We tried to evaluate the hydrological balance element each before and after the development work, through the researches of defining the varying hydrological balance owing to housing development in the vicinity of the ground surface and thereby setting up the modeling of hydrological balance system as basedz on the soil retention characteristics.

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One of the problems by which urban storm runoff are confronted is the increasing of runoff water for the rivers of the urban area. This incresing of runoff water is caused by the developments and urbanization around the river basin. This phenomenon of the incresing of runoff water produces many problems in the storm water drainage. The permeable facilities for storm water control are effective countermeasures for these problems. The values of permeability of the permeable pavement for controlling storm runoff are evaluated on basis of the research studies. And the functions of permeable pavement are investigated.

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A river discharge in urban area is composed of groundwater runoff and waste water. A seasonal observation of water level height and quality of water of about 60 wells was made toestimate the conductivity of non-polluted groundwater.
Groundwater runoff is evaluated by a monthly observation of river discharge and conductivity of water during 1984-1986 at Ochiai River, in Tokyo.

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A device melting snow on the roof named ‘snow disaster prevention net’ has been proposed. This device consists of net and rod essentially, where the roof is covered with the net and the rod is set beneath the net along the pitch of the roof. The mesh size of the net is small enough, so that the snow can not pass through the net, and thus a small space between the net and the roof is always maintained. Once the snow starts melting due to the solar heat or any other heat, the produced water will gather in this small space (or water lane)., and then the water will flow through it. The amount of the water may increase as going from the ridge of the roof to the edge. When the water level becomes higher than the net, the water has a direct contact with the snow, so that the snow melting process characteristic to this device is operating: This process results in an additional amount of the water, to be used for melting another snow subsequently, and this process is repeated in many times.
It is found that this device is particularly useful to melt the snow at the edge of the roof that is the most critical part of the snow load on the roof, and can reduce the snow load by about 10-20 percents without any heat energy except the solar energy.

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Based on state of the art for the estimation of pollutant run-off from a whole basin of a closed water bodies, a design scheme for the computer-aided system for the basin-wide management of pollutant run-off was presented. The analysis of the problems associated with the conventional ways of estimation for total pollutant run-off clarified a urgent needs for the introduction of computer-aided system to satisfy the accuracy and consistency during calculation, to estimate undetermined loading and export coefficients and to propose control plans explicitly for public. The system which satisfies these requirements was designed as a man-machine communication system on personal computer to promote applications to the management of small closed water bodies where professional personnel are not available.

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This paper deals with the simulation model for the prediction on the water quality on a lake. Of cource, there are a lot of system or the models for this purpose, there were few systems that could be calculated by the dialogue type. In this paper, we have developped the new system, by putting the several values according to the request of the personal computer, and the results of the simulations are presented on the color display. We are sure that this model could be used on the occasion for the decision making at the first or second stage for the sewarage system, planning or the environmental assessment.

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Field surveys were conducted to investigete the change of water quality with time and the mechanism of mass transport in the Tidal River Rokkaku, where water particles move toward up-and down-stream according to tidal action and turbidity maximum also moves in association with erosion and deposition of sediments. Relations between a cumulative water volume from the upward end of tidal reach to a point in downstream and salinity at the point are obtained. As a result, the salinity profile in the water volume is shown to be quasi-steadily fixed. Profiles of velocity and water qualities in a cross section of the river are very complicated due to topographical effect. The mass transport fluxes estimated from observed data in the center of the cross section have to be corrected to obtain the exact estimate of the mass transport fluxes through the cross section. The relationships between salinity and the concentrations of dissolved matters are similar to those between water volume and the concentrations of dissolved matters, because salinity is steadily distributed through the water volume.

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Using the new gas tracer technique, the stream reaertion coefficient was measured in the field. Ethylene (C₂H₄) is used as a tracer gas and Rhodamine WT as a dispersion and advection tracer. After the step-type-injection of both tracers, water samples are taken from three recoveries downstream.
The temporal distribution of the tracers are compared and analyzed for the decay rate of the gas tracer. The volatilization rate of ethylene in the flow is estimated by the peak method and the mass method. The mean velocity, the mean depth and the longitudinal dispersion coefficient are also calculated by the results of the dye study.The estimated value of the reaeration coefficient is within a reasonable range and shows good agreement with the predicted values.
The gas tracer technique proves to be very useful for the study of the reaeration coefficient of the shallow streams.

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Recently, water quality in receiving water has been polluted, and this problems effect on the aquatic products, sight-seeings and leisure industries.
From now on, ocean age has come. The international law of the sea with 200 sea miles was decided. It is important for japan to make clear how to preserve and to develop the sea. Therefore, we have developed the purification method which use the energy of the waves and the ebb and flow. And we think that this new purification method may help the preservation of the water quality and development of the sea and lakes.
“The purification system for the sea water area” can improve the water quality. For example, they are red tide, pollted river water, domestic sewage, oil pollution, storm surge, tidal wave, drift sand and splash of sea water. And this system demonstrates marine productivity eternally.

