An attempt to make environmental impact assessment of artificial beach and coastal revetment, using biodiversity as indicator, and consideration of new approach in creating an artificial beach

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In the present study, wide variety of plant and animal groups were investigated by several taxonomists, both in botany and zoology, in an artificial beach in Chiba-shi through all seasons. The results were compared with those of various environments in Tokyo Bay and an attempt to make environmental impact assessment in the artificial beach was made.Rather diverse environments did exist in the artificial beach :(1)In land part, plant communities such as planted wood, reed grassland and littoral grassland are recognized. In planted wood, naturalized plants were dominant and dead planting trees were distinct because of excess drying which was derived from lacking of mantle communities and sleeve communities. This drying also might be a factor of low diversity of insects and soil animals. Even in developed lands, reed grasslands, usually seen in estuarine tidal flats, appeared under favorable water condition ; in such reed grasslands, environment was wetter than in planted wood and biodive … More rsity also higher but naturalized species were conspicuous in inhabiting small animals.(2)Around high tide drift line, lower adjacent part to littoral grasslands, distinct environments occurred ; drifted Ulva around drift line was utilized by characteristic animals at this zone such as insects, mites and littoral oligochaetes.(3)In rocky intertidal zone on coastal revetment, diversity increased in the order of vertical concrete embankment, tetrapod and stone bond ; in particular on the large pebbles and drifted materials within stone bond, threatened species previously only known in estuarine tidal flats were observed, as well as distinct littoral soil animals.(4)On sandy and/or muddy bottom in intertidal zone, introduced shells increased in number and diversity was fairly poor. This is supposed to be related to the fact that amount of mud in this zone was less than that of estuary zone.Based on these results, when creating new artificial beach, important points to be taken into consideration are as follows : making plant communities which blocks sea breeze at least partiallys ; growing reed grasslands in upper intertidal zone ; stone bonds are preferable in making coastal revetment ; creating gentle slope part in foreshore that provides more muddy sedimentation. Less