The heavy rain event of July 2018 had left devastating damages by flood and sediment disaster. The failures of important structures, traffic and infrastructure networks had expanded the damage synergistically in space and time, exposing interdisciplinary issues. One of the most important missions of JSCE is to summarize and disseminate the lessons from the disasters for solving problems in social infrastructure in the future. This special issue includes valuable information obtained in disaster investigations from different disciplinary points of view, aiming to contribute the growth and development of interdisciplinary academic fields of civil engineering.

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 In this study, we detect detours of commercial vehicles during heavy rain in western Japan using machine learning technology, and analyze the cause of the detours. During the heavy rain of 2018 in western Japan, road regulation caused by this rain occurred over a wide area. There is probe trajectories generated by GPS which reveals the detour route taken. The necessity of taking the detour is one of the traffic failures caused by disasters. However, in order to reveal the detour, it is necessary for the road administrator to visually check and analyze the probe vehicle trajectory, which requires a lot of labor. So, in this study, we tried to detect detours during disasters by learning the probe vehicle trajectory under normal circumstances using a One-class support vector machine (OCSVM). As a result of detecting detours for Shikoku, even if the nearest detour route was accessible, we identified vehicles using more distant detour routes. As a result of analyzing the cause of the detour, it was suggested that the “risk” of the traffic failure is one factor.

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 It is important to measure the seepage flow behavior in the river levee caused by heavy rainfall and flood for estimating the safety factor of the river levee related to seepage. In this paper, the long term continuous field observations of seepage flow occurred in the leaking river levee during flood were carried out. Changes in pore water pressure at the local scale in the river levee and the permeable base layer were measured by using several driven piezometers to confirm the existence of seepage flow line or water level caused by a fluctuation of the water level in the river. Soil water contents at the different depths were measured by using several intrusive soil moisture probes. Observed soil water contents with time were used to estimate the movement of soil water storage of the back slope of the river levee. Through the observed variations in pore water pressure and soil water contents, the specific features of the seepage behavior in the leaking river levee are investigated.

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 Since the Great Hanshin earthquake, disaster volunteers have received increasing attention. Specifically, importance is placed on disaster volunteer efforts by university students. Thus, in this study we aimed to understand the actual situation in terms of disaster volunteer actions among Ehime University students during the floods of July 2018, and to clarify the relationship between university students’ disaster volunteer efforts and sense of self efficacy. Survey results revealed that activities in daily university life have an effect on the basic skills of working adults, and are also linked to changes in disaster volunteer mobilization through a sense of self efficacy and awareness of one’s importance. This suggests that creating and supporting an environment in which students can devote themselves to extracurricular activities such as clubs, along with regular university activities, is linked to university students' increased participation in disaster volunteer actions when future disasters occur.

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 This study investigated the rainfall characteristics in Okayama prefecture and the related flood damages in the Asahi River basin because of the Heavy Rain Event of July 2018, using statistical analyses, field observations, and numerical simulations. Results demonstrated the following findings. The return period of the severe rainfall event is over 50 years for the rainfall duration of over 24 hours. The massive flood inundations were caused by the riverbank failures because of the overbank and seepage flows observed at the prefecture-managed river sections in the Asahi River basin. The improvement project completed almost at the bifurcation point in the lower Asahi River presumably prevented the Okayama city from suffering flood damages, judged from the numerical results of the 2018 flooding and previous records of damages attributable to flooding of the same discharge.

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 Heavy rain in July, Heisei 30 caused an enormous damage mainly around Western Japan. Otsuki-cho, Hata-gun, Kochi-prefecture also suffered human damage by sediment disasters. The sediment disasters of this town included debris flows from Zero-order basins. The flows consisted mainly of rapidly flowing debris and slided farther than in the case of surface failures reaching even the flat fields. Zero-order basins, however, are defined as steep slopes. The countermeasures against sediment flows are not applicable for them. Our research suggests these facts as conditions for Zero-order basins which cause debris flowing ; stream bed deposit is over 2 meters deep, streams is over 100 meters long. Slope of bed stream is over 30 degrees, visible water catchment area is above the Zero-order basins. From the fact that the debris flows occurred at the Zero-order basins with the ratio of opening to depth over 22 percents, it became clear the ratio of opening to depth maybe one of the conditions for defining the Zero-order basins causing debris flows.

