ABSTRACT
Seldom does ow move far before entering some kind of channel. Consider, for example, runoff from the roofs of houses in urban areas. The water soon enters gutters, ows into a downspout, and goes through a buried pipe to the street curb. The water then ows along the side of a road and, in many parts of the country, will then enter a drain leading to a subsurface stormwater system. Or, as we will see later, urban drainage is often by constructed earthen channels. Even in rural areas, runoff from agricultural elds frequently ows into grassed waterways or open ditches. Does this mean that the procedures described in Chapter 5 have little or no usefulness? Certainly not, for they are used in the design of gutters, pipes, stormwater systems, waterways, and ditches. Also, ow in small conveyance systems is often approximated as similar to overland ow because it is not practical to divide every watershed into subwatersheds representing individual houses and elds.
