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FEMA's Outdated Flood Zone Maps 21

Oops409

Oops409

Mechanical
Apr 25, 2024
193
Only 3% of residents in Asheville, NC, for example, had flood insurance, according to an article I read. Looking at FEMA's Flood Maps, it is understandable why residents would not have flood insurance.

FEMA flood maps will need to be updated to reflect modern risks, and risks due to more and more urbanization and growth since maps were developed, along with whatever weather cycles we are now experiencing.

Screen_Shot_2024-10-04_at_2.44.28_PM_ufmkwl.png


Marion, NC below

Screen_Shot_2024-10-04_at_3.06.57_PM_mxaqdk.png


 
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This has been discussed before. No one and no political entity wants the flood zones increased (even when it makes sense) as it impacts property values and insurance costs. Its a nationwide problem.
 
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FEMA said:
FACT: Flood insurance is available to protect homes, condominiums, apartments and non-residential buildings, including commercial structures. A maximum of $250,000 of building coverage is available for single-family residential buildings; $250,000 per unit for multi-family residences. The limit for contents coverage on all residential buildings is $100,000, which is also available to renters. Commercial structures can be insured to a limit of $500,000 for the building and $500,000 for the contents.
Click to expand...

From FEMA's FACT SHEET: There is a Q&A of Myths and Facts. Does not require being in flood zone to obtain, but it is very limited in coverage amounts.


 
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There's a lot of core infrastructure type issues this country (and most around the world) will be facing. No one wants to be the bad guy and rewrite the laws, flood maps, building codes, etc proactively (when the risk is still "low")...so as usual the codes will be written in blood once enough people die.
 
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FEMA does budgets $300 million annually updating flood hazard mapping and risk analysis. And they budget an additional $200 million annually on flood plain mapping. It seems there should be some updated maps somewhere.
 
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A possible consideration is that the definition used for a flood zone which works OK in areas where the risk is storm surge, may be wholly inappropriate in Appalachia.
FEMA 100 year flood definition. said:
0.2 Annual Chance Flood Hazard,Areas of 1% annual chance flood with average depth less than one foot or with drainage areas of less than one square mile Zone X
Click to expand...
Perhaps in these areas less frequent flood lines should be identified on the maps.

The recent event flooded much of or in some cases beyond zone X which is defined as minimal hazard.
 
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Not strictly applicable to the US, but we have flooding in Australia as well. Experience here was that after any major event, there were arguments about what was covered. Riverine flooding, storm surge, overland flash flooding, storm water drain blockage, etc. Most insurance companies have now decided to cover all types of water damage automatically. Of course, that has dramatically increased the cost of home insurance. Companies which will issue insurance without flood coverage are scarce.
 
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I think the lesson here is that 500 year flood doesn't mean low risk. It means it's going to be catastrophic when it does happen.

Maybe FEMA can use some of that $500 million and update that definition.

California had its last 500 year flood in 1862.
 
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One lesson here is that because of the nature of the geography of Appalachia and the non uniformity of rain fall during hurricanes, these sort of 500 year events occur much more frequently than might be expected. They just do not occur in the same tributary very often.
As the flood plains create most of the relatively flat spots and most of the rest of Appalachia is crowded with mountains, this has been the economically best place to put roads, rail lines, supporting infrastructure (towns), and so on.
An alternative flattening the top of mountains to make build spots creates an exposed location subject to landslide risk, it works for airports.
Some areas of North Carolina are still impossible to reach after Helene destruction Oct 5 2024
 
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FacEngr,

From your link I found this video of a guy walking to Chimney Rock showing some of the destruction in that area. It shows how infrastucture used to run along river paths in the mountains.

At one point he mentions a wide washed out area was a 'Creek' NOT a River.. NO way to imagine a creek growing like that. He also states mostly Police there and looks like just locals/volunteers do the clean up themselves. He showed lots of helicopters and military crafts overhead and water drops being only visible FEMA aid.

FEMA flood insurance policy limits offer just a drop in the bucket.

Now that creeks have washed out to take infrastructure down stream and leave wide cuts outs, where do you build the replacement roads and infrastructure?

Do you cut into mountain and place the new roads beside the wash outs, to protect infrastructure from the next 500 year flood or do you do a massive earth works project to put the land back up the mountain, so that roads can be built back where they were? Likely in lots of cases private land owners owned property up to creek high water mark or even center line of creek....


 
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Interesting video about volunteers beng turned away and threatened with arrest early on, only to be called back hours later when being 'Officially' asked to help because government unprepared.

Video shows lack of clear lines of coummunication and directions early on, among all the agencies involved. Lack of adequate planning.

In this video a small private helicopter appears to rescue people in areas large military craft could not get into, and perhaps did not have sufficient resiurces.

Clash of Government wanting to lock everything down under their control, but time being of essence and insufficient time to wait on uncoordinated and under prepared government mobilization.

