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styles, although the river styles framework provides more explicit guidelines on the
criteria used to delineate river styles.
Use of ecoregions, process domains, or river styles reflects recognition that context matters. Distinct portions of an individual river network, as well as river
networks in different regions of the world, will differ in terms of process, form,
Fig. 2.18 Schematic illustration of two means of distinguishing process domains, using the North
St. Vrain Creek watershed (drainage area 340 km
2 ) in Colorado, USA as an example. In the upper
map, process domains are differentiated based on disturbance regime. The alpine and subalpine
portions of the drainage experience only snowmelt floods, whereas the montane portions also
experience floods from convective rainfall. Stand-killing fires and associated debris flows are much
more common within the montane zone than in the alpine and subalpine zones. In the lower map,
segments of differing channel gradient represent process domains. High-gradient segments have
narrow valley bottoms and lower gradient segments have wider valley bottoms
2.5 The 4Cs of River Health