Abstract
Climatically driven processes are important controls on the Earth’s surface and on interactions between the hydrological cycle and erosion in drainage basins. As a result, landscape forms such as hillslope topography can be used as an archive to reconstruct historical climatic conditions. Recent progress in the Structure-from-Motion (SfM) photogrammetric technique allows for the construction of high-resolution, low-cost topography data using remote-controlled unmanned aerial vehicle (UAV) surveys. Here, we present the climatic effects on the hillslope erosion rate that can be obtained from the drainage frequency of hillslopes. We quantify the centimeter-scale accuracy of surveys across 72 badland hillslopes in SE Taiwan, which is a tropical monsoon area with an annual precipitation of over 2 m. Our observations indicate that climatic erosion results in a higher drainage frequency and the number of furrows, instead of drainage density. Additionally, the morphometric slope index (MSI) has a strong positive correlation with erosion and its rate but shows a negative correlation with drainage length and a positive correlation with inclination. This suggests that the erosion pattern is due to gravitational mass wasting instead of hydrological erosion. MSI should always be calculated relying on the normalized slope length and is less applicable to landslide-dominated erosion. We, therefore, suggest that UAV-driven digital elevation models (DEMs) are integrated into erosion mapping to aid in identifying erosion patterns. We highlight the unique opportunity for cross-climate zone comparative studies offered by badland landscapes and differential rainfall patterns, with remote sensing techniques and the morphometric slope index.
Highlights
Landscapes evolve under the influence of external drivers and can be used as an archive for reconstructing historical climatic conditions
This study aims to evaluate the development of badland hillslopes in Taiwan using morphometric slope index (MSI), and establish the relationship between MSI and other topographic features
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Summary
Landscapes evolve under the influence of external drivers and can be used as an archive for reconstructing historical climatic conditions. Badlands are a common landscape formation in softer sedimentary rocks and clay-rich sediment and are distributed across climate zones, e.g., Midwestern North America, as well as the Mediterranean and Asian tropical monsoon areas. Badlands lend a unique opportunity to extend the understanding of climatic signatures in landscapes. The hydrological erosion in badlands causes high denudation rates and corresponding geohazards globally [1]. Badlands in Taiwan caused extensive landslides, mudflow [5], and denudation rates of around 9–13 cm per year [6], resulting in the Erren river, with its drainage area mostly in the mudstone badlands, having the highest mean sediment yield in the world of over 105 t/km2/yr [7]. Simple and systematic constraints on erosion help to improve the understanding of interactions of the lithosphere and the hydrosphere in topography
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