Title: Dams
Course: 2016FA-MCO-115-401 > Section: Module 3: Dams

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Dams

A dam is a structure designed to hold back water. “Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees (also known as dikes) are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are often used in conjunction with dams to generate electricity” [1].

Critical Infrastructure Sector

“There are over 87,000 dams in the United States, approximately 65 percent are privately owned and state dams safety offices regulates more than 77 percent” [2].

The dams sector includes dams, the hydroelectric plants that take advantage of dams, hurricane barriers, mine tailings, levees, dikes, navigational locks, other water retention or control facilities, and industrial waste impoundments. This sector impacts our country’s natural resources, environment, recreation, power supply, economy, and more [2]. The Sector Specific Agency (SSA) for the Dams Sector is the Department of Homeland Security (DHS).

This sector, “has interdependencies with a wide range of other sectors, including: Emergency Services Sector, Energy Sector, Food and Agriculture Sector, Transportation Systems Sector, Water and Wastewater Systems Sector” [2].

Why Are Dams Critical Infrastructure?

Dams are suppliers of essential services like electricity and water. Water that dams help to provide can be used for irrigating crops or for general (drinking) water supply.  Some dams are the only method of controlling flooding. In cases where a deeper river are necessary for boats to be able to navigate, a dam may be used to deepen the river. Dams provide vast areas of recreational parks, lakes, campgrounds, fisheries, and other benefits. Dams help the United States to be more financially stable and resilient.

Threats

Dams in the United States are a potential target for terrorists. Dam failure due to natural disaster is an eventuality that careful planning and adherence to proper procedure attempt to prevent. Maintenance and replacement of aging, worn, or damaged dams is essential to this sector of critical infrastructure. Any of these threats to dams (or a combination thereof) could cause great loss of life, great loss to quality of life, and have long reaching effects that would impact other critical infrastructure sectors and the nation as a whole.

Purposes

Dams can serve many different purposes and at times one single dam can serve more than one of these purposes. Several multipurpose dams were created under the Tennessee Valley Authority and these serve as good examples.  Dams can be used to direct water for irrigation and water supply, dams can make rivers deep enough to be navigated by boat, and dams can help control water in flood or drought [3] [4].

Preparation and Construction

To create a strong, durable, and safe dam the structure must be leak-proof, the pressure put on the dam by the water must be taken into consideration, stress of the movement of the Earth must be taken into consideration (including the stress an earthquake would cause), and even the effects of any ice that forms on and around the dam must be studied and measured [3]. Geologists (those who study the Earth’s history through its structure, especially minerals and rocks) are consulted and are often hired to perform a geological analysis of a potential site to be sure it can safely support a dam [5] [3]. The dam’s effect on the surrounding environment must also be studied and controlled.

In order to build a dam water must be cleared from the area where construction will take place. This is usually achieved through the use of a cofferdam. “A cofferdam is a barrier, usually temporary, constructed to exclude water from an area that is normally submerged [1]. It can be made of wood, concrete, or steel sheet piling and are normally temporary dams used in the construction of dams or bridges. In some instances it is necessary to create a cofferdam both up and downstream of where a permanent dam is to be built. Dam construction can take several years.