News Brief by Kip Hansen — 7 June 2024
The headline reads:
Their Florida ‘Paradise’ Keeps Flooding, but Some Can’t Afford a Solution
“In the Shore Acres neighborhood of St. Petersburg, rising water has become a constant threat. Many residents cannot afford to elevate their homes or move.”
Patricia Mazzei, reporting from St. Petersburg, Florida, for the New York Times, writes a heart-rending story about the poor-rich-people living in a “Paradise”, in a neighborhood with an average home value of $843,000, where most of the homes have boats and yachts tied to the dock in their convenient backyard canal.
Sometimes, especially when Gulf hurricanes hit Florida’s west coast, this neighborhood floods. In some parts of the neighborhood, high tide flooding of some streets and backyards occurs.
This is almost entirely a pictorial news brief. Readers can view just these four images and discuss the cause of the grief of these poor rich people:
“Preliminary results reveal that subsidence occurs in localized patches (< 0.02 km2) with magnitude of up to 3 mm yr−1, in urban areas built on reclaimed marshland. These results suggest that contribution of local land subsidence affect only small areas along the southeast Florida coast, but in those areas coastal flooding hazard is significantly higher compared to non-subsiding areas.” — Land subsidence contribution to coastal flooding hazard in southeast Florida Wdowinski et al. (2020)
“Mr. Batdorf, a real estate broker, said people were still buying in the neighborhood, even if only to demolish and rebuild. He likened the situation to when Tropical Storm Josephine flooded Shore Acres in 1996. Mr. Batdorf walked through knee-deep water back then to make sure a house his clients wanted had not flooded. The flooding did not detract the buyers. …. “I wrote the contract that day, in the water,” he said. “People love living here. It’s the convenience of where it is. It’s paradise.” — NY Times
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Author’s Comment:
Florida is famous for its vices and one of them, just to pick one out of the oh-so-many, is Miami’s Vice. Untold thousands of homes are built along the coasts of Florida within one to three feet of average high tide, with canals to bring the sea close to the homes – as in ‘just there, across the backyard’.
Global Sea Levels, are believed to be rising, on average, at a rate of about 1 foot (0.3 meters) per century as the Earth slowly warms up a bit out of the Little Ice Age, which ended sometime between 1750 and 1850 (opinions vary). There is every reason to believe that the sea will continue to rise, at that rate, maybe a tiny bit faster, for the foreseeable future, at least until the Earth begins to cool once more.
The rich and foolish continue to build homes and entire cities in places which they must know are in harm’s way – in threat of damage and destruction from the sea and its storms, which are driven by the incredibly powerful chaotic interactive processes of the atmosphere and the oceans.
Thanks for reading.
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Insurance?
Use the funds to rebuild on stilts.
Galveston did that starting in 1900. After the city was destroyed by the huge September hurricane, Galveston did two things: 1. started construction of a huge dike; and 2. raised the city up on stilts by about 17 feet. The elevation program was completed in 1911.
And it had a very large, positive effect. In 1915, Galveston was hit by another storm surge of the same magnitude as 1900. This time, less than 40 lives were lost, and the city was largely undamaged and completely unflooded.
Galveston was not raise up on stilts, although wood foundations may have been installed under some buildings as they pumped ~15 million cubic feet of mud/sand onto the island to raise some of it it the 17 feet you mentioned. The seawall was 17′ high, although higher than what is not mentioned. Today the oldest section of seawall appears to be about 6′ – 7′ above MSL – a guess on my part. From Wikipedia, “Approximately 15,000,000 cu yd … of sand was dredged from the Galveston shipping channel to raise the city, some sections by as much as 17 ft (5.2 m).[139] Over 2,100 buildings were raised in the process of pumping sand underneath. According to historian David G. McComb, the grade of about 500 blocks had been raised by 1911.” The article mentions that 1900 acres were destroyed. 15,000,000 cubic feet will only raise about 17 acres that height. So (although those are all estimates), the average rise over the area of destruction had to be considerably less than 17′.
