From the view point of the permeability of the clayey paddy field, the role of cracks are very important for the underdrainage. However, the water flow resistance in cracks has not yet been investigated. In order to develop the general theory for the underdrainage problems of the clayey paddy field, the water flow resistance principles were investigated theoretically and experiimentally. And the following results were obtained.
1. The maximum discharge from underdrain at the paddy field in Japan was about 1.9-3.5cc/sec/m. For this discharge, the Darcy's law can be established in the large cracks at the clayey paddy field without detailed consideration.
2. If the head loss and velocity are expressed by ζ and υ, the relation between ζ and υ are ζ= {α+β|υ1}υ. where α=24μ/B²ω;β= (n/R^2/3);μ is viscosity;ω is density of water; B is width of cracks; n is roughness of crack channel; R is hydraulic radius.
3. According to this experiment, the roughness of crack channel was 0.056 (m-sec). With the help of hydraulic calculation method for the network of channel, the permeability of crack network can be calculated using the roughness coefficient.
4. The resistance coefficients for turbulent and laminar flow were nealy equal when the Reynold number (R_e) is 5/B in this experiment. Therefore, the critical Reynold number _??_ Here, υ is velocity; B is width of cracks;υ is dynamic viscosity.

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As a result of pursuing the yearly change of cone bearing index and bulk density in the main objective farms A₆ and G₁₃, it was possible to clarify the drying process of ground in the marshy heavy clay soil of the Hachirogata lagoon to some extent.
Further, mainly the following matters were clarified through this study:
1. The initial aim of the drying is to make W_n≤W_LL (pF≅2.0)
2. The surface drainage is very important.
3. The meaning of each of the drying indexes, soil moisture, cone bearing index, bulk density etc, are to be considered.
Then it was found that in this connection the investigation of pF and crack should be performed and the change of bulk density is influenced greatly by the soil grading.

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The influence given by the history of drying from the seasonal and yearly changes of the physical drying indexes (mainly, qc, pF, and groundwater table) in the marshy heavy clay soil of the Hachirogata lagoon were estimated.
Mainly the following matters were clarified in this study.
1. The history of drying is restored clearly.
2. The hydrophilic nature of soil becomes weaker and the water holding content decreases with the progress of drying.
3. The relation between pF and qc was evaluated and the reason that qc becomes large suddenly at the boundary of a certain integrated pan-evaporation.
4. The relation between the groundwater level and pF can be classified into three change patterns.
We are enabled to judge by these patterns in what stage the drying of soil is.

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When a lagoon or an inlet which is connected to open sea by a long and narrow canal is closed at one end of the lagoon side by a closing embankment or a closing tidal gate for the purpose of freshenning reservoir construction, the water surface oscillations like standing waves, that is, secondary undulations, will be induced in the canal. The enlargement of the amplitude of water level variations will bring about the wave overtopping on the existing shore protections, and the current velocity fluctuations amplified will prevent the vessels from sailing safely in the canal. In the present paper, we shall propose one method for the artificial control of these amplifications, in which the closing sluices are operated. This method will be more effective and more economical in practical applications.
Hitherto, the phenomenon of secondary undulations has been dealt with using the linear long wave theory and the small amplitude wave theory, in which the principle of linear superposition holds good. This theory is effective in the case of U_r≤1, in which the parameter U_r has been derived by Ursell and equals hL²/H³ (h: wave height, L: wave length, H: water depth). However, in the case of the waves distorted due to non-linear terms, this principle no longer holds good. Hence, in this paper, we consider this unsteady problem as the non-linear long waves with finite ampitude and show an expedient analysis method founded on the new finite difference approximations by which the long wave equations are explicitly integrated. In order to investigate the convergency of this finite-difference approximations to the exact solutions of basic equations, we compare the calculated results with the experimental results. Furthermore, introducing the operating systems for sluices to the boundary condition at one end of the canal, we estimate the effects of control for the secondary undulations. The computational results show that the exact operations of sluices will exhibit the remarkable effects of controlling the amplifications of both water level and current velocity.
Besides, in the present paper, we go on with the above discussions through the application of this analysis method to Sakai Canal in Shimane Prefecture.

