Could a natural disaster completely isolate a large city in the modern world without destroying it?

Question

I'm trying to construct a society which has had a narrow miss with a natural disaster that has isolated them, scared them considerably, changed the culture, made many of them preppers, but didn't kill many/any of them. But I'm struggling to build a setting which has the right level of destruction, isolation, and fear without wiping the city out.

I'm looking to know if its at all possible for a natural disaster that:

• Completely isolates a large, modern, first-world city from the rest of the world.
• By large I mean 1 million people plus. 200 square miles plus.
  • Eg LA, Chicago, Houston, Phoenix, San Diego, etc.
• Forces the closure of all travel and freight into and out of that modern city. Road, rail and air are totally stopped.
  • No food.
  • No medicine.
  • No gasoline.
  • No mail.
• That lasts for at least 3 weeks,
  • Even with an effective emergency service giving a 100% response inside in attempting to get out.
  • Even with outside world giving a 100% response to attempting to get inside and help.
  • Even with multiple levels of functional, funded, non-corrupt government doing mostly the right things.
  • Even with a cooperating public following all the instructions.
• (if possible) cuts satellite uplinks.
• (if possible) prevents air drops of supplies.
• (if possible) directly kills as few people as possible, and leaves the city mostly livable after it passes.
• (if possible) Cuts off the internet and phone lines in and out of the town - no exchange of data with the outside world.
• (if possible) prevents satellite or recon planes from knowing people are still alive.

I know that tornados, floods, and hurricanes can blow/wash away roads, or flatten airports, but my understanding from decades of CNN is:

• Small towns (< 10,000 people) can be cut off for weeks when their only road washes away, but supplies can be airlifted in.
• Large city's (> 1 mil people) can loose a few highways to big twisters, but their full perimeter can be hundreds of miles, no disaster is big enough to wipe out all those roads on all sides without also taking out the city.
• Earthquakes can take out roads over a large area, but airdropping supplies is still possible, and non-elevated roads can be patched pretty quickly.
• Large cities can loose their airports to disasters, but that's unlikely to take out all the roads 100s of miles away as well.
  • If it does occur, the runway can be cleared by heavy machinery pretty quickly.
• A big, widespread disaster, like a tsunami or hurricane, could reasonably take out all these things, but some roads could be cleared quickly, and supplies can be helicoptered / airdropped in while roads and runways are being cleared.

The best I've got is: an unrealistic meteor shower that falls in a ring-shape that manages to take out every road, rail, and pipe leading into town, but magically leaves the city intact, except for one hitting the airport, followed by a "Carrington event" that wipes out everything electronic, ceasing all communications. That's pretty unrealistic, surely I can do better than that.

Is there any realistic way to completely isolate a million people in a modern city for a few weeks without killing them?

Answer 1

Totally possible. 2 million Australian's came very close in "20 bloody 20"

About 80% of your requirements were met in 2020. 12 days of total isolation is a little shy of your requirements. A few subtle tweaks is all you need!

Remember this image? It is computer generated and isn't real, but it is sourced from real data overlays:

So as a "warm up" to my real answer - Sydney came pretty close to meeting your requirements in late 2019 / early 2020. As multiple fires across multiple states merged into mega-fires, and multiple mega-fires merged together around Sydney's perimeter, and the media started experimenting with the term "gigafire", Sydney was cut off from all highways and the interstate rail, the airport was operating at low capacity due to smoke cover. The Sky was red and ash was thick - it was opaque to satellite and aerial photography (at least without IR photography). A few very long winding routes were still possible into the city - via Newcastle or along the coast IIRC, and the internet and phone lines remained live. However this came pretty close.

However on the opposite side of the country, it was even worse. Perth was completely cut off by bushfires. Perth is 1.9 million people, 6400 square km, and every sealed road between Perth and all other state capital cities were closed. There were food and medicine shortages. Many empty shelves. It was the first city in 2020 to run out of toilet paper. Fresh fruit and veg was also scarce.