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 In recent years, debris flow due to heavy rainfall has been frequent. In addition, the large amount of sediment is transported by debris flow flows into rivers, causing sediment-flood inundations with increasing damage. In the heavy rainfall in July 2018, it rained for a long time and over a wide area, and debris flows occurred at many places in Hiroshima prefecture. The existing earth and sand disaster alert information has not taken into consideration of rainfall on each slope and topographic and ground information. The spatial grasp of debris flow occurrence and quantitative risk assessment has not been established yet. In order to solve this problem, in this paper, the rainfall data of XRAIN with good spatial resolution and the feature of the slope failure site were examined for each mountain slope during heavy rainfall events. This paper also discussed the reliability of rainfall index R’ to the heavy rainfall with strong long-term precipitation in July 2018, which is different from previous disasters due to the heavy rainfall with strong short-term precipitation, such as August 2014 and June 1999.

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 The heavy rain occurred in July 2018 induced huge damage west Japan area including Hiroshima, Okayama, Ehime, Yamaguchi. Noro-gawa River basin in Hiroshima Prefecture was also damaged by the heavy rain. The synergistic disaster between land failure disasters and flood disasters can be found in Hiroshima Prefecture. This disaster was a typical example of synergistic disasters. This paper reports the consideration of the influence of sedimentations and driftwoods on Noro-gawa dam, flooding in the downstream basin region of Noro-gawa River.

 The main results of this paper are summarized as follows: 1) The damage of Noro-gawa dam, Noro-gawa River and Nakahata-gawa River were enhanced by the accumulation of sedimentations and driftwoods. On the other hand, the river blockade by driftwoods at the bridge in Nakahata-gawa River induced the flooding. 2) the estimated maximum inflow discharge to Noro-gawa dam and outflow discharge from Noro-gawa dam were 179m³/s and 173m³/s, respectively. 3) The inflow discharge to Noro-gawa dam was estimated, excluding influence of sediment discharge and driftwoods. 4) The estimated river discharges during the flooding were 180m³/s at the downstream of Noro-gawa dam, 230m³/s at Fujinami water level observation station and 430m³/s behind the connection point of two branch rivers.

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 During heavy rain in July 2018, record flood occurred in the Monobe River (Monobegawa) like other rivers. Fortunately, no serious inundation occurred, but the importance of prior measures for flood control and the difficulty of encouraging evacuation behavior in rivers with low flood frequency were recognized again.

 In this report, we report the summary of the flood and the flood forecast, the possibility that inundation damage had occurred without river improvement in recent years, the evacuation behavior during heavy rain in July, 2018, and the resident awareness survey in the Monobe River (Monobegawa). In addition, this report mentions the importance of flood countermeasures that combine hard (structural) measures and soft (non-structural) measures.

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 This paper explores variation properties of trip generation, trip attraction, intra-zonal trips, and travel time under transport network disruption in Tenno district happened in July 2018 due to landslides. The empirical results obtained by using multiple passive transport data show that (1) traffic volume per hour on the National Route 31 went down to around 300 vehicles at maximum due to a large number of short-distance trips traveling between affected area and a disaster response base, (2) recovery of train line did not really reduce the travel time on the National Route 31, and the average travel time had been 1.5 times longer compared to that before the disaster for more than two months after the disaster, and (3) travel time variability, which could not be explained by day of week and time of day, had been dominant for the first one month after the disaster.

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 In the heavy rainfall event in July 2018, long-lasting, widespread and weak rainfall caused much total rainfall over the broad area of mainly western Japan resulting in a big damage including over 200 deaths. As a result of analyzing a 20-km resolution huge ensemble database d4PDF20, the atmospheric circulation pattern that is similar to that of this event would not be expected to increase, but the amount of water vapor inflow into Japan will increase in the future climate. In addition, as a result of analyzing a 5km-resolution regional climate model RCM05, it is indicated that relatively intensive rainfall, that could be a trigger of disasters like landslide or flooding in this event, will become more intensive in the future. To sum up, the same atmospheric circulation pattern as that of this heavy rainfall event may not frequently occur, but if the same type of heavy rainfall will occur in the future, that event has possibility of causing much more total rainfall amount compared with last year’s event and the damage also possibly become bigger.

