Multiscale Insights in Landscape Dynamics, Approaches to Erosion, Terrain Analysis, and UAV Technologies
Authors: Doumit Jean 
Published: September 2024

Multiscale Insights in Landscape Dynamics, this book highlights om multiscale problems in digital terrain modeling.I am pleased to present this book, a multiscale terrain analysis experiment on the Lebanese territory based on Digital Elevation Models. In its eight chapters: Chapter 1, Geographic Information Systems analysis based on Digital Elevation Models (DEMs) varies with spatial resolution and dataset production method. DEMs with different spatial resolutions can lead to several results in the analysis. This chapter investigates the effects of DEMs on predicting soil erosion and deposition modeling on Lebanese river basins. Two DEMs at different spatial resolutions from two sources were used to calculate topographic and hydrological parameters for the prediction of the Sediment Transport Index (STI), the erosion-deposition based on Unit Stream Power Erosion, and the Deposition Model (USPED) considering only the topography factors expressed in DEMs. This chapter analyzes hillslope erosion and deposition rates in a GIS to estimate sheet and rill erosion patterns in 13 Lebanese river basins. A correlation analysis is applied to test the degree of similarity between the datasets and the effect of erosion and deposition on spatial resolution.Results indicate that drill erosion and deposition influence high spatial resolution DEMs due to the excellent terrain representation, especially the concave deposition forms.This result shows the increased rill erosivity of channel flow downstream and sediment deposition in concave areas. Chapter 2 objective was to develop multiscale models for the identification of erosion-susceptible areas, exploring the potential of different spatial resolution open-source Digital Elevation Models (DEM) (MERIT, SRTM, ALOS AW3D, and ALOS PALSAR).Topography and terrain derivative parameters significantly impacting erosion were calculated in a Geographical Information System based on geomorphometry algorithms and fuzzy logic functions proposed for evaluating each parameter on erosion risk in Lebanese territories. The objective of this research was to develop four different models based on topography parameters (slope and dissection index) and terrain derivatives (LS factor, profile curvature, stream power index, and topography wetness index) to assess the susceptible areas of erosion on the Lebanese territories and explore the potential of DEMs of different spatial resolutions. Topography parameters and terrain derivatives were computed from the DEM´s elevation, and some fuzzy logic functions were proposed to evaluate the influence of each parameter on erosion risk.The results showed that DEM use is a relatively easy and uncostly method to identify,Qualitatively, the erosion-susceptible areas (ESA) vary with the spatial resolution (scale) and are related to the DEM way of interpolation. From this study, we can conclude that in digital erosion modeling, the correlation varies with the type and resolution of the database used and influences the shape and geometry of the Erosion-Susceptible Areas.Chapter 3, The advanced uses of drones in geosciences, producing very high spatial resolution Digital Surface Models (DSMs) and Digital Ortho Models (DOMs) at various flight heights, led to different digital model scales. Relief plays a vital role in forming Ephemeral Gullies (EG). This Chapter focuses on predicting multiscale EG locations using the compound topographic index (CTI) and analyzing their geometrical characteristics, such as length, depth, and volume, of the three different spatial resolutions that DSM processes from different drone flight heights.Ephemeral Gully extracted from the three flight heights of 120, 240, and 360 meters were compared with each other to understand the effect of generalization at different scales. The results highlight the presence of two scales: a small-scale ephemeral gully expressed by the flight heights of 240 and 360 m and a much smaller scale in the level of microrelief of the flight height of 120 m.Chapter 4, The increasing use of unmanned aerial vehicles (UAV) and the production of high-resolution digital surface models (DSMs) lead to multi-scale results in terrain analysis, prompting new solutions to cope with multi-scale analysis. This chapter tested three indices – the local variance, texture, and fractal dimensions of the same study area with six different spatial resolutions DSM processed from different UAV flight height datasets at 20, 40, 60,120,240, and 360 meters. The higher spatial resolution DSM extracted from 20 meters of flight height was set as a base for a series of correlation analyses between the three indices to study the generalization at different scales. This approach could help understand