400 km of highways were closed, and a remote service station on the only sealed road into Perth needed helicopters to deliver supplies to the 250 truck drivers who were stranded there. With fires at the time also burning around Adelaide (my hometown - centre bottom), both ends of the road were shut due to fires. The temperature hit 49.8 celsius (121.64F).

The longest continuous period of complete isolation for the city was 12 straight days, however as the fire was controlled and escaped again the roads were re-opened and closed. 22 days in a month had total isolation. People were told to stay indoors and work from home. Outdoor work stopped. It was a warmup for Covid.

The airport didn't completely close, but there were long delays and cancellations as the city got blanketed in smoke and visibility went to 0. Planes got diverted or turned around but the wind subsided sometimes and allowed planes in.

So - for your scenario, once the fire starts, you only need to subtly change the wind to get your outcome (sans internet dieing):

• Stronger ash cloud over the airport. Keep the wind steady and no-ones flying in or out.
• Stronger ash cloud over the seaport so people can't work. If they can't breathe outside, they can't unload ships.
• Keep the fires burning up to the highway for a few more days. If crews weren't able to push the fires back on cooler, calm days, the roads wouldn't remain shut.
• Satellite and airborne photography suffer from anything in the air, thicker ash and it'd be pointless.
• Air drops couldn't be done in strong winds and zero visibility.

To cut Perth off from internet, you'd need to cut 5 undersea cables, this is quite an ask and unlikely to happen all at once. Cutting power will accomplish this. Ash clouds will ruin solar, strong winds can overwhelm wind generation (they drain power to apply brakes), and 0-visibility could affect fossil fuel power plant staffing, but cutting power in the Australian summer will kill hundreds of people from heatstroke however. A carrington event may take out all the ICs, and thus all internet and phone connections, and blow all fuses, but after resetting your circuit breaker your dumb Air Conditioner may still work. If a few dumb fossil fuel plants come back on line, or were shielded, you could have a society that is temporarily phone and internet free, but still air conditioned and has fridges to keep some food.

So to start it all, a Carrington event may be the answer. That caused sparks from telegraph lines. Sparks from modern power lines on 45 degree days with strong winds would start bushfires.

So the sequence of events is:

• Hot Australian summer. Typically "Catastrophic fire conditions" 45 degrees C. 40kmph winds.
  • Official advice from government on these days is "Leave your homes early, before a fire starts, as once it starts, it's too late to leave."
• Carrington event hits. A geomagnetic storm hit Perth.
  • Knocks out most ICs, killing the internet and phones.
  • Power lines spark out in the bush, starting numerous fires.
• Strong winds spread the fires quickly, crossing the Nullarbor highway and the Indian-Pacific rail line, closing Perth to all rail traffic and all road traffic not on dirt paths.
• Fires spread into inaccessible terrain around Perth, like the Jan 2021 fires did.
  • These fires can't be fought by ground crews as they're too remote. We can only fight them from the air.
• Ash cloud blankets the city.
  • Stay-at-home orders issued. It's too smoky to go outside.
  • Planes are unable to land as visibility is 0. They all Go-Around and then end up diverting to their alternate (Adelaide).
  • Ships are unable to be unloaded due to the Ash cloud.
  • Airborne water-bombers are unable to fly as the smoke is too thick, meaning we can't fight the main fire in inaccessible terrain.
• As usually happens after these heatwaves, cycles of low pressure air come in, bringing cooler temperatures but stronger winds and lighting.
  • these help spread the fire massive distances. ember-attack 20km in front of the fire is not unheard of.

How does it all end? - Floods or heavy storms

Typically Australian bushfires need a big soaking to go out. They can burn into Autumn in inaccessible scrublands being slowly attacked by water bombers waiting on a big downpour. These usually have their own issues like the Jan 2020 Canberra bushfire was weakened by a $500million hailstorm.

Once you've made them suffer enough, have one of the low pressure cycles bring heavy rains, and then a period of calm winds.

• Emergency services can get on top of this within a few days of this.
• Opening a road after a bushfire is quite involved. Safe-looking trees can reignite and drop flaming branches onto trafic, so the surrounding bush needs to be cleared if its burnt.
• All the signs, safety rails, and other infrastructure is burnt away, so speed is limited after a fire, further delaying resupply.

