Landslides and sinkholes are very common rainfall induced processes in Iran. Landslides cause widespread damage to social and economic infrastructure, as well as to natural features (Sarro et al., 2018). They have indirect and direct influence on major infrastructure, including human habitations, critically impacting land use change and rural to urban migration (Miura, 2019; Thakur et al., 2023). Landslide analysis commonly aims both to detect the failures, and to present the areas affected to generate inventories. These inventories contain information, including the spatial patterns of the landslides/sinkholes, the volume of the failed slope, and the type/data of failure (Mezaal et al., 2018; Wijaya et al., 2023).
Sinkholes Sinkholes develop and expand in a wide range of pedo/eco-climatic landscapes, throughout the world (Poesen, 2018, Bernatek-Jakiel and Poesen, 2018). They have effective impacts on landscape hydrology and have a main role in landscape evolution (Jones and Crane, 1984) including degradation. Meanwhile, this kind of erosion, as a sediment source fingerprint, is related to drainage networks (Bernatek-Jakiel, 2015) and it leads to channel extension (Higgins et al., 1990). It also intensifies annual gully head migration five times more than gully head retreats alone (Crouch, 1983; Daley et al., 2023).
To perform landslide and sinkhole detection, it is important to examine different accessible inventory of preceding hazards, their areal extent, and their map to identify other landslide and sinkhole-prone areas (Agrawal et al., 2017; Chen et al., 2018; Chen et al., 2021). The outputs are extremely reliant on the accuracy of the input data (Ghorbanzadeh et al., 2018).
The advent of advanced remote sensing technology has helped pave an efficient way to map surface changes, particularly changes in the landscapes accruing to extreme climatological events, anthropogenic factors, and ground shaking. Remote sensing is very beneficial as it allows for large-scale mapping of slope failures (Fernández et al., 2016). Remote sensing provides mostly updated data with relatively low resolution. However, “unmanned aerial vehicles (UAVs)” have become a very suitable tool for preparing low-cost, up-to-date, and precise field datasets (Ghorbanzadeh et al., 2019; Zhang et al., 2019). The use of “UAVs” in natural events and urgent situations is developing (Watson et al., 2019; Windrim et al., 2019), and compared to conventional tools, it has the potential to prepare data with better resolution (Brovkina et al., 2018). Recently “UAV” was applied in multi-hazard susceptibility mapping in the same hilly loess region of the current study by Kariminejad et al. (2022) where they reported sinkholes were the most perilous natural hazard, followed by landslides, and headcuts. UAVs have been used on several papers to collect various data for landslide inventories, and piping/headcut monitoring (Lin et al., 2010; Yang et al., 2015; Fernández et al., 2016), but analysis/classification of UAV remote sensing imagery to detect sinkholes and landslides are a less studied existing technique in the present research.
The approaches applied for image analysis/classification are mainly based of pixel and object which is extended for natural hazard detection applying various machine- and deep-learning algorithms (Hölbling et al., 2012; Dou et al., 2015; Mezaal et al., 2018). Recently, deep learning models have been applied for segmentation and classification of “remotely sensed imagery” (Du et al., 2019; Qayyum et al., 2019; Ghadi et al., 2022). In literature, DL-based automated techniques for sinkhole mapping are currently uncommon. Lee et al. (2016) employed light CNNs on thermal far-infrared (FIR) imagery to map sinkholes in the context of urban areas. Hoai et al. (2019) presented a sinkhole tracking approach that takes use of recent developments in CNN transfer learning on FIR imagery, however, it is still inconclusive if such methods would work in very complex semi-arid regions and using conventional (and usually more available) RGB optical imagery. As for landslides, there are few studies that employ VHR UAV photography in conjunction with DL algorithms for automated mapping. For example, Ghorbanzadeh et al. (2019) conducted an intriguing work in which they trained different CNN architectures to map landslides in a densely forested area of the Himalayas. Karantanellis et al. (2021) compared multiple ML models with “object-based image analysis” to determine the boundaries of two rotating slides in Greece. However, this research was performed in the context of only two landslide bodies.
The literature indicates that there are few studies that examine the use of UAV with DL to automatically map landslides and sinkholes, while none of them is tested in a semi-arid environment. The use of Deep learning framework is an innovative method for landslide and sinkhole detection. deep learning framework rather than UAV. Also, similar applications in semi-arid areas are scarce due to extraction difficulties from a little spectrum difference. By applying the “spectral information from the UAV-derived imagery”, in conjunction with the slope dataset, we have illustrated the efficiency of DL-based automated approaches and the benefits and shortcomings of applying topographic dataset, especially slope dataset, for sinkhole and landslide detection. We contrasted the output maps prepared by applying automated approaches with manually extracted sinkhole and landslide inventory datasets created from a variety of sources. The detected sinkholes and landslides were then validated applying “conventional computer vision validation techniques”.