Several rivers in the Omote-Rokko district, such as the Toga River and the Sumiyoshi River, are attracting local people to the river space thanks to their water-friendliness. However, the area where people are enjoying is obviously the bottom of river course, which becomes dangerous even for a small rain. It is necessary to properly inform the people about the danger of the flow in such a case. Therefore, we firstly investigated the traffic of pedestrians on the walkways and their behavior when a rain begins to fall with the aid of two monitoring cameras installed in the Sumiyoshi River. Secondly, we developed a runoff model based on a composite rational formula and carried out two dimensional simulations of rapid flow subject to intensive rains as a diagnostic tool. It was made clear that more than two thousands of people are using the walkways in the Sumiyoshi River every day and the river course can be divided into several zones which depend on a relative safety measure of hydrodynamic forces acting on a person.

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In 1869 the Meiji Government launched the policy of encouraging migration to Hokkaido and started reclamation of the Ishikari River Basin. In September 1898, when farmland reclamation had started to expand, the Ishikari River was hit by an unprecedented heavy flood that resulting in catastrophic damage and 112 fatalities. This disaster prompted surveys for flood control. Okazaki et al. made detailed investigations and observations on the 1904 flood of the Ishikari River. Based on these investigations, a flood control plan focusing on cutoff works was formulated, and those works were implemented for the half-century from 1910. This study reviews the effects of the flood in 1904, which served as the basis for the flood control plan, on the primeval Ishikari River Basin of the time, utilizing the results of investigations by Okazaki et al. We use two-dimensional flood flow numerical simulation to examine the effects of cutoff works. We also explain how the flood control plan had the effect on the basin development.

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The 2011 Tohoku earthquake triggered a series of devastating tsunamis mainly along the Pacific coast of Japan. The tsunami waves also attacked coastlines of Hokkaido Island, and were propagated to upstream in the Tokachi River. We caught the tsunamis by our video cameras from 2 places between 16:00 and 17:50 on March 11. Based on the recorded images, movies and water levels at some gauge stations, the celerity of tsunami waves was estimated between 4.1 and 5.8 m/s. The maximum wave height was observed around 22:08 (seventh wave). Finally, characteristics of the tsunami waves were also discussed in comparison with the cases of the 2006 Kuril Islands earthquake. Our results would provide physical characteristics of tsunami waves in rivers to prevent future disasters.

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We conducted numerical simulations in the coastal region of Sendai Bay for tsunami flood and chemical transport generated by the Great East Japan Earthquake, and discussed the applicability of the numerical simulations to early determination of spatial distribution of chemical pollution in tsunami deposit. The chemical transport simulation considered the spatial distribution of the storage facilities as the point sources of harmful chemicals. The tsunami-flood model reproduced the observed results of the tsunami waveforms at the wave gauges and the flood depth in the land. The simulated results of the chemical transport could roughly capture the region with the chemical pollution in the tsunami deposit, which implied that the numerical procedure could be useful for early zoning of the chemical pollution in tsunami deposit. The point source information should be improved to determine the chemical polluted area more accurately.

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The propagation of the tsunami into rivers in Hokkaido, generated by the 2011 Tohoku Pacific Coast Earthquake, is described using data from water level gauges in rivers. The tsunami first struck the Ohtsu (Tokachi River) and the Tottori (Shin-Kushiro River) gauge stations at the same time around 15:47 (UTC+09:00). The tsunami also intruded other six Class-1 rivers in Hokkaido. Detided water levels, recorded at the stations within these rivers, show the tsunami intruded several times, not once. Then a one-dimensional numerical method is applied to the simulation of the tsunami propagation up Tokachi River and Shin-Kushiro River in order to investigate the spatial waveforms and wave dispersion phenomena. The water levels estimated by the present method agreed well with those observed in both rivers, and significant differences were found in dispersive wave trains at the wave fronts in each river.

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This paper describes the basic characteristics of flow invasion generated by tsunamis over a land. Assuming the self-similarity distributions of flow depth and velocity in the shallow flow equations, the basic characteristics of invasion processes such as the front position, the inflow discharge etc., are obtained in connection with the temporal change of depth of inlet of the invasion. The authors derive the relations between the front position, the inflow discharge and the rising rate of water elevation at the inlet based on the self-similarity analysis. They also derive similarity functions of water depth and velocity distributions. In order to verify the theoretical findings, the numerical simulations and experiments were carried out under simple boundary and geometry conditions. It is pointed out that the exponents of time variable for the front position obtained from the simulated results and experimental results are in good agreement with the theoretical findings.