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To clarify the characteristics of water quality and pollutant loads in the Asahi River, Okayama Prefecture, we observed SS (suspended solids), turbidity, COD (chemical oxygen demand), TP (total phosphate), TN (total nitrogen) for over five years and identified hydrologic simulation models of pollutant loads based on the observations.
In the year of lower discharges, the concentrations of TP and TN became higher but the COD values and SS scarcely changed. Therefore, the pollutant loads of COD and SS decreased but TP and TN scarcely changed. The probability distributions of the water quality and pollutant loads observed for a year can be regarded as a log-normal distribution. Identified hydrologic simulation models of pollutant loads estimate well the daily pollutant loads if a yearly average discharge is similar to the year of estimating the model parameters.

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Die-off processes of coliform and enterococcus groups were investigated in the mixed-algal reactor with the retention time of 4 days. The results of this investigation indicated that both of coliform and enterococcus groups rapidly died off in the mixed-algal reactor.
The initial die-off rate coefficients of coliform group in the reactor were almost similar values to those of enterococcus group. The test of significant difference was applied between mean initial die-off rate coefficient of coliform group and that of enterococcus group. But there was no significant difference at the 10% level. However, compared with the results of the blank test at which no algae was existing in the reactor, die-off rates of E. coli, Klebsiella spp. and S. faecalis var.liquefaciens were much less than those of the blank test, respectively. Therefore, there is the possibility that the existence of algae proposes the preferable conditions for the survivals of E. coli, Klebsiella spp. and S. faecalis var. liquefaciens. The adsorption of coliform and enterococcus groups to the algae exerted no influence on estimating the die-off rate coefficients of them.

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To get clear ideas of improving rivers for recreational use, about 12, 000 photographs were taken along about 200 rivers through out the country. The results show that people gather and are fond of playing at particular spots such as sand bars, weirs and so on. Around sand bars, it iseasy to find good places for playing or swimming at the upstream of weirs, people can row boats and swim. River conditions, which mean the velocity of flow, the depth of water and the material of river bed, are closely connected with such river use. This information gives us valuable suggestions to plan and design rivers for recreational use.

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Residents' consciousness of neighborhood environment and their wants which are analyzed and identified by means of intensive questionnaire survey, are interpreted and formulated as the significant input information to planning process of a water-ront rehabilitation and development project In this study. The broad concerns of residents to river sanitation, open space, recreation activities, trail with greenery at riverside indicate that Doi river in Sakai City is one of remarkable environmental resources which are able to support comfortable life and from which residents might gain environmental amenity services. Several alternatives of development plans are designed on the basis of both stimulating disirable functional linkage among various services of space and facilities in and along the river. An amenity-services-oriented plan is judged to be an advantageous to lift up satisfaction level of residents in the evaluation process by surrogate experts.

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A framework of comparative studies on risk management is proposed forbetter understanding of similarities and differences of approaches to risk resolution in high-technology societies. The author shows methods, principles, and manners of risk managementpointed out by task groups for the selected four case studies, risks from use of detergent, lead, pesticides and in use of safety belts, in First US Japan Workshop on Risk Management. Various types of twodimentional frame are introduced in systematical process of comparison of risk management, which present 1) interdependent relationship among multi-actors, 2) resources mobilized and utilized in steps towards problem-solving, 3) handling of uncertain factors in management practice, 4) risk conception of interest groups in each stage of the cognition ladder, 5) upgrading reliability of methods of evaluating risk from viewpoints of vulnerbility of decision-making, 6) loser-gainer relation-ship, form and content of compensation systems.

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The selection of target chemical is the most important key element for effective controls on emission of chemicals. The environmental fate models are constructed for the purpose of using in such selection. Multi-regression equations are obtained by the analyses of the concentration level of selected chemicals in environmental elements. The values of prediction are in good agreement with tha t of measurement.

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ABSTRACT; This paper examines the role of three measures of reducing risks, i. e., probability reduction, damage reduction, and insurance. Probability reduction alone is usually emphasized in various risk management projects, and still it is the most importantmeasures among others. However, damage reduction and insurance might also be the useful measures to reduce the burden of risks, especially when the degree of risk aversion is high in the preferences of people. Thus, these two alternative measures had better be considered as well as probability reduction in order to explore the optimal combination. Aside from this aspect, risk-cost-benefit analysis usually assumes risk neutrality in the sense that the expected value of the benefit alone is compared with its cost. However, when people are risk averse, the analysis will underevaluate the benefit of the risk management project.

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In this paper, the following topics are discussed, (1) regulation of hazardous chemical substances and appropriate management level of solid wastes, (2) review of risk assessment and risk management and Oan example of risk assessment and risk management in solid waste disposal, for the case of dioxin genera ted from waste disposal facilities.

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The main disposal of the municipal refuse consists of the incineration for combustibles and the landfill for noncombustibles. However a trace of hazardous materials such as heavy metals in the dry cell batteries make all the more difficult to dispose of the solid waste. Especially, the fear that the dry cell batteries in the landfill may be caused whether mercury or other heavy metals will leach. The purpose of this research is to study of the movement of mercury and other heavy metals in the dry cell batteries in landfill. The movement of the heavy metals in the dry cell batteries were monitored using the landfill-simulated test cells. The experiment was just started and movement of the heavy metals were estimated to be very slow. The measures of the protection of the environment against the heavy metals in the dry cell batteries in landfill are the subject for a future study.

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