Interns Help Sycamore Delineate Wetlands

By Kayla Fenning, Summer 2023 Land Stewardship Intern

Many of those who are members of Sycamore Land Trust, or just fans of the outdoors, probably know what a wetland is, their ecological importance, and why it is so vital to reestablish and protect these ecosystems. But how do we know where a wetland is located? How do you even define a wetland? This is where a wetland delineation comes into play. As the United State’s saw an acceleration of water quality throughout the country in the late 60s, Congress enacted the Clean Water Act (CWA). The Act’s objective, specifically Section 404, was to maintain and restore the chemical, physical, and biological integrity of the waters of the US (USACE Wetlands Delineation Manual of 1987). Any landscape changes, whether that is dredging or building dams, you need to delineate a wetland and receive authorization and a permit from the USACE and the state’s natural resources or environmental management department.

Wetlands are fickle ecosystems. They serve as a transitional landscape between terrestrial and aquatic systems. Unlike forests or lakes, where the main component of the ecosystem is always present, wetlands have the unique ability to seemingly disappear during their dry seasons, sometimes for years at a time. This allows for them to be perceived by the public as seen as unimportant, allowing them to be easily dredged for construction projects or farming, especially due to their fertile soil.

So, how do you know where a wetland is, especially if you’re trying to figure it out in a dry season? This is where delineations come into play.

To delineate a wetland, you first have to figure out where you think the wetland is. This can be done through learning about the history of the site. In our case, we went to Sam Shine Nature Preserve. The area used to be a wetland, but 50 years ago had been dredged and a man-made riverine had been done to the site to prevent flooding for farming purposes. The reason why we need to get a permit, is that Sycamore is planning on adding Beaver Dam Analogs (BDAs) along the riverine. BDAs are man-made structures that are designed to mimic the ecological functions of a naturally occurring beaver dam. Although a beaver family has already started doing their ecological function (saving us both time and money, and further proving that nature never truly forgets), we want to help quicken the wetland restoration process.

To begin our delineation, we chose where we have already observed standing water courtesy of the beaver dam up river. Walking a few feet into the forest area, we found a center point and then measured and marked out a 10 meter diameter circle, and then a 5 meter diameter circle. Within the 10 meter diameter circle, the three of us took note of the species and the DBH (diameter breast height) of each tree that was found within our circle. From the 5 meter circle, we took note of the species of any saplings, shrubs, or woody vines. We also took note of any herbaceous plants that occurred within a 2 meter radius from the center. This we just eye-balled from our centerpoint (a relatively common practice). From there, we took note of the group of vegetation each species was considered by the National Wetland Plant List’s Wetland Indicator Status Rating. The ratings are Obligate (OBL – almost always occurs in a wetland, >99%), Facultative Wetland (FACW – usually occurs in a wetland, 67-99%), Facultative (FAC – equally likely to occur in wetlands or non-wetlands, 33-67%), Facultative Upland (FACU – usually occurs in non-wetlands, 67-99%, but occasionally in wetlands, 1-33%), and Upland (UPL – almost always occur in non-wetland, >99%). More than 50% of the composition of the dominant species from each circle must be OBL and/or FACW species in order to have ground to stand on as being considered a wetland. More than 50% cannot be just FAC species, as they can occur in both wetland and upland areas, so it would not be enough evidence to prove that the area is a true wetland.

Although it is important to know the species of the plants that are growing in our desired area, it is even more important to understand the soil composition. Soil is the driving force behind all plant and ecosystem development; wetlands are no different. Wetlands require some period of inundation that results in anaerobic soil conditions that will ultimately affect the plant composition of the area. Although hydrology is the driving force of wetland development, it is one of the least exact and most difficult to quantify categories in the delineation process. A general rule of thumb regarding when wetland hydrology criteria is met is when the soil is inundated for more than 5-12.5% of the growing season. This can also be recognized as 14 or more consecutive days of flooding, or a water table 12 inches or less below the soil surface. In order to get proper soil samples, we had to dig three 8-10 in holes randomly throughout our plot (thanks Sarah for your stellar digging abilities). The reason why you have to dig such deep holes, is that you want to ensure you are sampling the correct soil horizon (layer). Using a special soil coloring booklet, we took note of the color, value, and chroma of the soil samples. Soils that have a chroma less than or equal to 2 indicates long periods of inundation, which is indicative of a wetland.

We also took note of both primary and secondary field indicators that would indicate wetland hydrology. There are many that fall into each category, but I only listed the ones that we observed. Primary indicators include surface water during the growing season, aquatic fauna, sediment deposits, and water marks on trees (this shows that there was a recent time period of inundation in the area). Secondary indicators include surface soil cracks, crayfish burrows, stunted or stressed plants, and drainage patterns. It is important to note that two secondary indicators are needed if no primary indicators are present.

Once we finished with our two sites, I took the liberty of writing up the report. After some calculations, I had determined that the area of Sam Shine Nature Preserve was determined to be a wetland. Now, the report has to be sent to the USACE and the Indiana Department of Environmental Management where they will look at it and make their own determinations. If they allow the permit, we will move to the next stage of setting up the BDA.

Photos by Education Director Mary Welz: Summer interns (left to right) Mya Fayyaz, Sara Marie Carter, and Kayla Fenning, with Land Steward Daniel Layton. Eastern tiger swallowtail butterfly on buttonbush at Sam Shine Foundation Preserve.