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As behavior of tsunami inundation is varied by local topography and arrangement of buildings, high-resolution topographic data with several meters interval is required for accurate tsunami inundation simulation. However, the accuracy of tsunami simulation with high-resolution data is not examined enough yet. In order to verify the accuracy of tsunami simulation with high-resolution topographic data, basic hydraulic experimental results are compared with numerical results. Although reproduction of tsunami inundation behavior around structure is difficult by use of shallow water equation, the suitable spatial grid size for the tsunami prediction is able to be determined by Δx⁄√gh_maxT.

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This paper presents numerical simulation results for the run-up Tsunami in Tone River caused by the 2011 off the Pacific coast of Tohoku Earthquake. 2-dimensional shallow water equations are solved with unstructured triangular meshes which can express the shore topography smoother and in more detail. Calculation scheme is based on a cell centered finite volume method using modified Roe's approximate Riemann solver which can handle the moving wet/dry fronts correctly. The simulation results are verified by time series of water surface level measured at some water gauge stations located in the river as well as data collected by survey of flooding trace after the Tsunami. Propagation and deformation characteristics of the tsunami waves are discussed in detail by the results of numerical simulation.

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In the river and coastal engineering field, a lot of researchers have been dealt with wave run-up. Estimation of the height of wave run-up is very important for planning of disaster prevention, development of structures on the waterfront, and management from coastal zones to riverside. The authors simulate the wave run-up of a solitary wave under the conditions of breaking wave and nonbreaking wave using particle method. The accuracy validation of these results was done through comparison with the result from Synolakis's experiment. This study shows that the particle method is a useful method in estimating the relation between height of wave run-up and wave height.

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The capability of a newly developed three-dimensional estuary flow numerical model named as CIP-Soroban flow solver is investigated. The model is based on Constrained Interpolated Profile (CIP) scheme and the Soroban computational grid system. The model is applied to Tone River estuary, and is examined in detail to reveal its inherent capability of simulating the dynamic behavior of density flow in the estuary. The model is tested by the comparison with field observational data of velocity and salinity distributions. The test shows excellent agreement between the observational data and computed results.

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Habitat value for benthic organisms has been deteriorated significantly in many riverine estuaries in Japan. One of the most responsible factors for this seems to be the change of river topography, which has been led by the bottom sediment excavation, dredging and other riverworks. Typical topographical change shows deepened river channel and such change has induced enhanced seawater intrusion upstream and shift of bed material to finer grain. Kikuchi River which flows into Ariake Bay has experienced riverbed degradation in recent 50years. This has caused a significant decrease of the yield of a bivalve species, Corbicura japonica. We have pursued numerical simulation, analyzing the salinity and juvenile distribution, to estimate the habitat value for them among different river channel topography. Present channel which has been deepened from the past was estimated to have lower value and restoration plan in which riverbed is raised by 1m was estimated to provide good functional restoration.

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Two kinds of in-site measurement of mercury transport and transformation were attempted in Minamata Bay. First, we conducted highly-frequent (weekly) water sampling for mercury speciation in sea water with continuous current measurement at an observation tower during summer season. Second, monthly water sampling with measuring vertical profile of grain size distribution by LISST-100X at three stations in the bay was carried out. As a result of this research, the followings are clarified: i) Particulate and dissolved total mercury (T-Hg) in bottom layer was higher than that in both surface and middle layers; ii) Negative correlation between dissolved T-Hg and methylmercury (MeHg) was shown; iii) Annual particulate T-Hg and MeHg transport from Minamata Bay to the Yatsushiro Sea was estimated as 6kg and 0.05kg, respectively; iv) Vertical variation of grain size distribution of SS was not shown in winter, but significantly done in summer; and v) It is possible that source of mercury in bottom layer and surface layer is different.

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In order to make clear the material flow mechanism and the eco-system in the northern region of Kagoshima Bay, we firstly investigated the seasonal change in the water quality and phytoplankton composition utilizing the observational results. Then, we constructed a lower-trophic level model on the basis of the observation and investigated the material flow mechanism. As a result, the following findings were obtained; 1) The biomass of Bacillariophyceae is dominant among various phytoplankton groups through a year, 2) The lower-trophic ecosystem model constructed can reproduce well the seasonal change of water quality and phytoplankton biomass, 3) The change in DO near the water surface is controlled mainly by the net primary production.

