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Army Corps and Metro Water present updated Cumberland River flood analysis: 100‑year elevations rise in downtown; East Bank filling shows minimal downstream run
Summary
The U.S. Army Corps of Engineers and Metro Water Services told the East Bank Development Authority that updated flood modeling shows the 100‑year base flood elevation in downtown Nashville is roughly 1–2 feet higher under the new analysis, and recommended raising key road and property grades in the East Bank.
The U.S. Army Corps of Engineers (Corps) and Metro Water Services briefed the East Bank Development Authority on updated flood modeling for the Cumberland River and the East Bank study area, reporting modest increases in base flood elevations downtown and offering design guidance for resilient development.
Tom Falco (assistant director, Metro Water Services) reviewed the city’s obligations under the National Flood Insurance Program and noted Metro has adopted local freeboard standards — four feet for residential structures and one foot for nonresidential buildings — above mapped base flood elevations. He said Metro will use the study’s best available data for permitting and regulation ahead of formal FEMA map adoption.
Barry Moran of the U.S. Army Corps described the Corps’ flow‑frequency and hydraulic analysis. The Corps’ updated 2025 study revised the estimated regulated 100‑year flow and produced river stage changes that the team said translate to roughly a 1–2 foot increase in the 100‑year base flood elevation through much of downtown, with larger relative increases at more frequent events (the Corps cited increases on the order of several feet for the 10‑year event in places).
Moran and Falco emphasized that the East Bank overbank is heavily obstructed and—because of existing fill, bridges and other structures—carries only a small fraction of the river’s conveyance in large floods. The Corps reported modeling results in which a hypothetical complete raising of the East Bank produced minimal increases in river stage (measured in tenths of inches to a few tenths of a foot) at most locations; Moran described those impacts as very small because water in the East Bank overbank generally behaves like “standing water” rather than a high‑velocity channel.
Corps and Metro staff recommended elevating roadways and development areas so that emergency access and usable street and building space are available during floods — for example, raising key roads and grades by roughly 2–4 feet depending on location and intended use. Moran said his team had modeled scenarios up to a full bank fill; results showed only minor stage increases for the modeled cross sections but emphasized site‑specific design and maintaining drainage for local runoff.
The Corps said it will deliver final technical products to Metro in August and submit mapping materials to FEMA; Moran estimated the FEMA map adoption process could take two to three years. Metro and the Corps also scoped a next phase (Phase 8) to expand the analysis to a 2‑D model covering both riverbanks and upstream storage areas, work they expect to conduct in FY2026.
Why this matters: The updated study updates hazard elevations used for permitting, design and emergency planning. Metro staff said they are already using the best available data for regulation and recommended avoiding minimum‑standard construction practices such as below‑grade parking in flood‑prone areas.