Multiple times they've been extinguished by devastating floods or cyclones, so scenes like this road covered to a depth of 1m while still displaying bushfire warnings happen quite often:

Answer 2

The 2010 eruption of Eyjafjallajökull is an example.

The 2010 eruptions of Eyjafjallajökull were a period of volcanic events at Eyjafjallajökull in Iceland which, although relatively small for volcanic eruptions, caused enormous disruption to air travel across western and northern Europe over an initial period of six days in April 2010. Additional localised disruption continued into May 2010, and eruptive activity persisted until June 2010.

If you top it with bad weather at sea, disrupting the naval traffic, maybe even adding rocks falling due to the volcanic eruption, you have isolated the city without actually destroying it.

For a reference, the airport of Catania, in Sicily, is often closed when Etna erupts, and the annoyance for the city is usually some thick layer of volcanic ashes. They can block road circulation, and if the eruption goes on for long time cleaning efforts can get behind.

Answer 3

Occupation

https://en.wikipedia.org/wiki/Mosul#Government_by_the_Islamic_State_of_Iraq_and_the_Levant_(ISIL)

Mosul was a city with a population of over 1 million. It was captured by ISIS militants and was governed by them for 2 years.

The city in your fiction is occupied for only 3 weeks. A revolution takes place in the US with varying success - in most places rebels are overcome in a matter of days but by circumstances of geography, luck and skill the insurrectionists take and hold this city. Manhattan (on an island!)might be a good choice, or Austin or Atlanta - with local military moved to help in other areas, insurrections who have come to the city over the previous weeks take the city (possibly with some cooperation of local military) and cut access by tunnel and bridge. The persons holding NY are able to cut cell phone use. Rebels intercept air drops and boats attempting to bring supplies.

When it becomes clear that the larger insurrection has (for the moment) failed, the rebels effectively hold the city hostage while they negotiate terms. The US government is unwilling to dislodge the rebels because of the immense property damage and loss of civilian life that would produce. Through negotiation with some groups in the city and innovative military techniques in others Manhattan is restored to government control.

In addition to your traumatized city, for this scenario you might have other cities that fared less well. The idea of something like the Guangxi Massacre taking place in an American city would make a gripping story.

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There are a lot of great pictures I was looking at to illustrate this idea. I think though I will leave it unillustrated. Too close for comfort.

Answer 4

Wellington, New Zealand is in a earthquake risk zone and really only has 2 roads in or out.

One road runs through a steep gully which is prone to rock falls). The other one runs along the shore, so is at risk of post earthquake tsunamis; and I think is partially on reclaimed land.

Reclaimed land is land which used to be seabed, but had dirt/fill pushed into it, to make more usable land. Reclaimed land is prone to subsidence; like when you jiggle wet sand and it goes liquidly, like sinking sand.

The sea port and air port are also built on reclaimed land.

The upside, for the mean time, is Wellington has really good cafes and restaurants and lots of live theater, shows etc.

Answer 5

It is not just the disaster but the response as well.

Look at the Puerto Rico earthquake as an example, have the government utterly fumble emergency response, thus drastically prolonging isolation and building a mindset the the government will not help.

Consider combining effects.

To use Puerto Rico as a model, imagine if their had been a hurricane shortly after the earthquake cutting off sea traffic the whole island could have been isolated for even longer.

Combine anything else with a earthquake to get much more destruction with little initial loss of life.

A city does not need to be completely isolated to be effectively isolated, if there is only one shallow harbor left usable, supplies have to go through several steps to even reach the city drastically slowing down how fast they can be delivered.

Add a distraction.

Have a natural disaster followed by another worse natural disaster or a war in a different place in the same country, diverting supplies and manpower. I hate to keep using the same example but imagine how Puerto Rico relief would have been handled if Yellowstone had erupted at the same time or consider Australia during the fires if Russia had taken the opportunity to invade Europe.

