100-Year Levee Fixes
Public safety is the number one priority for the City of Dallas in all areas. For the Dallas Floodway, the Levee System protects lives and billions of dollars in property value. Two federal agencies and one municipality have interlocking roles and responsibilities for assessing levee capabilities: The U.S. Army Corps of Engineers, the City of Dallas and the Federal Emergency Management Agency.
After Hurricane Katrina, a National Levee Safety Program was instituted resulting in more rigorous and nationally uniform criteria for inspecting levee systems. Under this new criteria, the U.S. Army Corps of Engineers (Corps) issued Periodic Inspection No. 9 in March 2009 and rated the Dallas Levee System "Unacceptable". As a result, the City lost its 100-Year accreditation of the levee system which began FEMA's process to remap the areas behind the levees.
The City went into action to complete the 100-year flood protection improvements and to work with the Corps on the levee fixes which included 198 Operations and Maintenance (O&M) Improvements. Public meetings were held throughout the City and several other initiatives to keep the public updated on the process. The City completed the O&M Improvements in 2012. In February 2012, the City received the Corps' approval on the Section 408 application for the City's proposed 100-year levee fixes and installed 3.0 miles of cutoff walls at the East Levee and 0.5 mile of cutoff wall at the west levee.
The City and Corps continue their regular meetings and work to provide the highest level of public safety and direct oversight of the entire Dallas Floodway system, one of the largest systems in the nation.
A key component to grasping the process is an understanding of the words “rate,” “certify” and “accredit.” A different governmental unit is responsible for each.
Southwest District, U.S. Army Corps of Engineers
Q. Who rates the levees?
A. The U.S. Army Corps of Engineers.
In Dallas, it is the U.S. Army Corps of Engineers’ responsibility to inspect and then rate Dallas Floodway components that protect the City from Trinity River flooding. The Dallas Floodway levees built in the 1920s were improved and raised by the Corps of Engineers in the 1950s to reduce risks in Dallas from a Standard Project Flood that has a 1-in-800 chance of happening in any given year (also commonly called an 800-year flood). Inspections conducted by the Corps of Engineers are for the purpose of evaluating the system’s ability to function and perform as originally designed, and determining eligibility for the Rehabilitation and Inspection Program under Public Law (P.L.) 84-99, which provides Federal assistance for repair of flood risk management structures in the event of damages caused by a flood event.
These inspections are not directly related to the certification of levees under the National Flood Insurance Program (NFIP) administered by the Federal Emergency Management Agency (FEMA). In other words, an “Unacceptable” rating from the Corps does not mean that the levees are decertified for the NFIP.
In 2016, the Corps’ Fort Worth District issued a “Minimally Acceptable” rating for the Dallas Floodway in its Annual Inspection as part of its national Levee Safety Program. Public safety is the No. 1 priority of this program.
Annual Dallas Inspection Report
Q. Who certifies the levees?
A. The City of Dallas is responsible for obtaining certification of the levees.
Certification of a levee system by a professional engineer is part of the process for obtaining accreditation by FEMA for the NFIP, and is based on the ability of the levee system to safely pass a 100-year flood event. A 100-year flood has 1-in-100 chance of occurring in any given year.
Q. Who accredits the levees?
A. The Federal Emergency Management Agency (FEMA).
FEMA is responsible for drawing the Flood Insurance Rate Maps. These maps are an important component of the National Flood Insurance Program that shows what areas of the City are protected from a 100-year flood. This program is designed to mitigate future disaster losses nationwide by encouraging sound community-enforced building and zoning ordinances and to protect property owners by providing access to affordable, federally backed flood insurance.
In 2009, at the same time the Corps rated the levees “Unacceptable” for the 800-year flood event, sufficient concerns with the levees were also identified to prompt the Corps to withdraw support for a 2006 letter used by the City’s previous consultant engineer in certifying the levees for the City of Dallas in 2007. As a result of the formal withdrawal of that letter, FEMA then de-accredited the levees. But that action alone did not change any insurance rates, mandates or rate maps under the National Flood Insurance Program.
FEMA is now redrawing the 100-year Flood Insurance Rate Maps for Dallas. The City of Dallas expects to have the levees repaired and certified prior to FEMA completing the revised maps. If FEMA accepts the City’s certification package, FEMA could accredit the Dallas Floodway and its Flood Insurance Rate Map would again show the levees provide protection from a 100-year flood.
If FEMA does not accredit the levees, the new 100-year floodplain map would be drawn to reflect the inability of the existing levees to provide 100-year level of protection. As such, some areas behind the existing levees would be within the new 100-year floodplain. Mandatory flood insurance would be required for structures with mortgages that are Federally backed, regulated or insured at the time the new floodplain map becomes effective. Zoning restrictions would also be required in these high-risk areas.