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FloodSAFE California

FloodSAFE California

Department of Water Resources
3310 El Camino Ave.
Sacramento, CA 95821

Mailing Address:
P.O. Box 219000
Sacramento, CA 95821-9000

Effects of U.S. Army Corps of Engineers' Policy on Levee Vegetation in California


In the wake of Hurricane Katrina, the U.S. Army Corps of Engineers (Corps) embarked upon a process of reviewing and improving their levee standards with the goal of improving public safety. As part of this process, they reinvigorated and clarified national policy that would require the removal of all woody vegetation over 2 inches in diameter from levee systems throughout the country. This was done even though vegetation did not cause any of the numerous levee and floodwall failures in New Orleans.

The most recent descriptions of the Corps’ vegetation management policy are contained in the ETL 1110-2-571 “Guidelines For Landscape Planting and Vegetation Management at Levees, Floodwalls, Embankment Dams, and Appurtenant Structures” adopted April 10, 2009 (ETL) and the associated draft policy guidance letter, “Process for Requesting a Variance from Vegetation Standards for Levees and Floodwalls--75 Fed. Reg. 6364-68” (PGL).

On April 15, 2010, the California Department of Water Resources (DWR) and California Department of Fish and Game (DFG) submitted extensive comments on the ETL and PGL, explaining how the Corps’ vegetation management policy will reduce public safety in California, result in extensive and unnecessary environmental damage, and remove the Corps’ responsibility to assist state and local maintaining agencies in ensuring the integrity of California’s levee system.

California agrees with the Corps that public safety is the highest priority for flood management. California also agrees upon the importance of appropriate vegetation management on levees. Despite these common goals, California asserts that the Corps’ strict enforcement of the ETL and PGL will adversely impact public safety. This unintended consequence is due in large part by attempting to address complex technical, financial, legal and institutional problems with a highly prescriptive, one-size-fits-all approach to vegetation management.

Links to 2012 levee vegetation comments

Links to levee vegetation letters

Links to newspaper articles and research


Key milestones in the timeline of this controversy include:

  • 1955. The Corps' standard operations and maintenance manuals for the Sacramento and San Joaquin Rivers were revised to allow “brush and small trees” on the waterward slope of levees where desirable — these provisions remained in effect for the next five decades, during which no failures of project levees were attributed to the presence of vegetation.
  • 1958. California accepted responsibility from the Corps for the Sacramento River Flood Control System — substantial numbers of mature trees and other vegetation were present at that time.
  • 1996. The Water Resources Development Act (Section 202(9)) directed a review of the Corps' vegetation management guidelines, which are required to “address regional variations in levee management and resource needs. . .”
  • 2000-2001. USFWS and NOAA Fisheries proposed to adopt “jeopardy opinions” if the Corps failed to provide for additional vegetation on levees.
  • 2001. The Corps issued Engineering Regulation 500-1-1 (ER 500-1-1). The ER allows additional vegetation to grow on levees when such vegetation would preserve, protect, and/or enhance natural resources, and/or protect rights of Native Americans, while maintaining the safety, structural integrity, and functionality of the levee.
  • 2005. Multiple levee failures occurred in Louisiana during Hurricanes Katrina and Rita.
  • 2006. An Interagency Performance Task Force Final Report concluded that the flooding in New Orleans was caused by engineering and construction failures of the levees. Woody vegetation is not cited as a cause of levee failure.
  • 2006. The Sacramento River Bank Protection Interagency Working Group established a collaborative process among DWR, USFWS, NOAA Fisheries, the Corps, and others. Subsequent levee repairs have included substantial amounts of vegetation for habitat purposes.
  • 2007. The Corps signaled through a White Paper, and through other communications, that it intended to require substantial vegetation removal, apparently in response to the Katrina disaster (despite the fact that an Interagency Performance Taskforce concluded that the Katrina flooding was caused by engineering design and construction failures—not vegetation).
  • 2007. Multiple agencies sponsor the Levee Vegetation Symposium held August 28-29, 2007, and was officially called, “The Vegetation Challenge: A scientific and engineering examination of managing vegetation along California’s Central Valley levees that protect urban and rural areas from devastating floods” This symposium was sponsored by SAFCA, DWR, the Corps, and the Central Valley Control Flood Protection Board and led to the creation of the California Levees Roundtable.
  • 2007. The California Levees Roundtable (a collaborative process including the Corps), was established, ultimately leading in 2009 to the California Central Valley Flood System Improvement Framework which provided temporary exemptions from ETL compliance for legacy levees in the Central Valley and committed the Corps, State of California, and Resources agencies to ongoing collaboration on a long-term plan.
  • 2009. The Corps began to strictly enforce the ETL on existing and new levees nationally and for levee improvement projects in California.
  • 2010. The Corps proposed an updated draft of its vegetation variance process by issuing a draft Policy Guidance Letter (PGL), which is under revision and not final as of spring 2011. The process and criteria for getting a variance under the first draft of the PGL were rigorous and site specific, requiring significant resources (funding, staff time, and expertise) for local agencies to obtain variances. Many local agencies consider the PGL process as described in the first draft to be unjustifiably burdensome to undertake. Together, the ETL and PGL would require:
    • Removal of vegetation without any potential for a variance on the upper third of the river-side slope, the crown, and the land-side slope of all Central Valley levees. In the absence of a variance, removal of all vegetation over 2 inches in diameter on the remainder of the system would be required.
    • A highly detailed and costly variance process that would require site-by-site technical analysis and impose standards that are difficult or impractical for most local agencies in California to achieve.
  • 2011. The Corps proposed the System-Wide Improvement Framework Policy (SWIF). The SWIF’s intent is to collaboratively work with resource agencies and levee sponsors to transition existing levees to Corps standards while maintaining PL 84-99 rehabilitation assistance and adhering to the Endangered Species Act (ESA) and other federal environmental laws. The SWIF is a two-step process completed by the applicant that is composed of a Letter of Intent, which is followed by submission of a SWIF plan. The SWIF process:
    • Allows eligible local sponsors to implement levee improvements in a prioritized “worst first” way to optimize the achievement of risk reduction.
    • Acknowledges that implementing system-wide improvements will need to be done within a collaborative intergovernmental framework and that it will take time to develop and implement improvements in complex situations. Challenges include ensuring that both environmental and ESA considerations as well as levee safety imperatives are adequately served.
    • Recognizes that situations will vary across the nation and the SWIF allows for consideration of regional differences.

Links to 2012 levee vegetation comments

Letters about Levee Vegetation issue

Newspaper articles and research papers about Levee Vegetation issue

If you have comments or questions, please email us or send a letter to the mailing address shown to the left.

Page updated: Jan 5, 2012