A blue-line stream is any stream shown as a solid or broken blue line on 7.5 Minute Series quadrangle maps prepared by the U.S. Department of the Interior Geological Survey (USGS). A blue-line stream is a body of concentrated flowing water in a natural low are or natural channel on the land surface and may be any creek, stream or other flowing water feature, perennial or ephemeral, indicated on USGS quadrangle maps, with the exception of man-made watercourses. Such a designation probably is based simply on aerial photographs showing channel vegetation, but so far as the USGS is concerned, they have no specific hydrologic or biologic significance. Therefore, the blue-line stream has no rational relationship to recognized planning concerns.
Blue-line streams are not regulated by the District. Flood Hazard Areas included in Ordinance No. 458 and shown on the District’s Interactive Map are regulated by the District.