The Mobile-Tensaw Delta: Wetlands Status, Conservation, and a Documented Flood Risk

One of the largest intact wetland systems in the country

The Mobile-Tensaw Delta is a roughly 260,000-acre complex of wetland habitats -- submerged grass beds, cypress-gum swamps, and seasonally flooded bottomland hardwoods -- sitting in the river valley directly north of Mobile Bay, fed by the Mobile, Tensaw, Alabama, and Tombigbee rivers as they converge. It's recognized as one of the most ecologically diverse places in the country: its network of creeks, rivers, ponds, and oxbow lakes supports the greatest number of freshwater species found anywhere in the United States. For a land buyer, that scale and ecological significance translate directly into practical risk: informal, visual assessments of whether a piece of Mobile County land is 'wet' are far less reliable here than in an ordinary rural county, because the delta's boundary and its connected floodplain reach well beyond the obviously swampy core.

A real, current conservation story: 8,000 acres saved from logging

In 2024 and 2025, The Nature Conservancy purchased roughly 8,000 acres of forested wetland between the Tombigbee and Alabama rivers, at the top of the delta -- land that regularly floods and serves as important bird habitat and fish-spawning ground, and that was at real risk of being logged to produce wood pellets for export to European power plants. The purchase was funded by a $5.2 million gift from Holdfast Collective, the nonprofit majority shareholder of the Patagonia clothing brand, along with an additional undisclosed donor. In June 2025, The Nature Conservancy partnered with the E.O. Wilson Biodiversity Foundation to formally name the tract the Land Between the Rivers Preserve in honor of the late naturalist, with a dedication ceremony planned for fall 2025.

This is worth understanding not as historical trivia but as a live signal of the delta's current land-use pressures: a large, ecologically significant tract at the very edge of the wetland system was, until recently, an active candidate for industrial-scale logging, and it took a seven-figure philanthropic gift specifically to take it off that market. That's a useful data point on how real, and how recent, the tension between conservation and resource extraction remains in this exact geography -- a tension a land buyer evaluating any large forested tract near the delta's upper reaches should keep in mind when assessing what a seller's stated land use has actually been, and what a future owner's options might look like if wetland or floodplain designations apply.

A documented industrial hazard sitting inside the same wetland system

Separately, and just as concretely, Alabama Power's Plant Barry generating station sits directly along the Mobile River amid the delta's sensitive wetlands, holding back more than a century's worth of coal ash behind earthen dikes. An Inside Climate News investigation, reviewing Alabama Power's own legally mandated emergency action plans, found that a breach of the dikes separating Plant Barry's coal ash from the Mobile River would inundate roughly 25 square miles of the Mobile-Tensaw Delta with coal ash slurry. That review is part of a broader finding that Alabama Power's six coal ash pond sites statewide hold more than 117 million tons of coal sludge along the state's waterways, with hundreds of square miles at risk of inundation collectively in the event of a barrier failure. Plant Barry's pond specifically sits in a low-lying, flood-prone area, held by a dam built of dirt, clay, and coal ash -- construction the reporting describes as susceptible to failure from a hurricane, heavy rainfall, or ordinary structural degradation over time.

Alabama Power maintains that its closure plans and groundwater protections comply with current state and federal law, are approved by the Alabama Department of Environmental Management, and are certified by professional engineers, and the company says it is actively treating and removing water at the site and planning to excavate material to create a buffer from the river. This page doesn't take a position on whether that closure plan is sufficient -- but the documented, utility's-own-numbers 25-square-mile inundation footprint is a genuinely specific hazard fact, not a generic flood-zone disclosure, and it's directly relevant to any parcel near Plant Barry or elsewhere along the lower Mobile and Tensaw rivers.

What to actually check before buying delta-adjacent land

For any Mobile County parcel near or connected to the Mobile-Tensaw Delta system, get a formal wetlands determination -- a jurisdictional determination from the U.S. Army Corps of Engineers, not a visual assessment -- rather than assuming a parcel's buildable status from its distance to the delta's obviously swampy core, since the delta's floodplain and wetland boundaries reach well beyond the visible core. Separately, pull a current FEMA flood-zone determination for the specific parcel. And if the land sits anywhere along the lower Mobile or Tensaw rivers, or within a several-mile radius of Plant Barry or Alabama Power's other coal ash sites, it's worth asking directly whether the parcel falls within any mapped emergency-action-plan inundation zone -- that's a fundamentally different, industrial-hazard question from an ordinary floodplain check, and it isn't something a standard wetlands delineation or FEMA flood map will necessarily flag on its own.