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Reconstructing a Lost Delta Stream: The Dark Corner Stream Restoration Project

Arkansas Natural Heritage Commission - Tuesday, November 13, 2018
by Dustin Lynch

The Mississippi Alluvial Plain of eastern Arkansas, commonly known as the Delta, was originally home to the largest continuous system of wetlands in North America. This region is defined and shaped by the flow of its major rivers: the Mississippi, Arkansas, White, and St. Francis. The deep layers of sediment deposited by these waterways make it one of the most productive regions in the world for large-scale agriculture. As a result, the land has been largely cleared of native vegetation and drained for cultivation, leading to the widespread loss and degradation of wildlife habitat. Furthermore, agricultural runoff contains fertilizers, sediment, herbicides, pesticides, and livestock waste. Water testing typically reveals high concentrations of total suspended and dissolved solids, phosphorus, nitrogen, sulfates, biological oxygen demand, chlorophyll a, and fecal coliform.

Photo above right — Dark Corner wetland, pre-reconstruction. Photo by Timothy Vail, The Nature Conservancy (TNC), Arkansas Field Office.

The drainage canals and ditches widely used in the region separate rivers and their adjoining habitats from the rest of the natural aquatic environment and accelerate the transport of excess nutrients and sedimentation downstream. The effects of this pollution reach as far as the Gulf of Mexico, seasonally creating a low-oxygen “Dead Zone” that renders thousands of square miles uninhabitable by most marine life. On a local scale, the entrenched, heavily channelized nature of Delta streams results in turbid water conditions (cloudiness or haziness that affects the clarity) that are less than ideal for wildlife and human use alike.

Among the numerous waterways historically affected by these changes was Dark Corner Creek, a small stream in the Bayou DeView watershed. Historically, the stream drained an area of approximately 7,000 acres, but extensive channelization through the creation of ditches for agricultural use in the 1940s reduced the drainage area to 3,384 acres. Much of the Dark Corner watershed lies on Benson Creek Natural Area (BCNA), part of a system of 73 such public areas across the state managed by the Arkansas Natural Heritage Commission.

In 2012, The Nature Conservancy (TNC) identified BCNA as an ideal candidate for restoration according to the Natural Channel Design method developed by Dave Rosgen of Wildland Hydrology Consultants, a process that utilizes a number of scientific lenses to replicate as closely as possible the natural flow regime of the original watershed. Because the property is subject to a perpetual Agriculture Conservation Easement Program Wetland Reserve Easement (ACEP-WRE) under the Natural Resources Conservation Service (NRCS), NRCS provided funding dubbed “no easement left behind.” These easements (first implemented in the mid-1990s) provide economic benefits to landowners and are perpetual, with cost covered by NRCS. Currently the Arkansas Delta contains over 250,000 acres of these wetland reserve easements with 4,000-6,000 additional acres being enrolled every year.

With funding in place, TNC secured the services of a private specialized contractor, Natural State Streams, whose team specializes in all aspects of stream restoration including erosion control, stream bank stabilization, and native riparian planting and establishment. Personnel from the nearby Cache River National Wildlife Refuge provided technical assistance, additional funding, and equipment. The team determined the appropriate width, depth, and sinuosity (the natural meander of the stream) that would allow the stream to function as it did prior to alteration.

Photo at left — Stream channel construction on Dark Corner Creek. Photo by Timothy Vail, TNC, Arkansas Field Office.

The construction phase of the project brought many challenges. Due to heavy spring rains and a network of downstream beaver dams, the wetland proved difficult to drain for long enough to allow work to get underway. As quickly as levees could be breached, beavers (Castor canadensis) would rebuild dams, necessitating vigilant monitoring and removal throughout the process. Before water could be diverted into the newly constructed stream, precautions against erosion were taken. The installation of jute matting, a biodegradable material made of woven vegetable fibers, offered temporary protection until newly grown vegetation could anchor the soil. Cutting and planting stakes from black willow trees (Salix nigra) growing on-site ensured better survival. Finally, the removal of a culvert immediately downstream allowed as much unrestricted flow through the system as possible.

Photo below — The Dark Corner Stream Restoration Project. Photo by Timothy Vail, TNC, Arkansas Field Office.

Since the project’s completion in October of last year, water quality samples collected twice a month have evidenced its effect on the ecosystem. The data indicates that there is already a reduction in turbidity as the natural hydrology of the restored system filters nutrients and traps particulate matter. Further decreases are projected as vegetation in the floodplain takes hold. There has also been some reduction in nitrogen at the site, although it may take years for it to decline to historic levels.

Photo below — Reconstructed stream channel at Dark Corner Creek, summer 2018. Photo by Dustin Lynch.

A variety of aquatic species already utilize the newly constructed stream habitat. ANHC staff have documented fish species including largemouth bass (Micropterus salmoides), bluegill (Lepomis macrochirus), spotted gar (Lepisosteus oculatus), and banded pygmy sunfish (Elassoma zonatum), as well as a variety of invertebrates and amphibians. Grasses, sedges, and broadleaf plants are flourishing at the site and will ultimately provide much-needed food for wintering waterfowl.

While restoration of a small creek in eastern Arkansas may seem like a small piece of a very large and complex puzzle with far-reaching consequences, it clearly epitomizes the conservation adage “think globally, act locally.” It is the hope of all the contributing partners that the Dark Corner Stream Restoration Project can serve as an example for future efforts throughout the region to tackle some of our most serious challenges when it comes to wildlife, habitat, and waterways.

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