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Purpose and Goals

The California Levee Vegetation Research Program (CLVRP) is a partnership of policy makers, levee managers, and researchers within federal, State, and local agencies that was formed to conduct original scientific research to address the vegetation policy issues affecting the State and federal levee systems in California. The CLVRP undertakes research in a collaborative environment that builds upon existing knowledge about vegetation and its impacts on levees. This research is used to develop scientifically-based levee management policies and practical maintenance procedures that balance public safety, environmental stewardship, and economic stability.


The devastation caused in the southern United States by Hurricane Katrina in 2005 reminded flood risk managers across the nation of the severe consequences of levee failure, especially in deep urban floodplains. While many mechanisms of levee failure are well understood, the potential effects associated with vegetation on or near levees were not well defined. From 2009 to 2012, the California Department of Water Resources (DWR) and the Sacramento Area Flood Control Agency (SAFCA) partnered with a number of local, State, and federal agencies to undertake original scientific research to address vegetation policy issues affecting the State and federal levee systems in the California Central Valley. Since 2012, DWR has not only continued to support additional research to examine remaining data gaps, but has begun to incorporate the research findings into updated policies and procedures for ongoing monitoring and management of levee vegetation.

Research: The Foundation for Levee Management Practices and Policies

In August 2007, The Vegetation Challenge--the first research symposium on the issues associated with woody vegetation on levees--was held in Sacramento, California. At the 2007 symposium, many subjects were covered, but little science was available to either inform or base policy on.

To fill the need for more scientific data, the newly formed CLVRP brought together researchers to explore a variety of impacts to levee performance. The researchers investigated numerous issues, published reports on their findings, and presented their results at the Levee Vegetation Research Symposium 2012. The symposium covered:

  • Tree root architecture 
  • Slurry cut-off walls and roots
  • Slope stability and tree roots
  • Tree windthrow
  • Forensics of California levee failures
  • Effects of burrowing mammals
  • Burrowing mammal habitat associations
  • Grouting efficacy of mammal burrows

Following the 2012 symposium, the partner agencies of the CLVRP reconvened as a steering committee to evaluate comments from the symposium attendees, examine remaining data gaps, and assess future research needs. This effort led to the development of a working group and a new round of projects and research. Other relevant research on the effects of vegetation on levee integrity continues nationally and internationally.