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Sand movement analysis of the Tottori Sand Dunes using aerial photogrammetry by UAVs
Tadaomi SAITO, Takayuki KAWAI, Yoshiki TAKAHARA, Dai NAGAMATSU, Koji Inosako
Journal of Arid Land Studies ( 日本沙漠学会 ) 34 ( S ) 87 - 91 2024年 [査読有り]
研究論文（学術雑誌）
<p>The Tottori Sand Dunes, located along Japan’s Sanin Coast, are a UNESCO Global Geopark and a popular tourist attraction with millions of annual visitors. Monitoring of environmental conditions including sand movement is needed for the protection and utilization of the dunes. The objectives of this paper were (i) accuracy evaluation of aerial photogrammetry using three UAVs (Unmanned Aerial Vehicles: Drones) and two types of structure from motion (SfM) software and (ii) sand movement analysis in the dunes using the best results. For each flight, about 1800 vertical photographs (side overlap: 60%, and top-bottom overlap: 80%) were taken at altitudes of approximately 100 m above ground level using three UAVs for a 1500 km<sup>2</sup> area of the dunes. The obtained images were processed using two SfM software, PhotoScan Professional (currently Metashpae: Agisoft) and Pix4Dmapper (Pix4D), for building 3D models. The position data of survey piles in the dunes were used as the GCP (ground control point) setting for image processing and model evaluation. The results revealed that the accuracy of the models was significantly affected by the difference in the SfM software but was not greatly influenced by the difference in UAVs. The models generated from PhotoScan generally curved and had larger errors at the center parts and around the edges of the models (average RMSE=1.74 m), while the models generated from Pix4Dmapper had smaller errors throughout the entire areas (average RMSE=0.38 m). From the comparison of the models obtained from Pix4Dmapper, the characteristics of sand movement such as the movement of the ridge line towards the inland area, were elucidated in the dunes from 2016 to 2018.</p>
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Improving satellite-based global rainfall erosivity estimates through merging with gauge data
Fenta A.A.
Journal of Hydrology ( Journal of Hydrology ) 620 2023年05月
研究論文（学術雑誌）
Rainfall erosivity is a key factor that influences soil erosion by water. Rain-gauge measurements are commonly used to estimate rainfall erosivity. However, long-term gauge records with sub-hourly resolutions are lacking in large parts of the world. Satellite observations provide spatially continuous estimates of rainfall, but they are subject to biases that affect estimates of rainfall erosivity. We employed a novel approach to map global rainfall erosivity based on a high-temporal-resolution (30-min), long-term (2001–2020) satellite-based precipitation product—the Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (GPM-IMERG)—and mean annual rainfall erosivity from the Global Rainfall Erosivity Database (GloREDa) stations (n = 3286). We used a residual-based merging scheme to integrate GPM-IMERG-based rainfall erosivity with GloREDa using Geographically Weighted Regression (GWR). The accuracy of the GWR-based merging scheme was evaluated with a 10-fold cross-validation against GloREDa stations. Based on GPM-IMERG-only, the global mean annual rainfall erosivity was estimated to be 1173 MJ mm ha−1 h−1 yr−1 with a standard deviation of 1736 MJ mm ha−1 h−1 yr−1. The mean value estimated via GPM-IMERG merged with GloREDa was 2020 MJ mm ha−1 h−1 yr−1 with a standard deviation of 3415 MJ mm ha−1 h−1 yr−1. Overall, GPM-IMERG-only estimates underestimated rainfall erosivity. The underestimations were greatest in areas of high rainfall erosivity. The accuracy of rainfall erosivity estimates from GPM-IMERG merged with GloREDa substantially improved (Nash-Sutcliffe efficiency = 0.83, percent bias = −2.4%, and root mean square error = 1122 MJ mm ha−1 h−1 yr−1) compared to estimates by GPM-IMERG-only (Nash-Sutcliffe efficiency = 0.51, percent bias = 27.8%, and root mean square error = 1730 MJ mm ha−1 h−1 yr−1). Improving satellite-based global rainfall erosivity estimates through integrating with gauge data is relevant as it can contribute to enhancing soil erosion modeling and, in turn, support land degradation neutrality programs.
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Occurrence of wet and dry spells of rainfall in Bagan, Myanmar
Yasuda H.
Journal of Earth System Science ( Journal of Earth System Science ) 132 ( 1 ) 2023年03月
研究論文（学術雑誌）
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Yasuda H.
