Online ISSN : 1349-2853
Print ISSN : 0915-1389
ISSN-L : 0915-1389
Volume 28 , Issue 3
Showing 1-7 articles out of 7 articles from the selected issue
Original research article
    2015 Volume 28 Issue 3 Pages 109-123
    Published: May 05, 2015
    Released: August 12, 2015
     This study was conducted to reproduce long-term groundwater flow in Musashino Terrace using a numerical model and to clarify the relation between long-term groundwater flow change and land use change. The model used for this study is MODFLOW developed by the United States Geological Survey (USGS), which is the threedimensional groundwater flow model that uses the finite difference method. The simulation was conducted for 1976-2012 when land use data were available. We computed daily groundwater level for the period. Moreover, we analyzed the projected groundwater flow during 2013-2050, with meteorological data calculated using global climate models of four types. Groundwater variation and seasonal change that were caused mainly by rainfall were reproduced. We also calculated the decrease of the groundwater level and recharge area around some observation wells.
     The Mann-Kendall rank statistic was used for detecting groundwater flow trends. Results clarified the relation between the decrease of recharge area and groundwater level. That relation was affected by the decrease of permeable areas such as paddy fields, agricultural areas, and woodlands, and by the increase of impermeable areas such as building sites during 1977-2012. Future groundwater flow was also estimated, which clarified that the groundwater level can be expected to rise by the increase of moderately intense precipitation in the future if land use remains as it is.
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Technical note
  • Dai YAMAZAKI, Tomohiro TANAKA, Paul D. BATES
    2015 Volume 28 Issue 3 Pages 124-130
    Published: May 05, 2015
    Released: August 12, 2015
     A new formulation of the St. Venant momentum equation, the local inertial equation, was developed recently at the University of Bristol for stable and fast flood inundation modelling. The local inertial term of the momentum equation, which is neglected in the diffusive wave approximation, is additionally considered in the local inertial equation. Herein we demonstrate the manner in which flood inundation simulations can be stabilized by adding the local inertial term using mathematical stability analysis and numerical simulations. Mathematical stability analysis suggests the following two characteristics of the local inertial equation as important for computational efficiency: 1) time evolution of flood inundation is solvable explicitly using semi-implicit approximation of the discharge term in the Manning’s roughness equation; and 2) the type of the governing partial differential equations changes from a parabolic system to a hyperbolic system by adding the local inertial term to the diffusive wave equation. Both mathematical analysis and numerical simulations revealed that the local inertial equation is more computationally efficient than the diffusive wave equation, especially in cases of high- resolution inundation flood modelling in very flat regions.
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Commentary article
  • Minoru KAMOTO
    2015 Volume 28 Issue 3 Pages 131-136
    Published: May 05, 2015
    Released: August 12, 2015
     The Typhoon Committee (TC) was established in 1968 as an intergovernmental organization under the auspices of the United Nations Economic Commission for Asia and the Far East (UNECAFE) and the World Meteorological Organization (WMO) to minimize the loss of life and material damage caused by typhoons in ECAFE region. In 1974, ECAFE was re-designated as Economic and Social Commission for Asia and the Pacific (ESCAP). Thereafter, TC progressed to become ESCAP. Currently TC includes 14 Members and established technical working groups such as those for meteorology (WGM), hydrology (WGH), and disaster prevention and preparedness (WGDRR). The main pillars of TC activities are Annual Meeting, Integrated Workshop and Annual Operating Plan, which are conducted in the working groups or as cross-cutting projects. Activities are based on the science for research, training, and information exchange. Even given the recent difficulties of geo-political situation in the region, TC is actively implementing activities to promote and coordinate the planning and implementation of measures required for minimizing the loss of life and material damage caused by typhoons with intergovernmental cooperation.
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