Modelled tests on a key dam show that, under nappe flow over three different slopes on a stepped over-flow structure,unit energy in the flow cross section before the hy draulic jump increases with increasing slope,and H_dam/y_c similarly increases.As H_dam/y_c approaches a certain value, the rate of increase in the unit energy in the flow cross section slows.The pressure y_pat the bot tom of the cross section before the hydraulic jump in stilling basins demonstrates a posi tive linear correlation with critical water depth y_c to the water crest,with the number N of the steps not affecting y_p.Comparison of energy dissipation ratios at λ>1 and λ=1 (λ is the correction factor for pressure at the cross section before a hydraulic jump)reveals that the relative error amounts to about 7 %w hen H_dam/y_c=10, with this error decreasing to 1 %when H_dam/y_c ≥70.Experimental results also show that λ has a very strong linear correlation with y_p/y1(r =0.9999).