A Question of Resilience
Global warming, by rising the level of seas around the world and boosting the risk of floods, is increasingly threatening the world: once more, studies confirm. And the fact that most big cities, that host the majority of the world's population, are built by the water, as the C40 Cities Climate Leadership Group reports, makes the question even more serious. In the next century, the effects on cities such as New York and Miami, London and Sidney will be devastating, but the risk is particularly high for less developed countries, where natural calamities have always left damage beyond words. This article will take into consideration the case of the city of Venice, one of the most important UNESCO World Heritage sites in Italy and worldwide, constantly dealing with the problem of high tides, the reason for which the government has implemented a massive project to prevent floods and grant a better life to its citizens. It will also draw parallels with other cities to see how the different administrations are dealing with the problem of floods, eventually developing solutions to share technologies and knowledge in a collective effort to (perhaps) help most vulnerable countries. This is, after all, a question of the capacity of cities, countries and administrations to adapt to changing conditions. A question of resilience.
Studies on global warming and effects on coastal cities
A study conducted in 2013 by the University of Innsbruck shows the impact that rising temperatures and oceans will have on a number of UNESCO Cultural World Heritage sites, indicating the percentage of land loss by the various countries at different temperatures and different sea-levels for the next 2000 years. If the current global mean temperature remained steady for the next 2000 years, about 40 UNESCO sites would be affected by the rising water. The number of sites would rise to 136 if the temperature increased of 3° Celsius, a scenario, experts say, that is very likely to happen. and 7% of the global population would live in lands that will be below the sea level by that time. This is alarming, but even more shocking is another study by the World Bank, which shows the threat constituted by flooding to coastal cities and the cost it represents for administrations. It pinpoints which cities are most at risk and indicates how the overall cost for larger coastal cities could rise to $1 trillion a year if they do not adopt efficient measures. In order, these are the most endangered cities: Guangzhou (China), Miami (USA), New York (USA), New Orleans (USA), Mumbai (India), Nagoya (Japan), Tampa (Florida), Boston (USA), Shenzen (China), and Osaka (Japan), an order that varies greatly by considering the flood cost as a percentage of GDP: for Guangzhou (China), New Orleans (USA), Guayaquil (Ecuador), Ho Chi Minh City (Vietnam), Abidjan (Ivory Coast), Zhanjing (China), Mumbai (India), Khulna (Bangladesh), Palembang (Indonesia), and Shenzen (China), a catastrophe as such would mean a cost equal to more than 1% of their GDP. In short, data show how rising sea-level, by increasing the risk of floods, constitutes a serious threat especially for underdeveloped countries, whose economies would be seriously harmed. Does the world have a response to increasing floods? Let's take a closer look.
The case of Venice
The Italian city of Venice has gone through ages of great splendour: it originated a state that existed for over a millennium and it was a major maritime power during the Middle Ages and Renaissance, dominating the commercial routes in the Mediterranean and with the East. It is considered one of the most beautiful cities in the world and it is among the UNESCO Cultural World Heritage Sites.
Venice is a city built on water, rising on an archipelago of 118 small islands in a lagoon. The foundations of its buildings are constructed on wooden piles that are separated by navigable canals and connected by 409 pedestrian bridges. Most of the piles are still intact after centuries of submersion, but the city is slowly sinking into the water, and over the past years the situation seems to have worsened. This is happening because of different reasons: industrial necessities first altered the ground water in the lagoon and nowadays dumping from other cities is slowly eroding the piles. Moreover, the city deals with increasingly frequent and serious flood tides pushing in from the Adriatic sea in autumn and winter, a phenomenon that in Venice is well-known as “high water”. Several factors determine the level of the tide: the motion of celestial bodies, and meteorology, which varies a lot according to winds, rainfalls and so on. Over the last decade, episodes of exceptional high tide (over 140 cm) have occurred almost every year (+156 cm in 2008, +145 cm and +144 cm in 2009, +144 cm in 2010, +143 cm in 2012, +143 cm in 2013), with the result that life in the city is getting more and more difficult. If man can't beat nature, perhaps we will have to say goodbye to one of the most beautiful cities in the world soon. Or maybe not. In fact, Venice could have developed a smart solution to the problem of high tide.
The Mose project
The Mose project is realized to protect the city of Venice and the lagoon area, that measures 550 square meters, from high tide. It is constituted of mobile dikes that can temporarily separate the lagoon from the rest of the sea, defending Venice from exceptional events and also from the regular high waters. The project is commissioned by the Italian government, through the Ministry of Infrastructures and Transportation, and carried out by Consorzio Venezia Nuova, an union formed by several Italian companies, operating at the national as well as local level, that jointly worked at the construction of the barriers. The project has an estimated cost of 5493 million euros, it was started in 2003 and it is programmed to be finished in 2016.
The barriers are set at the mouth of Porto di Lido, Malamocco and Chioggia, the three passages through which the Adriatic sea propagates in the lagoon. The total number of barriers is four, and they are constituted of 78 independent floating platforms. This shape guarantees great flexibility in the defence of the lagoon: at different levels of pressure and height of the tide, the barriers can be closed to whatever degree is necessary.
The operating principle of the floating platforms is the same as submersibles, remaining on the sea bottom when they are weighted down by water, and coming to the surface when the water is expelled with compressed air, in order to prevent the water from flooding the city.
