Waterway classifications

How an agricultural waterway is classified is part of the permit process for maintenance projects on agricultural waterways. The classification first considers if the waterway is a natural stream, a modified stream, or an artificial ditch. The second consideration is if juvenile salmonids are present or expected to use the waterway during the construction window.

Streams that have not been altered are classified as natural and require an individual permit review.

The streamlined permitting process applies to altered streams and constructed ditches. Modified streams are channels that changed or moved a stream. Constructed ditches did not carry an existing stream but have been used to move water off property.

The expected presence of salmonids during construction is based on:

• the known presence or absence of salmonids,
• fish passage barriers,
• the quantity of water present or expected to be present during construction,
• documented temperature measurements of the water present during construction,
• the upstream size of the drainage basin,
• and the geologic characteristics of the waterway:
  • Is there a spring that provides continuous flow?

Check out our classification flowchart (155 KB) for more information. 

Is the waterway a backwater for or connection to a downstream body of water? View waterway classification maps by Agricultural Production District:

• Snoqualmie River (630 KB)
• Sammamish River (1.7 MB)
• Enumclaw & Upper Green River (1.3 MB)
• Lower Green River (552 KB)