Acqua alta

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Acqua Alta literally means "High Water". The phrase refers to the tidal flooding that periodically affects Venice, especially in the late fall. The city of Venice provides a Acqua Alta Forecasting and Warning that allows people to take action in case a hight tide is approaching.

An image from an Interactive Diagram dispaying which sections of Venice flood at each level of Acqua Alta

Effects of Acqua Alta

Flooding affects the physical infrastructure in Venice in a variety of ways, most of which have been recognized since the early days of the city’s existence. Manuscripts in the Venice archives chronicle the frequent requests for maintenance along the inner canals of the city ever since records were kept242. Natural erosion due to fluctuating tidal water levels is a fact of life in a place like Venice243. Construction materials are gradually weakened by the constant wet-dry cycles and by the natural salts and unnatural pollutants contained in the tidal waters. A simplified taxonomy of the primary elements of the city that are negatively affected by exposure to the salt water of the lagoon and canals includes:

Above-ground Infrastructure
Streets and Pavements

A Flood in Saint Mark's Square
Bridges
Docks
Underground Infrastructure
Utilities
Sewers
Private and Public Buildings
Artistic and Architectural Heritage* Churches
Palaces
Convents
Public Art
Street Furniture
Canal Walls

While there is no doubt that these elements of the built environment are to some degree harmfully impacted by the gradual, but incessant, assault of the waters of the lagoon, the precise extent of the overall impact of flooding on the state of conservation of today’s architectural and urban structures is hard to measure and the costs nearly impossible to quantify. What is clear is that there are several concurrent factors at play in the undermining of Venice’s built environment. Perhaps flooding is not the most destructive of all of the forces participating in the constant interplay between the liquid and solid components of the city. Many see “Moto Ondoso” (motor boat wake) as a major player in this arena244. Another potential – though perhaps unexpected – culprit is sedimentation, which is accused of engendering damage on canal walls through the clogging of underwater sewer outlets, leading to underground ruptures and thus to seepage and weakening of the mortars that bond together the bricks and stones of the canal walls245.
Without aspiring to actually quantify the damage done to these elements of the urban landscape, this chapter will instead use these pressing issues to delineate a path that would make these and other analyses much more feasible in the long run. In this manner, this chapter will attempt to demonstrate that Venice, like any other city in the world, would benefit from espousing the systematic approach I call City Knowledge.
The complexity of the relationship between the stones of Venice and the waters of the Lagoon is a great demonstration of the types of issues that could be better understood once a plan-ready City Knowledge infrastructure becomes available. The rest of this chapter briefly explores the nature of the interactions between natural and human-caused phenomena vis-à-vis the maintenance of the aforementioned elements of the Venetian built environment. The entire discussion will then focus on the indispensable foundation of information that is needed whenever we try to explore complicated relationships such as the one between stones and water in Venice. This chapter is therefore designed to highlight the knowledge infrastructure that can support such complex analyses. As mentioned, since 1988, the Venice Project Center of the Worcester Polytechnic Institute (WPI)246 has been at the forefront of the exploration of the causal relations that cumulatively produce the physical damage that is visible everywhere in Venice. In collaboration with UNESCO and other agencies, the Center has systematically collected a wealth of information about the phenomena connected with architectural damage and decay, both along the canals and elsewhere. Though none of these data connect flooding to structural damage per se, numerous correlations were tested out and verified, by relating a variety of independent and dependent variables that link the “waters” with the “stones”. These include: traffic levels, boat wake-loading, sedimentation, hydrodynamics, construction materials and maintenance. The numerous databases and Geographic Information System layers that have been created since 1988 make it possible to test many assertions and draw useful conclusions, but, despite their sophistication, they only hint at what could be possible if a true City Knowledge infrastructure were created and maintained in Venice. This chapter now sketches out the type of information that one would need to have accrued in order to measure the “before and after” of flooding situations and thus begin to hypothesize about the “cause and effect” of phenomena that can – at best – be treated as “natural experiments” over which there is very little design control.

