Three-dimensional simulation of offshore currents induced by a traveling typhoon of strong winds and low pressure was performed assuming initial two-layer stratification of the sea water. The typhoon generates horizontal circulation involving divergence due to the Coriolis force, resulting in vertical circulation, which flows through the density interface. Accordingly, part of the interface is raised. The interface shows a wave train, which has the near-inertial period and propagates onshore at almost the same velocity as the passing velocity of the typhoon. The interfacial waves show their largest wave height just in front of the edge of the continental shelf, after which they separate into three components: transmitted, reflected, and orthogonal waves. The orthogonal waves turn left over the shelf edge in the northern hemisphere.

抄録全体を表示

Social capital is defined as the factors promoting useful cooperative actions, such as social organizations and systems, norms, networks, people’s sense of values, consciousness and beliefs, held by members of the community and/or concerned external parties. It is argued that social capital can play an important role in the enhancement of communities’ disaster preparedness. Recently the importance of disaster preparedness has been widely recognized, and community based approaches have drawn significant attention. This paper attempts to clarify the key factors that local governments should take into account to in order to enhance a community’s capacity for disaster preparedness, through field observations and surveys in rural communities in Japan. Surveys were carried out in two communities of Tosashimizu city of Kochi Prefecture, which was highly affected by a torrential downpour in 2001. After the experience of the 2001 disaster, different actions were taken in the two communities during the catastrophic disaster of Typhoon 23 in 2004. Through key informant interviews and qualitative comparison of the two communities, it can be concluded that aspects of social capital such as 1) community leader’s leadership; 2) community’s bonds and networks; and 3) institutions and systems within the community should be considered to enhance a community’s disaster preparedness.

抄録全体を表示

The Civil Defense in Brazil needs to identify and differentiate floods and flash floods for the official registry. This study aims to quantitatively define and differentiate between floods and flash floods. Floods and flash floods are characterized by factors including the speed of water level rise and water flow; the hydrological response time to a rainfall event and the extension of the flood affected area. The hydrological definitions are ambiguous and make it difficult to distinguish between a flood and flash flood event. Even though some papers have mentioned that flash floods occur within 6 hours after an intense rainfall event, there is still certain subjectivity. This study proposes the use of the Operation Efficiency Index (OEI) as a quantitative means to distinguish between a flood and flash flood event. The OEI is defined as the rate of the time of flood concentration (Tc) to the operational response time (To) in the institution-community system. Tc and To are associated with environmental and human factors, respectively. When the OEI value is smaller than one, then flash floods occur. Otherwise the event can be defined as a flood.

抄録全体を表示