Journal of Great Lakes Research ( Journal of Great Lakes Research ) 48 ( 2 ) 468 - 477 2022年04月 [査読有り]
研究論文（学術雑誌） 国際共著
Water level change of Lake Tana, the source of the Blue Nile was analyzed. Correlations between the water level change and global sea surface temperature (GSST) were calculated and teleconnections were found. Prediction of water level was performed using a recurrent artificial neural network model. First, the seasonal change of water level was divided into three phases, the rising, recession 1, and recession 2 phases. The water level increased during the rising phase, decreased rapidly during the recession 1 phase, and decreased at a uniform rate during the recession 2 phase. To find teleconnections of the water level change in the rising phase with GSST, correlations between the level change and GSST were calculated. Sea regions on the Pacific Ocean indicated significant correlations with the level change at lag 0–1 month and lag 6–7 months. There was a strongly correlated sea zone over the western Pacific Ocean at time lags of 6–7 months. To predict water level change, SST time series of the correlated zone was applied to a recurrent neural network model. Predictions of changes of the rise of the water level of Lake Tana during the rainy season from teleconnections with SSTs via the neural network model simulated the observed changes well (r = 0.795). Prediction of the changes of Lake Tana's water level with a lead time of 6–7 months can greatly facilitate management of the lake's water resources.
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Teleconnection of rainfall time series in the central Nile Basin with sea surface temperature
Yasuda H.
Paddy and Water Environment ( Paddy and Water Environment ) 16 ( 4 ) 805 - 821 2018年10月 [査読有り]
研究論文（学術雑誌） 国際共著
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An integrated modeling approach for estimating monthly global rainfall erosivity
Fenta A.A.
Scientific Reports ( Scientific Reports ) 14 ( 1 ) 2024年12月
Modeling monthly rainfall erosivity is vital to the optimization of measures to control soil erosion. Rain gauge data combined with satellite observations can aid in enhancing rainfall erosivity estimations. Here, we presented a framework which utilized Geographically Weighted Regression approach to model global monthly rainfall erosivity. The framework integrates long-term (2001–2020) mean annual rainfall erosivity estimates from IMERG (Global Precipitation Measurement (GPM) mission’s Integrated Multi-satellitE Retrievals for GPM) with station data from GloREDa (Global Rainfall Erosivity Database, n = 3,286 stations). The merged mean annual rainfall erosivity was disaggregated into mean monthly values based on monthly rainfall erosivity fractions derived from the original IMERG data. Global mean monthly rainfall erosivity was distinctly seasonal; erosivity peaked at ~ 200 MJ mm ha−1 h−1 month−1 in June–August over the Northern Hemisphere and ~ 700 MJ mm ha−1 h−1 month−1 in December–February over the Southern Hemisphere, contributing to over 60% of the annual rainfall erosivity over large areas in each hemisphere. Rainfall erosivity was ~ 4 times higher during the most erosive months than the least erosive months (December–February and June–August in the Northern and Southern Hemisphere, respectively). The latitudinal distributions of monthly and seasonal rainfall erosivity were highly heterogeneous, with the tropics showing the greatest erosivity. The intra-annual variability of monthly rainfall erosivity was particularly high within 10–30° latitude in both hemispheres. The monthly rainfall erosivity maps can be used for improving spatiotemporal modeling of soil erosion and planning of soil conservation measures.
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半乾燥草原地帯における植生を指標とした井戸掘削地点絞り込み手法の開発
尾留川 侑里, 河合 隆行, 坂中 伸也, 土屋 竜太, 高槻 成紀, ツェレンプレブ バトユン, 森永 由紀
日本地理学会発表要旨集 ( 公益社団法人 日本地理学会 ) 2024a ( 0 ) 180 2024年
<p>半乾燥草原地帯で遊牧民が日常的に利用する水資源は地下水である。その地下水資源の現状を把握することは，資源管理の観点から重要である。しかし，現状の地下水探査技術には大型機器が必要であり，経済的にも作業的にも困難である。本研究では植生を指標として， 広大な半乾燥草原地帯の中から浅層地下水や土壌水分の状態を簡易かつ包括的に確認することを目的とする。</p><p> モンゴル国ブルガン県モゴド郡は，亜寒帯湿潤気候と半乾燥草原地帯の両気候帯の中間地域に位置し，植生豊かな地域である。モゴドの中で明らかに地下水が存在する地点に2400 m測線を設けた。測線内には湿潤平地，乾燥平地，ガレ場斜面が含まれており，これらの地形にはそれぞれ特徴的な植生が自生している。</p><p> 調査地には計72種が出現した。バイオマス指数を用いたクラスター分析の結果により28地点を3群に分類した。クラスターA群は乾燥した平坦地が，クラスターB群には湿潤の平坦地が，クラスターC群には斜面が該当する。CART法によって作成した分類樹木では，B群の特徴となる種は<i>Potentilla anserina,</i> <i>Poa attenuata</i>の2種であることが分かった。また，これらの種はA群とC群では出現しない。</p><p> 電気探査の解析結果とクラスター分類を照らし合わせると，湿潤平坦地のB群では，地下水面が地表面付近の浅層に到達している。A群では地表面は乾燥し高比抵抗であるが，深度約10mで連続した地下水面が存在している。これらの結果から，地下水資源へのアクセスを考慮する場合，周囲にB群が確認できるA群を最も優先的に掘削するべき植生指標と判断出来る。</p><p> 以上の結果から，植生を用いて地中の水文環境を推察することに成功した。今後は観測事例を増やし，さらなる推定精度の向上を目指す。</p>
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An integrated framework for improving watershed management planning
Fenta A.A.
