H056-0025
Development of soil erosion model for decontaminated sandy soils in Fukushima agricultural land

Wednesday, 9 December 2020
Poster
Seigo Fujiwara1, Shohei Kozuka1, Yuichi Onda2, Yoshifumi Wakiyama3, Toshiaki Anzai1 and Hiroaki Kato2, (1)University of Tsukuba, Tsukuba, Japan, (2)University of Tsukuba, Center for Research in Isotopes and Environmental Dynamics, Tsukuba, Japan, (3)Fukushima University, Fukushima, Japan
Abstract:
As a result of decontamination activities, 5 cm of topsoil was removed by heavy machinery from agricultural land and the land was covered with decomposed sandy granite soils. At bare land, vegetation that blocks raindrop impacts at grassland is eliminated and sediment discharge generally increases as soil erosion occurs easily. However, it has been reported that the amount of sediment discharge from bare land after decontamination reduced. This phenomenon has been observed and quantified, but has not been incorporated into soil erosion models. This study aimed to develop a soil erosion model considering the characteristics of decontaminated sandy soils.

Our study was conducted at a decontaminated farmland hillslope in Yamakiya district, Fukushima, Japan. We installed a USLE soil erosion plot (5 m wide and 22.13 m long). The topography in the plot was measured by Terrestrial Laser Scanning (TLS) method and Unmanned Aerial Vehicle based Structure from Motion (UAV-SfM) technique. RFID (Radio Frequency Identification) tags were used to measure the transport distances of soil particles. RFID tags were coated with cement, bronze powder, fluorescent paint and topcoat and had 3 – 5 mm size and 2.0 – 3.0 g cm-3 density. 100 RFID tags were set to the soil surface. Step-like erosion and deposition had been repeated and observed higher erosion on the lower slope position in 2019. Topographic data also showed steeper step structures in the eroded area compared to the depositional area. Transport distance of RFID tags in the step structured area was longer than the interrill area. Therefore, step-like erosion and deposition can be caused by surface runoff enough to detach the surface soil and high sand fraction which results in deposition. In addition, soil erosion process is mainly comprised of rill and interrill erosion. Thus, soil erosion models, such as WEPP and EUROSEM, are limited to these major factors. Recently, visual observation or small-scale experiments has been used to report the step-like erosion process though it has not been incorporated into soil erosion models.

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