Epsilon Archive for Student Projects

Abstract

Climate change effect the world in many different ways. A warmer climate will lead to more extreme weather such as drought and heavy downpours. As a result, the downpours that occurs in 100- and 500-years intervals, called 100 and 500 downpours, will happen more often. All the municipalities and county administrative boards in Sweden needs to adapt to these climate changes and protect its citizens from it. This report will go through different green and blue-green solutions to minimize the negative effects these downpours that Sweco has investigated for Håbo municipality. Blue-green solutions is solutions that use plants to bind water in a combination with different magazines that will catch up the rainwater. This report will focus on blue-green roofs, which is when you install plant beds with magazines to catch up some excess water, and also focus on the trees different water-uptake ability. This report will not talk about the economics for these solutions nor how long time it will take to install these solutions. The question of this report is “Which blue-green downpours solutions is most efficient to install in the center of Bålsta and where will the solutions be installed to increase Bålsta’s resistens against downpour?”.

The report notes which areas in the urban area of Bålsta in Håbo municipality that will have most negative effects of future downpours. Furthermore, this is a literature study and for this report a field study in Bålsta has also been conducted by the student. It breaks down similar studies to get an understanding of different tree species abilities to catch downpour through interception and through the root system, as well as which species that is common in urban areas and are also drought- and water-tolerant, this to get a picture of which tree species that will work well as protection against heavy downpour. Different green and blue-green roofs were studied to understand which to use. There can grow different species of plants on these roofs and an evaluation on which species can take up most water and survive drought periods was made. Different substrate for the plant beds were studied.

The result showed that it was most efficient to use blue-green roofs because of their storage capacity, and that some of them also has delaying and irrigation mechanisms. It exists both advantages and disadvantages with different tree species and blue-green roof solutions. It is also important to not plant invasive trees or other invasive plants. In conclusion, Bålsta should implement a blue-green roof solution with a compartment with a back system that is supplemented by a tray located underneath, to maximize the storage effect. On the plant bed in this solution, native meadow plants should be planted, and the bed’s substrate should be organic material with sand and pumice stone. The trees should be planted below the esker in Bålsta, at Gröna dalen, Dalvägen and Kärlekens väg. The trees that are most effective to plant below the esker is Giant thuja, Douglas fir and Black pine. At the roads in Bålsta, especially along Dalvägen and Kärlekens väg, Small-leaved linden, Ginkgo and Catalpa bignonioides should be planted.