Monday, 27 October 2008

Flood Risk in Florence: Forty Years On

[Written on the 40th anniversary of the 3-4 November 1966 floods in Florence.]

The night of 4 November 1966 was marked by severe storms, floods and landslides throughout central and northern Italy. At 3.30 a.m. the River Arno burst its banks in the Casentino area near Arezzo and by sunrise water had invaded the historical centre of Florence, reaching depths of 3.65 metres at the Bargello and 3.96 m at San Niccolò oltr'Arno. Water eventually came over the top of the Ponte Vecchio but thankfully failed to demolish it. Thirty two of the 112 deaths recorded in the 1966 floods occurred in Florence, and the impact upon architectural heritage, art treasures, archives and libraries was incalculable. The damage is symbolised by Cimabue's crucifix, a work dated 1290-5 that hung in the church of Santa Croce (flood depth 2.7 m) and which, despite painstaking restoration, was 70 per cent destroyed by the flood such that it now lacks parts of the face of Christ.

Marble tablets that indicate the maximum flood level in 1966 (and for some cases in 1844 as well) can be found on walls throughout the centre of the city, including inside the Municipal Theatre. Periodically, video cassettes and books of photographs are issued to commemorate the floods, which are clearly an important point of reference in the city's history and in the life of all Florentines over the age of 40. Ten years ago a major national emergency management exercise, Arno-30, was held in Florence using the 1966 floods as the reference event for the scenario that was enacted. Arno-30 took place only a few years after three seasons of serious flooding had again affected the western periphery of the city from Piazza Dalmazia to Campi Bisenzio, which in 1991 was well and truly submerged.

Despite these developments, many decision-makers in Florence still regard the floods as detracting from the city's image and hence as something that should not be remember very publicly. Nevertheless, commemorations will take place and the 40th anniversary of the disaster provides many people in the Italian emergency management community with the opportunity to reflect on progress--or the lack of it. This article will consider the heritage of the floods and some of its emergency management implications.

Updating the impact scenario

Anyone who has visited Florence in recent years will be aware that the city is very different from what it was like in the 1960s. Restrictions on traffic have been imposed in the centre. Electric and gas-powered buses now circulate, two new metropolitan tramlines are under construction (trams were abolished in Florence in 1957) and Eurostar trains arrive at Santa Maria Novello station via a high-speed intercity rail link. Many historic buildings have been comprehensively restored, though the restoration of Santa Maria del Fiore, the cathedral, is so complex and delicate that it is taking decades to achieve. Moreover, tourist numbers have increased relentlessly, adding to the general overcrowding. Despite a steady reduction in the population of the municipality of Florence, which is now about 350,000, extensive urban renewal is underway on the flat plains to the north and west of the city. Light industry is abundant here, and at Calenzano there is even an oil storage facility with remarkably similar characteristics to the one at Buncefield in the UK.

In 1966 most of the physical damage was wreaked by a combination of water, mud and heavy oil from ruptured central heating tanks. Since then, oil has been replaced by natural gas as the main heating fuel, but on the other hand there are now an estimated 10,000 cars in and around the city centre. Where the Viali di Circumvalazione, the inner ring-road, dips under the main railway line, it is extraordinarily vulnerable to sudden flooding. Moreover, the city's road network frequently suffers from gridlock and work to expand the A1 motorway so that traffic can effectively bypass the city will not be complete until the end of the decade. Hence the plan to encourage people to self-evacuate from the city centre, which was published in the telephone directory in 1991, was withdrawn several years later for fear that it would only lead to more gridlock.

Despite the best of intentions on the part of planners, the hazard scenario remains almost unchanged. In the late 1980s a river basin authority was created along American lines, but it has had only a limited effect upon hydrological planning. The Arno is a flashy river--more accurately a torrent with serious pretensions to become a fully-fledged river. In mid-August its flow can diminish to zero, engendering severe eutrophication problems. The effect of a mighty river flowing through the centre of Florence is actually created by weirs which in high summer pond the stagnant water. In November and March the Arno can flow over the Chiusa di Santa Rosa, next to the Ponte Vespucci, with awe-inspiring discharge, roaring furiously and sending up clouds of spray.

River management strategy

Unfortunately, an ill-considered strategy to bring the national economy out of stagnation was put into place in 1967, the year after the floods. Temporary restrictions on the implementation of the 'Ponte Law' governing urban planning led to six months of free-for-all in granting building licences. The result was sudden, massive urbanisation of the banks of the Arno upstream and downstream of Florence, including the main pressure points where topography forces the river into a gorge and funnel effects occur on flood-flows. In 1967 one of the most vulnerable of the Middle Arno Valley communities expanded across the floodplain by 75 per cent.

The intense levels of development in central Tuscany mean that there is little opportunity to regulate flows in the Arno by natural means. Dredging and levée building are held to increase the flood hazard downstream. Hence, where possible, the River Basin Authority uses semi-structural flood defence measures and has thus created many casse d'espansione, parcels of land that is held vacant so that it can be flooded with minimal effects. A major dam and reservoir, the Bilancino, have been constructed in the Mugello Mountains north of Florence. However, this will only affect the River Sieve, a relatively minor affluent of the Arno, and in any case most of the casse d'espansione are necessarily situated downstream of the city centre, as there are the only areas where there was still space for them.

