Nature | Venice: I am not making this up

Acqua alta: MOSE will fix everything

March 25, 2010 1 Comment

Now that I have pounded the subject of acqua alta into unconsciousness, you may be wondering if there are any solutions. It’s not unreasonable, I guess, to want to suppose that there could be some action(s) that would limit or even prevent water from inconveniently covering your street, even for only two hours.

Certainly many of the articles which continue to appear, year after year — there must be a workshop in a cave where some crazed Geppetto keeps producing stories on how Venice is being engulfed — tend to make it sound as if Venice’s health and future happiness depends almost exclusively on keeping the water out.

This is not acqua alta, it's just acqua.

So let me urge you, before we continue, to disregard, as far as you can, the drizzle of extravagant statements drenching almost every article about this project. Such as comments by journalists in love with their clever way with words (“…soaked Bruno Maglis have become more the rule than the exception…” You’ve got money for Maglis — or for any kind of shoes — but you haven’t figured out that you can take them off to keep them dry? Wow… And by the way, it isn’t true), or this, by an Italian professor of physical oceanography at MIT: (“”The gates are really the only solution.” Really? The only?), or the claim that high water really, really distresses the old people. All the old people I’ve ever talked to are the ones who make the least fuss about it of anybody.

The good news: There is no lack of useful and feasible ideas on how to limit or prevent high water in the city. In fact, we have been inundated by a plethora of proposals, many of them simple, easy, not damaging to the environment and cheap.

The bad news: Only one solution has been chosen, and it is none of the above. Sometimes referred to as the “floodgate project,” this savior is called MOSE. It is the biggest, most expensive, most drastic, most irreversible, heaviest-impact-on-the-lagoon-as-a-whole solution that anyone could have imagined. I say that because if there were a solution that could have been more drastic and more expensive, they would have picked that one instead.

What is it?

MOSE stands for Modulo Sperimentale Elettromeccanico, or Experimental Electromechanical Module. It consists of a sequence of a total of 79 steel caissons — boxes, really — lying on the lagoon floor, which can be raised to form a wall which will block an exceptional incoming tide.

Where is it?

A view from the Adriatic, looking over the Lagoon and the three "mouths," or inlets, through which the tide comes and goes every six hours. (R to l): San Nicolo, Malamocco, Chioggia.

The Venetian lagoon is enclosed by a long strip of barrier islands which block the Adriatic Sea except at three inlets (called “bocche,” or “mouths”) through which the tide passes every six hours, coming in or going out. This exchange of water is crucial to the lagoon’s ecosystem.

How does it work?

Each of the three “mouths” of the lagoon has been dug to accommodate a concrete frame installed on the bottom and sides of the channel. Attached to this frame, by means of hinges, are the aforementioned 79 metal boxes which normally will lie on the channel bottom, filled with water.

These diagrams show the steps involved. Note that one caption states that there 78 of these caissons; there are 79.

If an exceptional high tide is expected (or more than 110 cm [3 1/2 feet]) above median sea level, the water will be pumped out of the boxes and compressed air pumped in which will cause them to rise up and form a wall preventing the water from entering the lagoon. When the tide subsides, these caissons will be filled with water again and they will return to their dormant state on the inlet floor.

When will it be used?

The job of this colossal construction is to prevent — not just any high tide, but an exceptional one — from reaching the city. The frequency of a tide of this magnitude is predicted by the city as being four times a year.

Therefore, any high water up to 110 cm is going to come ashore just as it always has, and we will continue to break out the boots and merchants in low-lying parts of the city will continue to stow their merchandise and keep their squeegees at hand to sweep the receding water out the door. Their keening laments will also be primed and ready to go.

Who thought this up?

As with many large public works, it is the love child of politicians, engineers and builders. In this case, an assortment grouped together as the Consorzio Venezia Nuova (New Venice Consortium). These are not lagoon-huggers. Many of its members are in business, often doing the sort of work that MOSE requires.

1973: The Special Law for Venice is passed, which declares the city’s welfare to be of “preeminent national interest.”

1975: The Ministry of Public Works announces an international competition for project designs which would limit high water. Five projects are accepted for evaluation.

I will leap ahead here and spare you the year-by-year chronicle of yes/no, he said/she said, did so/did not, claims and counterclaims. It’s like Jarndyce and Jarndyce. A full account of this 30-year struggle would be a ponderous assortment of lists of names and companies and government agencies and ministers, environmental organizations, suits and countersuits at every level, from Venice itself to the European Court of Justice in Luxembourg. By now, the only people in the world who have not been involved in this in some way are you and me.

By now, 63 percent of the work is finished. But the controversy is still very much alive.

