Two rectangular experimental slopes are set on a bare slope in order to study the development process of rills (Figs. 1 and 2, Photo. 1). One slope is aimed to observe mainly the development pattern of rills (A-slope in Fig. 2) and another to measure the hydraulic conditions (B-slope in Fig. 2). Both have concrete partition walls except the lower end to eliminate the inflowing of water and sediment from outside the experimental slopes.
The electrical resistivity survey, the cone penetration test and the grain-size analysis are also carried out to survey the soil conditions (Figs. 3, 4, 5 and 7). The results of them show that the soil conditions are nearly homogeneous in the traverse and change remarkably from the middle part to the lower part along the longitudinal profile.
As for the hydraulic conditions, iL is recognized that the surface erosion occurrs when the rainfall intensity is above 1 mm/10 min (Fig. 8) and surface discharge is more closely related to the rainfall in 30 min than the rainfall in 60 min (Figs. 9 and 10). It is also observed that the sediment discharge per unit width at the end of the slope is nearly proportional to the square of the surface discharge (Fig. 13). Therefore, it can be considered that the sediment discharge per unit area at a certain place in such slopes is proportional to the length from the upper end to the place in a given rainfall intensity if the surface run-off coefficient is constant on the whole slope.
Next, we shall discuss the erodibility of the slope by using
_??_
where _??_ is the average erodibility coefficient, _??_the sediment discharge and the surface discharge at the end of the slope respectively and S the gradient of the slope. Using the values of _??_ and S obtained from the field experiment for the equation, we can obtain values of the coefficient key (Fig. 15). The figure shows that the value (_??_) decreases almost exponentially with the passing of time. This means that the erosible material of the slope decreases in the course of time.
Then, let us investigate the relationship between the slope of the experiment plot and the model slope in order to examine the theoretical model which can validly apply to the development of rills in the model slope (Kashiwaya, 1979). The relationship between variables which play important roles for the rill morphology can be expressed as follows ;
_??_(8-2)
with D; drainage density, υ; flow velocity, ke; erosion proportionality factor, w; width of rill, ρ; density fluid, μ, viscosity of fluid and g; acceleration of gravity. Assuming that p, p and g take the same values both in the prototype and in the model, we can obtain
_??_(9-1)
and
_??_
with RA; stream area number and H_o; Morton number, from eq. (8-2) by employing dimensional analysis. Therefore, it is said that the law of similarity can be established by using the above two equations. As for the number of rills in the steady state, let us introduce the next equation which is valid for the model slope;
_??_
with k; the number of rills, p ; the coefficient expressing the relationship between the number of rills and the total width of rills, r; the ratio of the branching coefficient to the joining coefficient and N; the number of initial rills. It is derived from the stochastic differential equation based on the two hypotheses; the joining probability is proportional to the number of rills and the branching probability is proportional to the relative width (width/depth). In the present slope, assuming that the number of initial rills N is proportional to the slope length and r is in inverse to N (Fig. 17) and using the value of p given in the field experiment (Fig. 16), we can obtain the theoretical number of rills in the steady state of this slope.

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This study defines the air layer between the ground and the 850 mb surfaces as the climatological atmospheric boundary layer, according to Kayane (1965). The monthly normals of the longwave radiation balance of the atmospheric boundary layer for 82 weather stations in Japan were estimated from the monthly normals off surface weather elements, with an aid of an experimental formula as follows
_??_
where B is the longwave radiation balance of the atmospheric boundary layer, a StefanPoltzman constant, T surface air temperature in K, e surface water vapor pressure in mb and ii total fractional cloudiness. The coefficient d_ij is given in Table 1. This formula was introduced recently by the author (Nakagawa, 1979) after parameterization of theoretical computations with surface weather elements.
The radiation map was drawn for each month based on estimated values. The results obtained are summarized as follows : The atmospheric boundary layer in Japan everywhere loses the heal due to the longwave radiation transfer, except for the northern Japan Sea coast region during winter, and the annual total cooling ranges from 8 kly/year on the Japan Sea side to 18 kly/year on the Pacific Ocean side of the Mainland. The distributionn of the monthly longwave radiation balance of the atmospheric boundary layer in Japan can be divided into two types, the winter and the summer ones. The winter type of distribution is characterized by the remarkable spatial differences in the cooling, especially by the sharp contrast between the Japan Sea and the Pacific Ocean sides. On the other hand, the characteristic of the summer type is that the distribution shows a general uniformity over the whole area of Japan, and that the form of the isolines is very simple. The distribution of the annual total is, therefore, characterized by the winter type because of its remarkable spatial differences and the long duration of its occurence.
Both the occurences and the exchange of the two types of distribution seem to be due to the contrary patterns of the annual variations in the longwave radiation balance of the atmospheric boundary layer between the Japan Sea and the Pacific Ocean sides. Then, in the present study, harmonic analysis of the monthly normals of the longwave radiation balance of the atmospheric boundary layer was used to investigate its seasonality in Japan.
The variance of the longwave radiation balance of the atmospheric boundary layer was large along the Japan Sea coast but small along the Pacific Ocean coast. It ranged from 616 ly²/day² at Fukaura to 24 ly²/day² at Owase. The first three harmonics proved sufficient to account for most of the variance in Japan. Mapping of the results revealed the first harmonic as the most important component in the whole area of Japan, especially on the Japan Sea side, with a winter minimum of the longwave radiation cooling. The importance of the first harmonic, with a late spring minimum, decreased and the second and the third harmonics were important comparably in the Kanto district and its neighborhood. The second harmonic increased also in western Kyushu. Along the Pacific Ocean coast region south of Poso peninsula, the importance of the third harmonic was greater than that of the second one.
According to the pattern of the annual variation in the monthly longwave radiation balance of the atmospheric boundary layer, the Japan Islands were divided into eight types of climatic provinces.

