Stream Levels

Stream level - This numbering system deals with the reverse scenario of Stream Order, it is the hierarchy of streams from the mouth (where they empty into the oceans) upstream identifying the main flow paths, but it also has a few caveats. Stream levels follow named features and pertain to an accumulated flow from that feature.


An example of a first order stream level would be the Mississippi where as a second order stream level would be the Missouri and Ohio rivers entering into the Mississippi.


The NHD stream level is calculated based on arbolate sum, name, and topological flow relationship from the subbasin pour point or main stem drainage within the HUC8 upstream. An initial table of stream levels was developed by Horizon Systems, Inc. at the 1:100,000-scale resolution to identify the stream level of the main stems drainage within each subbasin and can be used with the tools to update the stream levels within a particular subbasin.