Not to mention that these communities (which are all over south Florida) are themselves sinking. The fill dug to create the canals became the ground upon which the lovely homes were built. Coastal Florida was swampland.
I have previously seen street-level photos of those types of communities. However, I had never seen a satellite photo.
Obviously, the land upon which the houses were built cannot possibly be due to a natural distribution.
Any currents in the adjacent waters due to hurricanes, common thunderstorms, or even tides, are going to start removing material from the slopes of the fill. Eventually, the land surface in that situation HAS to come down!
Mr. Gravity is not your friend.
Way back in 1960, spring, I Visited relatives in Shore acres. My brother, cousins and I went fishing in the gulf. We caught so many fish my uncle said we have no room in the freezer, go bury them in the flower garden By the time we got a hole deep enough to put a fish it it the hole was full of water.
So, the Everglades reached right to the shore? (more or less?)
No – at least not in any existing developed communities. At the extreme southern tip of the Florida peninsula the Everglades discharges directly into Florida Bay … but that land is all Federally owned (Everglades NP and Big Cypress Preserve).
Craig ==> All of Shore Acres is in a FEMA Flood Hazard Zone “AE/(EL 9)” This means: “Zone AE is a high-risk area. Mandatory flood insurance purchase requirements and floodplain management standards apply.”
The EL 9 a zone of AE-EL9 means the structure is in the AE Zone with a base flood elevation [BFE] requirement of 9 feet.
The new building codes requirement for this area is for living spaces to be elevated to “BFE + 1 ft.” , that’s ten feet above some set seal level.
What have seals got to do with it?
They have to live somewhere
In most inland areas, seals would be an invasive species?
(Just a guess.) 😎
that’s the level seals swim at when they have their noses out of the water….
Structures existing prior to the adoption of revised building codes are grandfathered, but new structures must comply. Additionally, to qualify for Federal flood insurance or FEMA disaster relief assistance or even a building permit, the “fifty percent rule” applies. If the damage to a structure exceeds 50% of its value it must be demolished and replaced with a new code compliant structure. Consequently when a major storm impacts a coastal community, as happened recently in Fort Myers Beach and Sanibel, the owners of heavily damaged structures typically just sell out because the land values for waterfront property are astronomically higher than the value of any improvements, even if not damaged. Thus the community gets rebuilt with not only higher structures, but also much larger and fancier structures. The entire character of the community gets a makeover.
Today’s waterfront land values are so high in Florida that in some cases wealthy buyers snap up a $50 million dollar beachfront house that is 15,000 sf and 20 years old, tear down the existing home, and replace it with a 30,000 sf new home to the new owners specifications. “Tear downs” are dominant in waterfront communities. This is economic recycling of a highly valued limited resource.
Do not shed any tears for homeowners of waterfront properties in coastal Florida … for when their home gets damaged or destroyed in a storm, or the owner simply decides to sell out, they will be crying all the way to the bank.
Their real problem would be if the sea level started to fall. Who would want to pay so much money to live there if you can’t go there by boat .
Very few communities are “sinking” in coastal Florida. This is truly an exceptional situation involving only a very small area within St. Petersburg.
Peninsular Florida consists of limestone bedrock that is at relatively shallow depth (generally less than 10 to 20 feet below surface) covered with fine sand or silty sand soils. Ditto with the bays and river bottoms from which material was historically dredged to create new dry land (that practice ended 50+ years ago).
Sand and silt cannot consolidate and subside. Only clay soils consolidate and subside, and organic material tends to degrade and oxidize over time and with loading and thus subside. But almost none of the surficial soils or sediments in coastal peninsular Florida are clay (north Florida above the peninsula it is very different), while relatively small amounts of organic material are present, except in ancient freshwater swamps like the Everglades. There may be small pockets that are the exception, but that is not the rule.
Duane ==> See the most recent studies on Vertical land Movement, such as
https://www.nature.com/articles/s41586-024-07038-3
We were in Mexico Beach, Florida just after a direct hit from a hurricane. Almost nothing was left standing. Looked like a nuke had gone off.
