The time-varying moment (TVM) was used to analyze the non-stationary flood frequency in the North River and West River Delta and its response to the changing environment using the annual peak discharge records of Makou and Sanshui stations from 1960 to 2009. In comparison with traditional frequency analysis

TVM takes into consideration of varying characteristic parameters of hydrological time series and therefore gives better results reflecting the evolution character on the changing environment. The return period decreases with the appointed design discharges

while the design discharge increases significantly with the appointed return period

which is consistent with the phenomenon of more and more extreme hydrologic events in the North River and West River Delta in recent years.