10:45 〜 12:15
[HCG19-P06] 屋上緑地の残存と消滅に関する研究
キーワード：屋上緑化、維持管理、残存と消滅
Rooftop greening in Japan has more than 100 years of history and many different types of rooftop green spaces have appeared in recent years and some of them disappeared at the same time. Taking the current situation that they are a part of the urban landscape into consideration, it is very important to focus on the disappearance and survival of rooftop green spaces. From this viewpoint, this study aims to clarify the life cycle of rooftop green spaces, i.e., how they disappear and survive. Yamashima et al. (2021) clarified the process of disappearance and survival of rooftop green space in public facilities constructed by 2000, but this study enlarged the period range to 2020 and included private facilities.
A literature survey was employed to grasp the space composition of facilities and rooftop green spaces when they were installed. Specifically, design materials such as photographs, descriptions, and blueprints published in Shin-kenchiku (New Architecture) and various technical books were used and satellite images taken by Google Earth Pro were also used to examine the current conditions. In addition, surveys on the facility website, newspaper articles, and interviews with the persons in charge of facility management were conducted to clarify the reasons and time for changes.
As a result, the number of total cases was 757. Among the number of cases, some 178 facilities were owned by the public sector and 579 were owned by private ones, and the older the case is, the more some kind of change occurred in the building or rooftop green space. While the ratio of rooftop green spaces that survived was higher in public facilities, that of rooftop green spaces disappearing before buildings was higher in public facilities. Maintenance of buildings was considered a higher priority than rooftop green space in public facilities.
As for rooftop green spaces as a whole, when a new building was built, new rooftop green spaces were also installed in response to the ordinances established by the local government which mandated the building owner to set up them. When buildings were renovated for waterproofing or seismic retrofitting, plants were removed once to improve the entire rooftop area, and rooftop green spaces were not restored if the intention was to reduce the maintenance and renovation cost. While rooftop green spaces that did not exceed the useful life of the materials were maintained, rooftop green spaces were removed when there were design problems, when safety issues arose, when priority was given to expanding the functions of the building, or when only the management of green areas on the ground was carried out. Among them, there was a case in which trees used for rooftop green space were transplanted to the ground, leading to "memorization" of the rooftop green space. Furthermore, as indicated in the previous report, there were a few cases where rooftop green spaces were designated as cultural assets and preserved semi-permanently.
In conclusion, the excessive workload and high maintenance and management cost are thought to be the major factors leading to the disappearance of rooftop green spaces, and continuous financial support is considered to be useful to maintain rooftop green spaces for a long time. Besides, when rooftop green spaces are replaced, it should be discussed how and what to leave behind.
A literature survey was employed to grasp the space composition of facilities and rooftop green spaces when they were installed. Specifically, design materials such as photographs, descriptions, and blueprints published in Shin-kenchiku (New Architecture) and various technical books were used and satellite images taken by Google Earth Pro were also used to examine the current conditions. In addition, surveys on the facility website, newspaper articles, and interviews with the persons in charge of facility management were conducted to clarify the reasons and time for changes.
As a result, the number of total cases was 757. Among the number of cases, some 178 facilities were owned by the public sector and 579 were owned by private ones, and the older the case is, the more some kind of change occurred in the building or rooftop green space. While the ratio of rooftop green spaces that survived was higher in public facilities, that of rooftop green spaces disappearing before buildings was higher in public facilities. Maintenance of buildings was considered a higher priority than rooftop green space in public facilities.
As for rooftop green spaces as a whole, when a new building was built, new rooftop green spaces were also installed in response to the ordinances established by the local government which mandated the building owner to set up them. When buildings were renovated for waterproofing or seismic retrofitting, plants were removed once to improve the entire rooftop area, and rooftop green spaces were not restored if the intention was to reduce the maintenance and renovation cost. While rooftop green spaces that did not exceed the useful life of the materials were maintained, rooftop green spaces were removed when there were design problems, when safety issues arose, when priority was given to expanding the functions of the building, or when only the management of green areas on the ground was carried out. Among them, there was a case in which trees used for rooftop green space were transplanted to the ground, leading to "memorization" of the rooftop green space. Furthermore, as indicated in the previous report, there were a few cases where rooftop green spaces were designated as cultural assets and preserved semi-permanently.
In conclusion, the excessive workload and high maintenance and management cost are thought to be the major factors leading to the disappearance of rooftop green spaces, and continuous financial support is considered to be useful to maintain rooftop green spaces for a long time. Besides, when rooftop green spaces are replaced, it should be discussed how and what to leave behind.