Abstract

Despite mounting demand for a more sustainable worldwide water supply system, available reservoir capacity is relentlessly diminishing due to sedimentation. This fact, coupled with a decrease in the rate of dam construction, indicate an impending water supply dilemma. In the future, dams should be designed following a life cycle management approach rather than the typical short-sighted design life technique.Neither sustainable reservoir lifespans nor intergenerational equity is achieved through conventional cost-benefit analyses (CBA), which render all benefits and costs projected to occur more than several decades into a project as negligible. Consequently, future expenditures, including dam decommissioning or retrofitting with sediment management facilities, are regarded as non-factors in an analysis. CBAs have also historically failed to account for the impacts of sedimentation on infrastructure and the environment over time.Alternatives to the traditional application of the CBA do exist, however. These include dam owners establishing retirement funds or insurance policies, beneficiaries paying for rehabilitation or maintenance, and economists incorporating infrastructure damages and potentially declining discount rates into their analyses.To analyze the disadvantages of not managing sediment, a case study of costs caused from sedimentation impacts at Gavins Point Dam was performed. Impacts from sedimentation at Gavins Point Dam include, among many others, upstream municipal flooding and downstream bank stabilization and sandbar construction. The financial analysis considered the time value of money and showed that the value of expenditures to resolve sedimentation impacts is equivalent to 70% of the original construction cost. Including the costs of additional impacts would amplify this result. Design and operations decisions at Gavins Point Dam could have been drastically different, leading to a more sustainable project, if these expenditures from sedimentation impacts had been included in the initial economic analyses.It is recommended that multidisciplinary discussions occur at multiagency levels to consider changes to traditional CBAs for long-term water supply projects. These discussions should investigate the creation of funding to address sediment management at existing dams. The frequency of bathymetric surveys should also be increased, which would lead to a better understanding of the condition of our infrastructure. By pursuing these recommendations and integrating the aforementioned alternatives to the CBA, economic studies for reservoirs will be more accurate, reservoir lifespans will be more sustainable, profits will be extended indefinitely, and the economic burdens passed to future generations will be lessened.

Degree

College and Department

Ira A. Fulton College of Engineering and Technology; Civil and Environmental Engineering

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