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H. Yamanishi
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Journal : Lowland Technology International

 1 
PREDICTION MODEL OF INUNDATION IN PUMPED-FIELD LOWLANDS AND SCENARIOS FOR IMPROVING ITS PERFOMANCE N. Cao Don; H. Araki; H. Yamanishi; K. Koga
Lowland Technology International Vol 5 No 1, June (2003)
Publisher : International Association of Lowland Technology

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Abstract

During rainy season, frequent flooding by strom water is one of the most serious problems in lowland areas, causing heavy effect on transportation, agriculture, industry, and economic activities. As a result, the required drainage water levels in this area are generally lower than the water levels of boundary rivers. Under such circumstances, pumping system should be designed from a viewpoint of integrated control floods. The Nam Ha lowland, in Vietnam, bounded by four surrounding rivers, is selected as a case study. The operation scheme in this area is a key factor for drainage and flood protection. This developed mathematical model can be used as a tool to evaluate the present drainage system as well as flooding processes in the field as well as inundation areas and water levels along drainage channels. It is found that the proposed model can be applied to evaluate integrated flood control system for pumped-field lowland. Such an operating system provides an effective tool by means of which the drainage system can be operated appropriately taking into account of tidal effects, rainfall intensity, and reaching time of the rainwater.
HYDRAULICS OF GROUNDWATER FLOW AND MECHANICAL PROPERTIES AFFECTING AQUIFER SYSTEM COMPRESSION IN SHIROISHI, SAGA PLAIN N. Cao Don; H. Araki; H. Yamanishi; K. Koga
Lowland Technology International Vol 5 No 2, Dec (2003)
Publisher : International Association of Lowland Technology

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Abstract

Land subsidence in Shiroishi area in the Saga plain, Japan, has become noticeable since 1960s. Water supplied to agriculture has traditionally been a high priority for water managers in this region. Intense withdrawals of groundwater in excess of natural recharge have resulted in land subsidence in this region. Land subsidence can have several negative economic and social implications. Many problems associated with land subsidence can be observed in this area. In this paper, a numerical model that incorporated 3-D groundwater flow and I-D ground consolidation was applied to simulate groundwater level and ground consolidation. It is found that subsidence rapidly occurs throughout the area with the central prone in Shiroishi basin. Certain hydrogeologic parameters such as inelastic storage coefficient, elastic storage coefficient, and hydraulic conductivity of soil layers contribute significantly effects to both the rate and magnitude of consolidation. Moreover, a considerable reduction in discharge is supposed necessary for future development of the region to alleviate the effects of groundwater overdraft.
ESTIMATING THE POTENTIAL FOR CONJUNCTIVE WATER MANAGEMENT IN COASTAL PLAINS N. Cao Don; H. Araki; N. T. Minh Hang; H. Yamanishi; K. Koga
Lowland Technology International Vol 8 No 1, June (2006)
Publisher : International Association of Lowland Technology

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This paper presents the development and application of a conjunctive water management model for lowland catchments. The model incorporates a simulation model and a management model to simulate groundwater movement, ground consolidation and to search for the potential pumping amount of groundwater without violating physical and environmental constraints. The results reveal that groundwater levels in a coastal aquifer greatly vary in response to pumping. Consequently subsidence rapidly occurs throughout the area. The study also suggests that conjunctive water management can be used to improve water supply reliability, to reduce groundwater overdraft and land subsidence and to improve environmental conditions.
SEGREGATION OF MICROPHYTOBENTHIC CHLOROPHYLL-A FROM SUSPENDED PARTICLES DURING TIDAL CYCLE IN NANAURA MUDFLAT, ARIAKE SEA, JAPAN C.-H. Koh; J. S. Khim; H. Araki; H. Yamanishi; K. Koga
Lowland Technology International Vol 9 No 2, Dec (2007)
Publisher : International Association of Lowland Technology

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The fluxes of microphytobenthic chlorophyll a (Chl-a) and suspended particulate matter (SPM) in water column and their relationship against tidal current have been examined during 15-days of full spring-neap tidal periods in the upper intertidal flat of Nanaura, Saga, Ariake Sea, Japan. The flood-ebb and spring-neap tidal conditions influenced within-day and daily variability in the fluxes of Chl-a and SPM, in terms of tidal energy. The Chl-a flux decreased relatively at slower pace than corresponding SPM flux at stage of decelerating incoming tide, which indicated the segregation of Chl-a from SPM followed by the slower settlement at depositional period. This ‘decoupling’ trend was consistently observed during the high tidal energy period of spring, particularly during the lower wind period (0-1 m s-1), but this was no more prevalent during the low tidal energy of neap and/or higher wind period (3-5 m s-1).
HYDROGEOCHEMICAL DESCRIPTION OF GROUNDWATER IN A COASTAL LOWLAND PLAIN NEAR THE ARIAKE SEA OF JAPAN N. Cao Don; Mohan S. Kumar; H. Araki; H. Yamanishi
Lowland Technology International Vol 10 No 1, June (2008)
Publisher : International Association of Lowland Technology

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Abstract

In the management of water resources, quality of water is just as important as its quantity. In this paper, an investigation was undertaken to better understand the hydrogeochemistry and hydrologic framework of the Shiroishi plain in Saga, Kyushu, Japan. A network of production boreholes and wells distributed over the studied region were sampled and the waters were analyzed for major ions. The results reveal that, in areas near the shore, salinization is more serious at deeper layers. Geochemical analyses showed that the Shiroishi aquifer has bicarbonate sodium water, with an increase of electrical conductivity, sodium and bicarbonates contents.
Effect of trenches on the habitat of aquatic organisms in a salt marsh in Saga, Japan Y. Nagahama; K. Nishimura; H. Yamanishi
Lowland Technology International Vol 17 No 3, Dec (2015)
Publisher : International Association of Lowland Technology

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Abstract

Trenches were constructed to control the growth of Phragmites australis on a riverbank in the Ushizu River in Saga, Japan. However, the effect of these trenches on the habitat of aquatic organisms is unclear. The purpose of this study is to clarify the effect that trenches have on aquatic organisms in the tidal river. The burrow density of a type of sand crab (Ilyoplax deschampsi) and the abundance of aquatic organisms (such as fish and shrimp) in our trenches were measured. The number of I. deschampsi burrows around trench D was similar to that observed before trench construction. However, mud sedimentation was accelerated in shallow trench D’, which created a suitable habitat for this species. Additionally, we found shrimp and gobies in all our trenches. This indicates that artificial trenches do provide habitat for shrimp and gobies in riverside marshes. Moreover, an endangered species and many aquatic insects were collected. Our results suggest that trenches provide important habitats for rare fishes and aquatic insects, similar to that of a lagoon.
Co-Authors C.-H. Koh H. Araki J. S. Khim K. Koga K. Nishimura Mohan S. Kumar N. Cao Don N. T. Minh Hang Y. Nagahama