Dam Safety: One Dam
Thing After Another

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By Andy Yung, P.E., CFM

Countless dams and reservoirs serve communities around the world by providing sources for potable water, irrigation, hydroelectricity, flood control, retention for waste materials, recreation, wetland creation, and/or some combination of these. In the U.S. alone, the number of dams exceeds 90,000 and, while useful, they present a very real hazard to downstream properties due to the large volumes of water stored upstream. Through a proper maintenance program, it is possible to extend the usefulness of a dam well beyond a typical 50-year design life. However, many of these older dams are in disrepair and contribute to our nation’s deteriorating infrastructure. The consequence of failure could be catastrophic.

 

In the U.S. alone, the number of dams exceeds 90,000 and, while useful, they can present a hazard to downstream properties due to the large volumes of water stored upstream.

 

Financial Limitations

What is often not understood is that liability resulting from a dam failure ultimately rests with the owner of the dam. Therefore, responsibility to undertake maintenance and upkeep to ensure the proper operation of the dam becomes imperative.

With this in mind, there are several issues that potentially increase the risk of dam ownership. First, there is difficulty in developing funding for much needed maintenance, upgrade, and repair. While large dams often have funding backed by federal, state, or even local agencies, most dams in the U.S. are privately owned. For example, a developer may build a dam to provide a water feature for a planned residential neighborhood. But when the development is built-out, it is common for the homeowner association to take on the ownership of the dam. Often these associations collect fees for maintenance, but it is usually for the entire development, not exclusively for the dam and reservoir. So, when it comes time to rehabilitate, retrofit, or repair a problem at the dam, funds are usually scarce and there are no major outside funding sources for dam maintenance. Creative funding mechanisms need to be explored, mechanisms that perhaps not only benefit the dam owners, but also the community at large.

Adaptation

Second, there is the effect of downstream development. For many dams, the surroundings and environment of the dam location are much different than they were when originally designed and constructed. Development in the downstream pose new risks associated with potential loss of life and property in the event of a failure, increasing the hazard classification of the dam. As a result, it becomes incumbent on the owner to retrofit their dam to pass larger design storms in order to maintain the safety to downstream areas.

 

Awareness and Communication

Lastly, there is a necessity for public awareness regarding the risks involved with dams and reservoirs. There is a perception that living downstream of a dam provides added safety because it is holding back floodwaters. There is also a converse perception that living upstream of a dam provides little risk from flooding since development around the lake likely took into account the rise of reservoir levels during heavy rainfall events. Hurricane Harvey demonstrated the fallacy of such perceptions when so much rain fell that water was retained at higher levels than previously imagined (inundating upstream properties) and then subsequent releases to reduce lake levels occurred in excess of previous records (flooding downstream properties). For private dam owners, this means identifying ways to inform property owners of the risks associated with the dam. Public forums might need to occur with the dam owners inviting downstream property owners to attend so that they are aware of their risk.

Dam safety is an integral part of preserving our nation’s infrastructure by preventing failure that can cause loss of life and significant damage to property. Identifying financial resources, ensuring that the dam’s ability to pass a design flood given changing downstream development conditions, updating EAPs on an annual basis, and communicating risk to downstream property owners will all serve to mitigate some of the risk associated with dam ownership.