For the purpose of establishing a feasible method of land use planning, ft, is necessary to consider land use suitability and its background factors. Area suitability classification, applying Quantification Theory Type I, is the' method used for estimating the use suitability of areas of about one ha of land from the viewpoint of both agricultural and urban land use.
In this method, farmers would perhaps evaluate land use suitability from a very different viewpoint from salaried workers.
This paper clarifies the differences between farmers and salaried workers in their evaluation of land use suitability, originating from their individual lifestyles. It is also proposed that the sagacious selection of an evaluation group according to the purpose of evaluation improves the method's precision. In the classification of agricultural area suitability, farmers often evaluate land use suitability on the basis of various factors while salaried workers consider a relatively small number of specific factors. In the suitability classification of settlement areas, farmers tend to give high scores, to districts near their rural settlement, while salaried workers generally consider that the distance to the nearest station is of importance.
If we concentrate on the characteristics of these evaluation groups, it should be possible to carry out area suitability classification with much more accuracy than before.

View full abstract

Soil water content, solute and temperature profiles were measured in a partially frozen unsaturated sandy loam soil at two different initial water contents and at two different freezing temperatures. The water content increased with time in the frozen part of the soil and decreased in the unfrozen part of the soil. The amount of water migration in the soil with the high initial water content was greater than that in the soil with a low content. The solute profiles changed in a manner analogous to the water content profiles in the soil with the high initial water content whereas they were relatively uniform in the soil with the low content. The temperature profiles could be divided into three different regions: a frozen, an intermediate between frozen and unfrozen and an unfrozen region. The length of the intermediate region was greater in the soil with the high initial water content than in the soil with the low content, and this length increased with time. The temperature of this region was determined by the initial water content and was equal to the temperature at which the soil water started to freeze. It is considered that these results could be attributed to the rate of phase change from liquid water to ice in the intermediate region in which soil particles, liquid water, air and ice coexist.

View full abstract

Giving consideration to storage capacity, catchment area and benefit area, 4 representative ponds were selected from many irrigation ponds in various locations in the study area (the western area of the Kako river in Hyogo prefecture).
By questioning local residents and 3 years of observation from 1982 to 1984, the existing status of water management and the fluctuation of the storage volume were considered. The conclusions were as follows.
(1) The discharge from the pond had a negative correlation with the effective rain during the year and at the same time, it corresponded to the, water requirement according to the growth stages of the rice plant. That is to say, the discharge is composed of a trend component corresponding to stages in rice growth and a variable component influenced by the effective rain.
(2) There are about 3 periods of storage decrease during the irrigation season. The annual fluctuation can be represented by dividing the year into 7 periods.
(3) The fluctuation characteristics over the 3 observation years were divided into 2 types, little rain in the wet season (1982) and little rain in August (1983, 1984). In the former type the minimum storage volume was observed in the 2 nd decreasing period and the latter in the 3 rd decreasing period.
(4) In the same year every pond showed similar fluctuation. Particularly at the end of the midsummer drainage (the end of July) every pond was filled every year. This is important for securing the water in August.
(5) It was recognized that there was a high correlation between the pond index against water shortage and the storage volume per benefit area at the end of the irrigation season. By using the simple index, it was possible to determine the pond resistance to water shortage.

View full abstract

Eddy-diffusion-type interfacial mixing in a two-layered density current was investigated experimentally and theoretically. In this type of flow analyzed in the present paper, because both upper and lower layers are in motion, they cause a change in both the average salinity and the volume flow rate through this interfacial mixing. The mass flux, passing through the interface in both an upward and downward direction, can be separated into a turbulent diffusion component and a convection component, investigated in previous studies on the entrainment-type transport. This separation was achieved by integrating the two-dimensional convection-diffusion equation in each layer.
The mixing rate, defined on the basis of the one-dimensional mass conservation equations of both layers, was roughly inversely proportional to the Richardson Number in each layer, because of non-breaking of internal gravity waves. However, in a strict sense, the separated nondimensional turbulent diffusion flux of salt was inversely proportional to the overall Richardson Number, Ri, in agreement with the results obtained by Moore & Long. Also, the direction and magnitude of the non-dimensional convective flux which causes the change in the volume flow rate of both layers seemed to be governed by the parameter (α) expressing the degree of stability and turbulence of each layer, or in other words, the potentiality of one layer to entrain the other fluid particles. The functional relationship between a and C which is the constant in the power law of non-dimensional convective velocity, C=func (α), was obtained experimentally. The critical value of C when α=0 coincided with that of entrainment-type mixing which had been investigated previously, and when α=1.0 this coincided with the Moore & Long flow where W_m=0.