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In the northern region of Kagoshima Bay, DO concentration takes the minimum value at the bottom layer in winter. In order to make clear the mechanism of such characteristic behavior, we carried out some numerical experiments. Then, we predicted the behavior of the density stratification and DO concentration in Kagoshima Bay by utilizing some results of a global climate simulation model. As a result, the following findings were made clear; 1) the timing of the formation of hypoxia in Kagoshima Bay was determined mainly by the relative relation between the vertical mixing and the depth. 2) It was predicted that the hypoxia may become more serious in the future by the stabilization of the density stratification due to the long-term climate change.

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Diurnal and semi-lunar variations in the light intensity, suspended sediment concentration (SSC), chlorophyll-a concentration, and pheophytin concentration in the Chikugo River estuary are presented, with an emphasis on the effect of the SSC on the light limitation during phytoplankton growth. Vertical profiles of the photosynthetically active radiation (PAR) intensity and SSC were determined, and the light attenuation coefficient (k) was expressed using the regression equation for the SSC. The temporal variation in the euphotic depth was calculated from the PAR and k. The SSC was 20 mg/l during neap tide, and the euphotic depth was 2 m. Since the average SSC was 270 mg/l during spring tide and ranged from 100 mg/l at slack low tide to 450 mg/l at flood tide, the euphotic depth decreased significantly to 0.2 m on average. Phytoplankton bloom was observed during neap tide, and it results from the positive response of phytoplankton to light enrichment. During spring tide, light limitation hampered phytoplankton growth; consequently, the bloom collapsed and an increase in detritus was observed.

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Tidal urban rivers have severe environmental problems like massive fish death which was mainly caused by formation of hypoxic water mass. However there was little information on DO environments in large tidal rivers. To investigate DO environments in tidal rivers and its relation to floodings which are closely related to CSO(Combined sewer overflow) impacts, we conducted field measurements on water-quality environments in the Sumidagawa and Kandagawa Rivers, Japan. The result indicates that massive fish death in tidal reach of small urban rivers appeared frequently just after flooding events in summer seasons. The measured results reveal that DO on Sep. 9, 2010 were lower than 2 mg/ L in overall region of Sumidagawa River due to the flooding event. These facts indicate that inflows of CSO due to flooding events have an important influence on reduction of DO concentration in the Sumidagawa River.

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In this study, some observations were conducted in order to estimate the separating ratio of freshwater in the Ota Branch Rivers. A method for estimating a salinity profile was proposed based on observed salinity data. Moreover, the estimated salinity profile was compared with the observed salinity profile in order to confirm the validity of the proposed method.It was confirmed that the estimated salinity profile was almost similar to the observed salinity profile. It is considered that the separating ratio of freshwater is decided by the cross-sectional area of a river and freshwater ratio calculated using the estimated salinity profile. The observation results suggested that the retention of freshwater in a river channel of the Tenma River (one of the Ota Branch Rivers) occurred during neap tide.

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The solar radiation has been increasing globally since the 1990s (global brightening). This is the first paper that examined the effect of increasing solar radiation on primary production and hypoxic water in coastal area. We performed a numerical experiment using 3D hydrodynamics and ecosystem model in Ise Bay, where the annual solar radiation had increased by 13.3% from 1980 to 2010. The model results reveal that both the annual mean primary production and the hypoxic water area decreased by reducing solar radiation (10%) from the 2010 level. Our results illustrate how elevating solar radiation influences the coastal environment, particularly hypoxic water area, by using the numerical experiment.

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The behaviors of hypoxic water mass in Isahaya Bay have been investigated by analyzing the data of water quality and wind measured from June to September of 2009 by the Kyushu Regional Agricultural Administration Office. The front of hypoxic water mass responds sensitively to wind and tends to be perpendicular to the prevailing wind direction. When the southerly wind blows, the low density water mass near the water surface, which is rich of dissolved oxygen, is transported to the mouth of Isahaya Bay and the hypoxic water mass near the seabed is transported to the inner area. On the other hand, the northerly wind drifts the water mass near the water surface to the inner area and the hypoxic water mass near the seabed moves to the offshore direction. The continuous blowing of the southerly wind decreases the concentration of dissolved oxygen in the inner area, and that of the northerly wind increases it.