The inauguration of the Mose system took place on October 12, 2013 and today more than 80% of the project is completed. The Mose constitutes a defence for Venice against tides up to 3 meters (the highest tide registered until now is of 1.94 m) and against a rise in sea-level to 60 cm in the next 100 years. It protects Venice from the damages of the frequent high tide and from plausible catastrophic future events, thus improving the quality of life in the city.
Criticism on the project
The intervention in the Venice lagoon brought about by the Mose project was analyzed, with a critical eye, by Luigi D'Alpaos, Professor of Hydraulics Engineering at the University of Padova, who studied for several years the hydrodynamics of the lagoon. In his book, Fatti e misfatti di idraulica lagunare (Facts and Misdeeds of Lagoon Hydraulics), he directly addresses the events relative to the launch of the Mose project, pointing out how its realization substantially altered the natural morphology of the lagoon. The barriers prevent flooding when the tide rises but, according to the expert, the modified morphology of the lagoon constitutes a more serious problem: it needed to be taken into account in the outline of the intervention, because, he explains, it governs the hydrodynamics of the lagoon system. The problem, therefore, cannot be solved with the sole construction of the barriers, but it needs to be conjugated with the safeguard of the lagoon, which should be the principle before all actions. In reality, the opposite happened: the lagoon's morphology safeguard is an issue that was basically ignored in the design of the Mose project, with the effect that the construction of the barriers has worsened the conditions that brought to the current situation, because the barriers increase the wave motion, which is responsible for the erosion of the bottom of the lagoon. Moreover, the Mose project consists in a series of measures that are completely new in the engineering field, and therefore imply risks and potential problems that would not rise if, as D'Alpaos points out, the designers had contemplated already experienced solutions, such as the Delta Works in the Netherlands.
Mose in the world
From 2006 Italy, with the Mose project, is a member of the international network on flood defence I-STORM “International Network for Storm Surge Barrier Management” together with England, the Netherlands, Russia, Germany and the United States. The core objective of the network is to share information, experiences and good practices relative to the large movable storm surge barriers in the different member countries in order to optimize their management. In this context, the Mose project has been recognized as resilient, highly advanced for its technology but also in terms of the multidisciplinary plan that was adopted by Consorzio Venezia Nuova for the support of the coast, the restoration of the lagoon habitat and the monitoring of the most endangered urban parts and polluted sites. How are other cities reacting to the threat of rising seas and flood risk? Here we take into consideration some of the cities belonging to the I-Storm network in the European context.
I-Storm cities
London and the Thames Barrier
The Thames Barrier is one of the largest movable flood barriers in the world (520 meters section of the river). It is constituted of ten separate movable gates, 20 meters high, across the river Thames, and it serves the function of sealing part of the river from the sea. It protects 125 square kilometers of central London from flooding when the tide is high. It became operational in 1982 and it is operated by the Environment Agency. The closure of the barrier takes 1.5 hours, and until March 2014 it was carried out 174 times. As for Venice, the phenomenon of high tide has been registered in increasing number throughout the years, hence determining a more frequent use of the barrier.
Rotterdam and the Delta Works
The Netherlands are probably the most advanced country in terms of flood management. After the flood of 1953, in which nearly two thousand people died and 150.000 hectares of land were flooded, the Delta commission was inaugurated to execute the construction of a series of dams, sluices and barriers and therefore increase the safety of the Delta area, a project that has been sometimes referred to as the “eighth wonder of the world” because of its vastness. In 1958 the first storm barrier (Delta Work) in the river Hollandse Ijssel was already operational. By 1986 the Delta Works were finished, for a total of fourteen engineering projects, that shortened the length of the dikes of 700 km, improved fresh water supply for agriculture and the water balance of the area and encouraged traffic between the islands as well as waterway shipping. Recently, further developments have concerned the Delta Works because, due to climate change and the rise in the sea level, the existing dams had to be heightened, this being a clear sign that the reinforcement of barriers does not represent the end of the struggle against the sea.
In sum, the countries belonging to the I-Storm network have established cooperation and mutual interest in exchanging information and experiences in the field of flood defence. So far, the network only counts six countries, but flooding is a threat that is becoming global. The study on the UNESCO sites reports that more than 60% of the affected populations are in China, India, Bangladesh, Vietnam and Indonesia. These countries, characterized by big populations and weak economies, that could be seriously damaged in case of floods, do not have the resources to sustain costly remedies to the threat of the rising seas. Intuitively, one can predict that the future will not be rosy for them. History has showed us, with the tsunami of 2004 in South East Asia, the Katrina hurricane that devastated New Orleans in 2005, the 2011 earthquake and tsunami in Japan and the 2013 flood in the Philippines, just to give some examples. Places that were completely undefended and that are still struggling to recover their economies, after years. These days Bosnia and Serbia are being tragically flooded, with an increasing number of lost lives. The World Bank study has pointed out how civic authorities around the world should consider disaster planning and implement comprehensive insurance programmes to cover future losses – programmes that could be highly cost-effective given the fact that risks are highly concentrated and therefore investment is focused. This is a great advantage, but the problem for weaker countries remains. It is a fact that rising seas and an increasing number of natural catastrophes will eventually affect everyone. Therefore, it should not be considered as a problem of individual countries. Global action needs to be undertaken in order to face reality and help those countries that cannot cope with such losses. Only by taking one step at a time, starting from the extension of membership to more countries in the I-Storm network, to share knowledge and technologies against floods worldwide, to the creation of a global fund to address insurance programmes and flood emergencies, a comprehensive action will become truly effective in the battle against global warming. All administrations need to be aware of this fact: united we stand, divided we fall. It is a question of resilience.