Next: Why everybody isn’t excited about it

History, Nature, Problems, Water

Acqua alta: reviewing the basics II

March 9, 2010 No Comments

Here are two elements of high water which aren’t usually — perhaps not ever — mentioned, much less interpreted, in the typical story, the kind that likes using emotional words like “invade.” ( As in, “The water invaded the city.” Stormed the battlements. Conquered the kingdom, wrought havoc, death and destruction, setting towns to the torch and sending everyone into slavery. You know, the usual high-water scenario.) Where was I.

Venice is not sitting at median sea level. That wouldn't make any sense. — Venice is not sitting at mean sea level. That wouldn't make any sense.

One is what the numbers actually mean. Venice does not float like a lily-pad at sea level. The lowest area in the city, the Piazza San Marco, is already 80 cm above the water’s surface when the water is at mean sea-level. Therefore any height that’s reported isn’t as high as it sounds if we were just standing on a street somewhere, measuring upwards from our feet, because the starting number isn’t zero.

Example: 110 cm converts to three and a half feet, which sounds scary. But someone standing in the Piazza San Marco will have water reaching up only 30 cm from their feet, or roughly just below their knees (11 inches). Someone elsewhere in the city might well not have it even that high. Or at all. Because of Point Number Two.

Surf's up near the Rialto Market by the eponymous bridge. Just behind me there's no water on the ground at all, except for some rain puddles.

Point Number Two: Headlines blaring “VENICE IS FLOODED” imply that the entire city, all three square miles of it, is going under for the third time. In fact, a tide up to 110 cm will dampen 14 percent of the city. Not a huge percentage, I think one must admit. Up at 140 cm (the relatively rare Code Red, “exceptional high water”), it covers almost 50 percent of the city, which is more impressive, except that the frequency of a tide this high is fairly low — five times in the ten years between 2000 and 2010. And still, one isn’t referring to every square inch of Venice. Amost half of the city is still high and dry.

For all of Venice to be flooded, the tide would have to rise well beyond 200 cm (the epochal acqua alta of November 4, 1966 reached 194 cm). The city’s tide office doesn’t estimate above 200 cm, at which level 86 percent of the city would be underwater. I don’t say that would be entertaining, but it would be so rare that I’d suggest saving the doomsday vocabulary for it, and not waste the drama on more mundane tidal events.

This is the only example of this extreme solution to acqua alta I've seen so far. What it implies to me is that whoever owns this property isn't expecting to be available to sweep out any water. Or that whatever's inside is so valuable that it probably should be in a vault somewhere. My own experience leads me to wonder if a seal this tight wouldn't potentially force the incoming water up inside through some hitherto unnoticed crevice.

Our little hovel is safe up to the three-tone level. At four tones, it’s time to take the tarps off the lifeboats. We discovered that last December 1 at about 9:15, when the water reached the four-tone level and began to slide under our front door. Then I discovered it was also coming through a fissure in the wall under the kitchen sink, as well as up through a fissure in the stone flooring. That was more exciting than almost anything I can remember. So please don’t suppose that my viewpoint is the result of my not having to worry about water under the bed. I just want to recalibrate the popular perception of this phenomenon. Obnoxious. Not catastrophic.

We have a calendar, on sale at any newsstand, which traces the predicted tide levels each day of the year. But those are only estimates based on what’s normal. For more timely updates, I check the data on the city’s Tide Center website. You can also sign up to be alerted of the rising tide via text message (SMS) on your cell phone.

All these advisories are what make it really hard for me to feel sincerely sorry for anyone who might find that water had caused any damage to goods or appliances. It’s not like it comes like a thief in the night.

I leave you with the key phrase which ought to simplify the whole business if you’re here long enough to need to know it: Hip waders. Just do it.

The fact that the pump is working demonstrates the limitations of the barrier across the door. However, it's clear that without the barrier things would be much worse. I assume he's doing rough calculations of the power of the pump relative to the speed of the rising tide.

History, Nature, Problems, Water

Acqua alta: reviewing the basics I

March 8, 2010 No Comments

Let’s start with the most basic fact of all: Venice is sitting in the middle of a tidal lagoon. This means surrounded by water that rises and falls. I don’t mean to keep harping on this, because I know it sounds really dumb, but not much dumber than all those stories that get published and broadcast that make it sound as if water on the ground here were stranger and more upsetting than four sharks singing “Shine On, Harvest Moon.”

How high the water will rise might vary from the official prediction based on a few factors, but when it’s looking imminent I’ve definitely got at least one eye on the barometer, the wind sock (on the computer) and the moon. Wait, that makes three eyes. Well, you know what I mean.

This shopkeeper near the Piazza San Marco is keeping his high-water records this way.

Data on the tides began to be recorded regularly after an exceptional high water in 1867 (153 cm above average sea level). In 1908 various monitoring stations were installed to more precisely measure the height of the tides, and in 1914 the pertinent data on the barometric pressure and the direction and force of the wind were added.