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Influence of hydraulic conditions on the regeneration of mangrove forest was clarified at the Okukubi River in Okinawa Island, Japan. Field surveys for identifying structure of mangrove forest were conducted at 8 plots, where Bruguiera gymnorrhiza (L.) LAM. and Kandelia candel (L.) DRUCE. dominate. While bed-level variation, absolute bed-level fluctuation and non-dimensional shear stress during a flood were estimated by two-dimensional bed deformation analysis. Then relationship between density of seedlings and saplings of mangrove species and hydraulic conditions was evaluated from regression analysis. The density of maturing trees of mangrove species positively correlates with absolute bed-level fluctuation and non-dimensional shear stress. The result represents that regeneration of mangrove community is occurred at sites where sediments of bar surface is exchanged during the flood. Soft soil, which is easy to stick for mangrove seeds, is needed as the first stage of regeneration, and hence sediment movement is essential for forming regeneration site of the mangrove species.

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In Osaka Bay, eutrophication phenomena occur in the bay head while nutrient concentrations are decreasing in the western part of the bay. In this study, we conduct numerical experiments in artificial control of inflow load to manage material circulation in the bay. The simulation results indicated that the future improvement of treated water quality would not contribute to resolution of organic pollution and might change nutrient balance in the eastern part of the bay. It would also be difficult to increase artificially the primary productivity in the western part of the bay due to the limitation of nutrient load potential from land and strong tidal mixing.

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Quantity and quality of Coarse Particulate Organic Matter (CPOM) was investigated in Nakatsugawa River, Saitama during five floods occurred between July 2005 and September 2007. CPOM drift density, and fiber components were compared, Peak discharge was ranged from 54.3 m3/s in winter to 702.4 m3/s in autumn. For winter, summer and autumn flood, average drift density was ranged from 0.21 g/m3, 1.52 g/m3 and 2.84 g/m3 (dry weight), respectively. In high flood magnitude, CPOM was found to have highest in lignin but lowest in soluble organics. Conversely, in lower flood magnitude, exports were dominated by low lignin CPOM with high in soluble organics. There was a significant correlation between discharge with lignin (r =0.666, p<0.01) as well as with soluble organics (r = -0.722, p<0.01), Correlation in both hemicellulose and cellulose with discharge was not found, C:N was high in all floods ranged from 30.0 to 34.9, but TP was generally low (0.04%), Based on the quality, exported CPOM was different significantly between floods and are highly affected by flood timing and magnitude.

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It is important to evaluate the inflowing pollutant loads for the conservation of water quality of closed water bodies. In this study, system correlations between pollutant concentrations and water characteristics of river flow (such as signals of optical sensors, water temperature, etc.) were generated by ANN models. Continuous time series of COD, T-N and T-P were estimated well by the trained ANN models with the continuous measurements of water characteristics. The estimation accuracy of pollutant loads during single storm events were improved by employing the estimated time series of water qualities. Four rivers from two different watersheds (Lake Ogarawa and Lake Kasumigaura) were studied. The results of regression analysis showed that high correlations existed between specific accumulative loads and specific accumulative river flow rate. The regression coefficients were in the same order for the four rivers and most of them had high correlations with the area ratio of paddy field.

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In the Barato River, eutrophication has been occurring because of urban effluent and river cutoff improvements. To improve the water quality, additional water has been conveyed into the Barato River since 2007. This study aims to evaluate the effects of such conveyance on water quality. At the Jyobukobon, BOD was found to increase by conveyance from the Sosei River and to decrease by conveyance from the Ishikari River. At the Tarukawa-Goryumae, BOD was found to decrease slightly by water conveyance from the Sosei River but to show no clear changes in the year after conveyance from the Ishikari River. To evaluate the effects of water conveyance,an ecosystem model was developed that enables year-round predictions, including for the freezing season. A water quality simulation for four consecutive years estimated a decrease in BOD by about 1.0 mg/L at the Jyobukobon and about 0.6 mg/L at the Tarukawa-Goryumae. Also, nitrogen density was estimated to decrease by water conveyance.

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In order to evaluate the global warming effect on the water quality in a reservoir, we conducted sensitivity analysis as to the change of air temperature as well as its seasonal pattern at Urayama Reservoir in Arakawa River basin using a 3-D reservoir water quality simulation model of ELCOM-CAEDYM. The results of simulations showed that the increase of air temperature caused more water temperature increase in epilimnion than hypolimnion. Especially the increase of air temperature in summer caused more water temperature increase in epilimnion, which would easily lead to the water quality problems. The increase of air temperature also caused the decrease of total Chl.a in the reservoir. Especially the increase of air temperature in winter caused significant decrease of chlorophytes and cryptophytes. Cyanobacteria also decreased by the increase of the air temperature because the water temperature in summer became much higher than its optimum temperature.

