It is indispensable to forecast the snow depth to consider a counterplan of the snow removing. The short and midlle time weather forecast less than one week is practical condition, but it doesn't always follow that the long time such as more than one month weather forecast. There are many proverbs relationship between weather and ecology in snow country. The one of these is “the mantis lays eggs at high/low place when we get a heavy/light snowfall”.
The purpose of this paper is to forecast the maximum snow depth using the height of mantis's egg sacks considering the geographical characteristics such as the latitude, the longtude and the sea level.

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A field observation was performed in a reed field, measuring vibration of a reed, air velocity fluctuation, Reynolds stress, temperature fluctuation, etc. It was found that the honami occurs simultaneously with large vertical Reynolds stress peaks, which confirms that the honami is induced by organized vortices generated by a shear instability of flow. Measured vibration spectrum of a reed has a peak corresponding to the frequency of honami, and it attenuates rapidly in the high frequency area. A spectral response function is derived based on a vibration equation regarding live reed. The predicted profile of spectrum for reed vibration agrees very well with the result of measured one.

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This study deals with local scour in downstream of bed protection works. In order to establish the reasonable design of bed protection works, the experimental study was carried out in the case of sudden change in bed roughness longitudinally from a rough bed consisting of several types of bed protection works to a movable bed under dynamic and static condition of bed load. Variations of bed profile and the maximum depth of scour hole were discussed and flow characteristics, such as, velocity distribution and bed shear stress were measured at several stages of scour. As the result, we proposed a method to reduce scour depth by using rubble works.

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The structure of large-scale secondary flow in a turbulent meandering channel at a low Reynolds number is investigated using LDV measurements and flow visualization techniques. Coherent structure formed in a turbulent meandering channel flow incline to the secondary flow direction which depends on the distribution of transverse component of mean velocity. Large-scale shear layer consisted of three regions characterized by property of different shear in transverse cross section of a turbulent meandering channel flow was formed by the inclination of the coherent motion. The shear structure plays an important role to generate large-scale secondary flow in a turbulent meandering channel.

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Channel narrowing triggered by forced channel widening in three reaches of the Powder River in the US and the Sendai River in Japan was investigated. The reaches have been narrowed by newly formed flood-plains, main deposits of which originate in wash load material, much finer than the bed material of gravel. Wash load transport calculation was made to evaluate deposit rates on the beds with/without vegetation. Calculation results and the hydraulic conditions governing possibility of vegetation growth on the beds strongly suggest that the flood-plain accretion should be attributed primary to the vegetation growth. Hydraulic and geomorphic roles of vegetation and wash load were analyzed, and their practical application was proposed in terms of designing a stable width channel and controlling geomorphic change in a riparian bank.

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A series of laboratory tests was performed on the stability of organized horizontal vortices generated along the boundaries of bank vegetation, and the associated exchange of fluid momentum at the boundary of bank vegetation was measured by using a laser-Doppler velocimetry. The wavelength of the vortices is explained well by a linear stability analysis, suggesting that the vortices are generated by shear instability. At some value of width of main flow region without vegetation, the momentum exchange takes a peak value, where two vortex streets show a stable staggered array. A numerical computation employing SDS & 2DH turbulence model originally proposed by Nadaoka and Yagi was performed to calculate the 2D flow field, supporting the measurements.

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Second-order exact solution of velocity potential for nonlinear diffracted wave is derived analytically for the case of isolated cylinder. First, the surface profile calculated with the present theory is compared with that calculated by the Kriebel's solution and exellent agreement is confirmed. Then, wave profiles and wave crest height distribution around the cylinder are compared with corresponding results obtained by linear diffraction theory. Results show clearly that the second-order diffracted wave is important on wave diffraction. The derived solution is analytical and therefore it is easy to investigate the structure of the solution.

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How much the volume of wave overtopping and potential energy are gained has been investigated experimentally by propagating two-dimensional regular waves and irregular waves to a structure. The structure was composed of two parts. One is a sloping wall to promote the wave-overtopping and gain effectively the difference of water head. The other is V-shaped vertical walls to converge widely distributed wave energy. A relationship between the overtopping volume, head difference and the structure form has been obtained empirically. It enables us to determine the optimum form of a man-made structure to gain the required wave-overtopping volume and head difference.

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Water particle velocities and suspended sand concentrations near the bed were measured outside and inside of the surf zone under the condition of swell. The cross-spectrum analysis revealed that long waves, with periods longer than 30s, formed a partially standing wave on the beach slope. The suspension of sediments had close correlations with wave groups outside of the surf zone and with breaking-wave-induced turbulence in the surf zone. The strong turbulence and suspended sand with high concentration tended to be developed when the trough of the precedent wave was low. The largest contribution to sediment flux was due to the steady component. The contribution of infragravity motion was about 10 to 20% of that of the steady component. The variations of suspended sand concentration and nearshore currents in the infragravity range had strong correlation with the envelope of the incident wave.

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Oscillatory sheet flow is the sediment transport mode under stormy wave condition, so that a large wave flume almost comparable to the real sea condition is required for the reproduction. As an alternative, light and large artificial particles have been used in a relatively small flumes. However, the systematic differences can be found between data using natural sands and those using artificial particles. This study investigates the effects of particle properties on the sheet flow dynamics and discusses the validity of using the artificial particles. Systematic data analyses have been performed focusing on the concentration profile, velocity profile, transport flux and transport layer thickness.

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The dependency of accumulation process of sludge on the arrangement of membrane threads and on the crossflow velocity is investigated. The results showed that above a certain crossflow velocity, the accumulation do not occur. Further, threads arrangement was found to be influencing the sludge accumulation. But velocity and turbulence intensity in the space between membrane threads are constant independent of threads arrangement. So, a model is proposed that can explain beginning of sludge accumulation. This simulation is based on the collision of sludge particles onto the surface of membranes.

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