The study focused on how FRP deck responded to tyre loads and aimed to propose a method for light vehicles to cross a FRP pedestrian bridge with an FRP deck. The reinforcing plate was installed on the FRP deck, originally designed for pedestrian use only, to allow for the passage of light vehicles. First, a static loading experiment was conducted using a test specimen with the GFRP reinforcing plate installed on the deck made of GFRP pultruded pipes. The experiment showed that the strength against local loads improved by more than four times with the reinforcement. During the experiment, it was observed in the reinforced specimens that cracks occurred at the corners of a deck pipe. The FEM analysis revealed that the maximum stress occurs at the boundary between the corners and the web in the reinforced deck. It was also found that when the stress in the corners reaches the tensile strength, the strain there shows nonlinear behavior. Finally, based on the results of the FEM analysis, a simple theoretical calculation method for the bending stress in the reinforced deck was proposed.

 Wide-area inundation caused by external flooding can result in catastrophic damage to lives and property. To minimize these impacts, it is essential to provide rapid and accurate information about flooding after its occurrence. Against this backdrop, this study proposes a method for high-speed and accurate flood prediction by combining a high-speed flood analysis technique utilizing Dynamic Mode Decomposition (DMD) with a correction method based on inundation sensor data. A flood prediction system was developed based on the proposed method, and its accuracy was verified using the 2015 Kinugawa River flood event. The results demonstrated that: (1) incorporating the correction method based on inundation sensor data improved flood prediction accuracy, (2) the high-speed flood analysis enabled rapid predictions, and (3) setting an appropriate number of DMD modes to avoid overfitting was critical for ensuring computational stability.

 This study proposes a method for automatically extracting river cross-sectional and longitudinal profile data necessary for flood inundation analysis using digital elevation models (DEM) published by the Geospatial Information Authority of Japan. Using publicly available river centerline data and a heuristic for estimating the positions of the left and right banks, the proposed method automatically determines the extent of the river channel. Although several parameters require tuning during the process, manual intervention is minimized, allowing for practical use even at the individual level. To address the limitation that DEMs do not contain elevations below the water surface, the method estimates the submerged cross-sectional profiles using gradually varied flow calculations. Application of the method to the lower Ishikari River in Hokkaido demonstrates its practicality and confirms that the extracted channel data are consistent with existing cross-sectional survey results.

 This study showed a method to calculate the allowable wave height forecast for determining whether or not offshore construction work can be performed the next day, taking into account the error in the wave forecast predictions. Our previous study showed that construction work was possible if the forecasted wave height multiplied by the safety factor and that added with the RMS of the error were below the critical wave height for work, and its safety margin will be calculated. In this study, the allowable wave height forecast for offshore work the next day was estimated nationwide, taking into account the 90th and 95th percentiles of the forecast error. The forecast error distribution is often assumed to be normal, but in reality, of the 60 locations analyzed, only 17 followed a normal distribution, and the rest had a triangular distribution. Considering this error distribution, the allowable wave height forecast values for 60 locations nationwide were calculated and charts and tables were created.

 At the Port of Kochi, a coastal conservation project against tsunamis has been launched since 2017. This measure is called the “Triple Lines of Defense”. In formulating the “Triple Lines of Defense”, the following three proposals were compared. (1) Strengthening of coastal embankments through coastal construction, (2) Closure of the mouth of Urado Bay by a movable breakwater, and (3) Triple protection planned as an integrated project to strengthen the breakwater through port construction. In this paper, we will clarify the novelty of the Kochi Port “Triple Lines of Defense” project, and the knowledge gained from it and review the study process that led to the triple protection in chronological order.

 Public participation has been introduced in public projects to deepen people’s understanding of the project and to ensure smooth consensus building. However, there are many projects in which consensus building face difficulty, and when it becomes difficult, various social problems are incurred. In order to avoid such a situation, it is helpful to clarify the factors that cause the difficulty of consensus building and the transition process of the consensus building. In this study, we sent a questionnaire survey to the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) and local governments in Japan, and asked them about the projects in which they had encountered difficulties, focusing on the factors that caused the difficulties, and the transition process of those consultations over projects. The results showed that even projects that the consultations seem to be fairly simple can encounter difficulties, and that the causes vary from project to project. In addition, the results indicate that trust in authority can be a critical branch factor in the consultation process, and that procedural fairness factors, such as information disclosure, are fundamentally important in avoiding conflict.

 In our country, building a high-definition digital twin of urban spaces is a national policy, but the development of indoor spaces has not progressed. In recent years, it has become easy to acquire the 3D shape of indoor spaces as point cloud data using LiDAR installed on mobile terminals. By collecting a large amount of point cloud data from mobile terminals through citizen collaboration, it may be possible to complement the indoor spaces of the urban digital twin. However, due to differences in data characteristics such as noise and missing data, accurately registering point cloud data from mobile terminals is challenging. Therefore, this research proposes a method for robustly registering point cloud data, considering these characteristic differences. Comparing it with existing methods, it was confirmed that this method can accurately register point cloud data from mobile terminals, revealing the possibility of utilizing such data to supplement the digital twin.

 To measure land subsidence using satellite SAR data, PSInSAR analysis is effective because it can measure displacement with high accuracy, although it is limited to persistent scattering points only. Although PSInSAR analysis requires a large number of data observed under the same conditions to ensure measurement accuracy, it is possible to use Sentinel-1 SAR data, which does not have high spatial resolution but has a relatively high measurement frequency. In this paper, in the eastern Chiba Prefecture area, where the maximum land subsidence is about 2 cm/year, land subsidence was measured by PSInSAR analysis using Sentinel-1 SAR data of descending orbit for seven years from January 2017 to January 2024, and compared with the results of level surveys conducted once a year. The accuracy of displacement measurement by PSInSAR analysis using Sentinel-1 SAR data was about 5 mm, and the accuracy of displacement velocity measurement was about 1 mm/year, even when reference values were set for each relatively wide area.

 Currently, the method of evaluating the ecological impact of wastewater through biological responses is being utilized as a self-management technique by businesses. While previous research by the authors has clarified the ecological impact of algae due to effluent from Tandoku-syori and Gappei-syori Johkasou including grey water, there has been no case where the toxic substances responsible for these impacts have been identified, particularly for effluent from Tandoku-syori and Gappei-syori Johkasou including grey water. Therefore, in this study, the toxic substances were investigated through toxicity identification evaluation (TIE) from samples that exhibited harmful effects on algae growth. The study focused on 8 cases of Gappei-syori Johkasou effluent, 13 cases of Tandoku-syori Johkasou effluent, and 12 cases of grey water. As a result, it was estimated that oxidizing agents and non-polar organic substances were the inhibitory factors in the Gappei-syori Johkasou effluent, while PO₄-P, NH₃-N, and non-polar organic substances were the inhibitory factors in the Tandoku-syori Johkasou effluent. Regarding grey water, it was estimated that the toxic substances varied depending on the active ingredients in the detergents used in each household, and that metal components, possibly originating from water pipes, were causing inhibitory effects.