Environmental Research ( Environmental Research ) 236 2023年11月
Proper land use and management (LUM) planning is pivotal to curbing land degradation and ensuring sustainable use of limited watershed resources. Despite decades of research and development efforts, land degradation remains a serious environmental problem in many parts of the world. Issues regarding the sustainability of current LUM initiatives are due to poor linkages between the ecological and socio-economic dimensions of LUM decisions, and an integrated framework allowing LUM interventions to be properly planned and implemented is lacking. In this study, we developed an integrated framework to identify, evaluate, and propose LUM alternatives with ecological and socio-economic benefits. The framework comprises six components: (i) identification of land use problems and setting of objectives, (ii) identification of the best-performing land use-based integrated solutions, (iii) formulation of LUM alternatives and modeling of key indicators, (iv) cost-benefit analysis, (v) evaluation of the LUM alternatives with stakeholders engagement, and (vi) communication of the LUM alternatives to relevant stakeholders to obtain institutional and financial support for implementation. To demonstrate the use of this framework, we conducted a case study in the Aba Gerima watershed of the Upper Blue Nile basin in Ethiopia. This study used extensive plot- and watershed-scale observations (2015–2019) obtained under both conventional and improved sustainable land management practices. We analyzed changes in runoff, soil loss, soil organic carbon (SOC) stock, and land productivity of five LUM alternatives as compared to a baseline scenario (existing farming practices). The results showed that the LUM alternatives reduced runoff by 11–71% and soil loss by 66–95%, and SOC stock and watershed-scale land productivity were improved by 36–104% and 48–134%, respectively. Evaluation of LUM alternatives by stakeholders, including land users, policy makers, and researchers, produced divergent results. In particular, land users prioritized implementation of sustainable land management practices without altering existing land uses. The integrated framework developed in this study can serve as a valuable tool for identifying, evaluating, and proposing LUM alternatives and facilitating decision-making in planning and implementation of LUM practices in watersheds experiencing land degradation.
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Construction of Virtual Reality Space of the Tottori Sand Dunes using UAVs
SAITO Tadaomi, KAWAI Takayuki, OKASHITA Kisumi, INOSAKO Koji
沙漠研究 ( 日本沙漠学会 ) 32 ( S ) 187 - 191 2022年12月
<p>The Tottori Sand Dunes, located along Japan’s Sanin Coast, are a UNESCO Global Geopark and a popular tourist attraction with millions of annual visitors. However, the tourism opportunities offered by them are hampered by such problems as severe meteorological conditions and vast, undulating landscapes. Constructing a virtual reality (VR) space might be one solution to these problems. Recently, a technique that combined unmanned aerial vehicles (UAVs or drones) and structure from motion (SfM) photogrammetry has been attracting attention for generating 3D models. The main objective of this paper is to construct a VR space of the Tottori Sand Dunes using 3D models generated from UAVs. Another objective is to examine optimal photography conditions and model generation conditions to create beautiful but small 3D models for the construction of a VR space. Two types of UAVs were used to acquire the image data. Metashape (Agisoft) was used as the SfM software for data processing. A cross-platform game engine called Unity (Unity Software Inc.) was used to construct the VR spaces. VIVE Cosmos (HTC) was employed as a head-mounted display (HMD) with controllers for the VR system. As the results, the VR space was successfully constructed in Unity using a 3D model generated by a combination of UAV techniques and SfM photogrammetry. The optimal photography and model generation conditions were determined and used to generate beautiful 3D models for the construction of a VR space.</p>
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Yasuda H.