Damage to Public Infrastructure

If one considers the “public domain” only, then the above-ground infrastructure in Venice that is affected by flooding can be succinctly defined as: streets, bridges and docks. Moreover, Moto Ondoso (motorboat wakes) also damages all three elements, although streets are only marginally affected. The causal nexus between flooding, moto ondoso, and the corresponding damage to these artifacts is extremely complex to isolate, but one can start by simply knowing as much as possible about these three elements of the public realm that are subjected to the destructive force of water. The Venice Project Center has teamed up with a Venetian company called Forma Urbis247 to complete: (1) the mapping of over 1 million square meters of Venetian street pavements for Insula (top left); (2) the inventory of all of the 472 bridges in the city also for Insula248 (center left); and (3) the catalogue of all 1321 public docks in the city for the city’s department of public services249 (bottom left). These three major physical inventories create the backbone of a possible study of the effects that tides and moto ondoso have on them. By adding the digital elevation maps250 that the Magistrato alle Acque has developed, through the Consorzio Venezia Nuova251 (1988), it is possible to produce maps of the flooding of the streets of Venice at a succession of tide levels (bottom right).

Knowing how frequently these various tides occur leads to the identification of what portions of the city’s streets, bridges and docks get wet and how often. So, with only a modicum of approximation and extrapolation, it would be possible to arrive at reasonable estimates of the damage that can be caused by mere flooding. It must be noted that these data-gathering efforts have not been aimed at simply producing these maps, but also entailed painstaking surveys of the artifacts inventoried. Each of the Forma Urbis catalogues has resulted in an information system application that brings together the permanent (left) and ephemeral (bottom) characteristics of both the bridges (bottom) and the docks (left). In fact, whereas the state of conservation of an artifact will change and thus will need to be collected repeatedly over time (allowing the measurement of “damage”), the permanent aspects will never have to be recorded again, which is one of the advantages of a City Knowledge system. These user-friendly, multimedia information systems make it possible for the dynamic data to be maintained up-to-date through the creation of a new, time-stamped, stateof- conservation assessment every time an intervention (or mere inspection) takes place. One can begin to see how useful such “plan-ready” information would be if it were accessible to scientists and decision makers as well as to the frontline users who are in charge of the upkeep of the physical artifacts. This section shows how plan-ready information which is already useful in and of itself for the maintenance of various infrastructure elements can also become useful for second-order analyses such as this one about flood damage. The “emergent qualities” of City Knowledge are starting to emerge. The section also shows how useful it is to separate the “permanent” aspects of our maintainable municipal assets from the “ephemeral” ones, such as condition assessments. In fact, the condition assessments and the log of physical maintenance interventions to ameliorate the assets’ conditions can be themselves useful to measure damage over time and possibly correlate it with potential causes, such as flooding. A true City Knowledge system should always separate the slowly-changing from the fast-changing features of municipal assets. Moreover, these systems should also be constructed with provisions for updating of the data at whatever interval is appropriate. In this case, our systems can be kept up-to-date as a consequence of repairs, which entails that some of the conditions will actually improve accordingly. However the same system would also allow periodic check-ups of these structures to detect worsening conditions, as long as scheduled inspections were arranged by those in charge of the upkeep of these structures. Citizen reports and complaints would be greatly facilitated by the existence of a well-defined information infrastructure which attributes clear, unique labels to each object. By exploiting the standardized reference system, these reports could be logged and used as rough “condition reports”, thus feeding “free” information into the City Knowledge system252.

