Enjoying Iowa's inland seas

Coralville's Devonian Gorge was scoured out in the flood of 1993 and expanded by the Great Flood of 2008. (Marion Patter
Coralville’s Devonian Gorge was scoured out in the flood of 1993 and expanded by the Great Flood of 2008. (Marion Patterson/correspondent)

A brisk wind pushed whitecaps toward us that curled and broke on the beach below our perch on a bluff.

By focusing our eyes on the waves, it was easy to imagine we were on a New Jersey beach gazing at the Atlantic or staring westward at the Pacific from an Oregon bluff.

Lifting our gaze brought us back to Iowa. Ocean viewing affords expansive views of water but our Iowa waves were framed by trees on either side of the state’s largest lake.

Ask most people what Hawkeye State lake is biggest and most will say, “Okoboji” or “Big Spirit.” If the question were asked a century ago, they would be correct. At the time Spirit Lake, at 5,684 acres, was Iowa’s largest lake. Now the crown goes to Lake Red Rock. At 15,520 acres it’s nearly three times larger.

Red Rock — along with Saylorville, Rathbun, and Coralville — were created by the Army Corps of Engineers by building massive earthen dams to plug rivers that had a flooding history. In addition to their flood control function, dam building required buying thousands of acres of land that, today, give Iowans and visitors plenty of room for outdoor play.

The reservoirs and surrounding public land are popular places for boating, fishing, camping, hunting, birding, picnicking and hiking. They are among Iowa’s biggest parcels of public land.

Following floods in the 1920s and 1930s, Congress passed legislation and funding to build reservoirs across much of the United States, including four in Iowa. Most were built by the Corps of Engineers and some, in other states, by the Bureau of Reclamation.


Flood control dams function by maintaining what’s called a conservation pool. It’s the relatively low level the lake is held at during much of the year. When heavy rain or snowmelt threatens flooding, the Corps of Engineers holds much of the increased flow by raising a reservoir’s level.

For example, during normal weather conditions, Coralville Reservoir is about 5,280 acres. But in flood, it swells to 24,800. That’s a lot of water that doesn’t immediately flow past Iowa City and other downstream towns and farms. When the weather dries out, water is gradually released until the lake’s level again is at the conservation pool.

According to Allen Marshall, Communications Chief of the U.S. Army’s Rock Island District, Iowa’s reservoirs were built solely to control flooding. Recreation was just an ancillary benefit. But today most Iowans think of these big constructed lakes as places to play.

That’s also the case in Corps of Engineers Lakes in many states. Visitors to reservoirs in the Dakotas, in Kansas, or in many other states today discover modern campgrounds, swimming beaches, boat ramps, fishing, bicycling and hiking trails and places to hunt.

All of Iowa’s large reservoirs are home to bass, white and black crappies, white bass, wiper hybrids, carp, occasional northern pike, panfish and catfish. Fishing is usually most productive from a boat, but bank anglers sometimes enjoy abundant catches in the swift water below the dams.

Some of Iowa’s best birding, especially for large birds, can be found during migration when pelicans and waterfowl move through.

Typically flood control reservoirs are big enough for power boats to rev up their engines and run for miles at high speed, something not possible in Iowa’s normally diminutive lakes. That’s why they are favored by water skiers.

Hundreds of acres of public land surround big reservoirs. Much of it is an upland buffer that never floods. The rest is bottomland that is normally dry but under water when floods threaten. Much of this dry land is open to public hunting managed by the Iowa DNR.


America is a land of dams. At least 90,000 sprinkle the country. Many were built in early settlement days to provide power for grist and saw mills and as places to harvest ice. Later and larger ones were built in an attempt to control floods or generate electricity. Many western dams provide water for irrigating crops and domestic use in Las Vegas, Los Angeles and other places.

Sadly, many dams are old and in poor condition. Two failed in Michigan last year and one in Nebraska killed Vietnam Veteran Kenny Angel. Iowa’s own Delhi Dam breached several years ago but has since been rebuilt. Fortunately, the Corps of Engineers carefully maintains its dams.

The 1950s through ’70s were the golden age of American dam building, including in Iowa. Coralville, which opened in 1958, is our state’s oldest Corps of Engineers Reservoir, with Red Rock and Rathbun completed in 1969 and Saylorville in 1977. They are carefully maintained by the Corps of Engineers, provide wildlife and fish habitat, and are sites for outdoor recreation. They also have downsides.

