The monitoring data for snow covered areas for water resources management taken from NOAA-AVHRR are low in spatial resolution on the ground but have a short observation interval in comparison with LANDSAT-MSS or TM data. The NOAA-AVHRR data have some advantage when the weather is cloudy. This study aims to improve the spatial resolution of NOAA-AVHRR data and to calculate a percentage of snow covered area within one pixel by a ‘macro pixel model’. The present study also estimates precise a location of snow covered areas inside an AVHRR pixel with an aid of the past LANDSAT-MSS data which provide the temporal order for the melting snow. The accuracy has been evaluated by LANDSAT-TM data which are collected on the same day when NOAA-AVHRR data are observed.

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Experiments were conducted on the behaviour of the bubble plume in a step-stratification. The plume structures were divided into two patterns, depending on the plume number, P_Δ, the ratio of the stratification intensity to the bubbling rate. With P_Δ less than 10, the liquid plume breaks through up to the water surface, whereas with P_Δ higher than 10, a swell of the lower layer fluid forms on the interface. In addition, the height of the swell was described as a function of P_Δ. The water arriving at the free surface spreads radially along the free surface, and plunges into the water body. The spreading rate was expressed not only by P_Δ, but also by the ratio of the upper layer depth to the total one. Irrespective of the patterns, most of water rising into the upper layer, entrains the upper layer water, and falls down on to the density gap to form an intermediate layer there. The density distribution of the intermediate layer as well as the entrainment rate was measured. Then, using the entrainment rate and the volume flux of the plume, the evolution of the density profile was analyzed.

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Turbulent measurements are conducted for flow over rigid vegetation simulated by cylinders with equi-spacing, and the structure of turbulent flow over a vegetated bed is investigated based on the turbulence properties clarified by the experiments. When the water depth is lower than the vegetation height, the velocity profile is uniform and it increases proportionally to the square root of the slope; while, when the depth is higher than the vegetation height, turbulent shear flow profile appears even in the vegetated layer because of the turbulent momentum exchange with the faster surface flow region. The measurements of velocity and the Reynolds stress in this layer and the analysis of them clarify that the mixing length in this layer increases with the distance from the interface of the layer with the surface flow region and that it is non-zero at the interface. This non-zero mixing length at the interface modifies its distribution even in the surface flow region. These facts make it possible to describe the velocity profile of flow over vegetated bed including the vegetated layer.

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An experimental study effective to find the damping force, negative one or positive, is presented. Pressure on the underside plate of gates was measured when the gate was oscillated forcibly with an electric motor and crank.
Pressure with phase in advance of the gate displacement causes hydrauric negative damping force and the pressure with lag phase causes positive damping.
Experimental results show clear appearance of negative and positive damping force in relation to reduced velocity Vr=√2gΔH/fD, where ΔH: water level difference between upstream and downstream of the gate, f: frequency of oscillation, D: gate thickness.

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The Akasi Kaikyo Bridge whose main span length is 1, 990m would be the largest suspension bridge once it is accomplished. Its foundations are now under construction in site, as scheduled. Prior to the actual construction, some hydraulic problems associated with the construction procedure had to be solved particularly from an engineering viewpoint. A considerable amount of experimental works have been carried out for many years in laboratory and/or site. The successive three papers will state what kind of hydraulic problems had to be considered to establish the safest construction procedure. At first, the present paper will describe how a serious foundation scour problem anticipated in site is coped with based on many hydraulic experiments. All basic design guidelines for preventing a foundation scour will be given.

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In this paper, a design decision to reach to a final scour protection method for the pier foundation of the Akashi Kaikyo Bridge will be briefly described based on the results of hydraulic experiments. Five different kinds of protection methods are considered. The necessary dimensions for the finally employed rubble stone protection method will be shown in the present investigation. In addition, in order to prevent small floor sands from migrating through each rubble stone, a new and practical anti-scour scheme, i. e., a filter unit concept will be introduced. Using the filter concept in construction will be proven through a site experiment. Finally, the behavior of rubble stones when thrown in tidal current will also be described, considering such factors as current speed, sea slope, and sea material as well as the existence of large structure.

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In order to determine the feasible construction method for the large piers of the Akasi Kaikyo Bridge, many additional technical problems on hydraulics had to be solved, considering the details in the construction process. The topics which will be described in the present paper are (1) drag forces for various cross sectional caissons due to tidal current, (2) oscillation of caisson and moored working vessels in ocean and (3) the influence to neighbouring navigation channel. Particularly, the value of drag coefficient for a large circular caisson will be reported, which was obtained in the site with its Reynolds number 10⁸. All experimental results herein reported have been used in the actual design and construction of the largest suspension bridge in the world, i. e., the Akashi Kaikyo Bridge.

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A new procedure to asses a harbor tranquillity where the tranquillity is evaluated through the analysis not only of wave height but also of moored ship motion is firstly proposed. A numerical model proposed for predicting a ship motion in a harbor is summarized and applied to model tests and field measurements. A good agreement is shown between measured and predicted results. The model is also applied to investigating the effect of various structures on the attenuation of ship motion.

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Experimental studies on activated sludge processes with a continuously-fed reactor with sludge recycle or semicontinuously-fed batch reactor were conducted in order to investigate the effects of substrate C/N ratio and SRT on activated sludge catabolism in terms of the biodegradable fraction of the TOC substances uptaken. Upon the basis of both TOCand TN specific utilization rates instead of using oxygen uptake rate, the biodegradable fraction was estimated and considered to be affected significantly by the substrate C/N ratio and SRTs whether the feeding system is a continuous or a semicontinuous. Furthermore, filamentous bulking of activated sludge was confirmed in a continuously-fed reactor under various SRTs, but was not necessarily confirmed in a batch reactor although the biodegradable fraction in a batch reactor was very similar to or relatively lower than that in a continuously-fed reactor.

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