Wetland delineation: Overview

Abstract

While wetlands had been drained for agricultural purposes in many regions for hundreds of years or longer, once wetlands became appreciated for the environmental services they naturally provide society (e.g., floodwater storage, water quality renovation, bank and shoreline stabilization, and provision of essential habitat for fish, aquatic invertebrates, and other animals dependent on wetlands), people became concerned about wetland losses. Filling and the combination of dredging and filling were particularly destructive to wetland functions and altered the picturesque view that many wetlands offered, especially wetlands along coasts and large water bodies. Public concern sparked efforts to protect wetlands through three chief means: (1) acquisition of wetlands for the establishment of wildlife refuges, management areas, or nature preserves; (2) purchase of easements on private property to set aside wetlands for conservation purposes; and (3) passage of laws to directly or indirectly protect wetlands. For these purposes, it became important to identify wetlands on the broader landscape and to be able to delineate their boundaries on the ground. Such efforts often involved the production of wetland maps and required development of field-based procedures to delineate wetlands on the ground. The former is usually done for natural resource planning and land acquisition for conservation, while the latter are prepared to identify limits of "regulated" wetlands when designing construction in or near them. Before any of these activities can commence, wetlands need to be defined in such a way that they can be mapped through remote sensing techniques and by ground surveys. This contribution provides an introduction to wetland delineation with a focus on US practices. Wetland Indicators offers a comprehensive examination of the topic including the rationale behind many of the properties used for delineation.