the spatial resolution changing with scale and could be used for developing hierarchical DSM scale classiﬁcations.Chapter 5, Surface Roughness is a crucial geomorphological variable; no single deﬁnition exists. However, we use surface roughness within geomorphometry to express variability in a topographic surface at a given scale.Obtaining Digital Surface models (DSMs) at different scales and levels before Unmanned Aerial Vehicles (UAVs) appeared rare or impossible. UAVs with advanced photogrammetry software produce high-resolution DSMs. In this chapter, we tested terrain roughness at multiscale DSM generated from six different UAV flight heights of 20, 40, 60, 120, 240, and 360 meters. We tested an easily calculated terrain roughness index (TRI) and the vector roughness measure (VRM), providing an objective quantitative measure of topographic heterogeneity. The TRI and VRM values of the six DSMs were correlated to understand the influence of spatial resolution on terrain heterogeneity. Statistics and regression analysis revealed that the first three high-resolution DSMs saved the degree of roughness, and the last three generated from flight heights of 120, 240, and 360 meters lost the roughness degree with the loss of scale and spatial resolution. Chapter 6, Obtaining Digital Surface models (DSMs) at different scales and levels before Unmanned Aerial Vehicles (UAVs) appeared rare or impossible. UAVs with advanced photogrammetry software can produce high-resolution Digital Surface Models with several spatial resolutions at multiscale levels. In this chapter, we tested the Chord Ratio (ACR) method, decouples rugosity from the slope at multiscale DSM generated from six different UAV flight altitudes of 20, 40, 60, 120, 240, and 360 meters for the study and analysis of the surface to planar areas changes with spatial resolutions. The path of DSM to planar areas should pass by a series of surfaces: a planar slope surface and a boundary data surface to reach the horizontal planar surface.To answer this question, did the transition of multiscale Digital Surface Models to planar areas in the same study area have the same results?After calculating the multiscale rugosity, this chapter studies the similarity between these surfaces at multiscale by correlation and statistical analysis. Visually and statistically, planar areas of all flight heights are very similar. Correlation results showed a significant value difference due to cartographic generalization and spatial resolution.Chapter 7, The advanced uses of unmanned aerial vehicles (UAV) in geosciences, producing very high spatial resolution digital surface models (DSMs), and the various UAV flight altitudes have led to different scales of DSM. This chapter analyzed terrain forms using the Topographic Position Index (TPI), landforms extracted by the Iwahashi and Pike method, and morphometric features of three different spatial resolutions DSM processed from different UAV flight height datasets of the same study area.Topographic position index (TPI) is an algorithm for measuring topographic slope positions and automating landform classiﬁcations; Iwahashi and Pike developed an unsupervised method for the classification of Landforms, and we have used the techniques developed by Peuker and Douglas, a method classifying terrain surfaces into 7 classes.Landforms extracted from the three indices listed above at the three flight heights of 120, 240, and 360 meters were compared with each other to understand the generalization of different scales and to highlight which landforms are more affected by the scale changes. Chapter 8, Unmanned Aerial Vehicles (UAV) have recently become an attractive means of generating high-resolution Digital Surface Models (DSMs), leading to multi-scale results in terrain analysis. This has prompted new solutions to cope with multi-scale analysis.This study has developed a UAV capable of collecting meteorological values by mounting a meteorological sensor.At different flight heights of 50, 100, and 150 meters, aerial sensors collected photos, relative humidity, and temperature values in the Baskinta region (Lebanon). All images were processed using photogrammetric software to produce digital elevation models (DSM) and digital ortho models (DOM).Meteorological data are translated into a Geographic Information System (GIS) to produce digital temperature and relative humidity models.The study's significant results include building reliable high-spatial-resolution Digital Ortho Models (DOM) and Digital Surface Models (DSM) at different flight altitudes. Besides terrain data, humidity and temperature maps (sub-meter pixels) are produced to characterize a horizontal and vertical profile and evaluate the feasibility of mapping.Digital models adopted by GIS technology can yield a treasure trove of information. My message to the readers is: “Think spatially.”