Project Background and Objectives

Brackish water areas in estuaries of a city river have got unique natural environment and they have played important rolls in ecosystem preservation of the river and waters. However, reclamation and bank protection works in the estuaries have worsened creatures’ living environment. Few effective and consistent countermeasures against the environmental deterioration have been taken.

From the back grounds, the Yokohama Waterside Environment Study Group was established in cooperation with companies, the government, academic organisations and the communities on the assumption that they can improve the present eco-environment and get back creatures’ rich habitat once existed, if existent vertical bank protections have habitable structure for creatures; so that they can contribute to the restoration of the ecosystem and co-existence with nature. The group has been working on the promotion of environmental enlightenment as well as practice of the environmental restoration of the brackish water areas, aiming at environment restoration and conservation actively involving the citizens.

Project Abstract and Effects of Project

1. Researches on Planting Techniques for Bank Protections in Brackish Water Areas in the Yokohama Portside District
   To realise restoration of vegetation and planted bank protections in estuaries of a city river and examine plants that can be used for prevention of soil outflow and can also live in the estuaries, experiments to grow reeds and carex scabrifolia were done, using a wave-distinguish box and multi block. Vegetation monitoring has also been conducted every month as well as observation targeting at the citizens.
   The target area has been succeeded in root of reeds and also been a place of rest and relaxation for the citizens. In addition, events such as plant observation and rubbish clean-up have been held periodically.
   
2. Basic Studies on Invasion of Plants
   As a basic study, the number and kinds of plants that have invaded in the Yokohama Portside District by the use of river flow and the invasion routes were examined to consider the possibility of introducing native plants naturally in the brackish water areas.
   As a result, seven kinds of plants, excluding reeds and carex scabrifolia, were found as those which can be used for greening of the brackish water areas. It was also revealed that many seeds were carried to the estuaries by rain water and river after scattered according to each scatter pattern, and then sprouted there. Although further studies are needed, greening of the estuaries, using in-flow seeds can be expected as the river flows into the estuaries with many seeds. 
   
3. Background Studies on the Restoration of the Beach of The New Port of Yokohama and the Portside District
   Tide pools were made and then, various forms of concrete was piled in there or the estuaries to know effective forms of concrete’s surface.
   
4. Studies on Conservation and Restoration of Reeds in the Nojima Waterway in Yokohama City
   Reed communities in the Nojima Waterway have started decaying because a water way on the side of the Kanazawa bay was opened in 1994 and sedimentary soil has flowed into the Nojima Waterway. Thereupon, experiments of reed planting in the Nojima Waterway were done to establish techniques to conserve and restore reeds in the brackish water areas, and an analytic method for environmental restoration by maintenance works at the beach and estuaries was studied. The studies have been continued and establishment of green conservation techniques has been expected.
   
5. Opening of Exhibition Concerning Activities and the Brackish Water Area Seminar
   Seminars have been held for acquisition of right knowledge about the environment of brackish water areas in the river, more concern for the environment and resolution of problems related to ecosystem restoration of the brackish water areas. In the seminars, companies, the government, academic organisations and the communities discuss to better understand problems and solve them.

Distinctive Features of Project (Factors and Keys to Success)

The restoration of reeds in the estuaries of the city river, which has not been operated nationally, can be a reference for environmental conservation and restoration of a brackish area with complicated environmental conditions and many managers and users. What is more, by showing that citizens activities can deal with a river or sea although that seems difficult, citizens activities in other areas are expected to be encouraged, and citizens’ interest in water circulation in a forest, river and sea also expected to increase.

Relevant Websites

Yokohama Waterside Environment Study Group Website: http://www.yhama-mizubeken.org/index2.html

References

• Introduction of the Secretary of the Ministry of Environment Prize of The 3rd Japan Water Prize
• Yokohama Waterside Environment Study Group Website

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