Too much of a good thing? the role of detailed UAV imagery in characterizing large-scale badland drainage characteristics in South-Eastern Spain

ABSTRACT

Some arid and semi-arid areas experience high erosion rates as a consequence of their geological and climatic conditions. This can lead to the development of badland environments characterized by very high drainage densities and the occurrence of a range of distinctive landforms indicative of fluvial dissection. These occur along a spectrum of scales and vary from small-scale arroyos or ramblas to large-scale rills and gullies. Drainage networks comprising the larger landforms can be easily identified using traditional remote-sensing methods, such as satellite or aerial imagery, and are therefore amenable to morphometric analyses. The smaller landforms however are not so easily detected. As a result, studies to date have been largely restricted to their direct field observation which is problematic due to their inherent inaccessibility, often on steep, unstable slopes. However, with the advent and popularization of unmanned aerial vehicles (UAVs), also known as drones, those landforms and geomorphological characteristics, which were once invisible to remotely-sensed aerial data can be incorporated into more detailed research. By using one of the most extensively studied badland locations in Europe – the Tabernas Desert in South-Eastern Spain – this article describes the characterization of a large-scale drainage basin (294 m²) using high definition orthophotography and digital elevation model collected from an unmanned rotorcraft and processed using structure from motion software. Results provide an extremely detailed three-dimensional (3D) reconstruction of the study site, and solve one of the inherent issues working with such large scales, namely the significant difference between 2D and 3D measurements. The article concludes by comparing the results obtained with the UAV with those obtained using existing remotely-sensed imagery and by exploring the challenges experienced when working with bespoke high-resolution aerial imagery, such as when too much detail becomes an issue, and the role of this increasing resolution of observation in geomorphological and hydrological analysis.

KEYWORDS:

• Unmanned aerial vehicles (UAVs)
• drainage density
• badland
• three-dimensional (3D) measurements
• scale

Acknowledgements

The authors would like to thank Keele University’s Faculty of Natural Sciences and the Research Centre for Geography, Geology and the Environment for their support in funding this research.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1. The filter was changed so it recorded near infrared, green, and blue (NGB), and the camera’s firmware was replaced using the Canon Hack Development Kit (CHDK) including a UAV add-on.

Additional information

Funding

The authors would like to thank Keele University’s Faculty of Natural Sciences and the Research Centre for Geography, Geology and the Environment for their support in funding this research.