Dams and Levees
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. The average age of the 84,000 dams in the US is 52 years old. The nation’s dams are aging and the number of high-hazard dams is on the rise. Many of these dams were built as low-hazard dams protecting undeveloped agricultural land. The average age of the 84,000 dams in the country is 52 years old. The nation’s dams are aging and the number of high-hazard dams is on the rise. Many of these dams were built as low-hazard dams protecting undeveloped agricultural land. Both are in sad shape and rated a D for dams and a D- for levees by the American Society of Civil Engineers who are the engineers who build them. If they go, homes and vast stretches of land will be flooded and the environment literally drenched.
Luckily dams and levees are built and designed to last a long time but the key issue is that they be well maintained in that time.
Dams are classified based on their hazard potential, or anticipated consequences in the case of failure. The failure of a dam that is classified as high-hazard is anticipated to cause a loss of life. As of 2012, there are 13,991 dams in the United States that are classified as high-hazard, showing a continued increase in the overall number of dams with that classification. The number has increased from 10,118 high-hazard dams just ten years ago. Another 12,662 dams are currently labeled as significant hazard, meaning a failure would not necessarily cause a loss of life, but could result in significant economic losses.
Repair funding needs are significant, and vary according to who owns and operates the dam. The Association of State Dam Safety Officials estimates that the total cost to rehabilitate the nation’s non-federal and federal dams is over $57 billion. To rehabilitate just those dams categorized as most critical, or high- hazard, would cost the nation $21 billion, a cost that continues to rise as maintenance, repair, and rehabilitation are delayed.
Levees play a critical role in reducing the risk to public safety from potentially devastating flood events throughout the United States. Levees are man-made structures designed and constructed along the water’s edge to contain, control, or divert the flow of water in a flood event.
Levees maintained and operated by the USACE receive federal funding through the USACE Civil Works budget. However, the majority of the nation’s levees are not owned and operated by the federal government, and therefore must rely on cash-strapped state and local governments for investment. Currently, rough estimates put the cost to repair and rehabilitate the nation’s levees at more than $100 billion.
Annual floods can increase these costs. For example, after severe flooding in the Midwest in 2011, the cost to repair damaged levees on the Mississippi and Missouri rivers is estimated to be more than $2 billion. On average, levee and flood control facility damages average $4.2 bill ion annually for Corps levees.
The primary effects of flooding include loss of life, damage to buildings and other structures, including bridges, sewerage systems, roadways, and canals. But this is not all that happens. The whole environment changes. Both animal and plant life changes with the water level. The whole local ecology may well be ruined.
Drinking water treatment and water supplies will be affected. It may also cause the loss of sewage disposal facilities. Lack of clean water combined with human sewage in the flood waters raises the risk of waterborne diseases, which can include typhoid, giardia, cryptosporidium, cholera and many other diseases depending upon the location of the flood.
For further information see Dams and Levees.
Levee image via Wikipedia.