3 years later everything is rebuilt bigger and better. The modest beach homes replaced by monsters up on stilts. Restaurants and rentals filled up with tourists. Business is booming.
Sort of similar case as the poorer Holly Beach, Louisiana which was rebuilt after several hurricanes. Because of the mud the joke was first prize for rental cost was one week at Holly Beach, second prize two weeks. I actually knew someone who won some days there. Atchafalaya River mud goes west and pushed to shore. Despite improvements there are an increasing amount of indirect subsidies from several sources that are necessary to live on the coast. This is not helped by both private and government still building some on susceptible properties.
No offense to the mud as it is associated with great productivity.
Seattle and Galveston. Two low lying cities that rebuilt higher to prevent flooding. Changing the climate would have done nothing to help them. Spending billions of taxpayer dollars on CO2 in place of gravel fill would have seen more than a few political careers cut short, permanently.
Sorry to cut at right angles to you Kip, but my mind immediately transformed this:
“In the Shore Acres neighborhood of St. Petersburg, rising water has become a constant threat. Many residents cannot afford to elevate their homes or move.”
Into this:
“In the suburban neighbourhoods of London, England, rising regulations and taxes on cars – notably ULEZ – have become a constant threat. Many residents cannot afford either to upgrade their cars or to leave London.”
One of these is a real problem. The other is, at best, pixie dust. Which is which?
Neil ==> In Shore Acres, to qualify for flood insurance, a home has to be 10 feet higher than normal sea level (sort of) define as “Base Flood Elevation (set by FEMA) + 1 foot”.
and that is very costly if one is raising an existing home. As the NY Times article implies, many older homes are purchased, just to be torn down and a newer modern home built with adequate elevation — 10 feet of above ground basement!
The only two LOMA’s in the entire development (submitted and denied) had a Lowest Adjacent Grade to the homes at about 6′ below BFE (100-yr projected flood).
The Shore Acres neighborhood of St. Petersburg, Florida . . . ho hum, just another place on Earth where local land subsidence is a MUCH bigger problem than global sea level rise.
And the MSM is not smart enough to know the difference between the two factors!
Building on fill swamp where the fill has some place to go(in this case the canal and ocean) is never wise. Yes putting the houses on pilings word fix the problem.
ToldYa and mal ==> Yes, build on filled swap with canals cut and the material dredged material used to make the little peninsulas the houses sit on.
Same thing is happening to part of Miami Beach, and to Las Olas Isles in Fort Lauderdale. Both created in part using dredged fill (Isles is land plus artificial canals with docks in back yards in what in 1950 was mangrove swamp)—now subsiding, so streets flood during king tides.
The Isles solved the problem by installing one way check valves on all the street drains. 69 of them for several $million. About the price of two houses there.
So far Miami Beach has done nothing.
Rud ==> Yes, in my area we have water treatment plants that back up at King Tides — which just had check values installed this last winter.
I’m sure the availability of subsidized flood insurance has nothing to do with everybody’s attachment to the place. When the government stops offering that then I will believe the government’s alarmist press screeds.
Has anyone ever considered just the total amount of heat generated by our civilization: transportation, factories, power plants — you name it, even the body heat from 8.1 Billion people — as a factor in the temperature rise of the Earth? Some back-of-the-envelope calculations I’ve seen show that just the body heat of all the humans on the planet could increase the temperature of the atmosphere 1C in 168 years.
If those numbers are anywhere close to real, imagine what all the heat from industry and everything else we do might contribute.
Why the down votes – it is a valid question.
Only if that heat is retained fully? Or allowed to radiate in to space? Show us the calcs.