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It may be one of the important probrem in river and irrigation engineerings to estimate the stable profiles of beds of rivers and irrigation canals with movable beds.
In this paper, the dynamic equilibrium bed slope at the upstream of dams is discussed theoretically under the conditions that, the first is in the case of the non-uniform steady flow with the linearly varied width of rectangular cross-section, the sediments are mainly transported as the bed load. Variations in the bed slope at the upstream of dams are calculated analytically with the considerations of the bed-load transport equation based on the datum from sediment-sampling stations in various parts of Japan and the dominant discharge developed by using the flow duration data with bed-load relationship and the stage discharge rating curve, proposed by the author.
In addition, application of the fundamental equations which express the equilibrium bed slope and its profile being deposited at the upstream of dams to the observed field data are well explained and some probrems in the application are briefly discussed.

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Following a previous report, experimental investigations were made concering the wind pressure around a one-gabled house in the three-dimensional flow.
The inclination angle of roofs and the ratio of the height to the width of eaves of a model house were the same as in the case of the two-dimensional flow.
In this report, the direction of the wind is considered in such a menner that it has angles from the direction perpendicular to the up-stream side. wall at 0°, 30°, 45°, 60° and 90° and these angles were namend ‘the wind direction angles’.
From the results of investigation the following conclusions were obtained.
(1) In the case where the ratio of the height to the width of the eaves is 0.23, the wind pressure distribution on the central section of the house of which the roof has an inclination angle of 20° is comparatively stable for all wind direction angles, i. e. in this case the local pressures are less than in the other cases.
(2) When the wind direction angle is near 45°, the wind pressure distribution around a house of which the inclination angle of roof is larger than 25°is apt to show unstability, i. e. a large suction pressure appears on the roof of the down-stream side.
(3) Considering all things the house is desirable to be constructed so as to receive the wind action from a direction parallel to the house axis as far as possible.

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The following conclusions are found in this paper.
1. A rigid wheel rolling on the surface of deformable soil displaces the soil both vertically and horizontally. Horizontal deformation occurs either in the direction of motion of the wheel or opposite to it; both types of horizontal deformation may take place simultaneously over differents parts of the contact surface.
2. The contact surface of wheel and soil can be divided in to three zones, which are dependent on the depth of track and the instantaneous center of rotation of the wheel. In the case of t_r<0, the wheel may exhibit the cohesive, slip and skid zones, wheareas the wheel in case of t_r≥0 may have the cohesive or slip zone.
3. The location of the instantaneous center of rotation of wheel, the radius of wheel and the friction angle between rim surface and soil have considerable influence on soil particle trajectory.
4. Equations for estimation of soil thrust mobilized by a rigid wheel are derived.

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Increasing charactor and possiblity for estimation of efficiency of water consumption were examined.
Under the condition that the total evaporation (E) from soil surface is independent of the total transpiration (T) in the whole growing period of crops, the efficiency of water consumption (ψET) is expressed as follows:
_??_
where ψ_T is the transpiration efficiency and D is the yield. Since ψ_T of same crop in the same region and growing period is constant, ψ_ET is an increasing function of D and T and a decreasing function of E.
The increasing rate of ψ_ET decreases according as D and T become larger, but increases according as E becomes smaller.
On the other hand, the relation between E and T at many real fields may be given as follows:
E=a-b·T
0≤E≤a
where a is the evaporation from bare soil surface and b is a constant. In case the above relation comes into existence, ψ_ET is, as an example, expressed by the following equation:
_??_
From this equation b becomes a new factor for determination of ψ_ET.
Furthermore, ψ_ET can be estimated if the value of b is adequately determined.

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