Evaluation of the efficiency of LID Measures to Mitigate Surface and Basement Flooding Problems

Abstract

With the climate change and urbanization process, the frequency of the urban flooding’s occurrence has increased in the recent years. It brings great economic losses to the cities, especially to the basements of individual properties. Low Impact Development (LID), which currently advocated by more city planners for managing stormwater, is considered as a more sustainable way to mitigate urban flooding. Hence, this thesis aims at evaluating the efficiency of LID measures on surface flooding and basement flooding problem. In order to achieve the objective, MIKE URBAN software is employed as the analysing tool, and different modeling methods of LID measures based on this software are explored. The catchment area for the study is selected in the west of Majorna-Linné, Gothenburg, which has a record of basement flooding during the past extreme rainfall event. The model in MIKE URBAN was set up and calibrated by Göteborg Vatten, with the rainfall data of five, ten, twenty, thirty, and one-hundred-year’s return period. The simulation was run for pre- and post-LID scenarios. In the end, the flooding-vulnerable area was identified in the pre-LID scenario, and the mitigation efficiency of permeable pavement on surface and basement flooding is analysed in the post-LID scenario. It shows that, the permeable pavement has the on-site solving the characteristic. By implementing permeable pavement, both surface flooding and basement flooding have been mitigated to some extent. In the surface flooding, the permeable pavement has stronger mitigation effect with high return period. While in the basement flooding, the mitigation effect is more evident when the rainfall return period is less than twenty-year. Concerning one-hundred year rainfall, permeable pavement cannot completely address surface flooding nor basement flooding. Therefore, other solutions should be considered as a supplement of LID.

Popular Abstract

With the climate change and urbanization process, the frequency of the urban flooding’s occurrence has increased in the recent years. In terms of the projection given by Swedish Committee on Climate and Vulnerability, the average mean temperature in Sweden is higher than the global average by 3-5℃. In addition, changes in precipitation patterns and higher sea levels are anticipated. As a consequence, some cities have inevitably encountered urban flooding, which is in forms of surface flooding and basement flooding during the past extreme rainfall events. For example, Gothenburg (Göteborg), is a city that is very susceptible to the risk of urban flooding, it has also experienced several urban flooding events with the cases of basement inundation.
Urban flooding is highly relevant to us since it brings great economic losses to the cities, also to households whose basements are inundated from the backwater in the urban sewer network. It is claimed that the total annual economic loss (includes insurance company and individuals) in Sweden is around 400 million SEK. For households, the loss will be tremendous if the basements function as family activity rooms, which are nicely furnished and equipped with plentiful sports and electronic facilities. Traditional measures to mitigate/prevent urban flooding problem focus on engineering perspective, the city planners usually apply the hydraulic structures and facilities to handle the urban floods, such as reservoir, pipe system enlargement, and pipe diversion and so on. However, it is no more advocated now due to the huge investment and unsustainability it has. Low Impact Development (LID), which is considered as a more sustainable alternative, mitigates the urban floods by introducing on-site measures, for instance: infiltration trenches, vegetative swales, permeable pavement, rain barrels, green roof, bioretention pond, and cells to reduce/eliminate the need for centralized stormwater management.
Hence, this thesis aims at evaluating the efficiency of LID measures (permeable pavement in this case) on surface flooding and basement flooding problem. The catchment area for the study is selected in the west of Majorna-Linné, Gothenburg, which has a record of basement flooding during the past extreme rainfall event. In order to achieve the objective, MIKE URBAN software is employed as the analysing tool. The simulation was divided into pre- and post-LID scenarios. In the end, the flooding-vulnerable area was identified in the pre-LID scenario, and the mitigation efficiency of permeable pavement on surface and basement flooding is analysed in post-LID scenario. It shows that, by implementing permeable pavement, both surface flooding and basement flooding have been mitigated to some extent. For the surface flooding, the permeable pavement has stronger mitigation effect with heavier rainfall. For the basement flooding issue, most basement floods in this study area can be effectively avoided by implementing permeable pavement.
The results are very useful to the inhabitants who live in this studied area, the flooding-vulnerable maps could be distributed to them for a better understanding of the flooding risk of their own properties. Moreover, the modeled area for permeable pavement implementation can be helpful for both municipality and landowner to estimate their own investment.

• author: Luan, Xiangyu
• supervisor: Rolf Larsson
• organization: Division of Water Resources Engineering
• alternative title: A case study on Gothenburg city
• course: VVRM01 20171
• year: 2017
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Basement flooding, Hydraulic modelling, LID, Surface flooding, MIKE URBAN.
• publication/series: TVVR 17/5017
• report number: 17/5017
• ISSN: 1101-9824
• language: English
• additional info: Examinator: Magnus Persson
• id: 8927405
• date added to LUP: 2017-11-15 15:47:45
• date last changed: 2017-11-16 10:10:37