Answer 6

Air traffic is pretty hard to take out. There's only one thing that comes to mind that can do it: Volcanoes.

The initial conditions require a city on a peninsula and over a fair area the approach by sea is unsafe. Then there's a big quake that sets off two volcanoes. One cuts the landside connection, one cuts the part of the sea that was safe to approach. Nothing can approach by air because of the volcanic ash. Both volcanoes are throwing enough bombs that you are at great risk trying to go past.

The volcanoes can take out the utilities and they'll mess with but not completely block radio. In three weeks I think a data link would be jury rigged, but that assumes powered-up computers in the city to communicate with. (Take a sacrificial cargo aircraft, load a big spool of armored fiber optic cable, fly it as high as it goes, when it approaches the danger zone the pilots jump and it continues under computer control with the cable spinning out. When the engines fail it shuts them down and proceeds at best glide speed so long as that will clear the city. If it won't, the computer fires a self destruct. The hard part here is laying the cable fast enough.)

I do have a problem with the scenario, though--there will not be very many survivors after three weeks unless you have a source of fresh water.

Answer 7

Los Angeles after the "Big One"

This is something that's been seen in a couple of movies: Californians tend to imagine that in the future there's going to be a huge earthquake that will split Los Angeles and surrounding area off from the mainland to form a new island. In the movie Escape From LA the background of the plot is that, after the big earthquake, the rest of America sealed off LA as a kind of prison island to prevent the crazies from getting out. (This actually seems like a pretty good idea.) It could be a realistic way to achieve what you want (or at least, it would seem realistic to people who already believe in the inevitability of the "big one").

Answer 8

I think that limiting major cities to populations of 1 million plus ignores several realities of modern cities. For starters, there are only 9 cities in the United States which meet this population size request. Most cities are in 6 figure population sizes. That said, U.S. cities generally have significant metropolitan populations which if included would put them well over this figure (For example, I grew up in the Baltimore-Washington Metropolitan area, which includes the two cities and all their suburbs for a total of 9.75 million people (NYC has a population of 8 million and Los Angeles has 3 Million for comparison). The two principle cities in this statistical area both see a significant day time swell as people commute into these cities for work and return to smaller suburb communities where they live and are counted as population. This is quite common in most American cities, especially since the 1950s and could actually have devastating consequences in that should this occur during the day time, the city would its working population cut off from the families they support (consider that kids typically go to school locally in suburbia compared to their parents who are working in the urban center).

While it wouldn't be a city proper, the Manhatten borough of New York city is often times modeled for Wide Open Sand Box games for two reasons... it's got internationally known landmarks that will allow players to orient themselves with respect to the direction AND is notoriously difficult to evacuate, with only a handful of bridges and tunnels to the mainland. Consider the difficulty of evacuating Manhatten on 9/11, an event where an otherwise small area of the city was actually attacked (for an added bonus, the North Tower contained a major cell and broadcast tower for local NYC television and radio stations. When it collapsed, many local tv stations signals froze on the final signal which broadcast the start of the fall. Radio broadcasts also went silent (at this point, phones nationwide were jammed as people tried to get in touch with friends, family, and emergency services related to the attacks. Most major news networks also have posted the entire recording of the broadcast of the events to youtube and you can watch from first report to final collapse and beyond of the coverage, which naturally includes many erroneous reports (for example, there was a reported car bomb explosion at the State Department Building in D.C. that didn't happen in one networks coverage). Even then President George W. Bush, who was visiting Florida at the time, was in a communication quandary as he and his staff had difficulties calling the staff they needed to talk to (in interviews he would routinely point out that he pushed heavily to overhaul command and control communications capabilities on Air Force One).

9/11 isn't the only time Manhatten has displayed these issues in the past. On more than a few occasions, a minor issue in the power grid could cause a massive blackout in the North Eastern United States with the effects more evident in Manhatten than any other part of the state, mostly because the island is reliant on electircal transportation for it's function... a citywide black out not only kills the largest Subway system in North America, but it also traps alot of people in skyscrapers... and again, phone calls peak and jam up the phone networks frustrating communications.

