I am wondering if there is a way to estimate the ratio to peak value without calibration? What would be the most suitable value if I don't have a measured hydrograph to compare?
In case anyone is interested in knowing this, too: I found that the usual range is 0.05 to 0.15 (Bedient, Huber and Vieux: Hydrology and Floodplain Analysis, 5th edition, 2015).