Here are the numbers I’ve seen. I can’t vouch for their correctness, but I tried to get a couple of sources for each. Luckily, things like “mass of the Earth’s atmosphere” and “Joules given off by a human”, might be SWAGs, they’re unlikely to be political. So here they are:
Mass of Earth’s atmosphere: 5.15e18 kg
Density of Earth’s atmosphere: 1.2 kg/m^3
Volume of Earth’s atmosphere (mass/density = volume): 5.15e18kg/1.2kg/m^3 = 4.3e18m^3
Joules/second from a human being: 90.0 (Is his realistic? Saw it on a couple of different physics websites — physlink.org and stanford.edu
Total available human heat: 90.0 J x 8.1 Billion people:
7.29e11J/s
Energy required to heat up 1 m^3 1C:
specific heat of air: 1.006 kJ/kgC
energy required: 1.006 X 1.2 X 1C = 1.2KJ to warm 1 m^3 1 C
Energy needed to heat atmosphere 1C
1.2e3 J/m^3 x 4.2e18 m^3 = 5.04e21 J
J/s available to heat atmosphere 1C
7.29e11 J/s
Joules needed / Joules available:
5.04e21 J/ 7.29e11 J/s = 6.91e9 s = 219y
I used more conservative numbers in this calculation, so instead of 168 years for the mass of humanity on Earth to warm the atmosphere 1C, I got 217.
It’s my understanding that all heat is kept in the Earth system except for what is radiated into space. We pump heat from here to there to heat and cool our immediate surroundings, but all that heat stays in the system.
Now figure how much heat enters the system from power generation, factories, transportation, and every other thing we do. Is it an order of magnitude more than just humans:alive? Two?
Seems worth investigating to me.
The current wisdom is that the total energy use of all human activities, per year, is less that solar input for two hours.
The total mass of carbon sequestered in plant life on planet Earth is estimated at 450 gigaton (Gt C). Bacteria, fungi, archaea, etc. contain another 93 Gt of carbon. All animals are about 2 Gt carbon. Humans are only 0.06 Gt C.
Viruses have three times the mass of humans, bacteria are more than 1000 times more massive, and plants are 7,500 time more massive than humans.
We humans live on the plant by the grace of plants. Sometimes I wonder if they didn’t let us evolve so we would dig up the coal, oil and natural gas and return the CO2 to the plants. 🤣
I think I have said before…. that if there is a GOD…
… then HE/SHE must have planned it so that the coal was ready for our use, just when we developed enough to figure out how to use it.
We are therefore religiously bound to use that Coal.
For some reason, that idea really upset some of the AGW cultists 😉
Even taking that as absolutely correct, it only means that it would take 4,380 years for human energy output to equal a year of the Sun’s. We’re also not talking about equaling the Sun’s output, but just warming the atmosphere by 1C over100 years or so.
It’s late and I’m very tired. Is that math correct? Two hours Sun = approx 1 year Earth.
1 year = 365 days X 24 hrs /day = 8760 hrs, and if 2 hrs Sun = 8760 hrs Earth, then Earth X 4380 hrs = Sun.
“warming the atmosphere by 1C over100 years or so.”
Even if folks had average life spans of 100 years, it would seem that there is plenty of time for everyone to ‘adjust’ to such a small degree of change. (or am I not frightened enough.)
Two hours solar radiation occurs in 120 minutes as displayed on your wrist watch.
I have no idea what you fantasy calculations are about unless you are trying to determine energy produced by the sun. Fortunately, Earth receives only a tiny portion of the sun’s energy.
In case I was unclear, this is about the amount of solar radiation received at Earth’s TOA in two hours, which is about 100% of the energy humans use in 365 days. Human energy use is too small to have any impression on the planet’s energy budget.
If I was building there, I would build a house capable of floating when these high water events happen.
Its only money, after all.
Looooonnnggg anchor chain.!
Fastened to what?
Big deep pylons at each corner with a ring around each pylon allowing vertical movement only.
Floatation bags under the floor frame.
There must be some rock somewhere down under all that swamp fill !
Even if it is a long way down, there are other foundation systems that will easily hold pylons for a house in place.
But…… Money !!
My understanding is a number of dwellings along the Amazon are built that principle in order to accommodate the 40 or so feet annual change in river level.
