Abstract: Design flood estimation is one of the most difficult problems in Engineering Hydrology.Little progress has been made in the extrapolation of flood frequency curve by mathematics as yet. However,the latest studies reported in this paper show that the flood record can be expanded over thousands years by using the palaeoflood information,thus increasing the accuracy of estimating the flood events `Pith rare frequencies greatly.Also,the new developments in the estimation of the probable maximum precipitation/flood(PMP/PMF) are addressed.