Monitoring Campsite Soil Erosion by Structure-from-Motion Photogrammetry: A Case Study of Kuro-dake Campsites in Daisetsuzan National Park, Japan

Abstract

Camping in the mountain regions has several negative impacts, including soil erosion in the campsites. In many national parks, efforts to monitor and manage campsite soil erosion are insufficient or even lacking. Owing to the lack of implementation of formal management practices, the current and former Kuro-dake campsites in Daisetsuzan National Park (DNP) have suffered serious soil erosion. To gain more insights into campsite soil erosion, we investigated these two campsites by short-term monitoring through structure-from-motion (SfM) photogrammetry surveys with ground control points (GCPs). These surveys were conducted three times consecutively in the current (2017, 2018, and 2019) and former Kuro-dake campsites (2018, 2019, and 2020). Two sets of digital elevation models (DEMs) of the current and former campsites were produced with the resolutions of 0.015 and 0.025 m, respectively. We detected that the elevation changes exceeded by 0.03-0.04 m, using the DEMs of difference (DoDs) maps. Soil loss around the gullies was observed at each campsite. In the current campsite, soil losses of 2.20 and 0.30 m³ were identified in the periods of 2017-2018 and 2018-2019, respectively. In the former campsite, soil losses of 1.55 and 22.27 m³ were identified during 2018-2019 and 2019-2020, respectively. In addition, a large amount of exposed mineral soil with exposed rocks was observed at each campsite. Various erosion rates obtained in the short-term study indicated the importance of continuous monitoring. High-resolution and high-accuracy topographic products generated from the SfM photogrammetry survey enabled the detection of a small amount of campsite soil erosion and provided a new method to monitor campsite degradation. This study demonstrated that a simple closure of the former campsite in 1992 failed to reduce the impact of soil erosion. In the case of the current and former Kuro-dake campsites, burying the gullies with boulders and setting up boulders or wood fences at the termini of the gullies would be a potential solution to stop or mitigate further erosion. Thus, formal management including monitoring and maintenance of site conditions should be introduced to Kuro-dake as well as other unmanaged campsites in DNP.

Keywords: Daisetsuzan National Park; Soil erosion monitoring; campsite degradation; digital elevation model; national park management; structure-from-motion photogrammetry.