Monday, January 24, 2011

Technical Uncertainty and Flood Mapping

Soon to be almost 30 years since the publication of the article:
Baram & Miyares,
Managing Flood Risk: Technical Uncertainties in the National Flood Insurance Program , 7 COLUM. J.
ENVTL. L. 129 (1982)

And little academic literature or litigation dealing with what as head of HUD Flood litigation for the FIA and then FEMA from July 1, 1974 to July 1, 1986 I feared the most difficult challenge to the NFIP. Well I guess mission accomplished.

To focus more clearly on my concern I quote [with footnotes deleted] from the article:

"Legal challenges to the FIS can be expected to arise, at least in part, because technical uncertainty inevitably results in some divergence between results and objective reality. If the party challenging a floodplain management decision is successful in overcoming the usual judicial deference to agency expertise and secures judicial invalidation of the challenged decision, this can reduce or
destroy the credibility of the underlying FIS.
However, in the few reported decisions thus far concerning
NFIP, courts have shown much solicitude for the difficulty of the Agency's mission, and somewhat less for incidental injury to landowners. The court in Roberts stated: "factual certainty is not necessary, and an agency may regulate even though facts do not illuminate a clear path." The question of whether a single number (or elevation) can be the basis of regulation when, because of unavoidable
technical uncertainty, only a range of numbers can be
supported by the underlying studies has been considered by courts in other contexts."

I reviewed this language closely when the article was in draft and firmly believed then and now that it put those impacted and benefited from flood maps issued by the NFIP on notice.
What I have lost track of over the years as to whether better and more accurate mapping methods exist or have been developed to resolve any technical uncertainties or promote scientific correctness.
And my understanding of the very expensive efforts of the program to remap the country by first a consortium led by Michael Baker and also IBM and now a more extended array of contractors was doing anything more than providing updated contour interval data for the underlying display of the 1% annual occurrence flood plain. Notable exceptions for the maps from designation have in the past been areas behind the levees, dams, floodwalls, etc that at least in theory provide protection from the so-called 100 year flood. That standard by the way which I worked hard to incorporate in the NFIP regulations and even the statute and survive a study of its appropriateness mandated by Congress in the 80's was a compromise between the annual spring runoff and the flood of record. Note the STORM of record is never mapped. Also a ferocious efforts to reduce the mandatory insurance purchase reqirement to the 50 year flood standard was launced while the program was still in HUD. Instead some have argued for mandatory purchase in the 500 year flood plain.

When the program started mapping little of the country had 1Ft contour maps. Some of the country had 10ft contour maps and some had 100ft contour maps, all produced by the USGS. These all relied on calibration points of the NGVD control markers that unfortunately often are in flood prone areas in which soil subsidence makes them inaccurate sometimes up to several feet. NOLA and Houston are two good examples of such areas.
Efforts at reform of the NFIP are underway and most if not all do not consider mapping issues. I argue that the time has come to minimize conflict over the maps by having federal flood insurance policies, typically issued by the WYO companies, only issued where there is a designated 100 year (1% annual occurrence flood) and V zones which are Coastal High Hazard areas and largely mapped using different methodologies.
Still overall hoping someone will take on a discussion of mapping uncertainty and its actual application today as opposed to the early years of the NFIP.