Coastal environments in Okinawa are deeply ingrained in the cultural life, in particular religious ceremonies, of the region's residents. The disaster prevention projects that have been carried out in coastal areas in Okinawa to date have been done so without consideration to the nature and culture of the region. Instead, they have been undertaken with a view to functionality alone. Results of surveys on the relationship between the natural coastal vegetation and the stepped /low-lying upright hollow tide embankments show that the number of plant varieties tends to decrease with the transition from a natural beach environment to these man-made structures. While the number of plant varieties is greater with the low-lying upright hollow embankments, they cut off the beach from the inland areas and thus vegetation continuity is lost. On the other hand, the steps on the stepped tide embankments support vines and creepers that grow out towards the inland areas. The preservation and restoration of the nature and historic culture of these beach environments is a substantial problem confronting disaster protection projects in the coastal regions of Okinawa.

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We studied the utility of glyphosate-compound growth retardants on Imperata cylindrica, which is the species of river bank vegetation that is the most dominant in the entire country. The objective of this study is to reduce operation and maintenance costs for vegetation on sloped river banks. The first spraying of 400～500g/m² of the retardant was made when the Imperata cylindrica was at a height of 20 cm. The second spraying was made 45 days following the first one and with the same quantity of chemical. The results of our surveys on the fall cutting showed that the Imperata cylindrica 's height was suppressed by about 25% and its dry weight by about 41% compared to the control group.

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The coastal Japanese black pine forest is an artificial protection forest for coastal disaster prevention. The profile of soil hardness which influences on the root growth of the coastal Japanese black pines was examined in Kujukuri beach, Chiba Prefecture. The soil hardness was measured by soil penetrometer, Hasegawa type. The penetration value (S value) of soli became very small more than 70 cm in depth in the forest. The revegetation of the coastal sandy soil by Japanese black pines has been succeeded in Japan. It is important to investigate the influence of soil hardness on the growth of Japanese black pine forests because the sand fixation in the forests exceeding 30 years has increased in recent years.

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A field survey was conducted at the berm of the backshore to make clear the strategy of vegetative propagation of Carex kobomugi Ohwi which is the most dominant species at the seashore of Shonan district of Kanagawa Prefecture. As the results, 1) The density/1m² of the community was between 95.2士32.5 and 41.2土10.0 and the occupied area/plant was between 105.0 and 242.7cm² which density were not overpopulated. 2) Two types of rhizome which are vertical and horizontal were recognized. The plants growing at the center of the community had always vertical rhizome and all of forward ridge of the community were produced by horizontal rhizome. It was considered that the growing direction of rhizome was much related to the position of individuals in the community.

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