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Impact of Extreme Rainfall Event over Swedish Urban Catchments: A study on catchment characterization in the context of Aerial Reduction Factor and storm movement
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
2019 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The design practices of urban hydraulic structures are required to be based on enough safety measures in addition to cost efficiency for sustainable development. Overestimation of catchment runoff generated from a storm event can increase the project cost unnecessarily. For urban pluvial studies, use of Aerial Reduction Factor (ARF) helps to estimate the probable precipitation intensity inside a catchment. By understanding the necessity of using ARF from a national context and applying it in present design practices can pave the way towards sustainable design practices. In this study the applicability of ARF from Swedish urban context was analyzed. The urban catchments for fifty biggest Swedish cities were delineated and the catchment parameters were analyzed. Application of ARF depends on the size of catchment. To experience a significant reduction in catchment outlet discharge, the minimum catchment area for application of ARF was reported as 5 km2. According to the analyzed parameters, ninety percent of catchment sizes in Swedish urban area were found less than 5 km2, which are quite small in respect of ARF applicability. It was realized from the analysis that application of ARF within a single catchment is not much necessary for pluvial studies in Swedish urban catchments due to catchment properties.

In addition to rainfall intensity, rainfall movement also changes the runoff behavior from a catchment. When catchment’s flow velocity and direction through main channel and storm moving velocity and direction over the channel coincides with each other, then the outlet peak discharge magnifies in comparison to a stationery storm, known as resonance effect. The impact of storm movement over catchment was analyzed using HEC-HMS modelling with varying storm movement velocity over catchment. The analysis was performed on 12 catchments of different size and flow velocity. It was found that the peak discharge can increase up to 46 percent depending upon catchment characteristics. The flow velocity through all the delineated catchments of fifty cities were calculated using USDA’s NRCS TR-55 method and then compared with usual storm moving velocities in Sweden. It was found that, due to flat nature of Swedish urban areas, the flow velocities are very low (<2 m/s) in compare to average storm velocity (8 m/s), portraying the fact that there is limited probability that these velocities will coincide. But for any area where storm velocity is normally low, resonance effect can happen. Precise analysis based on local conditions are suggested while modelling a particular area, since impact of resonance effect can overrun the design considerations.

Place, publisher, year, edition, pages
2019. , p. 84
Series
TRITA-ABE-MBT ; 19718
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-266469OAI: oai:DiVA.org:kth-266469DiVA, id: diva2:1385436
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Available from: 2020-01-14 Created: 2020-01-14 Last updated: 2020-01-14Bibliographically approved

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2223242526272825 of 112
CiteExportLink to record
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Citation style
  • apa
  • ieee
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  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
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  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
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  • asciidoc
  • rtf