Dagvattenhantering vid flaskhalsområden : Klimatförändringar och vägen mot hållbar dagvattenhantering i Bollnäs
Sammanfattning: Flooding from extreme rainfall is already taking place today in Sweden's urban areas. In order tocreate sustainable stormwater management that reduces the risk of flooding, various factorsshould be taken into account such as the choice of method for management. Bottlenecks in thestormwater system mean wells with undersized outlet pipes. A bottleneck area in Bollnäs urbanarea has already caused flooding. The aim of this study is to investigate if there are more similarareas and to contribute to sustainable stormwater management for Helsinge Vatten. Themethods chosen for the study were a literature study and a case study with simulation andcalculations. The literature study was conducted to see how stormwater is handled and what theclimate looks like. The case study was conducted to evaluate the flows that occur during heavyrains. In the case study, a terrain model was first made that showed drainage directions andwater dividers. The calculations in the case study were based on the rational method forcalculating design flow. The climate is changing and as the temperature rises, so does therainfall. The risk of extreme weather increases as the annual average temperature rises and aglobal increase in rainfall intensities has occurred. In Bollnäs, the annual average temperaturehas risen since the measurements began in 1969. In the future, the average temperature can beexpected to rise to 3-5 degrees until the end of the century in Gävleborg. In heavy rain, floodscan occur, they are called pluvial floods and can cause major damage to properties and roads,among other things. There are many methods for developing and making the stormwatersystem more sustainable. Among other things, there is something called blue-greeninfrastructure and this involves green surfaces in the management of stormwater. There, forexample, the water is allowed to infiltrate, evapotranspire or slowly pass on into the system.These solutions also have other benefits, they meet several social needs and can bring ecosystemservices. After the simulation that was carried out, 37 catchment areas could be observed andcalculations for design flow were made based on, among other things, the area in thesecatchment areas. Sustainable stormwater management can be introduced in Bollnäs urban area,when new guidelines and greater cooperation between Helsinge vatten and Bollnäs municipalityare needed. Sustainable stormwater management could reduce the risk of floods in bottlenecks.However, it is not possible to locate any bottlenecks in Bollnäs urban area due to missinginformation about the storm sewers in Bollnäs urban area. More studies would be needed tolocate bottlenecks.
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