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Environmental Risk Assessment: Dam Removal

Updated on September 6, 2016

Environmental Risk Assessment: Dam Removal

In recent years, the magnitude of damming the natural flow of water has created, in some cases, ecological, financial and social costs to a variety of different stakeholders. These interested parties include private residents, the environment, dam proprietors and the government. According to ICF Consulting, collective explanations for dam removals are ecological, financial, and safety driven. In order to depict the prospective impact of the removal of a dam, human and ecological risk assessments need to be completed.

Why should dam removal be considered? First, stopping the natural flow of a body of water has effects on ecosystems. Examples of bionetworks that become stressed are vegetation, wildlife and aquatic populations. Moreover, safety should be a public priority. A dilapidated dam likely poses safety concerns for the public. This may be in the form of a breach or an individual incurring bodily harm due to a lack of maintenance. Financially, it cost money to maintain a dam. For example, there are dams, which may have been utilized in mill operations that no longer exist, today. These present safety concerns as well as financial concerns.


Hazard Identification

When considering whether or not to remove a dam a risk assessment needs to address municipal safety vulnerabilities. The assessor must consider the possibilities of an ill or non-maintained dam breaching. This could cost human life like it did in 1977 when the Kelly Barnes Dam in Georgia was compromised killing close to 40 people (Dam Failure, 2012). Correspondingly, assessments based on available quantitative data should be completed regarding the bacteria levels and the best and worst case scenarios, to human health, should a dilapidated dam simply break.

The 1977 Toccoa Flood, Report of Failure of Kelly Barnes Dam Flood and Findings (USGS, 2014)

Dose-Response Assessment

A dose-response assessment that examines what health complications at different exposure locations downstream from a dam must be conducted. When considering whether or not to remove a dam an assessment should include likely human hazards with regard to the dam and nearby residents that are downstream. The question must be probed; does removal of the dam affect water quality? Additionally, a study of how the removal of a dam may affect local land owners must be performed.

Exposure Assessment

Exposure assessments should answer questions such as: How much of a hazard is the public subjected to during a specific time period? How many individuals are unprotected due to a run-down dam during flood season and what is the risk to them? Do people utilize the area for recreation in the summer and could they be hurt because the dam has been neglected structurally? Importantly, the exposure assessment should contain answers regarding what type of contact to bacteria and sediments are likely to follow if the dam breaks during a flood. How would this effect the public health of a community? These are a just a few of the questions that need to be addressed during the assessment.

  1. Transparency

  2. Clarity

  3. Consistency

  4. Reasonableness - Employing these distinctive ethical approaches will aid an evaluator in making authentic assumptions about the risk involved in removing a dam (EPA, 2012).

Risk Characterization

An assessor should characterize the risk of added health complications in the exposed population regarding whether or not the dam is removed or remains. What are the uncertainties related to the removal of a dam? Furthermore, when an assessment is drafted and completed it should lend credibility to the project by utilizing characteristics such as:

Ecological Risk Assessment

In addition to a human health assessment, an ecological assessment must be performed, too. When assessing the removal of a dam from an ecological standpoint, one must consider the influence that the removal of a dam may have on fish populations, water bodies, and non-indigenous wildlife (EPA-Ecological Risk Assessment, 2012).

Ecological risk assessments are prepared in three stages (EPA-Ecological Risk Assessment, 2012).

  1. Problem formation

  2. Analysis

  3. Risk characterization

These must be conducted in that specific order.

Utilizing the EPA’s Ecological Risk Assessment model is essential. When considering ecological likelihoods in connection with dam removal, planning leads to problem formation. This permits a portrayal of exposure, such as sediment distribution, and its ecological effect on the vegetation, wildlife and aquatic populations that reside downstream from the dam. All of this data, qualitative and quantitative, is then analyzed.

Once ecological effects are known or presumed, a proper assumption, or “risk characterization” can occur. Then, results, findings and facts are to be presented to the stakeholders, client(s) first. This will allow the assessor to communicate the data and allow the stakeholders a better understanding about whether further data is needed, or monitoring is needed and how to perform observational tasks (EPA-Ecological Risk Assessment, 2012). Equally, this report is needed to address an assessment endpoint, which determines what’s worth protecting.

Data and Information

Although dam removal is not nearly as popular as dam construction once was in the United States of America, it is gaining momentum. Given that dam removal has been taking place on a somewhat regular basis, lately, prior studies’ data, quantitative and qualitative, can be used as a comparative tool. The data, which allows an assessor to create an accurate risk assessment, is derived from multiple studies. This research can be utilized as a comparative tool when making the decision whether or not to remove a dam or whether or not to restore a dam.

Also, as dam removal begins to become more prevalent, especially among small dams, more information is becoming available. Field based research such as, “…visual inspections and photographs of the dam site, soil sampling and excavations of portions of the embankment” will also be conducted by a variety of researches from various scientific disciplines such as geology and biology (USGS-Georgia Water Science Center, 2010).

A risk assessment is necessary when deciding whether or not to remove a dam. Dam removal seems like a good choice financially. Moreover, it seems like a public safety measure if the funds are not available to maintain such a structure. Ecologically, there are instances were fish populations have flourished once dams have been removed. Risk assessment is important to sustainability.

Ecology and individuals are interconnected thoroughly. The two are dependent on one another for long term survival. Think about that for a moment. Man needs nature to survive, and the Earth has been so polluted that it needs mankind to employ its knowledge of environmental management for long-standing survival. Proper risk assessment is a crucial part of nature’s relationship with man and mankind’s relationship with nature.

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Dam Failure. (2012).

Environmental Protection Agency. (2012). Ecological Risk Assessment.

Heinz Center for Science, Economics, and the Environment. (2002). DAM REMOVAL Science and Decision Making.

ICF Consulting. (2005). A Summary of Existing Research on Low-Head Dam Removal Projects.

U.S. Geological Survey. (2010). Georgia Water Science Center.

USGS. (2014).The 1977 Toccoa Flood, Report of Failure of Kelly Barnes Dam Flood and Findings.

© 2014 Suzanl


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