Grönområdens och designregns påverkan påavrinningskoefficienter för dimensionering avdagvattenanläggningar
The effects of green areas on design flow (Qdim) and required flow detention volume (Vd) were studied for different transport times, rain durations and rain intensities. The StormTac Web model was used for the calculations on a 36 ha urban catchment with green areas. Simulated runoff coefficients from different rain intensities and rain durations were used as input data, as well as new functions from literature data. The effects of 9 calculation cases were studied, where the following factors resulted in greater to smaller impact: (1) Return time; (2) Green areas, generally; (3) Average runoff coefficient, general uncertainty; (4) Functions impermeability-runoff coefficient; (5) Climate factor; (6) Linear function for green areas, rain intensity; (7) The Curve number method; (8) Rural and urban function, rain intensity and (9) Rain intensity. The same order of impact was valid for Vd except for the Curve number method which gives the 3rd largest and Rural and urban function the 5th largest impact. The variation of different specific assumptions regarding green areas and runoff coefficients gave Qdim = 1 600–2 700 l/s and Vd = 530–3 600 m3, so the assumptions made in the calculations have a clear impact. The new functions for which the runoff coefficients are not static but varying with rain intensity and rain durations are recommended for further studies.
Key words: design flow detention volume runoff coefficients rain intensity