  Robust estimators and different filtering techniques are proposed and their
impact on the determination of a wide range of turbulence quantities is
analysed. High-frequency water level measurements in a stepped spillway are
used as a case study. The studied variables contemplated: the expected free
surface level, the expected fluctuation intensity, the depth skewness, the
autocorrelation timescales, the vertical velocity fluctuation intensity, the
perturbations celerity and the one-dimensional free surface turbulence
spectrum. When compared to classic techniques, the robust estimators allowed a
more accurate prediction of turbulence quantities notwithstanding the filtering
technique used.
