Stream Orders

Stream ordering in a drainage network classifies the hierarchy of channels in a watershed.

Stream order classifications are established with reference to NIWA's River Environment Classification (REC); a database of catchment spatial attributes, summarised for every segment in New Zealand's network of rivers.

See: https://niwa.co.nz/freshwater/management-tools/environmental-flow-tools/river-environment-classification

Geomorphic Processes

Strahler classification — Figure 2. Stream order classification. Source: NIWA.

Network position	Order	Gradient	Landforms	Dominant process
Zone 1	1,2	High / steep	Headwater streams	Erosion
Zone 2	3,4	Mid gradient	Pool / riffle, tributaries	Transfer / storage
Zone 3	5,6,7	Low gradient	Main stem, floodplains	Deposition

Refer to Figure 1 for explanation of network position zones.