The Maps are not the Problem: In Perpetuating a Myth, Horowitz Misses the Key Point

Posted on June 13, 2016 By



Andy Horowitz’s recent New York Times opinion piece on the new flood insurance rate maps for New Orleans contains a number of inaccurate statements, fails to address the fundamental issue, and amounts to nothing more than picking on the “cash-strapped New Orleanians” as they continue the long process of recovering from catastrophic levee failures that occurred over a decade ago. Many of the shortcomings of this piece have been pointed out here and here. In addition to the factual errors that these critiques raise, Prof. Horowitz perpetuates a fundamental misunderstanding of flood risk and how our nation manages it. In no way do the new maps suggest that flood risk has been eliminated, as Prof. Horowitz claims. In perpetuating this inaccurate cliche, the article dances around but does not directly address a fundamental flaw in the National Flood Insurance Program.

“Safe from Flooding” is a Fiction

Prof. Horowitz’s statement that the new flood maps “declared most of New Orleans safe from flooding” is incorrect. The new maps merely moved some areas from the 1% annual chance flood risk area, the “100-yr flood zone” or the “special flood hazard”, to areas that are estimated to have an 0.2% chance of flooding during any given year, the so-called “500-yr flood zone.”  (A flood that has a 1% annual chance will have an average return of 100 years, while a 0.2% annual chance corresponds to an average return period of 500 years.)  This adjustment is an accurate reflection of the risk reduction provided by the Federal, state, and local investment in an improved levee, floodwall, and pump station system. (However, FEMA’s methodology does not account for the flood risk reduction benefits provided by numerous coastal restoration and community resilience projects.)

The article wrongly perpetrates the misconception that properties in the 500-yr floodzone are not considered at risk. As Prof. Ed Link, a nationally recognized flood risk expert at the University of Maryland, put it: “there is no mention of safe within the language of the FEMA program or the maps.”  In repeating this myth, Prof. Horowitz completely misses the point that these properties are at risk, that the maps accurately depict this risk, and that these property owners should pay into the flood insurance risk pool.


Mirabeau Gardens

FEMA’s online flood hazard webmap for New Orleans shows that the area around the London Avenue Levee Exhibit Hall and Rain Garden, what Prof. Horowitz describes as “the area around a new memorial exhibition at the site of a catastrophic levee failure”, is not shown to be safe in the new maps as he claims. The maps very clearly show that the area is subject to the 0.2 percent annual chance flood hazard. (By the way, the maps do not account for the rain garden that is part of the exhibit, another one nearby, or the many other “green infrastructure” projects in the area that are known to reduce flood risk.)



Zoomed out to the entire city, FEMA’s flood zone webmap for New Orleans shows that there are no areas in the city that have been declared safe, as Prof. Horowitz claims.  Likewise, for neighboring St. Bernard, Jefferson, and Plaquemines parishes.


New Orleans’ Flood Maps Advanced the State of the Practice

Prof. Horowitz is also incorrect to state that the flood risk analysis did not account for sea level rise, subsidence, or the probability of levee failures. All of these factors were considered in the technical analysis. It was a complex and tricky process, and there are legitimate questions about the assumptions and methods used. But what he bemoans as “six years of waiting and wrangling” was in fact a series of intensive consultations between national and local technical experts dealing with the very challenges that Prof. Horowitz claims were ignored.  This is what it takes develop, in an open and public manner, flood risk maps that adhere to national standards while also including local data and knowledge.  The result is likely the nation’s most comprehensive, computationally intensive, mathematically rigorous, and transparent attempt to estimate flood risk for a region. The northeast coast in the aftermath of Hurricane Sandy is the only region that we know of that comes close to the effort to create flood risk maps that accounts for changes in the climate and landscape.

In the face of these challenges, this is the effort it takes to have hydrologically correct flood risk maps for our coastal cities. Further, hydrologically correct flood risk maps is a necessary condition for an actuarially correct flood insurance program, the stated goal of many years of effort at flood insurance reform.

The implicit assumption throughout the article is that the maps are an inaccurate reflection of flood risk for the region, but the article does not attempt to make that case. In fact, his statement that the maps “reflect the most optimistic possible assessment” is a tacit acknowledgement that the flood risk depicted on the maps is in fact within the confidence interval of the technical analysis. It is clear the Prof. Horowitz does not like the outcome of the maps, and he does raise legitimate concerns regarding the outcome. However, in attacking the maps and the process that created the maps, he failed to address the fundamental problem with flood insurance in New Orleans or elsewhere in America.

Flood Insurance Risk Pool Needs to Include the 500-yr Floodzone

In moving areas from the 100-yr to 500-yr flood zone, the maps in no way imply that areas are safe. In fact, they explicitly state that there is a 0.2% chance that flooding will occur during any given year. The fundamental problem is that the flood insurance program currently exempts these properties in the 500-yr flood zone from flood insurance requirements. Because they are not required to pay into the risk pool, these residents are less likely to be aware of their flood risk. Expanding the risk pool to include these properties increases flood risk awareness of these residents. It is also another necessary condition for an actuarially correct and financially sustainable flood insurance program. The failure to address this fundamental flaw in the flood insurance program largely explains why attempts to reform the flood insurance program have failed. Arbitrarily changing the flood maps for New Orleans because Prof. Horowitz does not like the outcome does nothing to address this flaw.

Disaster InsuranceFEMAFloodFlood Hazard DeterminationsFlood MapsNational Flood Insurance ProgramNew OrleansResiliencestorm surge     , , , , , , , ,

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