Creating massive reservoirs requires evicting people who live in areas soon to be buried under water. Red Rock was once an Iowa town that was flooded out. It now lies under water, but the town’s legacy is giving its name to the lake. Today speed boats roar over once productive farms. Big dams also prevent fish from following ancient migration paths up and down rivers, and dirty river water dumps sediment when it enters a reservoir’s slack water. This siltation gradually shallows the conservation pool, reducing fish habitat and boating opportunities.

Dams may reduce flooding but they don’t guarantee to stop it. Massive 1993 and 2008 rains overtopped Coralville Dam to create mischief downstream. As Iowa suffers increasingly heavy precipitation, dams may become less effective in fulfilling their original mission.

Few big dams are being built in the United States today. Removal is the trend, and around 1,700 have been taken out since 1912, most in the past 30 years. Best known are Elwaha and Glines Canyon Dams in Olympic National Park, allowing salmon to again reach upstream spawning areas.

No one is proposing removing Iowa’s four large dams. Today they are pleasant and popular places to visit. We’ve enjoyed quiet walks in Coralville Reservoir’s woodlands and pulled husky crappies from its water. More recently we spent a delightful sunny morning watching Red Rock’s surface shimmer in an autumn breeze. We like the wooded and wild shorelines of our big reservoirs that contrast with the house-lined margins of Spirit, Okoboji and Clear lakes.

All of Iowa’s Corps of Engineers Reservoirs welcome visitors and have natural and constructed amenities. Some special features we enjoy at each follow:



Smack dab between Iowa City and Cedar Rapids, Coralville is close to the homes of hundreds of thousands of Iowans. We enjoy walking at the Macbride Nature Recreation Area, located on a peninsula jutting out into the reservoir. Ironically, the 1993 Iowa River flood that overtopped the dam scoured away millions of tons of soil and bared what’s now called the Devonian Fossil Gorge. It’s just below the dam and offers the chance to see fossils that gave the reservoir and nearby town its name. Lake Macbride State Park is immediately adjacent to the reservoir and is also a pleasant place to camp, boat, picnic or fish.


Iowa’s biggest lake, Red Rock Reservoir, is located between Pella and Knoxville about 100 miles from the Corridor. Created in forested rolling land, we think it’s the most scenic of the state’s Corps of Engineers lakes. During floods it swells to a massive 70,000 acres.


Saylorville is in Des Moines’ backyard and offers 5,950 acres of water in its conservation pool. That can swell to 16,700 during floods. Located just a few miles north of Iowa’s capital city, it is a popular outdoor recreation site close to the homes of many Iowans. We sometimes wrap up a Des Moines business trip with a stop at the lake on our way home.


Rathbun offers world class crappie fishing and is the site of the Iowa DNR’s Honey Creek Resort. It features a lodge, golf course, boat rentals, swimming and much more on the edge of the massive reservoir. Rathbun is the farthest reservoir from the Corridor but close enough for a long day trip. It’s the state’s second largest lake with a 11,000-conservation pool that grows to 21,000 acres during floods.

All of Iowa’s reservoirs are within day-trip range of the Corridor, but overnighting is helpful to better explore and enjoy them. In addition to Corps of Engineers Campgrounds several state parks with campgrounds are located along or near reservoirs. Private campgrounds also are common, and nearby towns feature motels and restaurants.

Iowa’s big lakes were created by the Army Corps of Engineers, but the glaciers carved several king-size lakes often more familiar to Iowans. Big Spirit, Iowa’s largest natural lake, hugs Minnesota in Dickinson County and is close to West Okoboji Lake. Renowned for 3,847 acres of clear water, West Okoboji is our deepest lake, plunging down 136 feet. Shallow natural Clear Lake is only slightly smaller at 3,684 acres.

Iowa may be a sea of corn and soybean fields, but nestled within vast swatches of crops are four massive reservoirs that are meccas of outdoor recreation.

Rich and Marion Patterson have backgrounds in environmental science and forestry. They co-own Winding Pathways, a consulting business that encouraging people to “Create Wondrous Yards.”

Give us feedback

We value your trust and work hard to provide fair, accurate coverage. If you have found an error or omission in our reporting, tell us here.

Or if you have a story idea we should look into? Tell us here.

Give us feedback

We value your trust and work hard to provide fair, accurate coverage. If you have found an error or omission in our reporting, tell us here.

Or if you have a story idea we should look into? Tell us here.