CLEARWATER FAQs
May 1, 2011
Q. Is Clearwater Dam still providing flood risk production benefits during the major rehabilitation work?
A. Because Clearwater performed so well during the 2008 and 2009 flood events, the Corps is confident that the dam will perform as designed through this high water event. However, the rehabilitation project is still not complete, prompting Corps officials to increase monitoring since April 25. No adverse changes have been observed, and confidence in the structure is high. The inspections monitor seepage conditions, settlement and movement. The rehabilitation work completed to date has reduced seepage levels. The dam is monitored through instrumentation and “eyes on” inspections.
Q. How is Clearwater Dam operated to provide flood risk reduction benefits?
A. The lake works by capturing runoff in its flood pool during heavy rain. After the river downstream begins to recede, water from the lake is released in a controlled fashion. Without the lake, all that water would roll downriver at one time. Flood crests would rise higher and spread over more land, causing more damage and possible loss of life. During the week of April 24-30, flows experienced at Poplar Bluff, Mo., would have been four times greater at times if not for Clearwater Dam.
Q. What will you do in the event of a flood near the Clearwater Dam?
A. The lake provides downstream flood damage reduction benefits. If it appears greater than normal amounts of water need to be released during and after unusually heavy rains, local officials will be notified as early as possible. Corps and local emergency management officials advise property owners, especially those with low-lying farm fields or homes, to consider whether they can move livestock and equipment to higher ground or remove belongings from flood-prone areas on only a few hours notice. If not, they may want to take precautions in advance of unusually heavy rains. Homes and mobile homes within the flood plain of the Black River (or any river) are always at some risk of flooding.
Q. How does the spillway work?
A. When the lake levels exceed elevation 567, water from Clearwater Lake will flow over the spillway and enter the Black River downstream from Clearwater Dam. Normally releases are made through the gated conduit. The spillway was designed to pass flows during extreme rainfall events. So even if large releases go through the spillway, the dam is performing as designed. The spillway protects the dam from overtopping.
Q. How quickly can the lake be drawn down?
A. There are too many variables to answer this hypothetical question. It depends on how high the lake is, how much water is still flowing into the lake, how much rain continues to fall and how high the river is downstream of the dam. The Corps has approved operating plans in place that enable it to assess and respond to various situations.
Q. What have we done to prepare for an emergency?
A. Local officials and news media have been and will continue to be notified of new developments. Local emergency management officials will advise property owners of the situation and appropriate steps to take. The Corps has updated and improved the Clearwater Emergency Action Plan. Procedures, communication systems and phone numbers are detailed, to include a list of emergency response team members and local emergency personnel. Coordination with local officials is ongoing.
Q. How confident are you that Clearwater Dam will continue to perform as designed even though the major rehabilitation is not complete?
A. Because Clearwater performed so well during the 2008 and 2009 flood events, the Corps is confident that the dam will perform as designed through this high water event. But, Corps officials caution against becoming complacent about the risks of living, working or recreating downstream of any dam. Complacency can cause people to fail to take action or even cause them to take inappropriate action in the event of an emergency and increase the risk to their property or lives. Also, once the rehabilitation project is completed and the dam is functioning properly, there will still be inherent risk to those downstream in the flood plain of the Black River. Clearwater Dam reduces downstream flood losses in most circumstances. But it has limitations, and flooding, even severe flooding, will still occur in the flood plain from time to time.
Q. How can I separate rumor from fact?
A. Corps officials remain committed to keeping the public informed. Don’t rely on rumors. For more information, please call the Clearwater Project Office at 573-223-7777. Also, more information is available on the Corps’ Little Rock District Website at www.swl.usace.army.mil.