Classifying Wetlands Part 2

Last week’s Wetland Wednesday mentioned 3 main criteria as part of identifying a wetland (wetland hydrology, hydrophytic vegetation, and hydric soils). – Today we’ll look at how plants and soils help scientists delineate wetlands.

In the field, scientists identify and sample soils and plants as part of wetland delineation. The LSU AgCenter groups plant species based on where the plant is naturally found as seen in the table below.

indicator_2Wetland plants have adapted to flooded soils. “Obligate” plants can tolerate water at high levels or when soil saturation is a normal condition to that area. Examples of these plants include the bald cypress (Taxodium distichum), or cattail (Typha latifolia) [3].

In contrast, plants that cannot handle flooded conditions for an extended period would naturally be in the “upland” area of land (i.e. winged sumac (Rhus copallina), eastern redbud (Cercis canadensis), or panic grass (Dichanthelium sp.) [3].

People delineating wetlands focus on a project area according to aerial and soil maps along with aerial photographs [1]. Delineators then take soil samples and determine characteristics seen in hydric soils which relate to cycles of flooding and drying. – Examples of those include oxidized soils, hydrogen sulfide (rotten egg smell) and organic bodies found on plant roots. Finally, the plant and soil types are compared, tested, then matched to determine wetland boundaries for mapping and policy purposes [1].

Wetland delineation is a tool for protecting and documenting these important landscapes which contribute to a healthy and functional environment. It is important to note that wetland delineation requires much more than just plant and soil identification. CWPPRA utilizes sound science, engineering, mapping, and geo-technical surveys in the process of planning, approving, constructing, and maintaining coastal Louisiana wetland restoration projects.


[1] Bedhun, Rebecca. 2018. “Watch and Lean Now: How To Do A Wetland Delineation”. Shoret Elliot Hendrickson Inc. Available: [September 9, 2018]

[2] Jon Kusler. “Common Questions: Wetland Definition, Delineation, and Mapping”. Association of State Wetland Managers, Inc. Available: [September 9, 2018]

[3] LSU Ag Center. 2018. Louisiana Plant Identification: Plant List. Available: [September 10, 2018]



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