The causeway across Tampa Bay goes underwater in thunderstorms. The area has not had a direct hit by a hurricane in a long time. When one comes directly up the bay…!!! It will happen.
They did build it high enough the first time did they.
mal ==> actually, the causeway has always flooded with storm surges….I lived in thr Tampa/St Pete area in the 1970s and it is more common than one would think.
Not sure if it’s true, but I read somewhere that early New Englanders seldom built homes on the coast for fear of storms- and that’s 3-4 centuries ago.
But they had common sense… needed it to survive. 🙂
Nowadays, common sense is not required for survival, except in extreme cases…
… called the Darwin effect.
Or the government back then had enough common sense not to subsidize disaster insurance.
Price flood insurance correctly and the over-building on the seashore will cease.
These days common sense is a rare
Look how often the predicted path of a tornado follows and brushes the coast of the US from Miami to Cape Cod.
Joseph ==> The northeast of the U.S. (New England) can and does suffer from horrendous storms, the famed Nor’easters.
Building in flood plains, far from the ocean, isn’t especially different although the reasons for ignoring the hazards may be different.
In the UK there has been a lot of housing built on flood plains over the last 30 odd years and floods happened so much that many people in those houses could not afford to pay the insurance costs. The Government had to introduce a special scheme with the insurers although that is due to end in a couple of years. Meanwhile building on flood plains continues apace, partly because cash strapped local authorities welcome the Council Tax residents of the new homes will pay.
And this is why native Americans who lived in teepees did not set up next to a river. Or so the story goes.
Just because fill material is dredged does not make it unstable or tending to subside over time. It depends upon the characteristics of the dredged material -say sand or shell vs. clay or marl, or a significant proportion of organic material – as well as the quality of construction. Subsidence is a function of clay materials that slowly consolidate over time, effectively squeezing water from the tiny void spaces within the material. Neither sand or shale consolidate – the void spaces are large enough that water drains quickly.
This is not a phenomenon associated only with dredged materials. Any land area with clay soils is subject to consolidation and subsidence, as well as heave (when dry clay soils are wetted again, they expand).
Stabilizing clay soils is a matter of allowing sufficient time to consolidate, or pre-loading the soils to higher pressures than expected post construction can prevent significant subsidence. However in a coastal area with tidal influences, where the soils are subjected to repeated wetting and draining and are close to sea level, that doesn’t work well. Organic fill simply makes poor foundations.
Peninsular Florida soils are mostly sand or sandy silt and therefore do not consolidate or subside. Even swamps do not have thick layers of organic material on top – dig down just a few inches then it’s sand all the way down to bedrock which is typically just a few feet below surface. But like any generalization, there are always exceptions.
As to determining what the issue is with this particular neighborhood in St. Pete FL, a geotechnical engineer’s forensic report would be needed. Poor dredge material? Poor construction method? Both?
Contrary to many of the comments here in this thread, most coastal construction in Florida has no problem whatsoever with subsidence. The focus in Kip’s post and the thread is on a truly exceptional situation here.
Duane ==> Building on filled marsh land, anywhere, is a problem. The satellite photos show clearly where and on what Shore Acres was built. Some of it was pine flat, most of it was marsh, which has been filled. All of it has had canals cut into it. All of it is at or near high high water and most below highest high water.
Tampa Bay, as you know if you live anywhere nearby in Florida, is prone to odd water level changes — running out when Gulf hurricanes suck water out of the by, and flooding, up over the causeway, when hurricanes or even just high southwest winds push water into the bay.
The shape of the tide cycle is funny as well (at least for those of us who expect even diurnal tides):
Lived in Florida 35 years, the first 14 in Tampa Bay area, further south since then. Licensed civil engineer and land developer. So I am extremely familiar with building and soil conditions here in south Florida.
Most coastal marshes or wetlands do not not have deep layers of subsidence prone organic soils. Barely scratch the surface in most wetlands here, less than an inch down, and you hit clean sands or silty sands all the way down to bedrock. Bedrock in most locations here is well less than 20 ft down, as little as 2 feet below surface. That is not conducive to subsidence.
