IPET Report 3 Vol VIII

probabilities are needed, as discussed in Appendix 8. The radius to maximum winds is handled
in a different manner. Examples of storm frequencies are also shown in Appendix 8.
Reliability Analysis
Reliability analysis is that part of the risk study that leads to an evaluation of the conditional
probability of failure (i.e., reliability) of structures, systems, and components when they are
exposed to the loads of a hurricane. The reliability analysis had three steps:
1. Specify the structures, components, and systems constituting the hurricane protection
system (HPS) for each drainage basin.
2. Define failure and identify failure modes and limit states for each structure, system and
component.
3. Assign conditional probabilities to HPS failure states for given water elevations caused
by hurricane conditions.
Two conditions were analyzed for the reliability of levees, flood walls, and pumping stations:
pre-Katrina and post-reconstruction and repair as projected for June 2006.
Appendices 2 through 7 contain an inventory of the structures, systems, and components in
each drainage basin that were considered in the risk analysis. Subsystems and components of the
HPS are shown in Table 10. The reliability methodology is described in detail in Appendix 10.
Table 10
Components in the Hurricane Protection System
1 Levees a. Embankment section (Reaches were defined on the basis of physical discontinuities -
geometric, physical, soils, and construction characteristics)
b. Foundation
2 Floodwalls a. Wall structure
b. Joints within a wall section
c. Transitions (joints and interfaces to other components)
d. Wall-embankment interface
e. Wall foundation
3 Closures a. Closure support structure
b. Closure structures - logs, gate, or other
c. Position – open or closed
4 Pump Systems a. Pump and motors
b. Power – grid availability
c. Emergency power (diesel generator)
d. Diesel fuel availability
e. Pump house structure
f. Operators – present or evacuated
g. Intakes – open or closed
Approach
The reliability of the hurricane protection system under potential water elevations due to
surge and waves was quantified using structural and geotechnical reliability models integrated
within a larger system description of each drainage basin. The reliability models for the HPS
VIII-42 Volume VIII Engineering and Operational Risk and Reliability Analysis
This is a preliminary report subject to revision; it does not contain final conclusions of the United States Army Corps of Engineers.