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 In The Misasa-gawa River (in the Ota-gawa River basin) overflowed and bank erosion etc. occurred during the heavy rain event of July 2018. In The Nenotani-gawa River (in the Ota-gawa River basin) was spared a great deal of damage by river improvement. In this paper, we report a damage and emergency restoration in the Ota-gawa River basin and examined the effect of river improvement in The Nenotani-gawa River.

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 On July 2018, a series of slope failures and debris flows occurred in wide area of Hiroshima Prefecture due to torrential rains. This event costed 133 lives. Besides this event, many landslide disasters were repeated in Hiroshima Prefecture. In recent years, serious landslide disasters occurred on 29^th June 1999 and 20^th August 2014, and they led to 32 and 77 deaths, respectively. In this paper, the profile of disaster, rainfall condition and rainfall index for landslide disaster, geological and geotechnical profiles of July 2018 landslide disaster were compared with ones of 6.29, 1999 disaster and 8.20, 2014 disaster, and the characteristics of July 2018 landslide disaster were summarized.

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 The heavy rain in July 2018 caused debris flow and river flooding in Higashi river, Shimata river system in the Osogoe area of Iwakuni City, Yamaguchi Prefecture. In this study, we conducted a record of the disaster situation and field survey using the UAV after the disaster in the Osogoe area. In addition, we conducted ortho-images production at the time of disaster, debris flow analysis, runoff analysis, and flood analysis. As a result, it is clarified that the flood in Osogoe district was caused by significant aggradation of riverbed due to the sediment and driftwood carried by the debris flow into the river and the obstruction of the flooding water due to driftwoods being caught in the pier. Moreover, there is a high possibility that river flooding would not occur if debris flow did not occur. Therefore, our results suggest that we need river management that takes into account the possibility of river flooding due to the complex disaster in river sections, where debris flow is assumed to flow directory into river.

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 Heavy rainfalls with band-shaped precipitation systems attacked the western part of Japan from June 28 to July 8, 2018, causing flood and sediment disasters in Hiroshima Prefecture. MLIT (Ministry of Land, Infrastructure and Transport) has operated XRAIN (eXtended RAdar Information Network) that consists of X-band MP radars and C-band MP radars.

 In this study, we show the meteorological conditions using the MesoScale Model and report the observed results in Hiroshima Prefecture during the heavy rainfall. It is confirmed that XRAIN can observe the spatio-temporal distribution of rainfall intensity with high accuracy compared with rain gauges. 3-dimensional rainfall intensity is interpolated using two X-band MP radars and describe the structure of the band-shaped precipitation system. As a result, it is shown the cloud top of the band-shaped precipitation system reached less than 8,000 m, which was lower compared with heavy rainfall on August 20, 2014. In addition, the band-shaped precipitation system observed around Hiroshima Station at 18:05 on July 6, 2018 has higher rainfall intensity than other band-shaped precipitation systems because of the water vapor supply from the south and atmospheric instability.

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 The heavy rain in July 2018 caused record-breaking floods in parts of the Gonokawa River that runs through the prefectures of Hiroshima and Shimane. A number of piping at the foundation of river levees had been observed in two sites which would lead to water leakage, sand boil, the failure and settlement of levee body.

 This paper focused on the river levee failure in the Shikaga district that is located at 27.8 kp to 29.2 kp on the left bank and where there was a large-scale sand boiling followed by the settlement of levee body. The soil layers of the levee body and its foundation ground that have been clarified by site survey and soil tests. The mechanisms of the failure have been estimated with the results of the unsteady saturated-unsaturated seepage analysis and trench survey. This paper also discussed the application of satellites with Synthetic Aperture Radar (SAR) to monitor the displacement of river levee.

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 The heavy rainfall from 5 to 7 July 2018 in the western Japan have caused severe flood damage. The Nuta River basin is one of the most suffered areas from the flood inundation, which was induced by overflows, bank erosion, and several levee breaches in tributaries. This study aims to reveal the runoff characteristics of the Nuta River basin and to discuss the causes of the flooding by numerical simulation results. We applied the Rainfall-Runoff-Inundation model to the river basin to discuss the rainfall runoff characteristics, taking the operations of Fukutomi and Mukunashi Dams into account. Two-dimensional flood flow simulation was carried out in the Funaki district of the river to clarify the flow resistance of tree growth in the reach. Numerical results show that the increase in flow resistance by tree growth is attributed to increasing in water level in the Funaki district in addition to the extremely heavy rain.

