What is Floods above a base?
Floods above a base meaning The gage height of the lowest bank of the reach in which the gage is situated. The term “lowest bank” is, however, not to be taken to mean an unusually low place or break in the natural bank through which the water inundates an unimportant and small area. (Linsley, 1942, p. 89.)The stage at which overflow of the natural banks of a stream begins to cause damage in the reach in which the elevation is measured. (U.S. Weather Bur.)See also Bankfull stage.
reference: USGS – Water Basics GlossaryWhat is