Do I have a Wetland, Ditch or Stream on my Property?

What are you restoring for your mitigation bank project? A ditch, stream, wetland or stream and wetland complex? It matters and will affect the definition of the permanent conservation easement boundaries that will be placed over your restoration project. And each one has its own nuances and easement boundaries and regulations.

Ditches

One challenge with ditches is determining what they were historically. They could have been a swale, a stream, small rivers, or a wetland basin. Or they could have just been dry land that was excavated for drainage. What they were historically helps guide what kind of restoration makes the most ecological sense. A tributary swale or stream should be restored as such, and not be restored as a wetland. And the easement boundary should match the appropriate ecological type, stream, wetland or stream/wetland complex.

Another challenge with ditches happens if they are a public drainage ditch system or judicial ditch administered by drainage law. This adds a complicating factor that existing drainage from open surface ditches and/or subsurface tile must be maintained for all upstream landowners. And another complicating factor that the volume and flow rate of water leaving the project cannot be increased to downstream landowners. Both of these factors required hydrologic modeling by a licensed water resources engineer.

Streams

Historically streams have been straightened for drainage and the challenge can be figuring out what the historical alignment was before it was straightened. Sometimes a review of historic aerial images can provide the answer, although quite often these streams were straightened well before the 1920’s when aerial imagery began. Other times site topography gives clues on a historical alignment. But quite often, there is no remaining evidence, and the alignment has to be derived from a set of tools including finding a reference reach, completing a Rosgen Stream Classification, using channel calculation tools, and hydraulic modeling. Once a stream alignment is determined, the conservation easement often matches the riparian area width. This is the area adjacent to and contiguous with the stream channel that contains riparian vegetation characteristic of the region and supports the geomorphological dynamic equilibrium of the stream (Merritt et al. 2017).

Wetlands

Historically ditches were routed through wetlands to drain the wetlands, and because wetlands usually occur on the lowest elevations of a property. For these projects the topography, soils and ground water are used to define the boundaries of what the restored wetland area should be. Historic aerial image analysis is a useful tool in analyzing what the wet area wants to be during wetter years. And restoring that wet area usually entails plugging a drainage ditch and/or draintile, rerouting draintile to maintain upstream neighbor drainage, or building a berm. A conservation easement over a wetland restoration project includes the wetland itself, and an equivalent area of upland buffer around the wetland area.

Stream/Wetland Complex

Stream/wetland complexes are very natural systems often found at the very top of a watershed as the headwaters that form a stream or river, or at the very bottom of a watershed when the stream or river meets a larger water body and a classic river delta forms. A stream/wetland complex exists when a single stream channel, or multiple braided stream channels, run through riverine wetlands located within the channel floodplain. Overbank flow from the channel(s) is the primary wetland water source (Brinson et al., 1995). Common stream types for anastomosed (multiple channels) stream/wetland complexes include Rosgen Stream Types E, C, or DA. And the easement boundary gets complicated because the stream and wetland systems are so interwoven that it becomes a compromise of setting aside an appropriate riparian area width for the stream easement in conjunction with the easement for the wetland and surrounding upland buffer.