Geofizika ( Geofizika ) 39 ( 1 ) 1 - 20 2022年
In the central dry zone of Myanmar, the mean annual rainfall is less than 1000 mm. Although rainfed agriculture is commonly practiced there, the feasibi?? lity of rainfed farming is compromised by the large fluctuations of rainfall and the frequent occurrence of dry years. The monthly distribution of rainfall follows a bimodal pattern. The intensity of the monsoonal rainfall from May to October is characterized by two peaks, an early peak (May???June) and a late peak ( August??? October), separated by the inter ??monsoon (July). The return times of dry and wet years make management of rainfed agriculture problematic. There is very little correlation between the early and late monsoonal rainfall (r = ???0.257). However, monsoonal rainfall is teleconnected to sea surface temperatures (SSTs) in certain areas of the Pacific Ocean in real time. Furthermore, at lag times of 6???9 months, there are teleconnections between the early monsoonal, inter ??monsoonal, and late monsoonal rainfall and SSTs in certain areas of the Indian Ocean and Atlantic Ocean. We used an Elman artificial neural network model to predict early monsoonal, inter ??monsoonal, and late monsoonal rainfall based on teleconnections with SSTs in the Indian and Atlantic oceans 6???9 months before the rainfall occurred. The correlation coefficient between the predicted and observed rainfall exceeded 0.7 in all three cases.
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複合的物理探査による農業用施設及び地盤中の流体・物質移動の高速可視化技術の開発
基盤研究(A)
研究期間: 2016年04月 - 2019年03月 代表者: 黒田 清一郎, 河合 隆行, 森井 俊廣, 佐藤 源之, 塩谷 智基, 斎藤 広隆, 藤巻 晴行
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複合的物理探査による農業用施設及び地盤中の流体・物質移動の高速可視化技術の開発
基盤研究(A)
研究期間: 2016年04月 - 2019年03月 代表者: 黒田 清一郎, 河合 隆行, 森井 俊廣, 佐藤 源之, 塩谷 智基, 斎藤 広隆, 藤巻 晴行
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複合的物理探査による農業用施設及び地盤中の流体・物質移動の高速可視化技術の開発
基盤研究(A)
研究期間: 2016年04月 - 2019年03月 代表者: 黒田 清一郎, 河合 隆行, 森井 俊廣, 佐藤 源之, 塩谷 智基, 斎藤 広隆, 藤巻 晴行
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モンゴルのアイラグ（発酵馬乳）の製造法の地理学的・生態学的検証
基盤研究(B)
研究期間: 2015年04月 - 2019年03月 代表者: 森永 由紀, 高槻 成紀, 尾崎 孝宏, 河合 隆行, 石井 智美, 田村 憲司, 上村 明, 多田 泰之, 伊藤 健彦, 小宮山 博, 篠田 雅人, ツエレンプレブ バトユン, 土屋 竜太, 浅野 眞希, 竹内 菜穂子
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モンゴルのアイラグ（発酵馬乳）の製造法の地理学的・生態学的検証
基盤研究(B)
研究期間: 2015年04月 - 2019年03月 代表者: 森永 由紀, 高槻 成紀, 尾崎 孝宏, 河合 隆行, 石井 智美, 田村 憲司, 上村 明, 多田 泰之, 伊藤 健彦, 小宮山 博, 篠田 雅人, ツエレンプレブ バトユン, 土屋 竜太, 浅野 眞希, 竹内 菜穂子
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Influence of polacrylamede application on structure stability of Ethiopian soils
Fujimaki H, Kawai T, Mamedov A.L
10th International congress on the Soil resources and environment conservation 2018年10月 - 2018年10月
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Aerial photogrammetry and three-dimensional modeling of the Tottori sand dune using UAV
Saito, T, Kawai, T, Inosako, K, Yasuda, H
Desert Technology 13 International Conference 2018年03月 - 2018年03月
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Estimation of hydrogeological structure combining groundwater-aeration-sound, ground-penetrating- radar and resistivity tomography in semi-arid area
Takayuki Kawai, Motoyuki Sato, Yasuyuki Tada, Ryota Tsuchiya, Yuki Morinaga, Masato Shinoda, Seiichirou Kuroda, Hiroshi Yasuda
Desert Technology 13 International Conference 2018年03月 - 2018年03月
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NMR and GPR sounding to characterize groundwater aquifer in sand dunes area
Chisato Konishi, Kunio Aoike, Takayuki Kawai, Seiichiro Kuroda
Symposium on the Application of Geophysics to Engineering and Environmental Problems 2017 2017年03月 - 2017年03月