Dam Watch — Critical U.S. Dams & Downstream Flood Risk

Colorado River · NV / AZ · 726 ft · Lake Mead

Downstream: Laughlin & Bullhead City, Needles, Lake Havasu City, Parker, Yuma — and the water supply for Las Vegas, Phoenix, Los Angeles and San Diego.

At risk: ~2.5 million in the downstream corridor

Failure would send a flood wave down the lower Colorado and cut water and power to the entire Southwest.

Colorado River · AZ · 710 ft · Lake Powell

Downstream: Grand Canyon corridor, then everything below Hoover Dam — a Glen Canyon failure would overtop Lake Mead.

At risk: Cascading risk to millions

Watched for 'dead pool' levels: below minimum power pool the dam can no longer generate electricity.

Feather River · CA · 770 ft · Lake Oroville

Downstream: Oroville, Gridley, Live Oak, Yuba City, Marysville, and the Sacramento Valley.

At risk: ~188,000 evacuated in the 2017 spillway crisis

Tallest dam in the U.S. Its 2017 spillway failure forced the largest dam evacuation in modern U.S. history.

Sacramento River · CA · 602 ft · Lake Shasta

Downstream: Redding, Red Bluff, Chico, and the length of the Sacramento Valley to the Delta.

At risk: Hundreds of thousands

Keystone of California's water system — failure would flood the entire Sacramento Valley.

American River · CA · 340 ft · Folsom Lake

Downstream: Folsom, Rancho Cordova and downtown Sacramento — one of the most flood-exposed cities in America.

At risk: ~500,000 in the Sacramento floodplain

Sacramento sits below this dam at a river confluence; a failure floods the state capital.

Missouri River · MT · 250 ft · Fort Peck Lake

Downstream: The entire lower Missouri River chain — Williston, Bismarck, Omaha, Kansas City, St. Louis.

At risk: Cascading risk down six dams

First in the Missouri River mainstem chain — a failure here loads every dam downstream.

Missouri River · SD · 245 ft · Lake Oahe

Downstream: Pierre SD, Sioux City, Omaha, Kansas City, St. Louis.

At risk: Millions along the Missouri

One of the largest embankment dams on Earth by volume.

Missouri River · SD / NE · 74 ft · Lewis and Clark Lake

Downstream: Yankton, Sioux City, Omaha, Nebraska City, Kansas City.

At risk: Metro Omaha & Kansas City floodplains

Cooper Nuclear Station sits downstream on the Missouri and depends on the river for cooling water — 2011 flooding put it on alert.

Columbia River · WA · 550 ft · Lake Roosevelt

Downstream: Wenatchee, Tri-Cities, Hanford, Portland–Vancouver metro.

At risk: ~2 million in the lower Columbia corridor

Largest power station in the U.S. The Columbia Generating Station nuclear plant and the Hanford site both sit downstream.

Columbia River · WA · 236 ft · Rufus Woods Lake

Downstream: Bridgeport, Chelan, Wenatchee, Tri-Cities.

At risk: Lower Columbia communities

Immediately below Grand Coulee — the two fail as a chain.

Columbia River · WA · 185 ft · Wanapum / Priest Rapids Lake

Downstream: Hanford Reach, Richland, Kennewick, Pasco.

At risk: Tri-Cities metro ~300,000

Directly upstream of the Columbia Generating Station nuclear plant and the Hanford nuclear reservation. A 2014 crack in Wanapum forced an emergency drawdown.

Tennessee River · AL · 137 ft · Wilson Lake

Downstream: Florence, Muscle Shoals, and the lower Tennessee River to the Ohio.

At risk: North Alabama river communities

Part of the TVA chain that also cools the Browns Ferry nuclear plant downstream.

Tennessee River · TN · 112 ft · Watts Bar Lake

Downstream: Spring City, Dayton, Chattanooga.

At risk: Chattanooga metro ~570,000

The Watts Bar Nuclear Plant draws its cooling water from this reservoir — a dam failure is a reactor cooling emergency.

Tennessee River · TN · 122 ft · Fort Loudoun Lake

Downstream: Lenoir City, Loudon, and the Watts Bar reach below.

At risk: East Tennessee river valley

Upstream of Watts Bar — its failure would surge into a nuclear plant's cooling reservoir.

Clinch River · TN · 265 ft · Norris Lake

Downstream: Clinton, Oak Ridge, and the Tennessee River at Knoxville.

At risk: Knoxville & Oak Ridge ~500,000

Above the Oak Ridge nuclear complex — TVA's first dam.

Tennessee River · KY · 206 ft · Kentucky Lake

Downstream: Paducah and the Ohio–Mississippi confluence at Cairo IL.

At risk: Ohio Valley communities

Sits at the mouth of the Tennessee — and inside the New Madrid earthquake zone.

Cumberland River · KY · 258 ft · Lake Cumberland

Downstream: Burkesville, Celina, Carthage, Nashville.

At risk: Nashville metro ~2 million

Was rated one of the highest-risk dams in America for seepage before a major grout-wall repair; Nashville lies downstream.

Caney Fork · TN · 250 ft · Center Hill Lake

Downstream: Smithville, Carthage, and Nashville via the Cumberland.

At risk: Middle Tennessee & Nashville

Long-running seepage remediation; classed a high-risk USACE dam.

Susquehanna River · MD · 94 ft · Conowingo Pond

Downstream: Port Deposit, Havre de Grace, and the head of Chesapeake Bay.

At risk: Upper Chesapeake communities

Peach Bottom Atomic Power Station sits on this river reach and relies on the Susquehanna for cooling.

Kern River · CA · 185 ft · Lake Isabella

Downstream: Bakersfield — directly in the inundation path.

At risk: ~400,000 in Bakersfield

Was restricted for years over seepage and an active fault beneath the dam; a major safety modification finished in 2022.

Buffalo Bayou · TX · 48 ft · Addicks / Barker

Downstream: West Houston and downtown Houston along Buffalo Bayou.

At risk: Houston metro ~7 million

Controlled releases during Hurricane Harvey flooded thousands of homes — the classic case of a dam decision harming residents.

Lake Okeechobee · FL · 30 ft · Lake Okeechobee

Downstream: Belle Glade, Clewiston, Pahokee, Moore Haven — the 1928 dike failure killed roughly 2,500 people.

At risk: ~40,000 immediately, plus South Florida water supply

A hurricane-driven dike breach here caused one of the deadliest disasters in U.S. history. Rehabilitated, but watched every storm season.