Table 4. Possible links between vegetation zones and flow categories in southern African rivers (modified from Boucher 2002).

Vegetation zone
Type of vegetation
Correlations with flow categories
Algae and submerged macrophytes
Perennials maintained by dry-season low flows
Lower wetbank
Mosses, ferns, sedges
Wet-season low flows
Upper wetbank
Sedges, reeds, herbs, grasses
Class 1, 2, and 3 intra-annual floods
Lower dynamic
Pioneer communities, annuals, young trees and occasional older ones
Reached by Class 3 and 4 intra-annual floods; too high for wetbank vegetation, floods too regularly for trees to establish
Tree and shrub
Trees and shrubs
Tree line maintained by 1:2 yr floods; whole tree and shrub zone reached by 1:2 up to 1:20 yr floods
Back dynamic
Outer limit of riparian species, semi-terrestrial
Reached by >1:20 yr flood