New Method for Automated Quantification of Vertical Spatio-Temporal Changes within Gully Cross-Sections Based on Very-High-Resolution Models

Fran Domazetović,Ivan Marić,Nina Lončar,Ante Šiljeg,Lovre Panđa

doi:10.3390/rs13020321

Abstract

Gully erosion is one of the most prominent natural denudation processes of the Mediterranean. It causes significant soil degradation and sediment yield. Most traditional field methods for measurement of erosion-induced spatio-temporal changes are time and labor consuming, while their accuracy and precision are highly influenced by various factors. The main research question of this study was how the measurement approach of traditional field sampling methods can be automated and upgraded, while satisfying the required measurement accuracy. The VERTICAL method was developed as a fully automated raster-based method for detection and quantification of vertical spatio-temporal changes within a large number of gully cross-sections (GCs). The developed method was tested on the example of gully Santiš, located at Pag Island, Croatia. Repeat unmanned aerial vehicle (UAV) photogrammetry was used, as a cost-effective and practical method for the creation of very-high-resolution (VHR) digital surface models (DSMs) of the chosen gully site. A repeat aerophotogrammetric system (RAPS) was successfully assembled and integrated into one functional operating system. RAPS was successfully applied for derivation of interval (the two-year research period) DSMs (1.9 cm/pix) of gully Santiš with the accuracy of ±5 cm. VERTICAL generated and measured 2379 GCs, along the 110 m long thalweg of gully Santiš, within which 749 052 height points were sampled in total. VERTICAL proved to be a fast and reliable method for automated detection and calculation of spatio-temporal changes in a large number of GCs, which solved some significant shortcomings of traditional field methods. The versatility and adaptability of VERTICAL allow its application for other, similar scientific purposes, where multitemporal accurate measurement of spatio-temporal changes in GCs is required (e.g., river material dynamics, ice mass dynamics, tufa sedimentation and erosion).

Highlights

Research about gully erosion is mostly aimed at quantification of different aspects of spatio-temporal changes in gully geometry, for instance, gully headcut retreat rate [4,15,19,20,21] or changes within gully cross-sections (GCs) [22,23,24,25]
Spatio-temporal changes within GCs include all changes in cross-section geometry caused by erosion and/or accumulation processes that have occurred at the chosen study area, within a certain time period
We propose that the sampling interval should be defined in regard to the research goals, spatial resolution, and accuracy of used digital surface models (DSMs)

Summary

Introduction

Erosion is one of the most prominent natural denudation processes of the Mediterranean [1,2,3,4,5,6,7,8,9], which causes significant soil degradation and sediment yield [10,11,12,13,14,15].Active gullies tend to grow as long as predisposing factors, such as lithology, vegetation cover, land use, terrain attributes, and climatic factors, sustain erosion processes and soil removal [16,17,18]. Erosion is one of the most prominent natural denudation processes of the Mediterranean [1,2,3,4,5,6,7,8,9], which causes significant soil degradation and sediment yield [10,11,12,13,14,15]. Research about gully erosion is mostly aimed at quantification of different aspects of spatio-temporal changes in gully geometry, for instance, gully headcut retreat rate [4,15,19,20,21] or changes within gully cross-sections (GCs) [22,23,24,25]. Spatio-temporal changes within GCs include all changes in cross-section geometry caused by erosion and/or accumulation processes that have occurred at the chosen study area, within a certain time period (e.g., day, month, year).

Methods

Discussion

Conclusion