Review of the Devastating Impacts of Woody Plants on Earthen Dams

Review of the Devastating Impacts of Woody Plants on Earthen Dams

Course Outline

The purpose of this (six-hour) course is to provide the inspector, dam safety regulator, engineer, landscape architect and consultant with the fundamental understanding and technical knowledge associated with the potential detrimental impacts of tree and woody vegetation growth on the safety of earthen dams. The objective of this course is to raise the knowledge level of detrimental effects of trees and woody vegetation growth on the safety of earthen dams. This course will also provide an understanding of the methods, procedures, and benefits of maintaining a growth of desirable ground covering vegetation on the embankments of earthen dams.
Dam safety engineers and consultants can utilize material presented in this courseas a reference for recommendations for proper maintenance of desirable vegetation growth, control of undesirable vegetation growth, and remediation dam design associated with the removal and control of trees and woody vegetation growth on earthen dams.

This course is based entirely on the Technical Manual for Dam Owners-Impacts of Plants on Earthen Dams as published by the FEDERAL EMERGENCY MANAGEMENT AGENCY, publication number FEMA 534 dated September 2005.

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of course materials.

Learning Objective

This course will specifically review and provide an understanding of the methods, procedures, and benefits of maintaining a growth of desirable ground covering vegetation on the embankments of earthen dams:

1. Advance awareness of the characteristics and seriousness of dam safety problems associated with tree and woody vegetation growth impacts on earthen dams.
2. Provide a higher level of understanding of dam safety issues associated with tree and woody vegetation growth impacts on earthen dams by reviewing current damage control policies.
3. Provide state-of-practice guidance for remediation design considerations associated with damages associated with tree and woody vegetation growth on earthen dams.
4. Provide rationale and state-of-practice techniques and procedures for management of desirable and undesirable vegetation on earthen dams.

Review of the Inspection and Evaluation of Zone 1, which begins on the upstream slope of the earthen dam embankment at about four feet below normal pool elevation.
Review of the Inspection and Evaluation of Zone 2, which includes the entire width of the crest of the dam. Zone 2 overlaps Zone 1 by one-half the crest width.
Review of the Inspection and Evaluation of Zone 3, which extends from the centerline of the crest of the dam to a point on the downstream embankment slope that is about one-third of the structural height below the crest of the dam. Zone 3 overlaps Zone 2 by one-half the crest width and is typically considered the least critical zone relative to dam safety issues associated with tree and woody vegetation growth.
Review of the Inspection and Evaluation of Zone 4, which extends from a point on the downstream embankment slope that is about one-third the structural height of the embankment to the toe of the downstream embankment slope. Zone 4 is one of the two most critical zones relative to dam safety issues associated with tree and woody vegetation growth as well as other potential dam safety issues.
Review of the Inspection and Evaluation of Zone 5, which extends from the mid-height of the downstream embankment slope to a distance of one-half the structural height beyond the toe of the downstream embankment slope. This zone typically contains the interception of the seepage line with the downstream embankment slope and potential boiling (soil piping) action beyond the toe of the downstream embankment slope.
Review of some common misconceptions about tree growth and tree root development.
Review of factual data about tree growth
Review of tree root development.
Review of recommended earthen dam inspection protocol
Review of procedures for determination of potential impacts of tree and woody vegetation growth on earthen dams.
Review of proper vegetation management on earthen dams.
Review of methods and procedures for maintaining desirable vegetation growth.
Review of controlling tree and woody vegetation growth.
Review of remediation design considerations associated with the removal of trees and woody vegetation from the embankments of earthen dams.
Use vegetative barriers such as bio-barriers, or use silvicides/herbicides/chemical treatment.
Review of typical Rootball and Root System Sizes for Various Tree Sizes
Review of typical Soil Parameters
Review of the optimum compaction moisture content as determined by ASTM D-698 (standard Proctor compaction test)
Review of formal state policies and/or operating procedures for addressing tree and woody plant growth issues.
Review of recommended phased-remediation procedure for removal of undesirable vegetation (trees and woody vegetation) from earthen dam embankments.
Review of a succinct factual presentation of costs associated with either continual proper vegetative maintenance or long-term dam remediation construction after tree and woody vegetation removal.

Intended Audience

This course would be very informative for professional engineers that are involved with the inspection or rehabilitation of earth dams.

Course Content

This course is entirely based on the Technical Manual for Dam Owners-Impacts of Plants on Earthen Dams published by the FEDERAL EMERGENCY MANAGEMENT AGENCY, publication number FEMA 534 dated September 2005.

The link to the course materials is as follows:

Review of the Devastating Impacts of Woody Plants on Earthen Dams (FEMA Publication 534)

Please click on the above underlined hypertext to view, download or print the document for your study. Because of the large file size, we recommend that you first save the file to your computer by right clicking the mouse and choosing "Save Target As ...", and then open the file in Adobe Acrobat Reader.

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.