The National Levee Safety Program: Do We Need a Standard for all Levees in the Nation?

ABSTRACT ONLY - re levees in the United States safe? That is a difficult question to answer as the United States does not have national standard for levee safety. As a result, levees across the country reduce the likelihood of flooding to dramatically different levels for different communities. For example, of the nearly 2000 levee systems in the USACE portfolio, about 35% of them have a likelihood of overtopping greater than or equal to the 1% annual chance event (100-year flood) in any given year, while about 30% of them have a likelihood less than or equal to 0.1% annual chance event (1000-year flood) in any given year.
This broad disparity in flood protection is due to varying approaches used to identify a design target elevation applied by inhabitants of the United States over the years. Early Native Americans generally raised earthen embankments to a level that would protect them from the largest flood they had seen at a given location. The flood control acts of the 1928 and 1936 led to construction of thousands of miles of levees, many of which set a target elevation equal to the 'Standard Project Flood'• (the largest reasonable flood that could be expected in the basin), which led to the robust designs with annual chance of overtopping near 0.1%. More recently, the 1% annual chance event target elevation has been a design goal for many communities due to how the National Flood Insurance Program (NFIP) is implemented. Never intended to be a safety standard, the 1%-annual-chance event is a desirable target elevation for communities as it is the lowest cost levee investment that will allow for unrestricted development to continue and provide relief from mandatory flood insurance purchase.
Given the opportunity of the National Levee Safety Program to promote national practices for levees, should there be consistent method to determine the target elevation for a levee? If so, how should a fair and impartial standard be developed that provides equal risk reduction for all? Should we establish a national standard focused on the levee? Or, should we follow the example of the Netherlands and establish an national standard that provides a minimum likelihood of becoming a flood casualty for every citizen living behind levees in the United States? This session will explore potential options for a national levee standard, including challenges and benefits for implementation across the country.