Since 2008 the Natomas area in the City of Sacramento has been under an effective moratorium on new development due to insufficient flood protection. The area is preparing to re-start development once the City receives a letter from the Federal Emergency Management Agency (FEMA) that lifts a flood hazard designation that was severely limiting the City's ability to develop in Natomas. The impetus for the change in designation is passage in 2014 of the Water Resources Reform and Development Act (WRRDA) (see here for earlier coverage of WRRDA), which formally authorized a federal flood control project for the area. Even though the project work won't be completed for a few years, authorization of the project allows Sacramento to receive a new zone designation that will allow for development.
The Sacramento area, which lies along the State's largest river (the Sacramento), is vulnerable to catastrophic flooding due in part to a levee system that was not originally intended to protect what now lies behind it - a large city. The Natomas Basin is completely surrounded by 42 miles of levees that protect it from flooding. Despite the U.S. Army Corps of Engineers' 1998 certification that the Natomas-area levees met 100-year protection criteria (meaning that the levees should protect the area from a flood with a 1% chance of occurring in any given year), the Corps determined in a 2006 study that, because the levees appeared to be vulnerable to underseepage, the Corps could no longer stand behind its earlier certification. Underseepage can undermine levee integrity during floods by causing subsurface erosion and lead to levee failure.
Part of FEMA's mandate is to classify the nation's flood-prone areas into flood risk zones, providing data needed for floodplain management programs and a basis for flood insurance requirements. As part of this effort, FEMA has developed "flood hazard zone" designations that reflect the flood risk of a particular community and related flood insurance requirements. The flood hazard zones are shown on Flood Insurance Rate Maps and can limit development and require residents to purchase flood insurance. The concept is to ensure that where levees are not up to the 100-year standard, additional structures cannot be built and residents must be insured until 100-year protection is reached.
In 2007 the City of Sacramento requested that FEMA designate the Natomas Basin as a Zone A-99, reflecting progress that had been made toward a 100-year protection level through the Sacramento Area Flood Control Agency's (SAFCA) Natomas Levee Improvement Project. Although this designation would require local homeowners to carry flood insurance, no restrictions would be imposed on new construction.
FEMA rejected the request for a Zone A-99 designation based on insufficient progress and funding for the Project, and instead chose the more restrictive AE Zone designation, based on the Corps's evaluation of the integrity of the Natomas area's Sacramento River levees. That evaluation concluded that the Natomas Basin levee system could not meet flood certification requirements due to significant problems with levee slope stability, levee height and underseepage.
Under the current Zone AE designation, the bottom floor of new buildings must be built one foot above the base flood elevation, or up to 20 feet of elevation in some areas. This effectively prohibits new construction.
Passage of WRRDA
In 2014 a Water Resources and Reform and Development Act was passed, formally authorizing the Natomas Levee Improvement Project as a federal effort. The Corps will upgrade 24 miles of levees in order to complete the work that SAFCA has started. Even though that work will not likely take place for a few years, federal authorization of the Project allows Sacramento to request a new FEMA hazard zone designation that will reduce new construction limitations.
The zone designation will not change until FEMA re-maps the basin. Once WRRDA passed, the City filed for an A-99 designation, which will still require that residents purchase flood insurance but will allow the city to issue building permits. The re-mapping process is anticipated to be complete this spring, and development will again move forward in Natomas.
While the City of Sacramento and the Natomas area are relieved that planned economic development and construction can resume, it's reasonable to ask whether it makes sense to continue to build in an area whose levees (1) will not actually provide sufficient protection for another few years, and (2) were relied upon to support tremendous growth before being determined insufficient. Both the federal and state governments are increasingly concerned about growth in floodplains and its policy implications.
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