In central Florence the Arno has been dredged and the river banks have been raised and consolidated. The main obstacle remains the Ponte Vecchio, as little can be done to increase the flow through it beyond 2500 cubic metres per second (at the peak of the 1966 floods the discharge was 4000 cumecs). A bypass tunnel has been proposed, but there is little support for the idea, as it would involve serious hydrological and geotechnical problems, as well as huge costs. At least, decades of hydraulic and hydrological modelling, and of improvements in regional meteorological forecasting, mean that the physical side of the problem is now exceedingly well known.

Emergency planning strategy

In 1992 Italy promoted a national emergency planning and management strategy, the Augustus Method, which has unified methods of assessing risks and organising the response to disaster. It is based on the codification of emergency support functions for efficient communication during crisis situations. With regard to emergencies in Florence it provides the formal mechanism for coordination between the municipal, provincial and national levels of civil protection administration.

In the early 1990s the City of Florence inaugurated a new emergency operations centre in Via dell'Olmatello, located on the western periphery of the city strategically close to rail links and the airport. It was recently enhanced by the construction of a two-storey, state-of-the-art emergency control centre, which is shared with the Province of Florence. The latter has offices close to the city centre and an equipment storage facility to the north at Sesto Fiorentino.

Links between Florence and the surrounding communities have gradually been strengthened, but there are currently problems with the evacuation arrangements. The City's Civil Protection service has a four-volume emergency plan that is being updated in a somewhat different manner to the Provincial administration's fully computerised plan. Ensuring compatibility of arrangements for notification, departure and arrival of evacuees is a delicate problem in a complex, congested situation like the Florence metropolitan area. Moreover, the civil protection office of the Region of Tuscany, which is also located in Florence, has been dogged by problems of ensuring compatibility between the emergency plans of the nine Tuscan provinces.

Emergency response arrangements

The Olmatello centre is also the co-ordination headquarters of volunteer organisations. In Florence the Venerable Company of the Misericordia has an unbroken tradition of emergency response operations that stretches back to AD 1245. It has been joined by a number of other organisations, including several that deal with forest-fire fighting. All of them are registered with the government for civil protection work and they regularly train and exercise their members in this field. Hence, Pietro Bortone, the chief emergency co-ordinator for Florence boasts that if necessary he can mobilise 1000 volunteers within ten minutes and 5000 within one hour: given the wealth of experience available in the area and the high degree of organisation, this is probably a fair assessment.

In 1966 the emergency response was dominated by the so-called angeli del fango—literally "mud angels". These volunteers were mostly students or other enthusiastic young people but they lacked training and specific skills. For the last 15 years emergency response has been heavily regulated and increasingly subject to complex planning. In a future flood alarm, squads of trained volunteers would immediately start work on sandbagging the national library and state archives (both of which are situated on the banks of the Arno), lifting major works of art out of harm's way and conducting other pre-programmed activities. The municipal GIS system has registered the addresses and details of all pensioners and handicapped people in floodable areas and this would be used to give them assistance with evacuation.

On the more negative side, although the Italian Fire Service is highly professional and fully trained in all forms of rescue, measured per head of the population it is the smallest in Europe. Currently, initiatives are being pursued to expand it, including beefing up the volunteer contingent. The abolishment of military conscription in the 1990s means that there is now no surplus of military personnel to conduct disaster work. No one yet knows whether the increased professionalism of volunteer civil protection associations will be sufficient to compensate for these deficiencies when the next major disaster strikes Italy.

Flood disaster risk in the 21st century

Coincidentally, 2006 also marks the 30th anniversary of the industrial accident that occurred at Séveso near Milan and the tenth anniversary of the catastrophic flood that swept through the villages of the Versilian Mountains west of Florence. The latter event, which killed 13 people, had an estimated recurrence interval of 700 years. It galvanised the Tuscan emergency planning community into action.

However, it is one thing to have small mountain villages under water and quite another to have a major city, many thousands of tourists and a priceless artistic heritage under threat. Emergency management in Florence, Tuscany and Italy is still under-funded, and despite strenuous efforts it is still in need of further professionalisation, as well as greater political and public support. Fortunately, the basic model and organisation are very sound. We can conclude that as a result of changing patterns of human activity the flood risk in Florence has not diminished, but in any future event the emergency response would be vastly more professional and well-organised than it was in 1966.

In conclusion, one should not forget the other risks. In 1993 a very serious terrorist attack occurred in Florence, and in 2000 a fatal plane crash occurred at the airport. Earthquakes are a potentially serious hazard in the Apennines north of the city, while landslides and occasional snowfalls are hazards to many roads in hilly and mountainous areas. Hence there is no shortage of work for the civil protection community in central Tuscany.