The mathematical model which can simulate inundation process in urban area due to heavy rainfall has been newly developed. The network model in which streets, livers and channels are treated as a channel network is used. The discharge hydrographs obtained by the runoff analysis in the surrounding mountainous area are imposed as the upstream boundary conditions. A simplified sewerage model is also incorporated. The model is applied to Kyoto city area. The computed results show a good agreement with the record of inundation depth distribution in 1935. It is also verified that this model can express the inundation process, namely, the temporal change of inundation water volume and inundation area.

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A 2D numerical simulation model of flow and bed evolution was developed which can evaluate the influence of groins to channel flows, as well as the shift effect of deep scouring separating from the banks in bend channels. In the present method, a hypothetical bed level concept is conducted to express the decrease of flow area due to groins, instead of the true bed level. And energy loss in the influenced region around groins is expressed by an added bed friction coefficient. The validity of the method is verified by the comparison of calculated results with experimental data. Furthermore, from the practical point of views, some discussions and considerations are made on the prediction of groin's effect, associated with the proper size and arrangement of groins in river engineering works.

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One of the most significant characteristics of debris flow is its intermittent nature. The intermittent flow occurred at debris flow front is caused by the jamming of particles and subsequent failure and remobilization of the jammed particles in the front. The present study proposed the model incorporated this mechanism into one-dimensional fundamental equations of unsteady debris flow. The numerical calculations of the model were compared with the experimental results. The agreement between the calculation results and experimental values was fairly well. The model was also applied to the debris flow occurred at Name River.

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The motion of a particle cloud falling through a quiescent water as well as horizontal motion of a suspension gravity current, resulting from impingement of falling particles, are investigated experimentally and numerically. A numerical model, based on LES with the Smagorinsky SGS model that includes buoyancy effects, is proposed. It is found that numerical results by the model compare well with experimental results as long as the concentration of the particle cloud remains high. The model is also applied to the domain containing a silt-fence on the bottom and is found to simulate deposit profile of the particles reasonably well.

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A longitudinal, artificial reef system is composed of a number of long submerged mounds, which are placed in the nearshore zone with the orientation normal to the shoreline. Incoming waves are refracted by the heads and longitudinal side slopes of these reefs, and thus their heights are enhanced for intensive wave breaking. A series of small scale model tests and numerical computations have been carried out to confirm the performance of the new reef system, which is found to be superior to the conventional lateral system. Wave heights around the reef system can now be estimated through numerical analysis. The present paper summerizes the findings of these studies for the purpose of providing the basic data for future development of prototype reef systems.

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The periodical solutions of linear long waves are obtained for the cases of both laminar and turbulent flow where the shear stress acts whole fluid domain. The solutions can take into account the variation of wave height due to the bottom topography and bottom friction. The decay modulus of wave height and so on obtained as the laminar flow solution are compared with those predicted by the laminar boundary layer theory, and it is shown that the boundary layer approximation cannot be applied to the case where the water depth is small and the wave period is long. By using the turbulent flow solution, the variation of reflection coefficient due to bottom friction is examined. The reflection coefficient is governed by not only the Iribarren number but also the number of waves on the slope and roughness height. The empirical roughness coefficient n is obtained by equating the bottom shear stress evaluated by Manning's friction formula to that evaluated by the present theory. It is concluded that the proper value of n is determined only by the bottom roughness.

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This paper examined the characteristics of wave runup on a circular pier of a bridge experimentally, and proposed the runup height formula. The experiments were carried out under a wide range of test conditions; the bottom slope ranging from 1:10 to 1:40, the deep-water wave steepness ranging from 0.004 to 0.05, the installed water depth at the pier from very shallow water to relatively deep water. After examining what parameters were effective to arrange the runup heights, we proposed the prediction formula of runup height under consideration of the bottom slope and deep-water wave steepness. The agreement between the experimental and estimated runups is very good and the correlation coefficient was 0.98.

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A field investigation was performed at the Tonegawa river-mouth and the south Kashimanada coast whose littoral environment changed drastically owing to the construction of river, port and shore protection facilities. Littoral drift with various time scales was described on the basis of analysis of sediment samples as well as measurements of waves, currents and turbidity around the river-mouth. Particle size analysis and measurements of γ-ray radiation were carried out for sediment samples collected along the shoreline and vertical core samples taken from the sea bed, revealing the temporal scales of sediment sorting and sedimentation processes. Measurements at the river-mouth were performed just after a flood, in which the resuspension process by waves, tidal flows and ocean currents was described for fine sediments deposited by the flood. Schematic diagrams of coastal morphological processes in recent 50 years were presented.

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Radial spread of oil spilled on the calm water is treated using the two layer model. Governing equations of oil layer are treated as the initial and boundary value problem employing the method of characteristics. Calculation is done for region behind a position where so called the front condition is satisfied. The front condition has been proposed through laboratory experiments using saline and fresh water. The front condition is given at the nearest one to the front of all the positions where the interface lifts up, since the first instability seems to occur there. Calculation showed good agreement with the previous laboratory experiments

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A new instrument that can measure oxygen demand at sea bottom has been developed; the continuous measurement is available by repeating open and close system. The results of the field measurement at the inner part of Hiroshima Bay, whose sediment is organically enriched or polluted, showed that the average oxygen demand was about the same as another reported values and ranging from 1.31 to 1.61g/m²/d. And the data during the low atmospheric pressure passing implied that marine environment disturbance might influence the oxygen demand strongly through curling up sediment.

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A dynamic model associated with daily air temperature and daily global radiant flux model was developed to simulate the growth dynamics of Phragmites austmlis. The biomass of shoots and rhizomes were analyzed with respect to various radiant flux, temperature curve and accumulated temperature under the condition of abundant nutrient. The variation of the biomass was related to the total accumulated temperature of early growing season by stored material of rhizomes and of photosynthetically growing season, and the ratio of the respective accumulated temperature, and the daily flux rate of solar radiation. Analysis of annual flux showed that the respiration of aboveground and belowground plant organs was an unavoidable component and changed the energy budget of utilizing photosysthesized materials, caused the variation of the biomass.

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It is important that it makes clear the cyclic process of water and water balance for the river basin. However water quality was changed by types of land use and geologic structure. In this study, we have compared the water chemistry of the Ishikawa river which land for housing makes rapid progress, with that of the Satsunai river which there are almost agricultural land. In the Satsunai river, the NO₃^- concentration found in the middle stream water of farmland were thought to have come from fertilizer. The Cl^- concentration is influenced the difference of population in the river basin. By analysis of oxygen and hydrogen isotopic ratios, the effect of geographic latitude is confirmed by comparing the Ishikawa river basin with the Satsunai river.

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