First ANYWHERE MEETING and WORKSHOP

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1 Weather induced Emergencies: Opportunities and Challenges. The responders perspective. Genoa, September 6, Palazzo Ducale Franco Siccardi Mediocristan: a world in which the experts, from the observations of the past, are able to measure the uncertainty of the future. (tunnelling? narrative fallacy?) Extremistan: a world in which in some cases the future escapes the measures of the experts and surprises them. Building up a Civil Protection Knowledge Base following Taleb s suggestions. Is it possible to capture together the randomness of the processes living in Mediocristan and the rare processes living in Extremistan. (see, for example: Rossi, F., Fiorentino, M., and Versace, P., (1984), Twocomponent extreme value distribution for flood frequency analysis. Water Resour. Res. 20(7), Franco Siccardi 1

2 First ANYWHERE MEETING and WORKSHOP The decision maker of Civil Protection, at all levels, from municipal to supranational agencies, is confronted with dealing with uncertainty. The issue is here discussed with an example concerning the risk conditions of the mouth of the creek crossing the center of Genoa, the Bisagno stream, and concerning the case of the largest near miss disaster I directly know. The case was presented in October 2011 in Rome to an audience of lawyers, journalists and Civil Protection people in order to clarify the social relevance of the uncertainty in the design of hydrometeorogical risk scenarios. I ll avoid to use the word probability, like I did in the original presentation, and I ll substitute the concept with ten thousand identical parallel universes. Obviously we don t know, before the event, what s the universe we are living in. Based on the mental image that the example produces in the minds of the audience, considerations are offered on the use of the concept of scenario for responders of modern Civil Protection Agencies and for a sound policy of Disaster Risk Reduction. Franco Siccardi 2

3 First ANYWHERE MEETING and WORKSHOP Ten thousand identical Thirrenian Sea with the city of Genoa on top The stream The soccer stadium The covered stream The mouth of the stream The city of Genoa lies on the northern part of the Thirrenian Sea. Mountains are very near to the sea. The divide between the Apennine south face draining to the Thirrenian Sea and the northern face draining to the Adriatic Sea is elevated to m a.s.l.. The distance between the divide and the sea border is km. with ten thousand identical cities of Genoa with the same urban planning developed in the same way Franco Siccardi 3

4 First ANYWHERE MEETING and WORKSHOP Here the view from the road on the left bank of the stream. You see the low arches under the railway station. The stream enters the arches and exits, after less than two km, to the sea. River hydraulics teaches that, when, in an underground river, the flow rate exceeds the max design value, the river reaches the inner surface of the cover. When the river reaches the cover the flow rate is reduced sharply, to values largely less then the flow in the moments immediately before. The reflux wave propagates very quickly back. Upstream, where is not covered, the river swells. The flow rate in excess overtops the banks and flows along the streets. Franco Siccardi 4

5 The event theater!99y, Sunday, October xxth. A football match was scheduled between the teams of Sampdoria and Milan, at three o clock in the afternoon. In all the Universes, A, B, C,, the match was postponed by the referee because of rain of extreme intensity, just at the beginning of the match. I did know the course of events, not only trough instrumental observations and chronicles, but also from the direct account of two colleagues, professors of Civil Engineering, who "participated" in the event. Fans, to reach the stadium must go to the railway station, which sits on the beginning of the cover of the stream, cross through underpasses the railway park and take one of the two embankment roads, for a little over a thousand meters. The event prediction Let us imagine that the day before Sunday's match, in the ten thousand identical universes, with ten thousand identical planets earth, with ten thousand identical Mediterranean seas, in ten thousand identical gulfs of Genoa with ten thousand identical cities of Genoa with identical urban development, forecasts have been made of the state of the weather for the next day. And imagine that ten thousand identical situations rooms did issue the same prediction. "In the area of the central warning region of Liguria, which contains, inter alia, the catchment of the stream near the soccer stadium, it will rain with extreme intensity in the period from noon until midnight - local hour. The rain depth of the event will be about 200mm, or possibly a little higher". Let's now examine one of the universes in which the event was warned, call it universe A and describe the event and its consequences. Franco Siccardi 5