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Ogouchi reservoir has a problem of the water quality deterioration accompanied with growth of Microcystis and Anabaena. Water samples from the diffusion of public sewerage system for the different water use on rivers were experimented about the blue-green algae growth on Ogouchi reservoir. Microcystis and Anabaena from the sample water of the fishpond has more proliferated than the sample water of river water with treated wastewater. In 2005, Microcystis and Anabaena, together with Oscillatoria of blue green algae, were first observed in Ogouchi reservoir; nevertheless, nitrogen and phosphorus outflow loads and volume of water to Ogouchi reservoir were almost same. While the Oscillatoria are actively growing in the Lake Kasumigaura, Microcystis cannot in there up to now. Similar phenomenon on the selectivity of growth about blue-green algae is confirmed at Ogouchi reservoir. As the results the absence of iron influenced plays a key role about decrease of Microcystis in Lake Kasumigaura. Therefore, the influence of iron in Ogouchi reservoir should also investigates for the future works.

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Sediment quality changes in reservoir influence downstream water quality. Therefore, already experimental study of water and sediment quality changes was done for 450 days using water and sediment. In this study, sediment quality model which predicts changes of anaerobic conditions in a reservoir sediments was developed. This model predicts changes of nitrogen, phosphorus and iron in sediment and porewater. The experimental results were simulated by this model. The computational results show the changes of the characteristics of organic nitrogen and phosphorus, nitrate nitrogen, phosphate. From the above results, in the sediment, could be demonstrated by simulation that proceeds mainly by nitrate reduction.

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Excessive phytoplankton growth as a result of eutrophication is considered problematic in closed waters including a reservoir. An introduction of a flow accelerating device may enhance self-purification potential of such the stagnant over-nutrified water, although the installation cases of the device have not so far been common. This study thus aimed to investigate flow dynamics caused by the device with ADCP, and changes of water quality parameters. The results were as follows: (1) The injected water reached at 50m far from the device during the non-stratification and stratification period. Marginal broadening at transverse direction was observed during the stratification period. (2) The stratified layer was completely destroyed at 10m close to the device, besides being mediated at30m far from it during the non-stratification period. A gradual breaking of stratification was also observed even during the stratification period. The overall efficiency of such a device thus depends on the strength of stratification.

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Yamaguchi et al.(2009) obtained data of hourly variation of sea surface winds for a 45-year period at each of the measurement stations in Tokyo Bay, Ise Bay and the Seto Inland Sea, by applying their specific method to the SDP wind data acquired at on-land meteorological stations located around the sea areas. This paper derives the 7 error indices for wind speed and direction during a 2 or 3-day period of persistent stormy conditions by using the estimated and measured wind data at each station to evaluate the error magnitude. More than 100 sets of the 7 indices were gathered from many storms over long-year measurement periods at several stations in each sea area. Statistical analysis for individual index and its synthesis reveal that the estimated wind data has a generally high accuracy in any of the areas and that the best precision is obtained for wind speed in Tokyo Bay and for wind direction in Ise Bay respectively.

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Manabe(1968) suggested an occurrence of typhoon-generated abnormally strong wind speeds reaching 93.5 m/s at Yakushima from the analysis of resin freckles left along annual rings on a stump of the 'Yakusugi'(Yakushima Cedar) with a tree age of more than 1,500 years. This paper gives a re-estimate of 70 m/s wind speed at a height of 10 m through reanalysis of the relationship between annual width of freckles in the recent years on the stump and annual maximum wind speed measured at Yakushima. An extreme value analysis for a sample of annual maximum wind speed consisting of measurements in recent years and data converted from around 1,500 year-long freckle records using the above-mentioned relationship indicates that the return period of wind speed may be around 2,000 years. An analytical consideration and Monte-Carlo simulation on typhoon-generated extreme wind speed imply that the abnormally strong wind speed event may occur in a time scale of around 5,000 years.

