Analyzing Rainfall-Runoff Relationships in Multiple Urban Catchments
Author
Németh, Fruzsina
Term
4. term
Publication year
2024
Pages
98
Abstract
This thesis examines variability in rainfall–runoff relationships in Danish urban catchments and assesses whether it can explain differences between calculated design parameters and their values reported in the literature. The study focuses on 12 well-defined residential catchments with detailed measurements from a national monitoring program. For each catchment, physical characteristics and sewer network attributes are compiled, surface runoff is calculated, and rainfall–runoff events are graphed to derive relationships and compare catchments with similar features. The work includes uncertainty analyses and categorization by catchment type, size, and drainage system, as well as an update to 2024 conditions, introducing a method to determine impervious areas and repeating analyses with the updated data. Findings align with existing research: calculated values for key design parameters such as the hydrological reduction factor, initial loss, and runoff coefficient are often lower than recommended literature values, indicating potential overdesign. No single explanation for the variability is identified, and the study concludes that analyses should be expanded to more catchments. From the historical data analysis, a possible approach to generalizing parameter variability is suggested based on the close linkage among runoff coefficient, hydrological reduction factor, impervious area coverage, and total catchment area.
Denne afhandling undersøger variationen i nedbør–afstrømningsforhold i danske byoplande og vurderer, om den kan forklare forskelle mellem beregnede designparametre og deres litteraturværdier. Udgangspunktet er 12 veldefinerede boligoplande med detaljerede målinger fra et nationalt overvågningsprogram. For hvert opland indsamles fysiske forhold og kloaknetkarakteristika, overfladeafstrømning beregnes, og nedbør–afstrømningshændelser visualiseres for at etablere sammenhænge og sammenligne oplande med lignende egenskaber. Arbejdet omfatter usikkerhedsanalyser og kategorisering efter oplandstype, størrelse og afløbssystem, samt en opdatering til 2024-forhold, herunder en metode til at bestemme befæstede arealer og gentage analyserne med opdaterede data. Resultaterne stemmer overens med eksisterende forskning: de beregnede værdier for centrale designparametre som hydrologisk reduktionsfaktor, initialt tab og afstrømningskoefficient er ofte lavere end anbefalede litteraturværdier, hvilket kan pege på risiko for overdimensionering. Der gives dog ingen entydig forklaring på variationen, og der konkluderes, at flere oplande bør analyseres. Gennem analysen af historiske data indikeres en mulig generaliseringsmetode baseret på den tætte kobling mellem afstrømningskoefficient, hydrologisk reduktionsfaktor, befæstelsesgrad og samlet oplandsareal.
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