REVISED ETL Guidelines for Landscaping and Vegetation Management

Transcription

1 REVISED ETL Guidelines for Landscaping and Vegetation Management Paige Caldwell, P.E. Emergency Manager

2 Overview Policy revision process Key points from the ETL guidance Illustrations of acceptable vegetation placement Photos of potential vegetation impacts Update on Corps research initiative

3 Revision of EM phases Phase I: A necessary first step (completed April 2009) Purpose: Clarify our existing guidelines, which are somewhat ambiguous, and, in the process, identify unknowns that require further research Products: (1) an Engineering Technical Letter, and (2) a scope for required research Phase II: The real work (ongoing) Purpose: Conduct research to establish both scientific and engineering grounds to reaffirm and/or revise Corps vegetation guidelines, and to better accommodate ecological enhancements to Flood Damage Reduction (FDR) Systems. Product: final guidelines, published as an Engineering Manual (EM)

4 Key points from the newly revised ETL guidance: Public safety is the number one priority of the USACE Levee Safety Program. This ETL does not establish new standards, but clarifies, and supersedes, those formerly presented in EM (Jan. 1, 2000). An Independent External Peer Review, conducted in 2008, and Independent Technical Review validated the ETL based upon existing and available engineering and scientific data. USACE is currently undertaking a two-year research program to enable reassessment of its engineering-based understanding of the public safety consequences of vegetation on FDR projects.

5 Key points (continued) It is essential that FDRs retain structural integrity, functionality, and safety; it is also necessary to be able to inspect, monitor, and flood-fight the projects. The local sponsor may request a variance from the standard vegetation guidelines as presented in the ETL. Fifteen feet, or to existing project easement, is the minimally accepted vegetation free zone (VFZ). To date, no research exists to justify a reduction to existing standards. The ETL discusses a limited range of conditions under which a variance to vegetation standards may be granted.

6 Key points (continued) Any addition of landscape plantings to existing FDR systems must comply with the project s Operations and Maintenance manual. New plantings with an engineering evaluation may be approved on a case by case basis. Once new projects are completed, O&M manuals will be updated to reflect requirements for vegetation maintenance. Planned research is intended to compliment the ETL guidance. The use of suitable vegetation, such as shrub forms of willows, riverward of the vegetation-free zone is encouraged as an environmentally beneficial means to moderate erosion potential of water currents and wave action.

7 Levee Section - Basic Sacramento District

8 Levee Section Basic, with floodwall on crown

9 Levee Section Basic, with Blanket Drain

10 Levee Section Basic, with Relief Well or Piezometer

11 Levee Section Basic, with Planting Berm

12 Levee Section with Ordinary High Water Mark above the Riverside Toe

13 Potentially Negative Impacts from Vegetation on Levees

14 Potentially Negative Impacts from Vegetation on Levees

15 Potentially Negative Impacts from Vegetation on Levees

16 Potentially Negative Impacts from Vegetation on Levees

17 Vegetation Research Objective: Develop a methodology (work plan) using nationwide research to study the effects of woody vegetation on levee integrity and stability; Identify failure modes where vegetation may accelerate failure; Select sites indicative of regional setting (varying climatic conditions, geographic and geologic influences, and soil type) to obtain a statistical acceptable database; Include root systems of different riparian woody vegetation species; however, noting that a given species does not always produce the same root morphology; Address the variation in soil properties and levee geometry.

18 Research Approach: The research work plan is divided into the following sections based on mechanisms and processes influencing levee integrity and stability, and data analyses of the research: Field Assessment/Laboratory Analyses Slope stability Root characterization Geophysical analyses (non-invasive) Pull-out tests (invasive) Overthrow Seepage and piping Overtopping erosion and riverside erosion Geological/geotechnical characterization Case Histories Engineering Assessment to Generate Fragility Curves Risk Assessment/Probability Analyses

19 Future Activities of Research Initiative: Secure field sites in Sacramento, New Orleans, Seattle, Portland, and Albuquerque (Northeast site has not been identified) Begin testing at selected site in New Orleans Conduct workshop to present initial findings and adjust work plan, if needed (mid-june) Present initial findings at the Infrastructure Systems Conference (20-24 July 2009)

20 Questions? The ETL is available at: