In most large-scale distributed hydrological models for flood forecasting, river cross-sections are approximated with rectangles or trapezoids, due to the amount of manual works needed to introduce a large database of surveyed river cross-sections into the models. In this study, we firstly investigated the difficulties for introducing surveyed river cross-sections into the Rainfall-Runoff-Inundation model, a distributed hydrological model, and then we proposed an algorithm for introducing the database of river cross-sections surveyed by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT), into the whole-Japan Rainfall-Runoff-Inundation model (JRRI model). With our proposed algorithm, we introduced in total 26032 cross-sections for the length of 7734.7 km, or 72.9 % of the rivers managed by MLIT, into JRRI model. Secondly, we investigated the effect of cross-section introduction on the accuracy of water level change predictions, through the comparative experiment of the heavy rainfall in the western part of Japan in 2018, with JRRI model with and without surveyed river cross-sections. The metrics of accuracy evaluation (NSE, KGE, RMSE, peak water level ratio, peak water level difference) are improved in the experiment with JRRI model with surveyed river cross-sections, suggesting that the negative baseline biases between observations and experiment outcomes have been eliminated. Especially, average and standard deviation of peak water level differences have been reduced from −2.04 m ± 1.70 m to 0.14 m ± 0.88 m. Overall, this study indicates that introduction of mass database of surveyed river cross-sections into large-scale distributed hydrological models can improve the accuracy of water level predictions for wide regions, and our proposed algorithm may serve it by allowing the introduction of mass database of cross-sections.

 A drag-force model is essential in practical predictions of flows around vegetation/urban canopies since it is too prohibitive to resolve details of the canopy elements and associated fluid motions, especially in environmental and geophysical applications. However, the macroscopic model has a clear bottleneck: how one can obtain a proper distribution of drag coefficient for practical applications. Here particular attention is paid to undisturbed flow as a representative velocity scale required in the empirical formulation relating the drag force to an obstacle with the flow around it. The present study clearly has shown that (i) employing the undisturbed flow as the representative velocity can improve the prediction accuracy, and (ii) the prediction accuracy of the drag-force model becomes deteriorated in nonequilibrium flows. While direct evaluation of the undisturbed flow performed in the current study is impractical in general, the approaching velocity that one can obtain from the disturbed flow field has presented its validity as an alternative to the undisturbed flow to some extent.

 This study constructed a rainfall runoff model corresponding to the characteristics of the Chao Phraya River basin, Thailand and projected future changes of the extreme river discharge in the Chao Phraya River basin with bias-corrected d4PDF rainfall data. As a result, the constructed model well reproduced past several severe flood events; thereby, the probability distribution of annual maximum river discharge at the Nakhon Sawan station between the past experiment in d4PDF and observation was in good agreement at a 4,000 m³/s or more. Future changes of annual maximum peak discharge and flood volume over 2000 m³/s were then projected with three different bias corrections to consider their potential uncertainty. They showed that its change ratio equivalent to a reproduction period of 100 years was 1.55 to 1.63 times for annual maximum peak discharge and 2.23 to 2.27 times for the flood volume, respectively. We could achieve robust impact assessment of climate change on extreme flood with three different bias corrections.

 This paper analyzes the sales recovery process from flood damage after the heavy rain of July 2018 in Japan, based on a questionnaire survey among companies which were affected by the disaster. Using the survival analysis, the recovery time of the sales to the previous level and to several intermediate levels were modeled. Subsequently, the impact of various factors, such as the inundation depth, damage to lifelines, and financing situations, on the rate and degree of sales recovery was quantitatively determined. It was revealed that the magnitude of the impact of each factor often differed between manufacturing and non-manufacturing industries; for example, the duration of water supply damage had a greater impact on the manufacturing industry. Furthermore, it was confirmed that the total sales damage estimated from the evaluation model in this method was comparable to that replied in the survey. Thus, the replies from the companies in the survey to the questions regarding the recovery process and sales were coherent, and the data presentation of the recovery process including unobserved time points by the survival analysis model was appropriate.

 The concentration of sulfide contained in the bottom sediment is important as an indicator of environmental pollution in enclosed coastal seas. Acid-Volatile sulfide (AVS) is widely used as an index of this sulfide concentration in Japan. However, AVS contains a large amount of sparingly soluble bound sulfides that have little effect on living organisms. Therefore, it is considered that the accuracy is low as an environmental index for evaluating the effect on living organisms. On the other hand, there are few measurement examples of dissolved sulfide because it is difficult to collect and analyze many samples in short time . We have devised a method to easily collect pore water from sediments and analyzing the dissolved sulfides contained in this pore water . The accuracy of this analysis method was examined and it was confirmed that sufficiently practical measured values could be obtained. As a result of comparing dissolved sulfide with conventional AVS at the survey site of Hakata Wan enclosed coastal sea by this method, it was found that the dissolved sulfide concentration is a highly independent index different from AVS and is an effective index for evaluating environmental pollution.