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 In this study, we analyze relationships between buildings location and flood damages in Mabi town, Okayama prefecture, and Ozu town, Ehime prefecture, Japan, where serious damage occurred due to the Heavy Rainfall in July 2018. We develop a historical building points database and apply the database to the damaged areas in order to compare building age and flood depth. The result shows that the 70% of high damaged buildings (inundation depth: 2.0-2.5m) in Mabi were built after 1979, and the buildings in both towns have moved into the high flood risk areas thorough their history. The “levee effect” are observed in the both towns, however, different development processes were existed in each towns.

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 A lot of bridges in Misasa River, Hiroshima prefecture were damaged due to 2018 western Japan floods. To clarify comprehensively the mechanism of bridge damages over the basin of the river, we conducted field surveys for longitudinal profile of damages in 94 bridges over Misasa River. The results showed that about 1/4 bridge was damaged due to the flood. The bridge damages occurred at the points in which the river width, span length and cross-sectional area became local minimum values. A non-dimensional cross-sectional area is proposed as an index for showing weak points of bridge against flood.

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 The rainy season front became active in western Japan from July 5 to 7, 2018 and consequently caused massive amounts of rain on a wide range from western Japan to the Tokai region. In Hiroshima Prefecture, where the Hattabara Dam is located, a heavy rain emergency warning was announced on July 6, and heavy damages occurred in various places. The Ashida River basin recorded a total rainfall of about 385 mm and therefore the Hattabara Dam reservoir received the largest volume of inflow since the start of its operation. The Chugoku Regional Development Bureau had prepared the implementation guidelines for adaptive operation ahead of other regions in the country. Under such conditions, the adaptive operation was implemented for the Hattabara Dam after confirming that the next flood would not occur based on weather forecasts as well as considering downstream river conditions and reservoir storage conditions. As a result of dam operations including the adaptive operation, the river water level at Chiishi site in the downstream reach lowered by about 50 cm, and the number of inundated houses was reduced by about 10. This paper describes an outline of the flood control operation, issues and measures toward the future.

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 Due to 2018 July heavy rain, many sediment disasters occurred in western Japan. Not only direct debris flows damage such as destruction of buildings, some places experienced several hours lasting flooding and sediment deposition outside the rivers at several kilometers downstream from the land-slides and debris flows occurrence area. In this study, we focused on Tennou, Kure City in Hiroshima Prefecture, aimed to consider the detail disaster situation and applied simulations. In Tennou, debris flows occurred and large boulders moved in upstream. Sediment movement occurred but didn’t caused flooding outside the river in mid-stream. And deposition and flooding occurred outside the river in downstream. At downstream, deposition occurred at upstream side of the box culvert and didn’t occur at downstream, it is assumed that blocking due to sediment occurred at the culvert. In simulations, we considered the culver blocking, and also considered sediment runoff for many hours which was different from debris flow. From simulation results, the flooding and deposition was first shown at the blocking culvert point. But during the runoff continuing, deposition inside the river become larger, flooding and deposition outside the river was also shown at more upstream area.

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 The Ashida River basin was suffered by intensive storm named as “West Japan Heavy Rain” from July the day 5th to 8th, 2018. The contents of this paper are constructed to two different aims. At the first part, the hydrological data such as rainfull, riverflow and dam pondage during the intensive storm were estimated. The rainfall intensity of every 1 hour and the cumulative values of rainfall at 4 observatorys in lower basin of the river were especially estimated. Considering to the rainfall depth of Fukuyama observatory, one day (187.0mm), two days (282.0mm) and three days (373.5mm) records were severally the past highest values. The probable rainfall intensity value of one day (the day 6th) was calculated about 1/130 years. The riverwater level and volume at Yamate observatory in the testfield area were the past highest values and exceeded the dangerous values during about 1 hour. At the secondary part, the 3-dimensional survey data used by UAV were analyzed in comparison with June and August. The damage of rivercourse way and shape over the test-filed area was made clear. And then from the viewpoint of vegetation, the damage due to intensive storm at July was made clear based on NDVI treatment.

