that, if used in species distribution models (SDMs), these data should enable modelling species’ micro-habitats and allow improving predictions for fine-scale biodiversity management. In the present study, we tested the influence, in SDMs, of predictors derived from a VHR digital elevation model (DEM) by comparing the predictive power of models for 239 plant species and their assemblages fitted at six different resolutions in the Swiss Alps. We also tested whether changes of the model quality for a species is related to its functional and ecological characteristics. Refining the resolution only contributed to slight improvement of the models for more than half of the examined species, with the best results obtained at 5 m, but no significant improvement was observed, on average, across all species. Contrary to our expectations, we could not consistently correlate the changes in model performance with species characteristics such as vegetation height. Temperature, the most important variable in the SDMs across the different resolutions, did not contribute any substantial improvement. Our results suggest that improving resolution of topographic data only is not sufficient to improve SDM predictions – and therefore local management – compared to previously used resolutions (here 25 and 100 m). More effort should be dedicated now to conduct finer-scale in-situ environmental measurements (e.g. for temperature, moisture, snow) to obtain improved environmental measurements for fine-scale species mapping and management.

Area and volume quantification of arctic thaw slumps using time-series of digital elevation models generated from radar interferometry

2021 ◽  
Author(s):  
Philipp Bernhard ◽  
Simon Zwieback ◽  
Irena Hajnsek
Keyword(s):  
Probability Density ◽  
Power Law ◽  
Volume Change ◽  
Digital Elevation Models ◽  
Probability Density Functions ◽  
The Arctic ◽  
Density Functions ◽  
Digital Elevation ◽  
Beta Coefficient ◽  
Area And Volume

&lt;p&gt;Vast areas of the Arctic host ice-rich permafrost, which is becoming increasingly vulnerable to terrain-altering thermokarst in a warming climate. Among the most rapid and dramatic changes are retrogressive thaw slumps. These slumps evolve by a retreat of the slump headwall during the summer months, making their change visible by comparing digital elevation models over time. In this study we use digital elevation models generated from single-pass radar TanDEM-X observations to derive volume and area change rates for retrogressive thaw slumps. At least three observations in the timespan from 2011 to 2017 are available with a spatial resolution of about 12 meter and a height sensitivity of about 0.5-2 meter. Our study regions include regions in Northern Canada (Peel Plateau/Richardson Mountains, Mackenzie River Delta Uplands, Ellesmere Island), Alaska (Noatak Valley) and Siberia (Yamal, Gydan, Taymyr, Chukotka) covering an area of 220.000 km&lt;sup&gt;2&lt;/sup&gt; with a total number of 1853 thaw slumps.&lt;/p&gt;&lt;p&gt;In this presentation we will focus on the area and volume change rate probability density functions of the mapped thaw slumps in these study areas. For landslides in temperate climate zones the area and volume change probability density function typically follow a distribution that can be characterized by three quantities: A rollover point defined as the peak in the distribution, a cutoff-point indicating the transition to a power law scaling for large landslides and the exponential beta coefficient of this power law. Here we will show that thaw slumps across the arctic follow indeed such a distribution and that the obtained values for the rollover, cutoff and beta coefficient can be used to distinguish between regions. Furthermore we will elaborate on possible reason why arctic thaw slumps can be described by such probability density functions as well as analyzing the differences between regions. This characterization can be useful to further improve our understanding of thaw slump initiation, the investigation of the drivers of their evolution as well as for modeling future thaw slump activity.&lt;/p&gt;

2020 hurricane impact assessment for the northern Gulf of Mexico: Hurricane Sally and Hurricane Zeta

Shore & Beach ◽  
2021 ◽  
pp. 56-64
Author(s):  
S. McGill ◽  
C. Sylvester ◽  
L. Dunkin ◽  
E. Eisemann ◽  
J. Wozencraft
Keyword(s):  
Change Detection ◽  
Gulf Coast ◽  
Regional Scale ◽  
Shoreline Change ◽  
Airborne Lidar ◽  
Digital Elevation ◽  
The Status ◽  
Northern Gulf Coast ◽  
Elevation Model ◽  
Beach Volume

Regional-scale shoreline and beach volume changes are quantified using the Joint Airborne Lidar Bathymetry Technical Center of Expertise’s digital elevation model products in a change detection framework following the passage of the two landfalling hurricanes, Hurricanes Sally and Zeta, along the northern Gulf Coast in late fall 2020. Results derived from this work include elevation change raster products and a standard set of beach volume and shoreline change metrics. The rapid turn-around and delivery of data products to include volume and shoreline change assessments provide valuable information about the status of the coastline and identification of areas of significant erosion or other impacts, such as breaching near Perdido Key, FL, from Hurricane Sally’s impact. These advanced change detection products help inform sediment budget development and support decisions related to regional sediment management and coastal storm risk management.

