What is "surface water" and what is "flood water"?

"Water diffused over the surface of land, or contained in depressions therein, and resulting from rain, snow, or which rises to the surface in springs, is known as 'surface water.' It is thus distinguishable from water flowing in a fixed channel, so as to constitute a watercourse, or water collected in an identifiable body, such as a river or lake. The extraordinary overflow of rivers and streams is known as 'flood water.' " (Keys v. Romley (1966) 64 Cal.2d 396, 400, 50 Cal.Rptr. 273, 412 P.2d 529.)