Recently, importance of river environment is getting recognized in Japan, so that river improvement taking river ecology into consideration, the nature-oriented method is one of which, is carried out. However, in present stage, relationships between habitat and living creatures are not clear. The purpose of this study is to make clear whether nature-oriented method distorts river ecology or not. Particularly, in this study, we evaluated physical environment and existence of aquatic insects around the nature-oriented bank and the concrete bank in a improved river (Gogyou river in Ibaraki Prefecture), based on those in a natural river (Kinu river in Tochigi Prefecture). As a result of comparing existence of aquatic insects around the nature-oriented bank with those around the concrete bank in Gogyou river, existence of aquatic insects around the concrete bank is more than those around the nature-oriented bank. One of the reasons is that the depth of water around the concrete bank is lower than those around the natureoriented bank. Consequently, to keep the depth of water shallow should be considered in river improvement on the flat low lands.

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For the evaluation of flood mitigation function of irrigation ponds, this paper analyses the performance of the Matsuzawa-ike pond, with its catchment area of 1.13km², during flood time, based on the records of water level in the pond and rainfall. It also gives a stochastic analysis, based on simulation using probable rainfalls at different levels and runoff model, on flood mitigation and its effect on flooding in the downstream of the pond. It clarifies; 1) the pond has decreased flood peaks by 37-98% in its overflow, for 4 cases of high flood with the maximum 10-minute rainfall intensity of 10mm and more, 2) the percentage of the mitigation is strongly influenced by the vacancy of storage capacity at the beginning of flood, 3) flood mitigation ratio in the floods with the return period of 5-200 years ranges 37 to 43% of the peak inflow, even under the condition of full water level at the beginning of flood, 4) the pond has the effect to reduce the frequency of inundation in the downstream from more than once in every year to once in 2 years

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The flood mitigation function of irrigation pond is largely dependent upon rainfall pattern. The analysis of pattern in actual rainfalls is necessary to evaluate the flood mitigation function at the actual stage. This paper analyzes the actual rainfall patterns of 10-minute rainfall for 7 years at the Matsuzawa-ike pond, by applying statistical concept of skewness to rainfall pattern. It clarifies; 1) the rainfall pattern in heavy rains is mostly similar to the hyetograph which has its peak at the center of the rainfall duration time, while the hyetograph with it peak in the latter harf of the time duration is popular for the 110 minutes around the peak, 2) the lowering of water level in the pond during flood season is effective to flood mitigation.

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A thermo-TDR probe has been developed for measuring thermal properties using a dual-probe heat-pulse technique of various textured soil (sand, loamy sand, and clay loam) at different soil moisture conditions. The thermo-TDR probe containing three parallel stainless steel rods in which every individual rod was 0.045m in length, 0.0025m in outer diameter, and 0.01m in rod-to-rod spacing. Temperature change as a function of time differed with the position difference of thermocouple located in the rod and handle part of thermo-TDR probe. It was observed that maximum temperature at a specific time was also varied according to the position of thermocouple in the rod (at the boundary between handle part and rod (z=0), at the center rod (z=L/2), and at the head of rod (z=L)). A weighted nonlinear regression method adopted for identifying thermal diffusivity κ and volumetric heat capacity ρ_c. Thermal conductivity λ was calculated from the relationship between κ and ρ_c data. In sand soil, maximum difference in ic at different sensor position was about 2.2×10^-7 m2· s^-1. Maximum difference in pc at different sensor position was about 0.6MJ·m^-3·K¹ at low water content (θ<0.07m³·m^-3), and the difference tented to narrower while A>0.07m³·m^-3. Difference in λ was about 0.9, 0.6, and 0.3W·m^-1·K^-1 for sandy, loamy sand, and clay loam soil, respectively. It has been suggested that the position of thermocouple located is important for measuring the exact thermal properties of any soil.

