In most urban and suburban areas, stream buffers are routinely eliminated or severely minimized as part of the development process. The developed landscape quickly concentrates accumulating runoff and conveys it to streams. Most of the runoff that reaches stream buffers is in the form of a concentrated flow rather than a sheet flow that might occur in an undeveloped drainage condition. In this concentrated form, the runoff crosses the area that would have been the stream buffer in a pipe or channel. The concentrated runoff also conveys directly to the stream the particulates and pollutants that would have been filtered and trapped by the buffer.

Protecting existing stream buffers and banks is far preferable to having to restore them and trying to mimic what nature had already established (Table 7.5). Stream buffers should be designed to provide at least a minimum width indicated by the specific site and stream conditions (Fig. 7.6). Effective stream buffers in developed or urbanized areas may range from as narrow as 20 ft to more than 200 ft, depending on the topography, the amount of impermeable area, and the degree to which runoff is concentrated. Most local ordinances and standards are amalgamations of experience and liberal borrowing from other standards. Communities that have stream buffer standards require a minimum total width of at least 100 ft, or they require the buffer to include the 100-year floodplain.