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Langmuir circulation is a large-scale secondary current which is generated by wind-induced water waves, and it plays some important roles on turbulence production and the transports of mass and momentum. Previously, many researchers have conducted studies on Langmuir circulation and related hydrodynamic phenomena. However, most of them focused on only hydrodynamic characteristics, e.g., generating mechanism and velocity streaks, and thus we lack for reliable information of the relation between a gas transfer and the Langmuir circulation. The goal of the present study is to obtain the relationship between a gas transfer velocity and the aspect ratio of the laboratory flume. So, in order to suggest a new physical model, DO measurements were conducted for each aspect ratio condition.

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Ten years or more have passed since large-scale poor cultured laver harvests which arose in the head of Ariake Bay in 2000 winter.However, except for cultured laver, fish catches including a bivalve has decreased and does not show even a sign of recovery. When the drainage gate is opened over a long period of time, it is thought indispensable towards the Ariake Bay reproduction to investigate the change and influence of the aquatic environment of Isahaya Bay and Ariake Bay before and after opening the drainage gate.In this study, the field observation on flow regime at the northern mouth of Isahaya Bay was carried out under the stratified and mixing condition twice in 2010. As a result, structure of cavity flow appeared at the mouth of Isahaya Bay in all condition of both flood and ebb tide. Now, various flow regime has produced on various conditions at the northern mouth of Isahaya Bay, if potential flow will be recovered by opening the gate, it is expected flow regime changes a lot.

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A laboratory experiment regarding diffusive oxygen transfer rate at rough sediment surface was conducted to compare with the analytical calculation, considering vortex shedding in the benthic boundary layer and biochemical reactions in the sediment. The reproducibility of the experimental results by analytical calculation was considerably improved by including terms for vortex shedding frequency in the diffusive boundary layer between the roughness elements and for non-steady variations in the diffusive oxygen transfer rate due to instantaneous changes in oxygen concentration in the flushed region. A simple method to estimate enhancement effect for Stanton number, which is a non-dimensional diffusive transfer rate relative to the mean velocity, the mean concentration in the bulk region, and the mean concentration at the sediment-water interface, caused by occurrences of vortex shedding was also presented.

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Existing empirical relations for the gas transfer velocity at wind-wave interface are expressed in terms of wind speed only, and so the difference in their estimated values may be caused by wave parameters such as the wave age. A new model of the transfer velocity describing the effects of wave breaking is formulated on the basis of hybrid models of Woolf (2005) and Soloviev et al.(2007). The model expression and the values of parameters are examined in comparison with existing empirical relations. The present model can estimate wave-dependent gas transfer velocities and shows that variations of wind-speed dependence in empirical relations may be based on the wave age. Also, the present model may describe the behaviors of laboratory data with the wave age.

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In this study, we propose a saving, economic and safe measurement on the topography change and the spatial distribution of water temperature and salinity at urban river mouth. Study site is Akashi river mouth in Hyogo prefecture, JAPAN. From the observation by camera monitoring and portable GPS survey, it was clarified the shape of river mouth bar was drastically changed by the flood. The results of observation by the radio control boat show that the existence of water-route at the site of right bank and deposition trend of river bed after the flooding. In addition, the relationship between salinity behavior and river mouth closure was confirmed by continuous monitoring at the right bank.

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The Sagami River flowing into Sagami Bay is the main source of sand to the Shonan coast of 16 km length extending between Oiso Port and Enoshima Island. In the upper stream of this river, large dams were constructed and large-scale river bed excavation had been carried out to obtain construction materials before 1967. These resulted in the decrease in sediment supply from 1.5x10⁵ m³/yr to 5000 m³/yr and the shoreline recession around the river mouth. In this study, an expected fluvial sand supply for reforming a river mouth delta of the Sagami River was investigated, using the contour-line-change model considering grain size changes. It was concluded that the expected sand supply from the river necessary for recovering the river delta within 30 years from the present was (1.0-1.5)x10⁵ m³/yr.

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The Sakawa River flowing into Sagami Bay has supplied rich sediment to the Seisho coast because of steep river. Sediment supply, however, has been reduced by river bed mining before 1967 and the construction of a dam in the upper basin. Since then, beach was eroded with a significant shoreline recession around the river mouth. In this study, an expected fluvial sand supply for reforming a river mouth delta of the Sakawa River with a steep bed slope was investigated, using the contour-line-change model considering grain size changes. It was found that the expected sand supply from the river necessary for recovering the river delta within 30 years from the present was 1.5x10⁵ m³/yr.