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Numerically analyzed inverse calculation by Finite Element Method (FEM) was conducted for evaluating soil thermal properties measured with 4 types rod length (L=1.25cm, L=2.5cm, L=5.0cm and L=10.0cm). For this purpose, thermal properties measured with the dual-probe heat-pulse (DPHP) technique was adopted as the input value. The virtual thermocouples were located along the rod position at z (z=0, z=L/4, z=L/2, z=3L/4 and z=L). Temperature distribution and temperature change with time (ΔT-t) data was also calculated using the FEM. The nonlinear regression method was adopted to identify thermal diffusivity and volumetric heat capacity. In order to determine the optimum length of heater rod for ΔT-t measurement, dependence of volumetric water content upon the equi-thermal property line was evaluated for above mentioned condition. After a heat pulse emission from heater rod, the temperature distribution (isothermal line) was observed to be an egg-shape along the rod direction of z in the shorter rod length. Egg-shape distribution occurred due to the finite length of heater rod and handle part of the probe. The maximum temperature change ΔT_m observed at above mentioned position was found to be at position z=L/2. The longer rod length, equi-thermal property at the relative rod length L_r distributed along with axis of L_r.

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Nitrogen removal performance in an aerobic filter tank was investigated through observed data on rural sewerage facility with submerged biological filters. It is found that mechanism of nitrogen removal in the aerobic filter tank can be explained by the first order reaction, when suspended solids are eliminated from an aerobic filter tank and effects of the detachment-and-elution of accumulated matters in it. It could be inferred that both nitrification and denitrification is simultaneously brought about the aerobic filter tank, as NOx-N is partly decomposed into nitrogen gas under the anaerobic condition of the tank. Also, it could be deduced that the ratio of the BOD to the T-N concentration has effected on nitrogen removal efficiency due to denitrification in the aerobic filter tank. The multiple regression equation is derived from observed data, which can explain nitrogen removal rate depends on five variables: influent T-N concentration, hydraulic loading rate, temperature, and dissolved oxygen in an aerobic filter tank. It can be concluded that it may be important to consider design and operation factors of the aerobic filter tank, based on the nitrification and sludge accumulation rates in the aerobic filter tank, in order to maintain stable nitrogen removal efficiency.

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In order to preserve water environment of lakes and lagoons, sustainable management of water cycle and elucidation of water quality formation are needed. In this study, we made a tank model for water quality estimation of lakes. This model consists of complex tank model that adopting the coefficients of concentration and simple lake model using retention time, and identified water quality of Toyano Lagoo in Kamedagou basin. We took into consideration about the influence of water management of agricultural use. We simulated effects on a water quality of the lagoon by this model for 2 cases. First, increase of delusion water to the lagoon is effective to decrease COD value in April. Second, decrease of irrigation water by decrease of paddy field area will cause use of COD value in mid-summer drainage season In case of lake in urbanizing watershed that has paddy field, this model can predict effects on water quality changes.

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Coefficient of subgrade reaction of the rubble mound in the foundation of the open pier or the mooring post is identified by the Kalman filtering in conjunction with the transfer matrix method based on the measurement of in-situ experiments of piles. The existing surface clay layer is removed and the dilluvial clay layer is replaced by the rubble mound to shorten the length of the pile above the surface of the foundation deposit. In-situ experiments were carried out for both the existing clayey layer and the rubble mound. Measured data for the inclinometer is differentiated to obtain the moment and integrated to obtain the displacement along the pile, and they are used as the input for inverse analysis. Identified coefficient of the rubble mound using these measurements is less than that of the dilluvial clay under the same level of the loading. Numerical results provide useful information for the design of the open pier and its foundation.

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The low cost and low energy are requested in agricultural facility to reduce the agricultural production cost. In the bend pipe flow, because of the centrifugal force, there is a pressure difference between in inside of and out side of curve pipe. In this condition, if the inside and out side of curve pipe were connected by pipe, the bypass flow is created in this route. In this paper, the characteristics of bypass flow were clarified. As the flow rate of bypass flow is proportional to main flow rate, so, if the bypass flow rate is measured, the main flow rate is known. The bypass flow rate is smaller than that of main flow; usually the flow meter in bypass route is very smaller than that of in main flow. The characteristic curve of centrifugal force to represent the hydraulic characteristics of the bend pipe with bypass flow was defined. By the experiment and analysis, pursuing method of this line was shown and meaning of this line was discussed as follows.
1) X-axis value of the intercept of this line and the hydraulic resistance line in bypass route shows the bypass flow rate.
2) The value of intercept of X-axis shows the possibility of maximum value of bypass flow rate.
When the bend flow meter was used in the field, what will be happen were discussed, specially the effect of filter to the flow rate of bypass route is evaluated by characteristic curve of centrifugal force.

