Florida expect as 14’ storm surge.
I am in Pennsylvania, and my house is 12’ above sea level. I am (say) five miles from a tidal river. I am at least twenty miles from salty water. If the nearby coast were to experience a 14’ storm surge, would my house be in danger? If not, why not?
I can see both sides of it. On one hand 14’ is 14’. Both are more than 12’. On the other hand, I am far from the sea and the river, and this area has not flooded in living memory.
From this PDF:
Inland Extent
Storm surge can penetrate well inland from the coastline. During Hurricane Ike, the surge moved inland nearly 30 miles in some locations in southeastern Texas and southwestern Louisiana.
I think the exact extent of inland surge would depend on duration and on the details of the river allowing the water to back up. If local officials are telling you to plan for flooding, you probably want to do so.
Just an observation – Superstorm Sandy back in 2012 produced a thirteen foot surge. When it hit my home town in New Jersey, the water reached historic heights, going up Main Street almost to the Borough Hall and the Post Office, which I would have thought well above any water rise. It drowned out entire neighborhoods in my town and the one on the other side of our river, to the point where most of the houses had to be knocked down because of water damage, and the towns forbid rebuilding on the lots because of the possibility of further surges in the future (despite any indication they had been that high in the past). Many downtown businesses were destroyed or flooded out. One bank (of very long standing) had its underground vaults flooded for the first time ever. They rusted and were rendered unusable. The building still sits empty.
I know of a woman who was awakened, sleeping on her couch in her living room, by water rising and soaking her. Her living room was above ground level, and had never even come close to flooding. The entire house had to be leveled.
My hometown, although on a river, is at least five miles from the Bay that is the closest approach of the ocean. No one expected this sort of water rise there.
The same storm sent surges of water high enough to flood warehouses near Tarrytown on the Hudson River, 25 miles north of New York City. I don’t think anyone expected that, either.
So a storm surge of fourteen feet can cause catastrophic and expensive damage even if you’re five miles or twenty five miles from the ocean. Believe it.
I would expect that the lateral extent of the storm surge would also depend on the local geography, especially the elevation of the land around you. If there’s a path that’s all below the height of the surge (such as a flat road) the water can follow it. But if there is a higher ridge between you and the surge, with no roads or rivers or valleys cutting through it, that might protect a property from the surge.
I would also expect some local “choke points” to be flooded higher than the height of the surge, as water is pressed from all sides.
Plus, it’s measured from the normal sea level. In the PDF example, your high tide may be 2 feet above normal sea level, and then you get at 15’ storm surge.
This means that the surge itself is 15’ above the normal sea level, but the water could be as high as 17’, because the tide is going to come in and add 2 feet to the storm surge at some point.
you know there are some perks about living in a desert valley surrounded by mountains
Not too many but at least this is one of them … well until 2080 or 90 when Palmdale CA is beachfront property …
Here’s a nifty map that shows based on the storm category (across the top) where the storm surge risk is.
During Hugo people evacuated to a certain school that was supposed to be above the storm surge levels. They ended up having to stand on desks to keep their heads above the water.
I think this is the documentary where that is described (but I haven’t searched around to see).
Keep in mind that storm surges depend on wind speed and direction too, as well as barometric pressure. Then the geometry of the shoreline makes a big difference.
On a simple day, the Bay of Fundy can have IIRC up to 40 foot tides, even though it is part of the Atlantic Ocean with typically 6 to 12 foot tides. Some bays with more difficult sea access have even lower tides. Tides are the water in the ocean sloshing. If a bay is shaped precisely to allow a large surge to build up, you can get high tides. If the inland waterway area is difficult for the water to get into, it will not finish filling before it’s time to drain out.
Winds make things worse. If the wind is blowing water onshore, that’s bad. If a very strong wind is blowing a surge of water into a funnel-shaped inlet for an extended period of time, that’s even worse. If it coincides with rising tide anyway, worse still.
A hurricane is a rotating wind vortex. As it hits land the side blowing onto the land will force a lot of water into whatever areas of the shoreline are vulnerable. The other side of the eye is blowing the other way, from land onto the water, and does not get this surge. So where you are in relation to the eye making landfall is all important. Also, if the storm is moving more slowly, that force blowing the water onto the land is going to be worse for longer, and more likely to still be happening when high tide rolls around. Combine it with the tides when the moon and sun align, worse still.
(It doesn’t have to be a hurricane. Venice is at its most vulnerable when there’s a weather system blowing strong north up the Adriatic, pushing all that water to the north end of the sea and into the Venetian lagoon.)