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The effect of wave action on the establishment of Zostera japonica, a brackish submerged macrophyte growing mainly in coastal areas, is discussed. The wave forces acting on Z. japonica were measured by using a small two components load cell installed under the bed of wave flume. The wave forces were too small to pull out Z. japonica shoot from bottom sediment. Sediment transport and bed form development under waves were also observed, and Z. japonica shoot was pulled out from the sand bed of flume when large ripples appeared on the sand bed in wave flume.

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This paper discusses the motion of fine bed sediment in Tone River Estuary by a vertical 2-D numerical simulation. The simulation model for stratified flow computation is based on k-..turbulent model which was already verified in the estuary by some existing studies. The model for SS transport contains a new formulation of SS concentration at the estuary bed which was deduced from a unified processing of some published flume experimental results and some field data collected in the estuary. Calculation result suggests that fine sediment transported from the river mouth by estuarine circulation becomes dominant in the lower estuary under saline wedge stagnation during non-flood season. On the other hand, the sediment from the upstream watershed may be still dominant in the upper estuary. The result is consistent with some published data about seasonal change of grain size distribution and chemical characteristics of the bed sediment collected in the estuary.

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The Great East Japan Earthquake Tsunami occurred on March 11, 2011 induced big change in coastal and estuarine morphology. Tanaka et al. (2011) has already made a report on these morphology changes. In this paper, subsequent morphology recovery process after the tsunami is investigated for several rivers in Miyagi Prefecture. It is found that at the Naruse and Natori rivers, recovery of the river mouth morphology is extremely slow due to limited amount of sediment supply from the adjacent coastal area with coastal structures interrupting longshore sediment movement, whereas the Nanakita River mouth and the Akaiko Lagoon show relatively quicker recovery. This result shows importance of sediment budget analysis and management covering not only riverine area but also surrounding costal area.

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In recent years, the heat island phenomena have become aggravated due to urbanization. Conservation and restoration of water areas, such as urban streams and ponds, are expected to mitigate the thermal environment. In this research, micro-meteorological observations and water temperature measurements are carried out in an irrigation pond in order to clarify the heat balance characteristics and thermal storage capacity in the water area. According to the field observations, validity of the heat balance on water surface was confirmed by evaluation of the heat balance of water body. In addition, a water temperature model is constructed to evaluate thermal storage capacity of other ponds with different water depth. It is shown that thermal storage effects are expected even in shallow ponds by the water temperature analysis.

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We examined the cooling effect of rivers under the conditions where surface water existed and where the water disappeared by drought. The followings were main results. There were differences on the surface temperature of the bridge and air temperature within river channel; they were clearly lower than surroundings under the condition of surface water existence, which was not observed in drought condition. However, air temperature above the bridge tends to be always lower than that of surrounding area. This tendency was consistent regardless of the existence of surface water in the river. The reduction of air temperature above the bridge was often observed under the condition where wind direction matched the direction of stream and where the wind speed was high. The influence of low temperature above the rivers reached around the double of river width in the transverse direction.

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A new technology to estimate velocity fields very close to a ridged wall by using a sequence of thermal images of the wall is proposed. We call this method Thermal Image Velocimetry (TIV). The principle TIV is the same as PIV (Particle Image Velocimetry) but utilizing thermal images instead of particle images. Although TIV can potentially obtain highly fluctuated turbulent fields, the surface temperature (ST) of the target wall should be sensitive to the velocity fluctuation nearby. We apply TIV to a building wall and discuss the performance of TIV. Insulation panels, Styrofoam^TM, are attached on the target wall. Styrofoam^TM decreases the volumetric heat capacity of the surface thereby increasing the sensitivity of ST to velocity fluctuations. The wind variations estimated by TIV correlate very well with those observed by a sonic anemometer.

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The objectives of this research are to establish the effective factors for rainfall interception in forest area, and to develop an interception model with micrometeorology and forest structural character such as LAI and crown density. Throughfall, stemflow and some micrometeorological factors are measured at the evergreen forest and the deciduous forest in Takayama City, Gifu, Japan, during 2009 to 2010. The tank-like interception model, which is considered the meteorological and forest stand structural parameter, is developed, and simulates some rainfall events to assess its performance and discuss the effective factors for interception. The results and findings are as follows. Interception rates varied widely in the case of small gross rainfall events. At the evergreen forest, throughfall is simulated precisely, however, underestimated in the case of high intensity rainfall events. It is necessary to modify the tank model parameters of leaf drip water. At the deciduous forest, the interception model considered phenology shows better performance than the model fixed crown density. Phenology is one of the most important parameters for interception modeling.

