Snohomish County Public Works Surface Water ManagementOpen channels include ditches, infiltration ditches, and swales. They convey water from the roadside or from pipe system outlets, and are typically composed of natural materials such as earth, grass, or rock. They are mapped to allow for inspection and maintenance as part of Snohomish County's National Pollutant Discharge Elimination System (NPDES) permit.ArcGIS FeatureLayerhttps://hub.arcgis.com/datasets/9799d91cf7aa4f50bd220b27791b423f_0engSnohomish County Open Data PortalPublicOpen Channel [Washington (State)--Snohomish County]Web servicesWashington (State)--Snohomish CountyWashington (State)Last Modified: 2023-05-04