International Levee Handbook Overview of the handbook Chapter 4: Operation and maintenance (O&M)

Chapter 4 - context

4.1 Applying Asset Management Principles to O&M Levee management life cycle This section explains how O&M fits into the entire life cycle of the levee (see Figure 4.1) Organisation of O&M This section explains the division of O&M into three roles: planning, O&M, and inspection. Importance of the O&M Manual The key elements in this sub-section include: - The benefits of an O&M manual - Suggested contents for a manual - Types of tasks the manual should define - Type of emergency information to include - Good practices for compiling & updating the manual

Activities and practices of asset management The most critical activities include: defining O&M objectives during design and construction; defining functional objectives, performance objectives and performance indicators; and determining when and how to decomission. General approaches to O&M This section explains the benefits of operating and maintaining using a risk- based approach (that takes flood risks associated with the levee system into account when prioritising O&M), and a sustainable approach (which includes maintaining the entire levee cross-section, effectively managing encroachments, understanding impacts of channel and foreshore morphology on the levee, and operating for the long-term). Scope of O&M and Chapter 4 Describes the types of data produced during O&M and where else in the handbook to find information related to that data. 4.1 Applying Asset Management Principles to O&M

The purpose of levee operation is to assure that the levee performs its flood mitigation role safely and according to its design. This section discusses the operation of the earthen embankment and only those auxiliary structures that directly affect its operation, such as closure structures. Levee systems are operated to fulfil three critical functions: To keep water out of a leveed area (eg closing closure structures) To get water out of a leveed area should it be inundated (eg pumping water out if it enters the area) To keep the levee resilient during flood and storm events. (eg flood fighting to improve levee resiliency) 4.2 Operations

Maintenance is critical to the long-term performance of the levee. However, even a perfectly operated and maintained levee may not provide the intended flood risk mitigation if there are flaws in its design or construction. In the maintenance section: Limits of maintenance Consequences of postponing maintenance Issues with earthen levees 4.3 Maintenance

Structure of Maintenance Sub-Sections All maintenance-related sub-sections address the following topics: What maintenance issues you are likely to see, what they look like, and why they are problematic How you can prevent these issues from happening How you can repair these issues if they happen How you can know when repairs are beyond O&M

Topics Discussed in the Maintenance Section of the ILH Encroachments Vegetation Management Burrowing Animals Erosion Depressions Settlement Seepage Instability Cracking Slope/bank protection Closure Structures Pipes Transitions Floodwalls The slides in the following sections were chosen to illustrate some of the techniques Chapter 4 uses to highlight and explain important concepts. These techniques include text boxes, bulleted lists, tables, photos, figures, diagrams, and caution boxes.

An encroachment is any structure not considered part of a levee’s design that, when placed on, over, under, through or near a levee, may have a negative effect on its structural integrity, its ability to mitigate flood risks, or on its access roads. Examples include pipes, boat docks, stairs, homes, swimming pools, poles, roads, etc. This section describes: Why encroachments occur on levees Why encroachments need to be controlled 7 elements of an effective encroachment control program Repairs of encroachment issues When repairs are beyond O&M 4.4 Encroachments

Reinforcing the levee to allow for permitting encroachments

Focus is on 3 levee performance objectives: Protecting the levee from external erosion Maintaining adequate access and visibility Preventing the development of vegetation-induced damage or defects This section also examines various countries’ policies for managing levees where woody vegetation is already present and managing levees that are free of woody vegetation. 4.5 Vegetation Management Vegetation management is the systematic and continual control of vegetation on and near levees. The primary purpose of vegetation management on a levee is to preserve levee integrity, visibility, access in the interest of public safety, and performance.

Summary of potential deterioration mechanisms associated with woody vegetation on levees

One method that is used in France to prevent levee damage from burrowing animals 4.6 Burrowing Animals

4.7 Erosion and Bank Caving

4.9 Settlement and Subsidence The excerpt below from Table 4.16 demonstrates the use of an “Observation/ Preventive measures” format that provides guidance about settlement-related issues.

