This study investigated the relationship between surface and air temperatures for five major crops grown under irrigated conditions (corn, wheat, alfalfa, potatoes, and sugar beets) during the primary cultivation seasons of 2016 and 2017 in the Magic Valley region of Idaho, United States. The surface temperatures of fields and normalized difference vegetation index (NDVI) values were obtained using Landsat-8 thermal imagery, whereas air temperature data were obtained from a nearby weather station. Surface temperatures tended to be higher than air temperatures but approached the air temperature when NDVI values were high. When limited to densely vegetated green fields (NDVI > 0.8), more than 75% of fields had surface temperatures within ±3℃ of the air temperature for all investigated crop types. The surface temperature approached the air temperature when the vapor pressure deficit was large, regardless of the crop type, suggesting that the vapor pressure deficit was a more important factor than the crop type. While further investigations are needed for validation, the proposed approach has the potential to estimate air temperature from satellite-observed surface temperatures with an accuracy of 2℃ without the need to identify crop types, when healthy, densely vegetated agricultural fields are available.

  We investigated the temporal variations in sediment yield from forestry work roads, the occurrence of shallow landslides, and the stability of topsoil on susceptible steep slopes in abandoned forests after plantation clearance within an area of Shirasu (Ito pyroclastic flow deposits) in Kagoshima Prefecture. Forest clearance was conducted in October 2007. Sediment yield from work roads peaked between October 2007 and September 2009, and then decreased over time; this decrease was due to an increase in the rate of water infiltration caused by vegetation spreading onto the surface of the roads, and onto the cutting and filling slopes. We also conducted a field survey to predict the occurrence of shallow landslides on susceptible steep slopes. The minimum values of topsoil thickness in areas where shallow landslides had occurred decreased with increasing slope inclination. The topsoil thickness of steep slopes on which landslides had not yet occurred exceeded the minimum values. Hence, there is a high possibility of the occurrence of shallow landslides on these steep slopes due to future heavy rainfalls.

  The Hazen-Williams formula was generalized in order to use the constants a and b of f ＝ aRe^-b, which represent the curves of the friction loss coefficient f and the Reynolds number Re obtained from hydraulic experiments for each pipe lining. Furthermore, a and b were calculated for each of the various inner surface linings based on the results of hydraulic experiments, and the coefficient C was obtained by a general formula, and it was shown that the values were constant regardless of the Reynolds number. In addition, the relationship between the quadratic curves of constants a and b and the coefficient C due to each inner surface lining was shown, and it was confirmed that there is an effect of viscosity and diameter.

  We set up two types of fishways in the ecological network consisting of river, drainage channel and paddy fields and investigated the fish population in the drainage channel before and after their introduction, as well as the species that used the fishways. Nine species using the fishway were found. Additionally, two of these species bred in the ascended paddy fields. Consequently, the number of species inhabiting the survey sections in the drainage channel increased from four to six, and the populations of four species increased significantly. Furthermore, the fish population increased when the water and the sediment deposition depths were large and the flow velocity was low. We believed that this diversification of fish communities resulted from the establishment of the fishways, which allowed fishes to move between water bodies and breed in paddy fields. Therefore, we revealed that the introduction of fishways can effectively improve fish habitats, and that it is necessary to consider improving the environmental conditions of drainage channels, such as the installation of wand pools and water depth works as well.