6 Theeventin theuniverse A Under pouring rain the most stubborn fans arrive at the stadium. Less than ten thousand in a structure that can accommodate up to forty thousand people. Under wet umbrellas they wait for the teams to take the floor. At three in the afternoon the two teams and the referee come out. The referee calls the two captains and verify, with them, the practicability of the field, which in reality is a quagmire. He throws the ball three times; three times the ball does not bounce. The referee whistles: the game is suspended. Fans run out to exits. Quickly start off on the two embankment roads to reach the train station. By now it is raining for three hours. The stream has already exceeded the level of flood banks but does not overcame the parapets. In the embankment roads the depth of water is up to tens of centimeters. Meanwhile, under the cover, the water level reaches the inner surface of the structure. The increased wetted surface sharply reduces the flow of the current. A wave of reflux explodes upstream from under the cover. The stream overcomes the parapets and expands on the embankment roads. It drags cars and pedestrians, bringing them within the current in the river bed or taking them toward the underpasses of the railway. It floods Vittoria square till to the sea. It floods the underpasses of the square and the shops, which fortunately are not open because it's Sunday. In an hour it's all over. The number of victims, due to the coincidence, entirely possible, but highly unlikely, of the postponing of the match with the retrograde explosive flooding due to the hydraulic conditions of the cover, it's tragic. Tragic for having, in addition, in the Universe A, swept two professors of Civil Engineering. Franco Siccardi 6

7 And now examine the event in the others universes: the universe B, C, D, E, F The second universe we examine, let us call it universe B, is obviously identical to universe A. Even in the universe B the most stubborn fans arrive at the stadium under a pouring rain. Even in the universe B they are about ten thousand. Under wet umbrellas they are waiting for the teams to take the field. Even in the universe B at three o clock in the afternoon, the teams and the referee come out. The referee call the two captains and verify, with them, the practicability of the field, which in reality is a quagmire. He throws the ball three times. Three times the ball does not bounce. The referee whistles: the game is suspended. Fans run out to exits. They quickly start off on the two roads embankment to reach cars, buses and trains. By now it is raining for three hours. Even in the universe B the stream is at the level of full bank. In the streets the water depth is up to tens of centimeters. It's hard to hurry away. The stream is scary. People are hurrying, not only because it's raining. But in the universe B the water level under the cover does not touch the concrete beams that support the road. The depth of precipitation the universe B got from noon to three o clock is slightly less then in universe A. The sudden wave of reflux does not form. In the universe B in less than an hour the fans are all away to safety. Many colds, but no injuries. The rain gives a few hours of rest. About nine o'clock in the evening it starts to rain again. The slopes are saturated by the rain of the early afternoon. The stream, already swollen, it swells even more. Around midnight, under the cover, the water level reaches the lower surface of the structure. The increased wetted surface sharply reduces the flow of the current. A wave of reflux explodes, upstream from under the cover. It overcomes the parapets and expands on the streets of the embankments. It drag parked cars, turning them within the current into the river bed or storing it towards the underpasses of the railway. Victoria Square, the subways and shops are flooded. Fortunately it's around midnight on a very wet Sunday in late October. No one around. No taxi. No buses. Only parked cars. Even in the universe B in just one hour everything is over. In comparison with the terrible disaster that took place in the Universe A, there are no victims. Only damages, large Franco damages Siccardi but only damages. 7.

8 The event in the universe B, that did happen in a moment of late night when the Genoeses were all at home is almost as unlikely-or likely- as that of the Universe A. And so, among others, two professors of Civil Engineering are still teaching hydrometeorology at the University of Genoa. They went to watch the match between Sampdoria and Milan, and survived because they were in the universe B, or C, or D.. So they discovered, after the event. Nassim N. Taleb, philosopher, essayist and Lebanese-born American mathematician, expert in financial mathematics, currently professor at the Politechnic Institute of the New York University and at the University of Oxford, published in 2007 "The black swan: the impact of the highly improbable". The book created intense controversy in mathematical circles. It deeply revises the paradigms of the forecast of future states of a system, based on the observation of past states. The thesis of the book, in essence, is that the human condition, which learns from experience, forces into a mental tunnel the predictions of what might happen. The prediction, or the scenario tunnel is formed by the experience of past events, among which the highly unlikely event almost never appears, because it is very rare one, and so almost never belonged to the experience. However, the harmful consequences of the highly unlikely event are so great that, although rare, they constrain our life. The decision maker of Civil Protection have to design scenarios of events affected by uncertainty, in which - fortunately rarely enters a black swan, a highly improbable event that creates disastrous consequences. Is the black swan to be taken into account? And how? Franco Siccardi 8