Tomonori Saita

AWARENESS SURVEY ON EVACUATION BEHAVIOR IN HOKUSATSU HEAVY RAIN DISASTER

In order to make clear the awareness in evacuation behavior in Hokusatsu heavy rain disaster, we conducted a questionnaire survey. The questionnaires were distributed to local sections where many rescuees reside, and the answers were analyzed by regarding the rescuees as the persons who could not determine an adequate behavior in a risky situation. As a result, it was clarified that many rescuees did not evacuate because of the action of normalcy bias and cognitive dissonance. In addition a possibility was suggested that the evacuation information for disaster might not be understood sufficiently by some residents and that it might delay the timing of evacuation.

FIELD OBSERVATION ON TIDAL CURRENT STRUCTURE ALONG THE NORTHERN COASTAL AREA OFF SHIMABARA PENINSULA

Recently, reduction of fish catch and poor harvest of cultured laver in the Ariake Sea have been a serious social problem. It is suspected that construction of the Isahaya Sea-Dyke causes deterioration of aquatic environment in the Ariake Sea. Although several studies on the aquatic environment have ever been carried out, the causes of the deterioration have not been understood clearly. In this study, in order to understand the role of tidal current in the tidal exchange phenomena in northern coastal area off Shimabara Peninsula, in situ measurements on tidal current by ADCP (Acoustic Doppler Current Profiler) and sea level by tide gauges were carried out.As a result of this study, it was observed that the phase of the tidal current near the coast proceeds. It is considered that it is brought about by oscillatory boundary layer. Findings of the present study imply that it is very important to carry out high resolution field observation and numerical simulation in order to understand tidal transport well.

CONTROL OF SEDIMENT TRASPORT BY BaNK BLOCKS WITH DIRECTIONAL RESISTANCE PROPERTIES

The problem of beach erosion in our country grows more and more serious, so we must countermeasure against this problem without delay. Then we develop a effective method (we call the blocks used in this method BaNK block) to control sediment transport to cope with this serious problem. In this paper, we examine the fundamental properties of this method by laboratory experiments and field works in Nogita Coast. Firstly, we investigated the condition of flow occurrd when BaNK blocks were set in a wave progressing field by laboratory experiments. We confirmed that this method could make a flow at bottom layer and made a proper layout of BaNKblocks dear. Secondly, we set two kinds of blocks in Nogita Coast and observed a sediment transport around these blocks. By this field works we confirmed that sediment was transported by BaNKblocks to the direction we expected. From these results, we confirmed the possibility of beach nourishment by using BaNK blocks.