So the short answer is - the surge depends on a lot of things, especially geography and wind direction…
Also keep in mind, the warmer the water in the gulf, the more water the storm is carrying. This will come down as rain as the storm moves north and cools. Add a foot or three of rain draining into the river estuary to the dozen feet of water coming upriver, and you can get an “aggravated situation”.
From an article in NYT today - effect of wind:
Even as some parts of Florida’s coast experience a catastrophic surge of seawater over their shores, Hurricane Ian has pushed water out of Tampa Bay, leaving it less than a foot deep in some areas.
The phenomenon, reminiscent of what occurred during Hurricane Irma in 2017, is likely to last only a few hours — and could suddenly reverse, with damaging results.
The outward flow is sometimes referred to as a reverse, or negative, storm surge. A storm surge occurs when high-speed winds push ocean water onshore, but in this case the winds drained the bay instead of flooding it.
Don’t forget tidal influence. I also live in NJ. We had about 15" of water in our house during Sandy. The “eye” of the storm made landfall in my town or immediately next to it. This happened at high tide with a full moon. The normal tidal swing here is about 5’ and a full moon can add a foot or more to that. Had it been low tide or a half-moon, we may not have had any water at all. We’ve since elevated our house and (hopefully) are safe. In order for us to get water in our living area, the entire island would have to be under nearly 10’ of water. BTW, we are about .5 mile from the ocean on one side and what is called the bay (technically a sound, I think) on the other. In our case, the flooding came from the bay side.
I do a Google Streetview of some areas of Sarasota - Bird Key, Bay Isle - and some of those houses don’t look more than a few feet above the water level when the Google cameras were doing their rounds. How did anyone think that was a viable location to build?
Footage from Fort Myers shows a shark swimming in the flooded street (you have to scroll down through some amazing videos to find it):
Part of the issue we’re going to see is that typically the Gulf side of Florida doesn’t actually get hit by hurricanes, or at least not ones going west to east very often. The more typical outcome is that it hits the eastern coast of Florida, then hits the Gulf side of the state after expending a lot of energy at landfall. And most importantly, there isn’t really storm surge when a hurricane is coming from land and heading out to sea like they typically do.
So my suspicion is that a lot of that stretch of coast probably has a bunch of stuff built in places that they wouldn’t build it if they were expecting storm surge. Kind of like hurricane Sandy- that part of the country hadn’t been hit by a real hurricane in a long time, so that even a relatively paltry Category 1 storm like Sandy still did an undue amount of destruction for a storm its size.
I think the fact that your hometown is on the river had a lot to do with it . I am in NYC, about 8 miles from the ocean and 4 miles from the bay. There was no flooding in my neighborhood from Sandy. The closest flooding was a couple of miles away, where there are some creeks that empty into the bay.
Oh, there’s no doubt about it – the water has to get there somehow. The point is that my town is pretty far upriver, and, to my knowledge, has never flooded that far in historic times. Ditto for the flooding of Tarrytown, NY, well up the Hudson from New York Bay and even further from the ATlantic.
as others have said, it is complicated. Of all the factors mentioned, the speed of advance of the storm is one of the most important. The ocean is an inexhaustible source of water. When the bulge (height of the storm surge) reaches to coast, the amount of flooding is a matter of time. If the storm is moving quickly the flooding will be less. If slowly, more flooding. When a storm approaches faster is (almost) always better. If you live within a few miles of the coast then net wind speed can be important (net speed is the rotational wind speed ± speed of advance), but for most people, water is the major threat. Your height above sea level is only one factor.
But as we saw also in Texas a few years ago, or just now in Orlando, rainfall is also a factor. There are two threats - water that has nowhere to go in a flat area like Orlando, or water than has one place to go (like we’ve seen with a not-hurricane in Kentucky), if a foot or two falls in an area where it all funnels down into a smaller valley it will raise the overall level several feet. More incline means faster moving water, which worsens the outcome. Even in a relatively flat area, a few feet of elevation will make all the difference to the neighbouring areas.
And… slow-moving is a risk here too because the part still over the warm ocean is picking up water to deposit on the land.
Are you sure about that? A hurricane is not a spinning object. It’s the overall pattern of air movement.
As a general rule of thumb, the hurricane’s right side (relative to the direction it is travelling) is the most dangerous part of the storm because of the additive effect of the hurricane wind speed and speed of the larger atmospheric flow (the steering winds).