When the water surface is surging rapidly as a result of wave action, the stage to be recorded is the mean of the elevations of the peak and trough of the waves.
(the water surface; is surging rapidly; as a result of wave action) (the stage; to be recorded; ) (the stage to be recorded; is; the mean of the elevations of the peak and trough of the waves; T:When the water surface is surging rapidly as a result of wave action)
the water surface the stage the stage to be recorded
is surging rapidly to be recorded is
as a result of wave action
the mean of the elevations of the peak and trough of the waves T:When the water surface is surging rapidly as a result of wave action