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people and property from larger, less frequent flooding events, such as the 100-year and 500-
year flood events. For purposes of this plan, the levee failure hazard will refer to both
overtopping and breach of a levee as defined in FEMA’s publication “So You Live Behind a
Levee” (http://content.asce.org/ASCELeveeGuide.html)
• Overtopping: When a Flood Is Too Big—Overtopping occurs when floodwaters exceed the
height of a levee and flow over its crown. As the water passes over the top, it may erode the
levee, worsening the flooding and potentially causing an opening, or breach, in the levee.
• Breaching: When a Levee Gives Way—A levee breach occurs when part of a levee gives
way, creating an opening through which floodwaters may pass. A breach may occur
gradually or suddenly. The most dangerous breaches happen quickly during periods of high
water. The resulting torrent can quickly swamp a large area behind the failed levee with little
or no warning.
Levees are usually engineered to withstand a flood with a computed risk of occurrence. Many
levees in Kansas were largely constructed to protect agricultural land and are not built to design
standards established to protect people and property. Their presence can, in some cases,
generate a false sense of security.
Levees have been constructed across the State by public and private entities with varying levels
of protection, inspection oversight, and maintenance. Currently there is no one comprehensive
database of all levees in the State. However, significant strides have been made toward
compiling such an inventory. In 2010, FEMA published the Midterm Levee Inventory (MLI)
database of levees. The MLI contains levee data gathered primarily for structures that were
designed to provide protection from at least the base (1-percent-annual-chance) flood. Levees
that provide protection for less than the base flood event are included, but only were data was
readily available. The MLI was developed to complement the USACE National Levee Database
(NLD). During development of this plan update, USACE was in the process of integrating the
MLI with the NLD to provide a more comprehensive database of levees. Every effort was made
during development of this plan to consider all known levees from both databases.
The levee failure hazard proifile and risk assessment in this plan are further discussed in four
categories:
1. Levees in the USACE levee Safety Program
2. FEMA Accredited Levees
3. Levees that are both in the USACE Levee Safety Program and Accredited by FEMA
4. All other levees
Levees in the USACE Levee Safety Program
The Levee Safety program (LSP) was created by the USACE in 2006 to assess the integrity and
viability of levees and to make sure levee systems do not present unacceptable risk to the
public, property, and environment. Under this program the USACE conducts levee inspections.
These inspections are used to rate levee systems to determine compliance with operation and
maintenance requirements, understand the overall levee condition, and determine eligibility for
federal rehabilitation assistance under P.L. 84-99.
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