For events longer ago, historians can only turn to various chronicles and accounts in which the quantities aren’t always easy to assess. As in: “The water rose high enough to ruin the wells.” A flooded well would, in my view, be much more distressing than some water on the floor, seeing as the supply of fresh H2O in Venice was not infinite.

The main high-water factors are the following:

The season. If the acqua is going to be alta, it will usually be between September and April. Articles which refer to its frequency are often misleading because they use aggregate numbers which give the impression that it’s a monthly occurrence all year long. While there might be pesky clusters of high water events in winter (as happened this year), the likelihood plummets to June; it has never been recorded in July and August.

Phase of the moon. The tides are highest and lowest when the moon is full and when it’s new. Actually, the moon is the only component to this phenomenon which isn’t even the tiniest bit likely to swerve from the forecast.

Atmospheric pressure. When it’s low, the water is high. When it’s high, the water is low. If we tap on the barometer and see that it’s gone to the bottom of the scale, there’s no getting around the likelihood that the water will be high. The barometer won’t tell us how high, but we can look out the door and make a guess. A barometer is a great friend to have because it cannot tell a lie.

Wind. If the scirocco is blowing, it will definitely aggravate the situation. The scirocco is also obnoxious because it’s warm and humid (get one blowing in the summer and you’ll wonder if you took the wrong exit and ended up in Amazonia). But as it’s from the southeast, it will blow into the lagoon and — putting it very simplistically — push against the tide and prevent it from going out in a timely and efficient fashion. On the contrary, it seems to work very hard to keep all the water in the lagoon all at once. I try to avoid anthropomorphizing the natural world here, but I have to say that sometimes it seems like the wind just does it on purpose.

When a strong scirocco is blowing, I don’t hear wind so much as I do the heavy surf rolling up in close-order-drill on the Lido’s Adriatic beaches. It’s a deep, rumbling sort of roar off in the distance, impossible to mistake for anything else.

Yes, the water is rising in the Piazza San Marco. But the owner of the cafe clearly is not too concerned, otherwise he wouldn't have bothered setting up all those chairs and tables.

There is a warning system to alert the city that within an hour, water will be rising in the Piazza San Marco (the lowest point in the city) and, by extension, at other various low-lying areas. This information comes from a monitoring system at the mouth of the lagoon at San Nicolo, and at other points in the lagoon.

Until two years ago, the citywide warning system was a few sirens which emitted a sequence of rising wails. The first time I heard them they woke me from a deep sleep in the middle of the night — a sudden violent tone swooping upward, overlapped by another one just following it, and then by a third. Scared the hoo out of me — it was like the Three Weird Sisters in Macbeth going mad.

But what they didn’t tell you back then was how much water was going to come ashore.

Two years ago, the system was refined. Now there is only one siren-swoop, after which comes a steady tone which indicates the maximum predicted height. One tone = 110 centimeters above sea level. Two tones = 120 centimeters. Three tones = 130. And four tones = 140 and above. This is what they sound like. I can tell you they’re very effective. There may not be any way you can ultimately prevent water from coming indoors, but you cannot possibly say you had no warning.

This tide-level notice board at Piazzale Roma gives the height of the tide in real time, indicates whether it is rising or falling, and what time the next maximum (or minimum) will be. And how high or low. Very useful, if you happen to be at Piazzale Roma. — This tide-level notice board at Piazzale Roma gives the height of the tide in real time, indicates whether it is rising or falling, and what time the next maximum (or in this case, minimum) will be. And how high or low. Very useful, if you happen to be at Piazzale Roma.

Nature, Problems, Water

Acqua alta: some plusses and minuses

March 5, 2010 2 Comments

I realize it may sound strange to refer to there being “plusses” to acqua alta. Let me just say I don’t mean “plusses” in the sense of winning a large chunk of the lottery. But there are in fact some positive aspects to it.

The tide has dropped and left our street looking clean but feeling a little icky under our feet.

For instance, many Venetians have told me that acqua alta is a good thing because it washes the streets. This is true. Unfortunately, it also deposits a fine layer of silty slime. And while it does remove some of the dog poop, it also leaves detritus behind, so the general landscape isn’t much prettier than it was before the water rose. So, you know. We could go on like this, pro and con, all day.

But let me point out something that is hardly ever remarked on, in the many and varying accounts of this event: Acqua alta is actually a very good thing for the barene (the lagoon’s marshy wetland islets). If we can focus our minds briefly on something other than our own immediate convenience, it’s worth remembering that the lagoon has its own needs which are being met ever more rarely. So if it likes a good soak, I don’t see why it (by which I mean the whole ecosystem: microorganisms, plants, birds, etc.) can’t have it. Also — speaking selfishly — rowing when the water is high is magic.