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A new volcanic island named Nishinoshima Shinto was formed soon after the submarine volcanic eruption occurred about 800km south of Honshu in April, 1973. The Hydrographic Department of Maritime Safety Agency has continuously observed from aircraft the phenomena of the submarine volcanic eruption as well as its growth into a new volcanic island and the process of subsequent topographical changes. The result showed that large-scale coastal erosion occurred along the south coast of the island. The coastal process of the new volcanic island is very much interesting and important for geomorphological study.
The Hydrographic Department carried out aerial photogrammetric surveys of the island ten times during the period from December, 1973 to January, 1978. These surveys revealed that the new volcanic island continued to grow according to active volcanic eruptions till August, 1974. The tendency thereafter was towards the reduction in size of the island due to the tranquillization of volcanic activities and the effect of active coastal erosion. Comparing the coastline of the maximum growth in August, 1974 with the latest coastline in May, 1977, it was found that the coastline retreated maximum 170 metres along the southern coast for a distance of 900 metres. To the contrary, the coastline along the northern bay formed by the old and the new islands advanced maximum 80 metres.
In the process of the retreat of the coastline, there were two remarkable erosional stages with a calm stage in-between. The first erosional stage was from August to October, 1974 when the coastline retreated maximum 120 metres. The second erosional stage was from November, 1975 to August, 1976, and the coastline retreated more than 50 metres at this stage. The coastline in the calm stage was stable and the change was negligible. The process of the coastal erosion was closely related to storms attacking this locality. Namely, five typhoons passed over this area in the first erosional stage and five others in the second stage, while there were no typhoons visited there during the calm stage. In the first erosional stage, it was the main cause of the remarkable coastal erosion that Typhoon No.16 in 1974 passed northward on the west of Nishinoshima Shinto, as it caused strong southerly wind blowing to the south coast of the island. In the second erosional stage, Typhoon No. 20 caused similar coastal erosion in 1975.
It was the effect of submarine topography that the eroded area was confined to the southern coast of the new island. Nishinoshima Shinto is a central cone of Nishinoshima submarine volcano. Nishinoshima old island westward and the several reefs northward, located several hundred metres apart from the new island, are parts of a somma of Nishinoshima submarine volcano. On the other hand, there is no somma to the south of the new island, where a flat sea floor deeper than 20 metres is widely extented. Accordingly, the north and west sides of the new island are protected by the comma from wave attacker, while the south side is exposed to wave erosion.
The stable coastline in the calm stage was held by the resistance of lava stuffed in craters and those flown from such craters. In the erosional stages, lava stuffed in craters remained from wave erosion and stood as stacks above the sea surface. A new abrasion plafform with a width of more than 100 metres appeared along the south coast after the coastal erosion. The terminal depth of this platform was about 15 metres, which indicated the depth of the wave base of vigorous abrasion.

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We have studied some influences of zoning of the City Planning Act which established newly, urbanization promotion area and control area, and focussed both on the urbanization in Hadano-city, Kan agawa Prefecture, and various changes in the rural areas around it. We found two “discrepant areas” where some discrepancies between the substantive region and the planning region have occurred by the City Planning Act.
One is the case of the Imaizumi and Nishiotake area, which was included in the urbanization promotion area, though it had good agricultural area from historical and geographical points of view, and the inhabitants there are concerned with operating agriculture. So, if this act had not been enforced, it would have firmly kept its character as an agricultural village. Included in the urbanization promotion area, this area has been changed by the influence of increasing houses around the Ohatano station and constructing the connecting road with the Tomei expressway. The other is the Horinishi area. It was included in the urbanization control area, though its urbanization had been expected to be immediate as it was located along the extention of the residencial and the industrial sectors, both of which have been developing with the Shibusawa station as their center. As mentioned above, the Horinishi area is on the direction of the urbanization in Hadano, where considerable parts of farmland have already been converted into urban uses without any sign of resistance, so it may become a part of the

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