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 The railway and toll roads which connected Hiroshima and Kure were collapsed due to the heavy rain disaster in July 2018. As a result, the railway transportation service had been stopped, and heavy traffic congestion had occurred. In order to improve this situation, the authors proposed disaster adapted temporal public transportation service, “disaster-adapted BRT (Bus Rapid Transit)”, in order to ensure rapidity and punctuality of bus service. In order to ensure rapid service, BRT bussed were allowed to pass the closed highway with U-turn at interchange. And also, road authority prepare bus lane on toll road. These measures were quite difficult to introduce in normal situation. however, that realized quite quickly by strong cooperation among various related organizations.

 This paper introduces the detail concept and methodology of these measures and aim to analize the effectiveness of introduction of these measures.

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 This paper clears characteristics of Heavy-rain Warning (warning and emergency warning) by Japan Meteorological Agency and Evacuation Promotion Information (preparedness, advisory and order) by municipalities, and their relationships through a case study of the heavy rain event of July 2018. Consequently, it is cleared that among those for whom Evacuation Order was issued, Evacuation Advisory was issued beforehand for only less than 60% of them, and Evacuation Preparedness, Advisory, and Order were issued in order for only less than 50% of them. In addition, municipalities are recommended that Heavy-rain Warning or Sediment-related Disaster Warning should associate with conditions to issue Evacuation Promotion Information, but the results imply that their usage were different among them.

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 Field observation and numerical analysis were performed for the debris flow which was happened in Kumano, Hiroshima in July, 2018. Three debris flows were happened and the debris flow from the north valley attacked the residential area and damaged many houses. The debris flow composes of wide graded sediment. The results of the numerical analysis show that the debris flow approached at the residential area in 50 sec. and the average speed on the slope is 9m/s. The information of the inundation area and the debris flow depth can be used to consider the evacuation method in case which people cannot evacuate in long distance during the heavy rain.

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 Evacuation information such as evacuation advisory is one of the important information to urge evacuation of residents during heavy rainfall disasters. There is a possibility that the user needs to move to another facility in welfare facilities for the elderly.

 This paper analyzes the relationship between disaster prevention meteorological information and evacuation information in heavy rain in western Japan. Furthermore, the issue of evacuation in welfare facilities is analyzed. Many municipalities did not announce evacuation preparation information. And the welfare facility had difficulty in judging the evacuation.

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 Middle reach of the Takahashi River, which flows from north to south in the western part of Okayama Prefecture, was severely damaged by flooding due to the heavy rain of west Japan in July 2018. We investigated the flooding state of the confluence part of the Takahashi River and its tributary the Nariwa River, and the downstream section of the Takahashi River managed by Okayama Prefecture. As a result, many inundation damage occurred in the area where the Nariwa River near the confluence part and the Takahashi River downstream from the confluence point parallel to the National Route 180. In this study, the flooding mechanism was clarified by field survey of the disaster state and performing flood simulation. And, in the Abe area of Ochiai town near the confluence of the Takahashi River and the Nariwa River was severely inundated during the flood. Although a land lock gate was installed to prevent from inundation there, it was not closed during the flood event. Therefore, we investigated the effect closing the gate on the inundation state, it was clarified that the flood damage can be reduced by closing it.

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 Due to the heavy rain of July in 2018, several levees of the Oda River flowing through the Mabi district of Kurashiki City and its tributaries, the Suemasa River, the Takama River, and the Madani River, were breached. Inundation area reached 1,200 ha in Mabi district and maximum inundation depth was more than 5 m, and eventually 51 people died there. First, in this study, the inundation state was clarified by the field survey. And flooding scenario was examined using an integrated flooding simulation model that analyzes the flood flow of rivers and the inundation flow from the breaching points. At first, the analysis was performed without breaching condition of levee to estimate the time to start overflowing the levee. Then simulations under breaching condition was carried out to clarify the inundation process. Numerical results of inundation depth show in good agreement with the field surveyed results.

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 Due to 2018 July heavy rain, debris flows occurred in mountainous residential area and caused serious damage in western Japan. Mountainous streams where debris flows occur extending from valley exit are often concealed with culverts upstream of the residential area. In Kobe City and Hiroshima City, culverts existed upstream of the residential area were blocked with sediment and debris flows moved down along the roads connected to culverts. Furthermore, the roads slope were steep, and debris flow in Kobe showed high mobility due to containing fine sediment from granite sediment, sediment have extended widely in residential areas. In this study, we aimed to consider the disaster situation focusing on culverts and roads existing on residential area from field surveys. And we also conducted numerical simulation to describe the disaster scenario and to consider and to propose safe landuse in residential area.