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In recent years much attention has been paid on urban local climate such as heat island phenomenon and severe rainfall. Urban heat island is known as a phenomenon where urban temperature is higher than rural temperature. Whereas investigation for urban heat island phenomenon has been reported in many cities (e. g., Sakakibara et al., 1996), the investigation of water vapor distribution is still poor. Spatial and temporal distribution of water vapor is as important as air temperature, because local severe rainfall is caused by convergence of water vapor. On the basis of field measurements in Matsuyama plain, we found that urban absolute humidity is lower than rural absolute humidity. Following the manner of urban heat island phenomenon, we call the phenomenon 'urban dry island phenomenon'. The object of this study is to analyze the feature and cause of urban dry island phenomenon.

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This paper proposes an empirical model, "Albedo model" to estimate the change in the albedo, al, of Chao soil associated with salt accumulation on the soil surface and the volumetric water content, θ, of the soil surface. A basic element of the model is derived from experimental results by a new method, "Box method". It is seen from the box method that (1) al in a dry state is larger than that in a wet state but the difference becomes small as the crystallized salt mass, M_crystal, increases, (2) al decreases with the increase in θ, for 0.05≤θ≤0.30. From these results and a similarity law of the dependency of al on θ, the albedo model was created in this study. The model made it possible to calculate the albedo of Chao soil with an arbitrary θ and M_crystal.

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Turbulent mixing process during nocturnal periods was investigated in urban area. Measurements of turbulence within and above a surface layer were conducted using Doppler lidar, sonic anemometer, and radiosonde in an urban residential area, Koganei, Tokyo, in February and October 2010. Vertical distribution of the vertical velocity was observed at the height from 59 m to about 1,000 m. The mixing process in the surface layer strongly depends on the atmospheric stability. Outer-layer turbulence hardly contributes to the development of the surface layer in the stable condition even though there still remains a residual turbulence or a downward flow from clouds. Meanwhile, the turbulent mixing extends up to 300 m from the ground in near-neutral atmospheric condition. We also observed that a low-frequency vertical motion in outer-layer correlated negatively with horizontal velocity, which is rather than vertical velocity, near the ground under near-neutral stratification.

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We propose a new measurement technique, Velocity Image Velocimetry (VIV), to obtain two-dimensional velocity fields in the atmosphere. Observational data was obtained by one Doppler lidar, and a pattern tracking method was applied to the radial velocity fields. The lidar observation was conducted at an urbanized area in Tokyo. We analysed three cases which have different mean wind speeds and flow structures. The non-dimensional radial velocity error is 20 to 40 percent. It is suggested that there are a proper time interval of the lidar scanning depending on the mean wind speed, and the interval should be constant. We also applied a simple velocity correction method using observed radial velocity, and compute two-dimensional divergence fields. By comparing with the distributions of radial divergence, analyzed 2D divergence fields reproduce more realistic values, indicating the validity of VIV.

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Asian dust (yellow sand) is mostly produced over Govi and Taklimakan region and transported by the Jet Stream toward Japan from the former region. A proper estimation method of source area of dust outbreaks will be better for operational estimation of dust transport to Japan. This study examined correlation between the threshold wind speed of dust outbreak and the subsurface soil moisture condition, and developed regression formula of the two quantities. It was examined how the method for dust outbreak decision by comparison with estimated threshold wind speed and actual wind speed was effective, using the regression formula incorporating thermal inertia estimated with actual satellite and surface observation data.

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Large-eddy simulation was implemented for airflow and thermal diffusion in an urban canyon. To evaluate the performance of the LES, the mean velocities, standard deviations of turbulent fluctuations and mean temperature estimated by the LES are compared with those obtained by wind-tunnel experiments. The results show that the LES can capture the flow and temperature within the canyon, and accurately represent the effect of the wall heating on flow within the canyon. Though the previous studies only focused on the vertical cross section, it is found that two axisymmetrical vortexes are formed in the horizontal cross section with a large clockwise vortex in vertical cross section irrespective of the wall heating conditions. The horizontal vortexes are enlarged by wall heating, and horizontal turbulent fluctuations are increased. Thus, the thermal environment within the canyon is affected not only by the vertical large vortex, but also by the horizontal turbulent flow.

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