Johansen, C.

Schaarup-Jensen, Kjeld

Thorndahl, Søren Liedtke

English

Today it is common practice - in the major part of Europe - to base design of sewer systems in urban areas on recommended minimum values of flooding frequencies related to either pipe top level, basement level in buildings or level of road surfaces. Thus storm water runoff in sewer systems is only proceeding in an acceptable manner, if flooding of these levels is having an average return period bigger than a predefined value. This practice is also often used in functional analysis of existing sewer systems. If a sewer system can fulfil recommended flooding frequencies or not, can only be verified by performing long term simulations - using a sewer flow simulation model - and draw up extreme event statistics from the model simulations. In this context it is important to realize that uncertainties related to the input parameters of rainfall runoff models will give rise to uncertainties related to the corresponding extreme event statistics. This paper illustrates this problem in a case study with two different values of one input parameter - the hydrological reduction factor - in two otherwise identical operations of the MOUSE LTS model. The use of a long historical rainfall time series makes it possible to draw up extreme event statistics covering return periods of as much as 33 years. By comparing these two different extreme event statistics it is evident that these to a great extent depend on the uncertainties related to the input parameters of the rainfall runoff model.Today it is common practice - in the major part of Europe - to base design of sewer systems in urban areas on recommended minimum values of flooding frequencies related to either pipe top level, basement level in buildings or level of road surfaces. Thus storm water runoff in sewer systems is only proceeding in an acceptable manner, if flooding of these levels is having an average return period bigger than a predefined value. This practice is also often used in functional analysis of existing sewer systems. If a sewer system can fulfil recommended flooding frequencies or not, can only be verified by performing long term simulations - using a sewer flow simulation model - and draw up extreme event statistics from the model simulations. In this context it is important to realize that uncertainties related to the input parameters of rainfall runoff models will give rise to uncertainties related to the corresponding extreme event statistics. This paper illustrates this problem in a case study with two different values of one input parameter - the hydrological reduction factor - in two otherwise identical operations of the MOUSE LTS model. The use of a long historical rainfall time series makes it possible to draw up extreme event statistics covering return periods of as much as 33 years. By comparing these two different extreme event statistics it is evident that these to a great extent depend on the uncertainties related to the input parameters of the rainfall runoff model

    Aalborg UniversitetUncertainties Related to Extreme Event Statistics of Sewer System Surcharge andOverflowSchaarup-Jensen, Kjeld; Johansen, C.; Thorndahl, Søren LiedtkePublished in:Proceedings of the 10th International Conference on Urban DrainagePublication date:2005Document VersionPublisher's PDF, also known as Version of recordLink to publication from Aalborg UniversityCitation for published version (APA):Schaarup-Jensen, K., Johansen, C., & Thorndahl, S. L. (2005). Uncertainties Related to Extreme EventStatistics of Sewer System Surcharge and Overflow. In E. Eriksson, H. Genc-Fuhrman, T. Hvitved-Jacobsen, A.Ledin, P. S. Mikkelsen, & J. Vollertsen (Eds.), Proceedings of the 10th International Conference on UrbanDrainage: Copenhagen, Denmark, 21-26 August 2005 (pp. 1-8). Institute of Environment.General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            ? Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            ? You may not further distribute the material or use it for any profit-making activity or commercial gain            ? You may freely distribute the URL identifying the publication in the public portal ?Take down policyIf you believe that this document breaches copyright please contact us at vbn@aub.aau.dk providing details, and we will remove access tothe work immediately and investigate your claim.

Uncertainties Related to Extreme Event Statistics of Sewer System Surcharge and Overflow

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Uncertainties Related to Extreme Event Statistics of Sewer System Surcharge and Overflow

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