A view of one of the nearly submerged barene in the northern lagoon, enjoying its bath almost as much as we're enjoying rowing around in a little Venetian sandolo.

Back in town, here are a few of the positive and less positive aspects of acqua alta, as I see them:

It doesn’t last long. Acqua alta is a tidal event. Unlike your raging rivers, it has a predictable time frame. The tide comes in for six hours, and goes out for six hours. True, sometimes it doesn’t go out as much as it should, but it eventually does go out. This coming and going means that it’s really bothersome for only about two hours.
It’s fairly tranquil. Inexorable, I grant you. Anyone who hasn’t watched the water rising near one’s front door (as we have) hasn’t fully grasped the fundamental meaning of “Time and tide wait for no man.” But the typical reports of high water in Venice make it sound as if Niagara Falls is pouring through your living-room window (CNN once referred to the “Adriatic bursting its banks.” Banks? Bursting? Are we suddenly in Holland?), when in reality it’s more like the bathtub slowly overflowing. Water in both cases, I agree, but not really the same.
It is predictable. True, raging rivers are also predictable, but some of the factors influencing acqua alta, such as the direction of the wind, can change. In addition, we get plenty of warning. If you don’t want to wait for the sirens to blare, just look at the barometer. (You do have a barometer, don’t you?) The lower the pressure, the higher the water. Check the sky: Full or new moon? There will be more pronounced highs and lows. Wind from the southeast? Not good; it will prevent (or slow) the regular retreat of the tide. We want a southwest wind (garbin) or better yet, northeast (bora). Those will settle acqua alta’s hash.

I’ll tell you what’s really annoying about acqua alta, apart from the distraught articles that keep getting published. It’s not that you have to put on boots for a few hours. It’s that:

When the tide goes out, it leaves all kinds of detritus
This is a modest example of a street not long after the tide has gone out. Clumps of eelgrass and bits of reeds are unavoidable and even not so ugly. It's the other stuff, pieces of plastic and styrofoam and general junk littering every wet street that are ugly. Unavoidable, fine. But there is no telling when, if ever, someone is going to sweep it up.

all over the sidewalks. Stuff that was just floating gently comes to rest on whatever pavement was just below it when the last inch retreated. Also, if anyone puts out a plastic bag of garbage the night before (yes, despite the warning sirens — dumb, I agree), that bag will be floating around the street and either settle on the pavement somewhere or drift out to sea. Neither case is highly desirable, though obviously the second is worse.

Once the water lifts your bag of garbage, it's not yours anymore. So hey, let it go wherever or however it wants to, who cares.

The garbage-people will be extremely slow in collecting the trash and/or — make that just “or,” they can’t seem to do both in the same day, even when the sun is shining — sweeping away the detritus, which means the streets look more or less like a slum. The garbage-people are slow because … I’ve tried to understand this… It may be because they are already so desperately overworked that high water adds an insuperable burden (you’re believing this, yes?), and because they are otherwise urgently and industriously occupied in setting up or taking down the temporary walkways over the high water (sometimes yes, mostly no). But they seem to get a special pass on their normal work when the acqua is even moderately alta. I can’t explain it, except to compare it to the mysterious sore throat which a kid who doesn’t want to go to school suddenly develops when it rains or snows.
Transport gets all scrambled up,
not only for taxis and barges but also some vaporettos and/or motoscafos. They have to change their normal routes because the high water prevents them from passing under certain bridges. There are alternatives by which they resolve this temporary dilemma, but it adds inconvenience to your own trajectory. As for heavy work boats and taxis, they either have to pick another route from A to B, or wait for the tide to turn. Tiresome, true, but hardly the stuff of calamity.
Your front door swells. If you have been so unfortunate as to have even an inch of water come inside (and for many people, this just means it has reached the edge of a staircase leading up to their apartment, not the apartment itself), and your front door is made of wood, it will soak up the water and then want to stick. It will take a while to dry out. Like, maybe weeks. You may end up having to sand it down some. Irritating. Not disastrous.

Acqua alta? We'll just put that lamppost up higher. This was one of the more clever responses to the big one of November 4, 1966. Also, you can see that the dogs love it.

I think if you’re going to live here you need to accept the fact that you’re sitting in the middle of a tidal lagoon. If that creates really too many problems, it might be good for you to consider moving. At least to the second floor, or maybe across the bridge to the mainland. No more worries about the tide coming ashore over there. All you have to deal with there, even as nearby as Mestre, are rivers and rain and totally inadequate storm drains. Which leads to flooded basements full of water that actually has little or no natural urge to recede. Fun.

No emotional articles about that, though. Who cares about a foot of water in somebody’s garage? Nobody — at least not until that somebody snaps a picture of a person rowing around the car or trailer.