And in all fairness, I can't imagine anybody ever expected this to happen in the mountains so far inland. Clearly if you build on the coast, you should be aware of the risks with that decision, and choose to take that risk, since hurricanes are frequent events on the coast. But in Appalachia you would never expect a 500 year event or plan for it...


Yet is was forecast in advance.


Isolated areas of North Carolina received 30 inches (76 cm) or more of rainfall from Helene, and widespread accumulations of 15 inches or more were also reported. While these kinds of rainfall totals are not unprecedented along the Gulf Coast from particularly nasty tropical storms and hurricanes, they are extraordinary for areas well inland. in by

 
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As I indicated previously a hurricane crossing Appalachia is very different from the impact of the same storm on the coast.

[URL unfurl="true" said:
https://www.scientificamerican.com/article/why-appalachia-flooded-so-severely-from-helenes-remnants/[/URL]]To be clear, Helene would have been devastating no matter where it hit, given that it dropped a truly enormous amount of rain—more than 18 inches across swathes of western North Carolina, with three-day totals that were well above 20 inches at multiple stations. For context, a three-day-long precipitation event in Asheville, N.C., the largest city in the most-affected region, is considered to be a once-in-1,000-year occurrence if it produces 8.4 inches of rain.
Click to expand...

I first experienced kind of event during Hurricane Camille, watching all sorts of material float past on the Potomac River, downstream of the storm impact area.
[ul]
[li]Formed August 14, 1969[/li]
[li]Dissipated August 22, 1969[/li]
[/ul]

[URL unfurl="true" said:
https://en.wikipedia.org/wiki/Hurricane_Camille[/URL]]The storm dropped torrential rainfall of 12 to 20 inches (30 to 51 cm), with a maximum of 27 inches (69 cm).[28] Most of the rainfall occurred in Virginia during a 3–5 hour period on August 19–20. More than 5 inches (130 mm) of rain fell near the North Fork of the Tye River in only half an hour with the grounds already saturated from previous rains.[30] Many rivers flooded across the state, with the worst being the James River in Richmond with a peak crest of 28.6 feet (8.7 m). Many rivers in Virginia and West Virginia set records for peak flood stages, causing numerous mudslides along mountainsides. In the mountain slopes between Charlottesville and Lynchburg, more than 26 inches (66 cm) of rain fell in 12 hours, but the worst was in Nelson County where 27 inches (69 cm) fell. There, rainfall was so heavy that reports were received of birds drowning in trees, cows floating down the Hatt Creek and of survivors having to cup hands around their mouth and nose in order to breathe through the deluge. Though the official rainfall was recorded as 27 inches (69 cm), unofficial estimates are much greater. Some estimate that more than 40 inches (100 cm) of rain fell at Davis Creek. Most gauges were washed away; however, it was reported that an empty 55 US gallons (210 L) drum that was not even in the center of the heaviest rainfall had 31 inches (79 cm) of water in it after Camille passed. "So much rain fell in such a short time in Nelson County that, according to the National Weather Service at the time, it was 'the probable maximum rainfall which meteorologists compute to be theoretically possible.'"
Click to expand...

When you get point rainfall that is described as "probable maximum rainfall which meteorologists compute to be theoretically possible." mitigation becomes impossible. Fortunately each storm follows it's own path, so a repeat in the same place is unlikely.

This is likely a flaw in our implementation of engineering related to Noaa Atlas 14 Point Precipitation Frequency Estimate. The return frequency tells us only about spot of interest, it tells us nothing about the frequency of return in larger areas, such as a watershed.

Continental Scale Regional Flood Frequency Analysis seems to be an area of active research.
The USGS does publish Flood Frequency Reports (this is the first time I hunted for this page).

This explanation is offered on the subject of return frequency.
100-year-flood-its-all-about-chance

LINK
Making informed decisions from these reports is impeded by the reports defiantly being NOT user friendly.
 
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Yes, when I saw the damage done in Western NC, I immediately thought of Camille. Nelson County VA has very similar topography to those areas in NC.

The western NC flooding is not really unexpected. The same thing happened in 1916 to Asheville. They thought they were more ready this time, but preparedness cannot always overcome Mother Nature.

 
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In Puerto Rico, Hurricane Maria wiped out the maker of almost all IV "mini"-bags.

Both are plants operated by Baxter International.
 
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If this is going to be the new norm, somebody needs to take a look at every manufacturer-supplier of high necessity, or strategic goods/services and suggest that, if any one facility supplies more than 25% of the market, that they duplicate their operations in an alternate region.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."
 
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The US didn't do it for baby formula, I doubt any such steps will be taken in any other area.
 
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With everyone trying to do just in time delivery, minimizing storage between producer and end user, factory disruptions are bound to create trouble.
 
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