The uppermost lock is St John's, below Lechlade; the lowest is Richmond, but this is a half-tide lock, keeping the water above at a level corresponding to half that of flood tide.
It is therefore interpreted as a flood tide delta.
There was 12 feet of water with a strong flood tide.
Approaching Salter's Lode Lock somewhat fast to get steerage, as going with a serious flood tide.
It is said that a flood-tide, with a westerly wind, and ice in the Neva, would sweep St. Petersburg from the face of the earth.