scholarly journals On the potential of very high-resolution repeat DEMs in glacial and periglacial environments

2010 ◽  
Vol 4 (1) ◽  
pp. 53-65 ◽  
Author(s):  
J. Abermann ◽  
A. Fischer ◽  
A. Lambrecht ◽  
T. Geist
Keyword(s):  
High Resolution ◽  
Laser Scanning ◽  
Airborne Lidar ◽  
Primary Data ◽  
Glacier Area ◽  
Airborne Laser ◽  
Multi Temporal ◽  
Rock Glaciers ◽  
Data Source ◽  
Very High

Abstract. The potential of high-resolution repeat DEMs was investigated for glaciological applications including periglacial features (e.g. rock glaciers). It was shown that glacier boundaries can be delineated using airborne LIDAR-DEMs as a primary data source and that information on debris cover extent could be extracted using multi-temporal DEMs. Problems and limitations are discussed, and accuracies quantified. Absolute deviations of airborne laser scanning (ALS) derived glacier boundaries from ground-truthed ones were below 4 m for 80% of the ground-truthed values. Overall, we estimated an accuracy of +/−1.5% of the glacier area for glaciers larger than 1 km2. The errors in the case of smaller glaciers did not exceed +/−5% of the glacier area. The use of repeat DEMs in order to obtain information on the extent, characteristics and activity of rock glaciers was investigated and discussed based on examples.

scholarly journals Aerosol distribution around Svalbard during intense easterly winds

2010 ◽  
Vol 10 (4) ◽  
pp. 1473-1490 ◽  
Author(s):  
A. Dörnbrack ◽  
I. S. Stachlewska ◽  
C. Ritter ◽  
R. Neuber
Keyword(s):  
Sea Salt ◽  
Airborne Lidar ◽  
The Arctic ◽  
Aerosol Layer ◽  
Atmospheric Conditions ◽  
Sea Salt Aerosols ◽  
Aerosol Distribution ◽  
Weather Situation ◽  
Low Level Jet ◽  
Aerosol Plume

Abstract. This paper reports on backscatter and depolarization measurements by an airborne lidar in the Arctic during the ASTAR 2004 campaign. A unique weather situation facilitated the observation of the aerosol concentration under strongly forced atmospheric conditions. The vigorous easterly winds distorted the flow past Svalbard in such a way that mesoscale features were visible in the remote-sensing observations: The formation of a well-mixed aerosol layer inside the Adventdalen and the subsequent thinning of the aerosol plume were observed over the Isfjorden. Additionally, mobilization of sea salt aerosols due to a coastal low-level jet at the northern tip of Svalbard resulted in a sloped boundary layer toward north. Mesoscale numerical modelling was applied to identify the sources of the aerosol particles and to explain the observed patterns.

scholarly journals Avalanche situation in Turkey and back calculation of selected events

2014 ◽  
Vol 14 (5) ◽  
pp. 1145-1154 ◽  
Author(s):  
A. Aydin ◽  
Y. Bühler ◽  
M. Christen ◽  
I. Gürer
Keyword(s):  
Simulation Software ◽  
High Mountain ◽  
Identification Algorithm ◽  
Black Sea Region ◽  
Mountain Ranges ◽  
Digital Elevation ◽  
Back Calculation ◽  
Elevation Model ◽  
Very High ◽  
Rapid Mass

Abstract. In Turkey, an average of 24 people die in snow avalanches every year, mainly in the eastern part of Anatolia and in the eastern Black Sea region, where high-mountain ranges are close to the sea. The proportion of people killed in buildings is very high (87%), especially in comparison to other European countries and North America. In this paper we discuss avalanche occurrence, the climatic situation and historical avalanche events in Turkey; in addition, we identify bottlenecks and suggest solutions to tackle avalanche problems. Furthermore, we have applied the numerical avalanche simulation software RAMMS (rapid mass movements simulation) combined with a (digital elevation model) DEM-based potential release zone identification algorithm to analyze the catastrophic avalanche events in the villages of Üzengili (Bayburt province) in 1993 and Yaylaönü (Trabzon province) in 1981. The results demonstrate the value of such an approach for regions with poor avalanche databases, enabling the calculation of different scenarios and the estimation of run-out distances, impact pressure and flow height.

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