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 The torrential rain disaster on July in 2018 causes serious damages on infrastructure in Chugoku and Shikoku region. In Hiroshima prefecture, even though the potential risk of the disaster was widely announced, the evacuation rate was low. This study collects the articles on local newspapers related to evacuation of inhabitants in order to clarify the reactions of local government and of inhabitants to the disaster. The intensive investigation of the articles clarified that the delay of evacuation judgement of inhabitants or late opening of evacuation sites by local government were caused not only by normalcy bias, but also too fast progress of disaster danger under the synergetic territorial rain disaster. In future, an appropriate alert for evacuation on the basis of “fail-safe” concept and an effective allocation of volunteers are necessary.

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 In rain disasters of railways, there are also sediment inflow disasters originated from mountain streams away from railroads. Therefore, it is also necessary to observe rainfall in the watershed of the mountain stream, then regulate train operation in rainy circumstances based on it. However, the distance between the railway rain gauges for the operation regulation during rainfall is sometimes wider than the localized heavy rain area. Thus, we are considering applying the amount of rainfall analyzed with radar and rain gauges. In this paper, we clarified the size of the watershed and the distance from railroad to the furthest part of the watershed based on cases of sediment inflow disasters occurred in the past. And we analyzed focusing on distance dependency of rainfall at the time of disaster. As a result, it was found that the distance from railroad to the furthest part of the watershed is about 1.3 km. Since the correlation between the analysis precipitation amount of the mesh just above railroad and that of the area within 1.3 km from railroad is high, it is suitable to use the analytical precipitation amount with 1 km mesh size for the maintenance object.

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 The objective of this paper is to offer a comprehensive review of environmental flow (e-flow) research of the world. We reviewed 779 articles in 77 countries published from 2009 to 2016 which handle with e-flows. The publications were investigated from the viewpoint of objectives, types of e-flows, methods and verification. We found that the purpose of the e-flows has been shifting from protecting individual organisms to enhance soundness of whole riverine ecosystems. Accordingly, the indices also expanded from commercial fish such as salmonidae to diverse objects such as plants, biological communities and food webs. A new eco-hydrological method which tries to quantitatively combine flow regime and ecological responses has been increasing. More verifications after e-flow applications are required. Also, in order to manage sustainable water resource use under climate change, it is necessary to deepen the discussion about the role and objective of environmental flow in the future condition.

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 There is a sediment inflow disaster that originates from mountain streams in the rain disasters of railways. In the past, there is also an accident that the train runs over a little sand and derails. It takes a lot of time to evaluate the risk of the mountain stream, because there are a huge number of mountain streams along the railway, and those basin are outside the railway sites. And, there is a possibility that variation due to the risk judgment ability of the investigator may occur, because the mountain stream is mixed with various factors such as topography and devastation condition of the river bed or the riverside slope. Therefore, it is the task to create a method that is able to efficiently and effectively evaluate the risk of mountain streams in railways. In this paper, it shows the method for evaluating the risk of the small sediment inflow from the mountain stream of the railways neighborhood by easy investigations. Specifically, it shows a scoring table for evaluating the risk of mountain streams created by statistical analysis based on the data of disaster and non-disaster mountain streams.

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 Energy loss in a manhole which is a junction of rainwater pipes and/or combined pipes is an important factor for more accurate calculation of inundation. The authors have formulated energy loss coefficients in two-way and three-way circular drop manholes where one or two inflow pipes are connected with an outflow pipe. Since there are few researches on the four-way manhole where three inflow pipes are connected with an outflow pipe like one at an intersection, we conducted experiments on energy loss in a four-way circular manhole to which three inflow pipe and an outflow pipe with several kinds of inner diameter of the pipes and flow rate. We successfully obtained energy loss characteristics in the manhole with experiments. Furthermore, we developed formulas on the energy loss coefficients on the manhole, considering structural elements and hydraulic factors on pipe and manhole. The results calculated with the formulae are agreed fairly with the measured values.

