Usa wetlands: Nwi-plus classification system

Abstract

The original classification system used to inventory and map US wetlands was based on the Cowardin system with its descriptors based on soil, vegetation, hydrology, and water chemistry. This system was extended with hydrogeo-morphic descriptors (the LLWW descriptors: Landscape position, landform, water flow path, and water body type) to enable functional assessment of wetlands. The resulting system, the NWI+ database, is used to classify wetlands according to both Cowardin and LLWW types and can predict function for the wetlands in a watershed. The 11 functions predicted routinely are surface water detention, coastal storm surge detention, streamflow maintenance, nutrient transformation, sediment and other particulate retention, carbon sequestration, bank and shoreline stabilization, provision of fish and aquatic invertebrate habitat, provision of waterfowl and waterbird habitat, provision of habitat for other wildlife, and provision of habitat for unique, uncommon, or highly diverse wetland plant communities. The LLWW descriptors can also help to predict the impact of change on wetland functions. Results of assessments are published in reports, and an online mapping tool is available.