Another incident was the effects of Hurricane Sandy, which caused a generator to kill the southern half of the island's power, including pumps keeping subway tunnels free of water from the storm surge of the storm... again, transit was out for days. In all cases, Manhatten, when in emergency, can become a prison, and a commute of maybe an hour can take as much as 9 hours for a person to make, depending on where they are in the city. In wide open video games, closing off bridges and tunnels out is easy to do, making the play space defined but not artificially constricted. Compare this to Wide Open games in non-NYC inspired locations, which have to find a way to limit the game world to the game map through other means (Rockstar, who make GTA series and Red Dead Redemption series of games has only made two maps where the game map wasn't confined to an island (both Red Dead Games mix impassible water barriers with mountain barriers) while almost all GTA games are set on islands despite their real life counter parts not even coming close to Islands (Vice City is Miami which is a very small land area... but not an island, IV is Liberty City which is NYC, but if it was built on a small island chain, and San Andreas (GTA: San Andreas and GTA V) is California and Nevada/Southern California respectively if it was an island).

Answer 9

Major undersea volcanic eruption near Oahu

The city of Honolulu has a population of nearly 1 million people. A major eruption would effectively shut down air traffic (cf. Eyfyallayöküll), and an undersea eruption could make shipping hazardous as well. In addition, fiber-optic cables to the island could be badly damaged or destroyed, cutting off internet and phone communications.

You'd have to fudge a few things, though:

1. Our best geological understanding is that the volcanoes that formed Oahu are pretty much inactive these days. While minor eruptions are possible (if unlikely) over the next few hundred years, they would only affect a small portion of the island.

2. Oahu, owing to its convenient location in the middle of the Pacific, actually has several undersea cable links connecting it to the rest of the US, Japan, Guam, and other points in Oceania, as well as the other Hawaiian islands. There appear to be seven separate landing points for these cables on Oahu, dispersed widely enough that an undersea eruption couldn't take out all of them. You'd have to imagine a Universe where Oahu is not as well connected, or perhaps where some of the cables just happened to be out of service when the eruption hit.

3. Even if the eruption is nicely positioned to not drop "bombs" and lava on Honolulu itself, ashfall will still cause some mortality among those with breathing conditions.

On the other hand, if this is for a work of fiction, then the average reader will already associate volcanoes with Hawaii and be more willing to accept #1. And maybe you could justify a "research trip" to Honolulu to "gather information" for the work, which seems like a nice perk.

Answer 10

This more-or less happened to Santa Cruz in the 1989 earthquake. Landslides cut off the main road (Highway 17), and other landslides cut the coast road (Highway 1) in various places. People who lived through it say that there were some back roads such that you could get to San Jose via Watsonville or La Honda, but basically it was cut off. At the same time, the telephone system went down for various reasons.

Power was restored, after a few days, but things did not return to "normal" for almost a month.

This was a Medium-Sized Earthquake. In the event of a 9, you might see the entire Bay Area cut off for weeks, and certain places like Half Moon Bay or Santa Cruz cut off for months.

[I was in San Jose at the time, and noticed that there was NO NEWS coming from Santa Cruz or Scotts Valley. I tried to call people I know, but the phones were out.]

Answer 11

Look up the 1998 Ice Storm in Montreal. It pretty much closed the city for about a week. It cut power to regions east of the city for weeks, and in some cases months (in the dead of winter).

If you get enough ice, it destroys any part of the infrastructure that involves hanging wires from poles. In Quebec's case, I believe 1200 of those large steal-frame high-voltage transmission towers were destroyed as well as about 30-35k wooden poles.

That much ice can close airports and rail links. Montreal is an island. At one point, the temperatures went up a little and the ice began to melt. Much of downtown was closed as large sheets of ice came sailing off building. All but one of the bridges over the St. Lawrence were closed as well as ice sailed off the superstructures and came crashing into the bridges.

This was caused by about 100 mm (about 4 inches) of freezing rain. Do that in a cycle every few days and you get a city that can't function.