Study cases of stormwater pond’s forebays in Sweden and international state-of-art
Examensarbete för masterexamen
Arce Rama, Lucía
Stormwater pollution is one main contributor to stormwater degradation. For this reason, many countries integrate best management practices (BMPs) to manage stormwater and reduce its pollution. Wet ponds are one possible BMPs to implement, widely applied internationally and in Sweden. A study made in Sweden concluded that the costs of construction are as significant as the cost of operating and maintaining these facilities. Therefore, there is a need of having more efficient designs, thus, some Swedish municipalities are interested in knowing more about the use of forebay. Some guidelines from different regions and countries and previous works are investigated during the literature review part of this thesis. Furthermore, an interview study has been made to investigate the existing design criteria in Sweden and an analysis of the design in existing cases of pond with forebay. Lastly, an example of the application of the design criteria in a case study is presented. Most of the local guidelines from different regions purpose design criteria based on the area or volume of the pond or based on a rain event. Few of them mentioned specifications about the shape of the forebay, even though the relationship between length and width is an important parameter when it comes to hydraulic efficiency in wet ponds. The results of the interview study made in Sweden shows that most of the design criteria applied in other countries are being applied in the country, however, there is a lack on unification. Furthermore, based on the analysis carried out in the studied cases in Sweden it is possible to notice that most of them do not follow the local guidelines from different regions. Some of the cases are clear examples of the importance of considering how is the system upstream and the importance to do maintenance of the forebays. To apply the design criteria important factors to consider are available space and the system upstream. The conclusions of this work are the lack of theory when it comes to forebay design and that a methodology that takes into account more parameters is missing. Additionally, Sweden’s design criteria consider most of the local design criteria from different counties, however, most of the studied facilities are not following these criteria. Furthermore, there is a lack of maintenance in the existing forebays in Sweden.
BMP; forebay; maintenance; pre-treatment, stormwater management; wet ponds.