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This paper shows a simple system for seismic risk evaluation of small earth dams. The data of site investigation for damaged dams and “Database System on Small Earth Dam for Preventing Disaster” is used to this system and the neural networks are applied to the proposed methodology. Factors of earthquake damage are assumed to be 16 characteristics of a dam and an earthquake;(1) dam type, (2) dam height, (3) crest length, (4) crest width, (5) upstream slope, (6) downstream slope, (7) soil classification of embankment, (8) era of dam construction, (9) rehabilitated history, (10) damaged history, (11) topography, (12) surface geology of dam site, (13) soil property of dam site, (14) geological age, (15) distance to epicenter and (16) acceleration at dam site. The case study through the Geiyo Earthquake in 2001 in which the objective area is Ehime Prefecture is conducted and availability of the system is evaluated.

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Time marching approach (TMA), solving steady flows in pipelines with the method of characteristics, is applied to system 1 and system 2 having 1345 and 3100 pipes, respectively. The existing TMA solves the steady flows of system 1 and 2 in CPU time of about 30 minutes and six hours, respectively, with personal computers (P III 1.7GHz). The TMA is enhanced by the aid of the network analysis basedon the information of “Tree” in the graph theory, with which heads at nodes are modified in the computational process. With this the steady flows for system 1 and 2 are solvable in about CPU time fifteen minutes and one hour, respectively.

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We estimated the seismic stability of slope by comparing the findings of conventional circular slip calculation with those of pseudo-static elasto-plastic finite element analysis. For a homogeneous slope with simple shape, the result using the critical horizontal seismic coefficient and maximum shear strain distribution obtained by finite element analysis, exhibited agreement with the one of circular slip calculation. On the other hand, in the case of slope with the complex shape, the indefinite circular slip surface was obtained by using the circular slip calculation. However, the finite element analysis simulated the realistic failure surface applicable to the practical design. The centrifuge pseudo-static tilting model test reproducing the seismic effect was carried out. The finite element analysis employing the elasto-perfectly plastic constitutive model satisfactorily provided enough data to correlate experimental results.

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As a conformity field system to future re-land readjustment, the author and others has proposed the Road Removal-Type Contour Plot Field System (RRC-PLOTS), and as for this field system there is a major feature in the point which expands field lot to contour line direction at the time of re-land readjustment. In order to apply this field system, it is necessary for the object field to satisfy several conditions for characterizing this, but the fields which have the condition such as that at present stage are few. Because of this, as for the application object of the same construction method there is a tendency which is thought quite it is little, has become also the cause of obstructing the spread. With this manuscript, “ expanded RRC-PLOTS” was proposed as the field form which eases the restriction in regard to such application, the fact that extensive application is possible was shown. In addition, discussed is that it should examine conditions (namely, the time for moving between lots by crossing ditch levee, the areal reduction and the weeding area), comprehensively at the time of deciding the field form.

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In asphalt pavement, the surface course and the binding course is composed in two or three layer, and it is using the asphalt mixture which quality is different from in each layer. The finding out of the elastic modulus of each layer is important in the theory structure design of asphalt pavement. This paper presents a method of determining the elastic modulus of each layer by using a multi-layerd specimen with different pavement mixtures in bending test. In this method, elastic modulus of each layer is computed by backcalculation based on results of actual measurements and displacement or strain obtained through two dimensional elastic analysis by finite strip method. The results from a series of experiments on the elastic materials have demonstrated the validity of the present method. The other experiments have made it clear that the present method can beeffectively applied to determining the elastic modulus of each layer of asphalt mixtures in the low stiffness state.

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Laboratory experiments were carried out to study the influence of surface soil hardness, ponding water depth, mass and dimensions of coated seeds, falling height on seed penetration depth of sprayed direct seeding of rice plants which is one of the most important direct seeding methods. As the result, 1) Because of water resistance under inundation condition, to obtain appropriate seed penetration depth, surface soil must be too soft when puddled soil are not yet settled down. 2) By the same reason, seed penetration depth can be increased by the mass of seed coating or falling height only when surface soil is very soft and ponding water depth is not so deep. 3) For the reasons stated above, it is necessary to obtain appropriate seed penetration depth in sprayed direct seeding of rice plants as seeding into puddled soil surface soil just after puddling.

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