| Co-Investigator(Kenkyū-buntansha) |
MIZOGAMI Shoji Kumamoto University, Dept of Civil and Environmental Eng., Professor, 工学部・環境システム工学科, 教授 (20135403)
SUZUKI Atsumi Kumamoto University, Dept of Civil and Environmental Eng., Professor, 工学部・環境システム工学科, 教授 (50040390)
FURUKAWA Kenji Kumamoto University Dept. of Civil and Environmental Eng., Professor, 工学部・環境システム工学科, 教授 (60029296)
HARADA Hiroyuki Kumamoto University, Dept of Civil and Environmental Eng., Associate Professor, 工学部・環境システム工学科, 助教授 (20222234)
MATSUDA Hiroki Kumamoto University, Dept. of Earth Science, Associate Professor, 理学部・地球科学科, 助教授 (80274687)
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| Research Abstract |
(1)Numerical analysis of tidal flows and ocean waves were performed for all of Ariake-sea and the both estuary of Sirakawa and Midorikawa rivers. Velocity field characteristics and concentration distributions of suspended solids in those areas were evaluated as a function of tidal levels and river inflow rates. Also, numerical methods for analyzing the form of tidelands and their gullies were developed. Hazard Mapping for Storm Surge based on Interaction between Storm Surges, High Waves and Tide, and Their Maximum Occurrence Prediction were developed. Quasi-three dimensional ocean circulation model POM (Princeton Ocean Model) was applied to the simulation of current and material transport in the bay, which has complex bottom topography. Numerical scheme for advection computation in POM was changed from the central difference to TVD scheme to improve its transportability. Test simulation made clear the effectiveness of the modified scheme in advection term.
(2) Bottom soils ware classifi
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ed to seven clasters by claster analysis with four variables, mad content, sulfieds, COD/I gnission loss and COD/mad content, and it was found that major species are different by claster. Also, authors proposed a richness index, IR, which quantitatively shows richness in benthos in tidal flats. The index is defined by the equation, IR = H' x WWU, where H' is diversity index by Shannon function and WWU is the wet weight of benthoses in unit area. The feature of the clasters of tidal flats was presented by the index in some degree but the clear difference in the index between clusters was not found, hi this year, some factors supposed to influence on the index were examined, and it was found that the appropriate length of dried period on the tidal flat may be desirable for the richness of benthoses.
(3) Denitrification capability of the tidal flats in Ariake Inland Sea and Yatsushiro Inland Sea was estimated and factors that affect denitrification were determined. It was found mat denitrification capability was largely influenced by die silt and clay content of mud. Therefore the denitrification rate of tidal flats in Saga area where the silt and clay content of mud was much high was higher than the other tidal flatsexamined. And the denitrification capability is highest in summer when the source of nitrogen and carbon was rich because of heavy rainfall in the rainy season and Denitrifying bacteria was active. The objectives of this study is to evaluate the tidal action and benthic animals such asseawom in denitirification activities of the tidal flat in Shirakawa river. Experimental were conducted to determine the dependence of denitirification rate on sediment character using tubes filled with costal marine sediment both with and without sewaorm. Based on the tidalaction-dependent decrease of NO3-N concentrations, denitirification rate were calculated. The result indicate that the effect of bioturbation on denitirification rate ware influenced by sediment COD levels and redox potential.
(4) On the basis on sedimentary facies, diatom and benthic foraminiferal assemblages, and ^<14> C ages of 4 piston cores, 21 to 44 meters in water depth, off Kumamoto, environmental changes in the central part of the Ariake Sea were examined during the last 10,000 years. As a results, it is clarified that marine water invaded into the area around 50 meters below a present sea level about 9,500 yrBP, and the whole area off Kumamoto became to be underlain in the central bay environment same as a present about 7,400 yrBP. Further, the marine environment spread to inland continuously and covered entirely all over the present Kumamoto Plain area about 5,400 yrBP.
(5) The aim of this study is to check the Contingent Valuation Method (CVM) using double-bounded dichotomous choice (DB-DC) method. Since CVM uses Stated Preference (SP) data, it can measure existence value of non-market goods. However, reliability of the evaluation is inferior to Revealed Preference (RP) Method. It is necessary to check the bias based on SP data when value of non-market goods is evaluated by CVM. There are two targets in this paper. One is a test of evaluations by CVM through different payment types. Another is to check and to get rid of a starting point bias and a yea-saying bias in DB-DC method. In this study, two types of payment way were applied. One was based on new taxation, and another was based on tax reallocation. The evaluations through two payment types were compared with theoretical results, and reliability of the evaluations by CVM was tested. Less
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