Some of the line work was updated using the 1986 photoquads quads. Several quadcoverages had to be generated in-house from 1986 photoquads. The in-house generated quads display less detail in the coastal areas. The hydrography was initially generated by major drainage basin. The county coverages were clipped from the drainage basin coverages.
Tributaries converge to produce higher order.
If there are level 3 tributaries that enter the level 2, the first is given the next stream number. If there are any level 4 tributaries that enter the level 3, the first is given the next stream number. In cases where the units digit is not zero, the units digit supercedes the tens digit. Linear section of streams. Region is the first subdivision of HUC11.