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 This paper aims at development of a non-hydrostatic quasi-three dimensional model for the flow in undular and hydraulic stilling basins. It is challenging for the depth-integrated model to calculate the flow separation at boundary surfaces (water surface and bed surface). To solve this problem, a non-hydrostatic quasi-three dimensional model considering flow equations on boundary surfaces (Q3D-FEBS) was derived. Q3D-FEBS was applied to the undular and hydraulic jump experiments. The calculation results are in good agreement with the observation data such as water surface profiles and velocity distributions of the undular and hydraulic jump. Moreover, it was showed that Q3D-FEBS can calculate the breaking process of the undular jump and formation of the surface roller. Finally, the applicability of Q3D-FEBS for the flow in hydraulic jump stilling basins was discussed against observation data of a large scale hydraulic model experiment.

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 In this study, an auto-regression-driven deep neural network model was developed using deep learning techniques and non-linear time series analysis to estimate the variations in water quality in coastal areas. This model employs a local prediction model to analyze the auto-regression characteristics of the non-linear water quality system combined with an extrinsic deep learning model to express the relationship between water quality parameters and external factors such as tide and weather.

 By combining both models, two water quality parameters were estimated: the electrical conductivity in a tidal river and the concentration of dissolved oxygen in the bottom layer of an enclosed bay. Both models showed high accuracy in the estimation of the two water quality parameters. However, the auto-regression-driven deep learning model demonstrated a superior performance, particularly for water quality parameters that are affected by several internal state variables such as physical, biological, and chemistry processes.

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 It is crucial to reveal transport mechanism of dissolved gases through free-surface in open-cannel for proper management of water quality in natural rivers, water treatment flumes and raceway tanks. Although many physical and phenomenological models have been proposed, not much is known about local distribution of the gas transfer velocity. Hence the present study leads theoretical equation of developing concentration boundary layer in open-channel flow, and we measured streamwise variation of concentration boundary layer thickness by using an extrafine needle-type DO probe. Our theory suggested the local gas transfer is controlled by two significant terms, i.e., streamwise gradient of mean velocity and relative intensity of turbulence diffusion. Focusing on the open-channel flows including partly submerged strip roughness zone, we could explain formation mechanism of concentration boundary layer by comparison with the present theory.

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 To derive flood risk curves considering spatiotemporal rainfall variability, frequency analysis of basin rainfall has been combined with thousands of normalized profiles of historical rainfall considering dependence of rainfall on duration. This study proposed to consider their further dependence on spatial concentration of profiles for deriving tributary flood risk curves. The scheme was applied to four major tributaries of the Yodo River basin, Japan. Comparing with a previous method, the proposed one better estimated flood frequencies at small tributaries (the Kamo and Katsura Rivers), keeping performance at large one (the Kizu River). Local flood risk curves were then derived around their confluence. Around the Kamo River, the proposed method showed better agreement in 100-year flood damage with reference data than the existing method. This study realized more reasonable estimation of the severity of flood risk and its spatial distribution.

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 To calculate the return period of previous heavy rainfall events and to simulate rainfall data under a future climate, AMeDAS analyzed rainfall data for the 28th year is used in previous studies. XRAIN data that corrected using DPR data on the core satellite of the GPM mission is used in this author’s previous study, we generate the extreme rainfall events. However, the data used for calculation is for 3 years, it is not enough compared to the previous study. In this study, we improve the analysis method to obtain the favorable result when the observation data is not enough in the focusing area. And the improve analysis method is applied in Kochi area where observation data is not exist.

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 Plants exhibit various growth and molecular biological responses to stresses caused by external forces. It is therefore possible that remaining vegetation in river channels might possess information of floods which plants received in the past, as growth and molecular biological information. In this study, to test this possibility, we performed loading experiments in which flow with several hydraulic conditions were applied to plant samples (Arabidopsis thaliana). In the experiments, we analyzed growth and molecular biological responses associated with reactive oxygen species in Arabidopsis plants exposed to the stresses. It was demonstrated that plant diameter can be expressed by the first order system in which plant diameter is inhibited without alteration in the duration of growth. In addition, we also showed that expression of genes involved in the regulation of reactive oxygen species might be correlated with drag. Taken together, these results suggest the possibility that hydraulic information of floods in the past can be obtained from plants.

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