The Largest Dam in Ohio Is a 205-Foot Towering Behemoth

Written by Fern Damron
Updated: August 3, 2023
© Anne Kitzman/
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The William Harsha Dam is Ohio’s largest dam and is located in Clermont County, along the Little Miami River. It is 200 feet high and 1,450 feet in length.

The number of dams across the United States continues to grow. As of 2022, there are over 90,000 dams in existence in the country alone. While the reasons for dam construction vary between locales, the largest dam in Ohio serves a couple of roles for the surrounding communities.

According to the reference librarians at the Clermont County Library, the dam also has a particularly interesting and dubious history behind it. In this article, we’ll explore that history a bit and look at the dam’s infrastructural services.

We’ll also talk a little about its effects on the surrounding wildlife and what can happen when a dam failure occurs.

Where Is the William Harsha Dam Located on a Map?

Ohio’s largest dam, the William Harsha Dam, sits in Clermont County along the Little Miami River. This waterway, which is an important tributary of the Ohio River, originates near Springfield, Ohio, and ends just east of Cincinnati.

Who Built It and Why?

The United States Army Corps of Engineers ordered the construction of the William Harsha Dam in the 1960s. Like any dam, its purpose is to control the flow characteristics of a body of water. While some dams use this control to generate power, this one does not.

Instead, it serves a couple of different purposes for the people who live nearby. Giving rise to the primary feature of the William H. Harsha Lake, formerly East Fork Lake, the dam creates a reservoir spanning nearly 2,200 acres.

Beautiful sunrise at William Harsha Dam in Batavia, Ohio.
The William Harsha Dam sits on the Little Miami River in Ohio. The US Army Corps of Engineers ordered the dam’s construction.

©L Dixon/

Flood Control & Water Supply

In response to the massive flooding of the Ohio River in 1937, the state legislature passed the Flood Control Act of 1938. This act allocated tens of millions of dollars to the creation of infrastructure that would help control the Ohio River, and both prevent and help alleviate future flooding. But while ideas began to form in the mid-1940s, construction on the dam and its related projects would not begin for over 20 years.

The Army Corps of Engineers first mentioned their plans to construct a series of dams in Southwest Ohio in 1963. In 1966, amidst opposition, state legislators directed $500,000 of the state budget towards the support of the East Fork Lake construction project.

One year later, in 1967, then-representative William H. Harsha began to lobby for the continued allocation of funds required to construct the dam. Both parties cited economic growth, clean water supply, and flood control as reasons for supporting the project.

Controversy Surrounding the Dam

While construction on the dam began in 1970, it was not without its fair share of controversy.

In the mid-1950s, as protesters successfully put a halt to other dam projects, more people began to seriously examine the effects of modern industry, construction, and chemical use on the environment. Rachel Carson would publish her work Silent Spring within the decade, sparking the beginning of the environmental movement that would lead to the creation of the EPA.

Additionally, locals raised concerns that the nearby Elk Lick Burial Mound, an important historic site, might suffer damage. In the end, the site would not be harmed. However, the construction of the dam meant that more than 150 families would need to relocate, giving up their homes and farmland. Rather than start a discussion, the Army Corps of Engineers began its use of eminent domain in the fall of 1967 to clear out residents.

Around the time of the evictions, a local opposition movement began to take shape. People began to raise concerns about the validity of the project and the dam’s ability to serve the purposes outlined in the plan. In 1968, the Corps of Engineers itself admitted that the dam may only mitigate flooding in the short term and may potentially cause worse flooding in the future. 

In 1969, five displaced landowners filed a lawsuit against the Corps, calling into question the motives for the dam project. They believed that the primary reason for the dam’s construction was to create a recreation park, citing that flooding had never been a major issue in the river valley. In fact, they stated, less than $1,000,000 in flood-related damages had occurred over the last century.

Nevertheless, construction on the dam project continued.

The beauty of East Fork State Park and the William H Harsha Dam Lake in Ohio, USA
Ohio’s largest dam is the William Harsha Dam, and it is located in Clermont County.

©Anne Kitzman/

Environmental Damage & Further Suits

The Army Corps of Engineers endured several more lawsuits in the following years after the formation of the EPA. From the ground-breaking ceremony of the dam’s construction in 1970 to its completion in 1979, the Corps would be confronted several more times by activists, lawyers, and government officials alike over the environmental damage it was causing. In fact, multiple stop-work orders were issued concerning safety, drainage, and pollution.

Ultimately, an argument based on the sunk-cost fallacy would serve to lift the injunction against the project in 1974. Over the next five years, the construction of Ohio’s largest dam would continue to completion.

What Animals Live Near Ohio’s Largest Dam?

Many terrestrial and aquatic animals make their home in the state park surrounding the dam. Deer, foxes, and raccoons roam far and wide across the park’s woodlands. Multiple species of birds, like song sparrows, swallows, and meadowlarks, also frequent the area.

Additionally, the lake is full of fish and other animals that share the waters. Geese paddle across the lake’s surface, and largemouth and smallmouth bass can be seen feeding on surface insects. Blue catfish trawl the waters further down.

While the wildlife surrounding the lake is beautiful, the dam seriously affects the area’s water quality. Due to nutrient pollution by agricultural runoff, the water held back by Ohio’s largest dam suffers from large blooms of cyanobacteria. These bacteria, often called blue-green algae, can quickly produce massive colonies when conditions are right. While these bacteria are important parts of the ecosystems they reside in, sudden large blooms can be indicative of ecosystem imbalance.

Although they are not always toxic, some blooms can produce poisons that can kill animals that come into contact with them. Even non-toxic blooms degrade the quality of the water. Most often, fish, birds, and other animals that take up residence in the body of water are affected. However, toxic blooms can also kill or injure humans and pets.

it is always best to avoid these large blooms.

What Would Happen if Ohio’s Largest Dam Dam Failed?

Perhaps unsurprisingly, the failure of a dam can cause the exact type of flooding that it was designed to prevent. Depending on how the structure fails, it can quickly release large quantities or even all of it retained water. When this happens, major damage and loss of life occur downstream.

In most dam failures, incidents such as “overtopping” are where water overflows the top edge of the dam and foundation settlement. Settling can cause the formation of cracks that can degrade the integrity of the dam. Also, improper sediment filtration can cause water to work around the dam. Left unchecked, seepage can cause “piping“, which degrades the stability of the embankment material that supports the dam.

Relative to the number of dams in existence, dam failure has so far been fairly rare. However, dam failures have occurred in every single U.S. state. Over the last 17 years, nearly 200 dam failures and nearly 600 near-failure incidents have occurred. Some, like the South Fork Dam failure of 1889, have been catastrophic. The flood resulting from this incident killed over 2,200 people and injured many more. In addition to human suffering, the waters also caused tremendous animal life and habitat loss.

As existing dams across the country continue to age, the risk of their failure continues to increase. Therefore, it should be important for residents of any area to know their proximity to the nearest dam.

The Featured Image

The beauty of East Fork State Park and the William H Harsha Dam Lake in Ohio, USA
Ohio's largest dam is the William Harsha Dam and is located in Clermont County.
© Anne Kitzman/

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