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Murphy DEP Signals That New Jersey Is About To Repeat The New Orleans Katrina Debacle

Climate Emergency Is Increasing The Intensity Of Rainfall And Extreme Storms 

DEP rainfall study ignored recent excessive rains from tropical storms Ida and Henri

NJ DEP Signals They Will Continue To Rely On The Outdated 100 Year Design Storm

The continued reliance on the 100-year protection standard represents an organizational failure by the Corps and Congress, which are still tailoring their responses to the last disaster, said Bea, an emeritus civil engineering professor at the University of California-Berkeley who led an independent forensic analysis of the levee failures after Katrina underwritten by the National Science Foundation. (NoLa.com)

Despite the science and recent repeated massive flooding, the NJ DEP is signaling that they will continue to rely on the outdated, scientifically flawed, and unreliable 100 year storm in upcoming climate adaptation regulations.

That 100 storm forms the basis for several critical DEP regulations regarding stormwater management, flood plain mapping, coastal zone management, land use, water resources, and planning and design standards that apply to development.

I explained the significance of the flawed 100 year storm in this September 4, 2021 post:

The US Army Corps of Engineers recently were forced to admit a similar huge engineering blunder due to reliance on flawed design standards, a $14 billion mistake: (Federal Register Notice, 4/2/19)

Southeast Louisiana, including the Greater New Orleans area, is generally characterized by weak soils, general subsidence, and the global incidence of sea level rise that will cause levees to require future lifts to sustain performance of the HSDRRS. The HSDRRS project authority did not provide for future lifts. Engineering analysis indicates the HSDRRS will no longer provide 1% level of risk reduction as early as 2023. Absent future levee lifts to offset consolidation, settlement, subsidence, and sea level rise, risk to life and property in the Greater New Orleans area will progressively increase. USACE will notify FEMA once the system no longer provides the 1% level of risk reduction, which may result in the loss of accreditation required for participation in the National Flood Insurance Program.

The signal from DEP is loud and clear, and has been repeated at least 3 times in the last few months.

Most recently, DEP signaled this in Senate testimony by Murphy DEP Commissioner Latourette to the Senate Environment Committee on February 10, 2022. In his testimony, Commissioner LaTourette highlighted the findings of recent research on increased rainfall (that study is discussed below).

Previously, DEP had authorized and in November 2021 released a seriously flawed rainfall study. That study was limited in scope to the 100 year storm, and it did not consider “excessive rains from tropical storms Ida and Henri”, see:

That Nov. 2021 released study explained the significance of rainfall data:

Despite these established trends in extreme rainfall, recent flooding disasters and the range of climate-related risks and vulnerabilities associated with extreme rainfall, design standards and regulations in New Jersey currently utilize climate data from NOAA Atlas 14. …

Since several locations in New Jersey and surrounding states have experienced record rainfall events since 2000, or at least rainfall events that are among the highest in the pre-2000 record, it is likely that the Atlas 14 values underestimate the rainfall extremes that factor in the more recent years of data. This work documents these changes and proposes adjustments to the Atlas 14 rainfall extremes to better align them with the more recent climate record.

Curiously, the study limited the scope of the analysis to the 100 year storm, and did note even consider more extreme storms:

a. Computation of recurrence interval rainfall amounts

Using the array of 29 PDS at each station, rainfall amounts corresponding to recurrence probabilities of 50%, 20%, 10%, 4%, 2% and 1% (i.e. 2-, 5-, 10- 25-, 50- and 100-year storms) were computed by simulating the methodology used in NOAA Atlas 14

The study acknowledged this serious flaw, but in an elliptical way:

Although not the only valid theoretical distribution for estimating extreme rainfall probabilities, the use of the GEV has been standard practice in prior extreme rainfall analyses

Regardless, despite this flaw – and DEP scientists’s criticism that the study failed to consider “recent excessive rains from tropical storms Ida and Henri” – DEP issued a praiseworthy press release touting that flawed study:

In that press release, DEP not only signaled, they outright affirmed that they would continue to rely on 100 year storm, but with slight increases documented by the study:

Notably, the studies will provide  the scientific basis for the ongoing development and modification of rules to be introduced under the state’s NJPACT (Protecting Against Climate Threats) and NJREAL (Resilient Environments and Landscapes) initiatives as directed by Governor Murphy’s Executive Order 100.

The DEP’s own press release revealed the flaws in the study and noted it’s reliance on the 100 year storm:

Among other storm types studied, what is often referred to as the 100-year, 24-hour storm is included. A 100-year storm is one that has a 1 percent chance of occurring based on past historical records and represents the total amount of rainfall likely to fall within a 24-hour period. […]

The long-term projections were developed from a combination of 47 climate models under moderate and high future emissions scenarios. The modeled storms included those with a 50% chance of occurring each year (also known as a 2-year storm), a 20% chance of occurring each year (5-year storm), a 10% chance of occurring each year (10-year storm), a 4% chance of occurring each year (25-year storm), a 2% chance of occurring each year (50-year storm), and a 1% chance of occurring each year (100-year storm).

The DEP was involved in designing the scope of the study. The DEP limited that scope to the 100 year storm and did not even consider the 200 – 500 year storms.

The DEP’s “worst case” storm was the current 100 year storm.

The DEP Science Advisory Board (SAB) “peer review” raised a large red flag on this flaw:

7) Because it uses past events as analogs, it would seem that LOCA downscaling used in the Projected Changes report is constrained by what has happened in the past. How does this method account for the possibility—or perhaps likelihood—that there may be future events that have no historical analogs?

8) Finally, there is one last point that may be difficult to directly address but perhaps could be discussed as a caveat in the Atlas 14 report. Given that the report documents the sensitivity of recurrence levels to individual heavy rain events, how would the recent excessive rains from Ida and Henri change the results?

Here is how the NOAA researchers replied to comment #8:

This is another excellent idea, but unfortunately outside the scope of the original project. As an off- shoot of this project, the website http://precipchange.nrcc.cornell.edu has been developed. This site updates station-based extreme rainfall statistics annually, so updated results that include Ida and Henri will be available in early 2022.


Given the importance of this issue, it is highly unusual that the DEP SAB peer review document curiously eliminated comment #8!

You have to scroll to the bottom of the researcher’s response to those comments to even find comment #8!

I don’t think deleting a comment about excessive rains from Ida and Henri” was an inadvertent or honest error.

I think DEP intentionally eliminated question #8 because it undermines the credibility and reliability of the study.

As I wrote back on September 4, 2021 (link above), tropical storm Ida was greater than a 100 year storm, and it illustrated that NJ DEP’s regulations that formed the basis of the design for billions of dollars of “resilience” projects were totally inadequate, largely because they rely on the 100 year storm.

The volume of water from a 200 – 500 year storm would far exceed the small percentage increases documented in the DEP’s flawed study, which was based on the 100 year storm.

In Part 2 of this post, I will explore the New Orleans Katrina experience to illustrate the implications of DEP’s continued reliance on flawed design standards, like the 100 year storm.

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