View full abstract

In this paper, the authors propose a new method for low-water analysis of river fl ow by means of the function of moving mean daily rainfall.
The recession curve for successive no-rain days is expressed by the multi-exponential-type recession equation (11), or fractional type (12). As the decreasing characteristics of each exponential term of Eq.(11) are nearly equal to those of T_k-days of moving mean daily rainfall γ ^(T_k') and each T_k is a time constant which is defined by the reciprocal of the exponential constant c_k respectively, Eq.(12) can be transformed into Eq.(37) which is composed of the sum of γ^(T_k'). Eq.(37) represents the response function of a linear run-off system and that of a linear tank shown in Fig. 2 (a) .
Our proposed process for analysis is as follows.
1) Recession constant b of Eq.(12) is estimated from recession curves of observed river flow rate and the exponential recession constant ck corresponding to b is calculated using Eqs.(18)-(30).
2) Time constants Tk' to ck are defined by Eq.(40) and Tk'-days of moving mean rainfall γ^(T_k') are calculated using daily rainfall data.
3) After the non-linear parts of the run-off system are cut off by the supposed Fixed-Maximum-Discharge (FMD) and Fixed-Maximum-Rainfall (FMR), proportional constants a_k are botained as the partial regression coefficients by multiple regressional analysis shown in Eq.(41). In this case, FMD=25 mm/d and FMR=50 mm/d were adapted as the most desirable values and values of ak are shown in Table 5.
4) The low-water flow rate of the river in the long term is estimated using Eq.(39).
The results of analysis on the Egawa River and Honmyo River are shown in Fig. 8 and Fig. 9, respectively.

View full abstract

Our wave maker for the production of interfacial waves is composed of a swinging plate positioned at the boundary layer and a box containing the pivot of the plate. The swinging plate produces inverse water flows in upper and lower layers, which are converted into an interfacial wave. Wave height can be estimated by the transmission rate of kinetic energy to the 2 layers of water flow. A unique transmission rate can thus be obtained.
A decrease in the wave height indicates dissipation of wave energy. The dissipated energy was shown not to be converted to another form of energy such as potential energy by the mixing of the 2 layers. The dissipation was viscous at the boundary layer, side walls, bottom and inside the fluid. The wave height decreased exponentially with increasing distance.

View full abstract

The characteristics of the response of a channel discharge induced with operation were discussed.
The following indexes were introduced to evaluate the conditions of response with operation (see Fig. 1).
(1) Index of beginning of response is K_Q=0.1
(2) Index of progressive state is K_Q=2/3
(3) Index of ending of response is K_Q=0.9
in which, the discharge component is defined as in eq.(A).
_??_(A)
Q; discharge, suffix b shows the uniform flow just before operation and suffix e shows the uniform flow at the end of the response.
A simple and useful equation (B) was derived as a result of solving the linearized diffusion analog model with in the effective range of X.
_??_(B)
X; Distance represented non-dimensionally, T; time represented non-dimensionally.
The validity of eq.(B) was confirmed in the transition range of the dynamic wave (X<<1, T<<(Froude number) ²) and the kinematic wave (X>>1, T>>(Froude number) ²).

View full abstract

Rainfall is a factor which produces soil erosion and the magnitude of the rainfall force has been shown to be the rainfall factor in the universal soil loss equation.
In order to calculate the rainfall factor, a method based on the hourly rainfall is used.
To determine the rainfall factor in some areas, it is desirable to obtain the average value over as long a period as possible. However, in general hourly rainfall data in Japan are not obtained from a long enough period to allow accurate calculation of the rainfall factor.
It is therefore desirable to simulate the hourly rainfall and analyze it by using long-term data.
In this paper, we simulated the hourly rainfall with an autoregression model and compared the simulated data with actual rainfall data. The results showed the propriety of the simulation model.
Furthermore, the results obtained from calculating the R value (rainfall factor) using simulated hourly rainfall showed fairly consistent agreement with the results obtained from using actual data.
This simulation model will contribute to compensating for the shortage of hourly rainfall data when it is used for analysis.
Data used in this calculation were obtained from the hourly rainfall collected at the Shimonoseki Meteorological Observatory over a period of 28 years (from 1956 to 1983).

View full abstract

A stochastic-conceptual runoff model for a small mountain basin which can provide the output and information for the dynamic behavior of a runoff system is presented.
This runoff model takes into account the effects of heterogeneity on the hillslope and soil moisture movement in the A-horizon on the storm runoff process, and consists of five sub-models: a hillslope parameter generation model, a ponding generation model, an overland flow model, a through-flow model and a baseflow model.
This study shows that the hydrograph and ‘partial area’ or ‘variable source area’ concept of storm runoff production can be reproduced accurately by the runoff model presented.

View full abstract