Skip to main content
King County logo

The classification of a waterway is one of the key components of the streamlined permit process for maintenance projects on agricultural waterways.  The first component of the classification is whether the waterway is a natural stream, a modified stream, or an artificial ditch. The second component describes the expected presence or level of abundance of juvenile salmonids during the standard construction window.

The streamlined permitting process applies to modified streams and artificial ditches.  Streams that have not been straightened and have had minimal alterations are classified as natural and require an individual permit review.  Modified streams are man-made channels that carry a previously existing stream.  Artificial ditches are man-made ditches that do not carry a previously existing stream.

The expected presence of salmonids during construction is based on a variety of information including the known presence or absence of salmonids, known fish passage barriers, the quantity of water known or expected to be present during construction, documented temperature measurements of the water present during construction, the size of the upstream contributing drainage basin, and the geologic characteristics of the waterway (e.g. Is there a spring that provides continuous flow?  Is the waterway backwatered from a larger downstream body of water?).  The decision tree for expected presence of salmonids can viewed on our classification flowchart (Acrobat pdf).

View waterway classification maps by Agricultural Production District (Acrobat pdf format):

For questions about the Agricultural Drainage Assistance Program or ADAP, please contact Brian Sleight, Supervising Engineer, King County Stormwater Services Section.