Sustainable Drainage Systems Assessment and Optimisation-A case study for Lussebäcken Catchment, Helsingborg

Abstract

Increase of urbanization and climate change are one of the factors that have been highlighted to influence hydrography. This is resulting in an increase in peak flow within an urban watershed. Downstream flooding and increased pollution are the problems that arises. To solve this, the sustainable urban drainage system techniques are adopted for reducing peak flow and increase baseflow. This thesis studies the assessment and optimisation of multipurpose constructed structures used in drainage systems in the Lussebäcken catchment in Helsingborg to reduce the possibilities of flooding while serving an environmental task. The water is transported from an upstream high plain catchment with a good fall height through Ramlösa ravine and discharges in the Råå Brook near the sea. Downstream within the low-lying area are residential buildings, industries and roads that are sensitive to flooding. Using the computer software MIKE URBAN with MOUSE engine, rainfall runoff was simulated and flow in the network system was computed. Three scenarios have been simulated; before 2008, when no additional ponds were added, the current situation with new constructed ponds and wetlands added to the model and a proposed modification to improve the regulation of the already existing infrastructures. The results show an improvement of over 20% of reduction of the peak flow in the main stream around the most critical area for the current situation over the 2008 situation and 8% more of improvement is obtained by regulating the output of one of the ponds. From the obtained results the main improvement could be made when storing capacity to the network rather than regulating the existing ponds.

Popular Abstract

Drastic increase of population, urbanization, climate variability and extreme precipitation are the main challenges on urban storm water management worldwide. These put many regions over the world to be more vulnerable for flooding. Due to human activities within the watersheds that have resulted in changing of river morphology and urban hydrological cycle, are still dominating. As the results, the urban runoff hydrograph is affected and result in increasing of the urban runoff peak flow. This is a problematic for the existing urban drainage pipes. To handle the addition flow would be a tough problem to the decision makers and planners. The storm water control measures techniques such as the sustainable drainage system has been adopted around the world cities.

Sweden has the one of the Europe countries adopted these techniques. Based on the problem of flooding and increase of urbanization in Helsingborg city, the sustainable drainage system techniques have been also implemented and adopted by municipality planners in Helsingborg to tackle the impacts of runoff flooding on infrastructures and property of the people. The constructed ponds and wetlands have been prioritized, even these measures are implemented there, the performance of those constructed ponds and wetland has still remain the issues to maximize its benefits.

This thesis studies the use and performance of combined use structures in urban drainage systems in the Lussebäcken catchment, Helsingborg to reduce the happening of flooding while serving an environmental task. The main control structures are artificial constructed ponds and wetlands in which water is stored, regulating the flow of the water stream and preventing a fast raise in the water level. This ponds also serve an environmental task because fauna and flora can develop in them, giving added natural value. A MIKE URBAN model was used to simulate the rainfall-runoff process. First of all, the model was validated with real data.
This model was modified because ponds and wetlands have been added since the setup of the original model. Afterward it was further modified with the proposed measures to improve and optimize the performance of the already built measures. Three different scenarios were performed to simulate the process. First scenario is a simulation of the model without addition measures, second scenario is a simulation of the model with addition ponds and Third scenario is Proposed optimization of the ponds. The results were displayed and the change of peak flow with added measures were identified. A reduction in the peak flows in the water stream for big rainfall episodes is accomplished.

The decrease of peak flow in the main stream is close to the 20% for the added ponds and a further 8% is gained after optimizing one of the ponds. According to this result, the reduction of peak flow is achieved, and the base flow is also increased in the ponds by storing water long time which is increased the infiltration the ponds. Even this were achieved, the further study is recommended for simulating runoff with connection of ground water flow. Mike she, or Mike 21 software's and other similar software's is recommended in order to simulated 2-Dimensional flow.

• author: Nsabimana, Bernard and Utande Estallo, Néstor
• supervisor: Johanna Sörensen
• organization: Division of Water Resources Engineering
• course: VVRM01 20191
• year: 2019
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Hydraulics, hydrology, Sustainable Drainage Systems, urban, Modeling, MIKE URBAN
• publication/series: TVVR 19/5009
• report number: 19/5009
• ISSN: 1101-9824
• language: English
• additional info: Examiner: Rolf Larsson
• id: 8992832
• date added to LUP: 2019-08-23 13:23:28
• date last changed: 2019-08-23 13:23:28