We do not have any oil production here, the biggest cause of subsidence in the Los Angeles CA area. Our groundwater table typically is anywhere from 0 ft to 10 ft below surface, so groundwater withdrawal is not a cause of subsidence as it is in some locations such as in the Ogallalla Aquifer of the Great Plains.
Even in the Everglades, the largest freshwater swamp in the US, where organic muck is the principal soil type, the muck layer is typically less than 6 ft deep sitting directly on limestone bedrock or sand. Virtually none of what was once the predevelopment Everglades has buildings erected on it; rather most Everglades development was for agriculture, primarily cane sugar and vegetable farming.
Again, very little subsidence has been experienced in coastal peninsular Florida. There are some pockets that serve as the exception, not the rule. Including Miami which is often cited here at WUWT as a hotbed of coastal subsidence. Miami gets periodic flooding during storm events that coincide with king tides, but that is simply because Miami is on very low ground and always has been. Every city in the US periodically gets flooded or at least the storm water management systems are temporarily overwhelmed, whether in coastal areas, river valleys, or even in desert areas that experience flash flooding.
The largest source by far of flooding in Florida has been storm surge associated with hurricanes. As we recently experienced with Ian less than two years ago. Subsidence is not a major issue here.
Duane ==> Newly built homes built on filled marsh are prone to subsidence. Miami see some subsidence, just under 2 mm/yr, which is what I have reported here for years. Shore Acres is built on filled marshland, and has tide running in and out in the canals. Look uo the recent Lidar study of Tampa/St Pete that looked for sinkholes and you’ll see the subsidence of this neighborhood. Not shocking, but not nothing.
The worst is that marshlands are marshlands because they are at or near local sea level. They are marshland because they flood. Adding a couple of feet of reclaimed muck to the little housing peninsulas between dredged canals is just that and does not raise them high enough to be safe from the eventual subsidence or storm surges.
When it’s not enough to just live in a state frequented by huge storms, one must pay huge amounts to live at the water’s edge and then blame my nat gas stove.
People pay top dollar for waterfront property because they value it highly for views, recreation, and lifestyle. They are happy to own homes in such areas. Do not cry for homeowners on waterfront properties in Florida. They are crying all the way to the bank when they sell, regardless of the condition of any structures erected on them, which are considered disposable.
I have a friend who lives on Chincoteague island, Va. Every decent coastal storm that arrives with high tide will flood her backyard.
When I lived down there many years ago, such “land” was called “fill.” Sand was pumped from the natural bays and inlets onto the surrounding low-land where people would then build houses, mansions and castles just a few feet above high tide. After a decade or so of periodic high-tide and hurricane flooding (natural events), new construction had only the garage and storage on “ground” level with living space above. Ten feet above. And built to withstand hurricane winds.
Some people adapt … the ones with money,
When I lived down there many years ago, such “land” was called “fill.” Sand was pumped from the natural bays and inlets onto the surrounding low-land where people would then build houses, mansions and castles just a few feet above high tide. After a decade or so of periodic high-tide and hurricane flooding (natural events), new construction had only the garage and storage on “ground” level with living space above. Ten feet above. And built to withstand hurricane winds.
Some people adapt … the ones with money,
Flooding from Hurricane IanThe devastation of a more than 12-foot storm surge could have been worse if Sanibel was heavily developed. However, the Sanibel Plan, the City’s comprehensive plan emphasizes conservation over development which greatly reduced the potential economic impact from more loss of structures on developed property, since conservation lands are not developed upon. As climate change-fueled hurricanes and sea-level rise increasingly threaten barrier islands, it’s more crucial than ever to protect vulnerable areas.
https://storymaps.arcgis.com/stories/d4208c7bfc7642ba85de8dedcbdf6592
Legislation, building codes (and limits) and sky-high insurance rates for both private development and public construction such as bridges and utilities will be required to limit the foolish development in South Florida and other flood-prone areas.
If you can’t finance it, you can’t build it.