Development of the tidal flat and eelgrass (AMAMO) field creation system with the effective use of the dredged cohesive material

摘要

The number of tidal flats is rapidly shrinking by the reclamation accompanying land development etc., and the movement toward artificial tidal flat creation has taken place in various places. On the other hand, dredged cohesive soil such as sludge has been, in great volume, accumulated on the seabed. Therefore, the demand to dredge such soil and to utilize it as artificial tidal flat material strongly arises.In fact, everywhere in the country, there were a number of AMAMO fields along the shoreline functioning as "the marine cradle" in which marine lives grew. However, as the result of pollution and reclamation caused by population concentration, factory construction, and etc. accompanying high economic growth, the AMAMO fields had almost disappeared. Thus, the demand to regenerate the AMAMO fields once disappeared and to regain the rich sea comes to be heard from people.The technology developed in order to respond to such a demand is "the tidal flat and AMAMO field creation system with the effective use of the dredged cohesive material". This system consists of two technologies.One of them is the tidal flat creation method which uses the biodegradable sheet. Although it was problematic to secure a predetermined slope and to execute sand covering work due to the dredge ground being soft with high water content, the problem has been overcome through the indoor and site experiments. In short, maintenance of an artificial tidal flat was realized by combined use of a sand covering method which used partition embankment for slope protection and the biodegradable sheet made from com element.The other technology is the AMAMO sowing method. In this method, the "AMAMO sheet" in which the AMAMO seeds are inserted in coconut mat or biodegradable nonwoven fabric and lozenge wire net is laid on the seabed, and the sprout and growth of AMAMO is promoted. This method considers environment using the biodegaradable nonwoven fabric and the coconut mat which is plant fiber, prevents the outflow of an AMAMO seed or seedling with high probability, reduces the diver works, and further makes significant cost cut possible.