Browsing by Author "Lehtovuori, Laura"

The trend and aim in urban planning at the moment is to build compact urban areas where the new districts are constructed in the vicinity of the old infrastructure and existing areas are supplementary built. This increasing amount of built environments can cause unmanageable flooding if at the same time the amount of impervious areas grows. Green infrastructure is one solution that can improve storm water management in urban areas by retaining and delaying water. This study focus on the green roofs as a one example of green infrastructure storm water management solutions. The study examines the green roof potential of Helsinki and the potential to improve storm water management in Helsinki. In this thesis there are three research sites by which Helsinki is examined as a whole. These three research areas are Itä-Pasila, Pihlajamäki and Veräjämäki. These areas are planned and constructed in different decades by the times when different ideals have dominated. Itä-Pasila is a densely built area where there is a limited number of small green spaces and large concrete buildings dominate the view. As for Pihlajamäki, it is an example of suburb that is built by 'lähiöteoria' (suburb theory) principle. Even though the buildings are also large concrete-block buildings they are surrounded by large green areas. Third site is Veräjämäki, which represents an example of single family residential area where there are own plots around every house. In this study LiDAR data, collected by the City of Helsinki, is used to examine what are the green roof potentials in these three research sites, if the green roofs would be fitted to all of the roofs that have a 10 degree or a lower pitch. The storm water management study combines rain and runoff data measured from the test green roofs of Lahti and rain and flow rate data measured in Helsinki. In this research frame there are two intense rain events, 16.2 mm/4 h and 24.6 mm/8 h, which occurred in Helsinki. To these two rain events there are combined retention capacities that are calculated from test green roofs. In conclusion classified SLICES land use data is used to examine division of land use classes in Helsinki area and for this there are combined land use classification and green roof potential of the research sites. In this study the results are that in the areas like Itä-Pasila and Pihlajamäki there is potential to fit green roofs to the area. But in Veräjämäki the most part of the roofs have higher than 10° pitch so in similar areas there is no great potential for fitting green roofs. In the storm water management study, it was realized that collected data included many sources of errors that affected to these research results. However in general it is possible to say that the green roofs reduced the amounts of runoff in studied rain events. But at the areas similar to Veräjämäki the retention capacity of existing green areas is so effective that green roofs did not have significant influence to the outflow. Through SLICES land use classes it is possible to see that there are many densely built areas in Helsinki and if urban areas will become even denser, the number of areas like Itä-Pasila and Pihlajamäki can increase. For these areas green roofs can be, like other green infrastructure, a way to improve urban storm water management. However in urban planning there are still limited ways to implement green roofs. But as this research has realized there are potential areas in Helsinki for fitting green roofs and in these areas green roofs can have a positive effect to storm water management in examined rain events. In this way there might be a need to clarify tools to take green roofs into account in urban planning so the potential of the roofs would be taken into use.