Wetland Classification: Geomorphic-Hydrologic System

Abstract

The geomorphic-hydrologic classification treats wetlands as wet landforms, with wetlands being defined as “areas of permanently, seasonally, or intermittently waterlogged to inundated soils, sediments, or land, whether natural or artificial, fresh to saline” without recourse to identifying the vegetation type that may inhabit them. Water, through its geological/geomorphic, hydrological, and biotic interactions also drives biological productivity resulting in these wet landforms being inhabited by mosses, sedges, reeds, rushes, heaths, and forests. In the geomorphic-hydrologic classification, wetlands are separated into two fundamentally different types: 1. terrain-conforming, occurring in hollows and channels, covering plains/flats, and residing on vales, slopes, cliffs, and hill-tops; these may generate wetland sedimentary deposits, or they may simply be wetted land surfaces without any sedimentary deposits; and 2. self-emergent wetlands whose deposits accrete and rise into mounds above the land surface. Based on landform type and water regime 22 non-genetic primary categories of terrain-conforming wetlands are recognised which can be further subdivided by using descriptors such as size, shape, water salinity, vegetation cover, amongst others. Self-emergent wetlands can be differentiated into several types based on the composition of their accretionary material. The objective of the geomorphic-hydrologic wetland classification is to capture the global range of wetland types, and to base the classification and its associated descriptors on a hierarchical and systematic treatment of the two fundamental factors which determine the existence of wetlands: land and water.