Local residents and schools have planted floating heart seedlings on different occasions. Regeneration of the floating heart community, however, is not so easy in a lake with an already weakened ecosystem. Due to the revetment, the waves were so rough that they often washed away the floating hearts before their roots were fully grounded. In this situation, we had to take steps to alleviate the waves coming from the offing.
Our attention focused on the traditional method of river improvement, a “brushwood mattress (brushwood breakwater)” (Fig. 6). The brushwood breakwater is constructed as follows: first, logs are hammered into the lake bottom to form frames; and then the brushwood fascines are filled in the frames. By using the logs and brushwood from the watershed forest thinning for the brushwood breakwater, we can simultaneously conduct both forest conservation in the catchment area and lake revival (Fig. 7). Construction of the brushwood breakwater developed a new dimension of the Asaza Project by broadening its horizons to the overall catchment basin, including the headwaters.
The forest coverage of the Lake Kasumigaura catchment basin has decreased down to 20%. Neglecting forest depletion and deterioration will harm the maintenance of healthy water circulation in the lake. In this sense, it is urged to implement forest conservation, with the total catchment basin in view. Through the adoption of our proposal, the Kasumigaura Construction Office of the Ministry of Land, Infrastructure, and Transport now conducts a lakeshore vegetation zone restoration project, which involves large-scale construction of brushwood breakwaters. This project has paved the road for the forest management from the catchment-wide point of view. At present, the Forestry Agency also takes part in this project. A project beyond the ministerial boundaries is proceeding with a non-profit organization as its nucleus.