It is important for a levee maintainer to be able to identify the signs of levee slope instability. Look for the following three visual signs of an unstable slope in both the levee embankment and foundation soils below the levee: 1. Slumps: these appear as isolated areas of near-surface soil on a slope that has slightly to moderately dropped down-slope and exposed underlying subgrade (occurring only on the face with no evidence on the crest, Figure 4.42). 2. Slides: may be seen when the soil has dropped down a slope, exposing a near-vertical scarp (portion of the inside of the levee) at the top of the slide. This could cover a large area. See Figure Tension cracks on the slopes or crest: tension cracks (see Figure 4.44) appear either as relatively straight single or multiple cracks parallel to and above the top (scarp) of a slide or slump Instability

Recognizing slope instability 4.11 Instability

Cracking This table can help you understand how to know what type of a crack you are looking at and which type is a higher concern.

Levee Slope and Bank Protection One of the highlights of this sub-section is a table with photos illustrating the different types of levee slope and bank protection with a brief description and details on the maintenance needs of each type of bank protection. This is an excerpt from that table.

Closure structures are removable, watertight mechanisms used during flood events to seal off levee segments whose heights have been reduced below design grade by an intersection with a roadway, railway or other crossing. This section looks at: Types of closures Preventing closure structure failures Examples of: trial closure policies, why it is important to have trials, a competition for the fastest closure structure installation Maintenance methods and repairing closure structures Determining when repairs are beyond maintenance Note that closure structures do not include demountable defences located on top of a levee, which raise the level of defence at time of flooding. However, the principles of maintenance of demountable structures are similar to those of closure structures Closure Structures

Closure Structures: Text box example (Box 4.47) CLOSURES INVOLVED: Six closures including two sandbag closures and four aluminium panels BEFORE: 1996 flood event, 40 men were required for 5.5 hours to install one of the sandbag closures AFTER: three men (an equipment operator and two labourers) in less than 12 minutes This text box describes an annual competitive training exercise sponsored by the Sunsbury Municipal Authority in Pennsylvania, USA, used to improve the efficiency of the people responsible for closing the structures. Briefly:

Part 1:Culverts and discharge pipes Why they are a concern Maintenance – avoiding internal erosion Maintenance – avoiding external erosion Maintenance – avoiding levee instability Repairing culverts and discharge pipes Maintenance of pipe system components 4.15 Culverts and Discharge Pipe Systems Culverts and discharge pipes are pipe systems that are built under, over or through a levee to provide drainage as part of the flood risk mitigation system or to function as utility pipes for gas, irrigation, water supply or electrical/communications cabling. The two parts of this section cover the following topics: Part 2: Utility pipe and line systems Why they are a concern Maintenance of utility pipes and lines Repair of utility pipes Determining when repairs are beyond O&M

Pipes: Text box example (Box 4.49)

A flood risk reduction system may include levees and other structures such as walls and gates, in which the geometric configuration of the continuous line of defence differs. A levee transition is a well-known weak point on the levee. It is a location characterised by an often visible or measureable change in geometry of the levee cross-section, material type, loading or strength. Section 4.16 looks at: Deciding whether a transition zone is problematic Preventing internal and external erosion at transitions by maintenance Repairing erosion at transition zones Determining when repairs are beyond maintenance 4.16 Levee Transitions

The key items discussed in this section are: Preventing flood wall deterioration Repairing common flood wall problems Determining when repairs are beyond maintenance 4.17 Flood Walls Flood walls (see Section ) are flood risk mitigation structures of either gravity or cantilever design. In the context of levees, they are used when space does not allow increasing the levee cross-section, the right of way is not available, or the levee foundation cannot support the weight of the additional earthfill. A well-designed and constructed flood wall can provide long-term service while requiring minimal maintenance and fiscal resources. Figure Concrete flood wall, St. Louis, Missouri, USA

Thank you ILH Chapter 4 Team Lead: Rachael Orellana US Army Corps of Engineers *Please note my last name has changed from Hersh-Burdick to Orellana To download the International Levee Handbook go to: