We attempted to determine the distribution of benthic animals and to quantify their population densities focusing on the life traces on a tidal flat. By processing digital photos taken from a radio controlled helicopter equipped with geographical positioning system, distribution of nest holes on the tidal flat of Imazu was obtained with the thirtieth effort of manual surveying on site. Benthic animals that build nests on tidal flat of Sone, Fukuoka prefecture represent about 50 per cent of population on the tidal flat, among them shrimps and crabs represent about 8 per cent. On the area where the percentage of clay and silt exceed 50 per cent, shrimps and crabs represent 28 per cent by wet weight. Distribution of a mud crab (Yamato osagani: Macrophthalmus japonicus) was identified by the distribution of the holes they make.

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Many studies have shown that the riparian forest suppresses the light intensity, primary productivity and the abundance of stream invertebrates by canopy shading in headwater streams. However, most studies were conducted at the stream-reach scale, whereas the light intensity seems to vary at smaller scales. We conducted a field survey to reveal the spatial pattern in the light intensity at consecutive riffles and the response of stream scraper assemblages to the light gradient, in a Japanese headwater stream. Canopy opening varied considerably (4-38%) throughout the study segment. Some survey points located in stream reaches without riparian forest showed greater degree of canopy opening. Difference in the abundance and species composition of canopy trees and understories may be responsible for generating the variation in the canopy opening. Analyses using a generalized linear model revealed that canopy opening significantly and predominantly explained the variance in density, biomass and taxon richness of stream scrapers. These invertebrate parameters were high at survey points with greater degree of canopy opening. The density and the biomass of many dominant scraper species also increased with canopy opening. These results imply that the quantity and the diversity of scrapers responded to the light gradient at the spatial scale smaller than the stream-reach. We suggest that the variation in the light intensity at a small spatial scale, which might have been even treated as an error, is an important determinant of the spatial distribution of stream scraper assemblages in headwater streams.

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Effects of river mouth closure on fish fauna were studied in 11 rivers in the northern region of Okinawa Island. We investigated the occurrence of fish species and recorded physical environmental variables, i.e., water level, flow velocity, water temperature, and the width of the river mouth at high water, in the tidal river areas over four seasons. There were significantly fewer fish species in rivers with completely closed mouths than in those with open or incompletely closed mouths, particularly those species depending strongly on the sea and tidal river areas. This was presumed to be due to low salinity and obstruction of fish migration. Among the rivers with completely closed mouths, marine fish species occurred only in the Zatsun River, where the salinity changed with the tide. This shows that marine fish species are able to survive in tidal rivers, even when the mouth is completely closed. In two rivers with completely closed mouths, no larvae or juveniles of Rhinogobius species were found in the spring season, suggesting that the closed mouths obstructed the migration of these species. There were significant positive correlations between the number of fish species and the range of water-level fluctuation and the width of the river mouth at high water, two indications of the degree of river mouth closure. We suggest that the water-level range and the width of the river mouth at high water provide valid indices of the effects of river mouth closure on fish fauna.

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We made an interview in mountainous region for this research to classify a tendency of the environmental awareness of local inhabitants. The examinees of this research are 24 inhabitants of Wakayama prefectural Kozagawa town. An analytic way is to group items of the environment consciousness and distill the factor of an environment change by using a KJ method and a factor analysis. As a result, inhabitants recognized a natural environment as 4 factors. These are “agriculture and forestry”, “living”, “civil engineering” and “aging”. Also, the recognition that 4 factors related to each other was not almost seen. That is to say, these tended to become one. In addition, inhabitants recognize the change by comparing a regional natural environment with a fact such as secular change of residential district. A formative process of environmental consciousness of inhabitants is revealed in this research. Environmental awareness is formed by being concerned with their living. It is necessary to adopt the opinions of local inhabitants in an environmental policy of recent years. The opinions of inhabitants are influenced by each environmental awareness. So, the process of commitment of inhabitants is important in developing an effective environmental policy. Therefore, it is necessary to consider the way of adopting the opinion that utilized an environmental awareness tendency.

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[in Japanese]

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For flood prevention projects, it is important to determine which stand structure variables of riparian forests have the greatest affect on flow resistance. Numerous studies have used hydraulic model experiments to investigate flow resistance, but stand structure dynamics are difficult to incorporate into such experiments. This study examines how river bed grain size reflects the degree of flow resistance by stand structure. We used three sizes of grain: D50 (grain size at 50% of grain size distribution), fine grain (< 0.075 mm) and very fine grain (< 0.005 mm). Two kinds of multiple regression analysis were used. The first analysis used forest floor elevation, stand structure (density, clear length, basal area) and floor vegetation (height, coverage ratio) as the independent variables and D50 and fine grain content as the dependent variables. The second analysis excluded floor vegetation from the independent variables used in the first analysis. In the first analysis, stand density and clear length were identified as the stand structure factors that most greatly affect flow resistance. In the second analysis, it was difficult to identify the degree to which stand structure factors affect flow resistance. These results indicate that consideration must be given to the effects of micro-topography and floor vegetation when the effect of stand structure on flow resistance is examined for river beds with the three grain sizes. The stand structure variables identified as influential, i.e., density and clear length, are important in studies on flow resistance. In studying riparian forests at different stages of succession, identifying stand structure factors that greatly affect flow resistance may enable examination of how spatiotemporal changes in stand structure influence the flow resistance.

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Unjou water and Tsushima's famous water in Obama City, Fukui Prefecture, were surveyed for spring discharge and water temperature by sampling as frequently as every other day from November 2007 to April 2009. Conclusions were as follows. First, the average spring discharge of Unjou water was about 1 L/sec, and that of Tsushima's famous water was about 0.5 L/sec. Second, both springs ran out of water in January and February, and flow was decreased in July. Third, the average water temperature of Unjou water and Tsushima's famous water showed a tendency to increase in summer and decrease in winter. Fourth, the minimum average water temperature of Unjou water and Tsushima's famous water was about 14 degrees Celsius, and the maximum was about 16.5 and 18 degrees Celsius for Unjou water and Tsushima's famous water, respectively. Fifth, spring discharge of Unjou water and Tsushima's famous water dramatically decreased when a snow melting system was put into operation. Sixth, it is desirable to utilize not only groundwater but also the heat of groundwater and river water to aid in the melting of snow.

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