Damage to Underground Infrastructure

The next category of items that can be damaged by water includes objects under ground, namely the infrastructure for electrical, water, gas, telephone, street lighting and sewage services, composed of pipes, ducts, valves, manholes, inspection wells, cables, etc. Insula S.p.A. has worked on these sub-systems since it was originally chartered by the four main utility companies (electricity, phone, gas and water) who own 48% of the shares – the remaining 52% being owned by the City253. One of the goals of Insula is to eventually produce a maintainable map of the underground infrastructure in Venice. The effects of flooding on subterranean utilities could be much more predictable with this sort of city knowledge at one’s fingertips. Work below street level could also be coordinated in such a way as to avoid waste and redundancy. Once in place, these systems would represent practical applications of city knowledge principles. The first major system to showcase these principles was SmartInsula, the pioneering and award-winning application which formed the backbone of Insula’s sophisticated information system that was developed by a UNESCO team in 1997254 and has since evolved way beyond that initial application. The challenge that Insula is now experiencing lies in keeping such rich systems up to date. Insula needs to constantly update bathymetric measurements, bridge conditions, work progress and much much more. Truly emergent, self-sustaining, city knowledge systems delegate data entry to the most appropriate external user, or to beneficiaries of the work – in other words to the end users of the system. In fact, the major technical difficulty for Insula so far has been in decentralizing the data entry, while reconciling accounting systems with technical or engineering systems (frequently CADbased), and integrating them with geographical information systems (now web-GIS). Many difficulties are being eliminated by forcing compliance with a desired file format as part of a contractual stipulation with outside contractors. Internal adherence to this standard tends to be harder to enforce. As the entire GIS system is ported to the internet, web-based applications to assist contractors in submitting the appropriate digital documents and files are beginning to relieve internal staff of data entry tasks255. Another web-GIS that deals with the underground and embodies some of these principles has been developed by Dr. Enrico De Polignol and Dr. Lapo Cozzutto for the Environment Department of the City of Venice. The Sistema Informativo del Suolo (S.I.S.) was initially dedicated to the selfreporting of core-sample analyses about contaminated sites in Porto Marghera. Private companies are entering all of the data into this system, through a password-protected internet browser and the data are later analyzed and mapped semi-automatically by the system256. The system has recently been incorporated into a more ambitious Sistema Informativo Ambientale (S.I.A.) which is a web-GIS system that will also include information about electromagnetic pollution and green amenities257. Even though we did not collect data about underground utilities ourselves, the paragraphs above have illustrated how custom-made systems to manage urban information of that sort can be created and can be allowed to later “grow” on their own. The difficulty becomes how to keep these systems up-to-date. A true City Knowledge system should not only provide the technical means to capture periodic updates in computer databases (as discussed in the previous section), but should also include logistical and administrative mechanisms to make these updates actually happen. When possible, the task of keeping the information up-to-date should be left to “customers” of the system, through web-based self-reporting mechanisms, as was done in the S.I.S. system described above. What is still missing, to allow a sustainable use and re-use of these data repositories for more complex, higher-order analytical studies, is a clear definition of “informational jurisdictions” and a mutually beneficial agreement to share the information between different agencies – two basic tenets of the City Knowledge concept.

Damage to Private and Public Buildings

The next big category of physical objects that could be impacted by frequent floods includes all buildings: public and private. By implication, this category also includes all of the stores, shops, restaurants and all other businesses housed in these buildings. Flooding affects all buildings and businesses in its path. Moto ondoso, on the other hand, only affects buildings along the canals. Using the information systems developed, it is possible to know how many buildings are affected by floods at any tide level. For example, during a tide that reaches 130 cm., 9,124 buildings come into direct contact with the acqua alta out of a total of 15,486 buildings in the entire city (including the Giudecca). The system does not allow the prediction of whether or not the interior of each individual building actually gets inundated with tide water, although a specific inventory on the piani terra was conducted by the city in 1999 to answer just such a question258. Insula S.p.A. has been actively working to increase the elevation of public streets to around 1.2 meters – a process called rialzi – in order to reduce the number of buildings reached by high tides. The owners of private buildings and commercial establishments affected by acqua alta are doing whatever they can to protect their property from floods: using small barriers, impermeable membranes and vasche259 to seal out the water, and even installing sophisticated drainage systems to direct the water to sump pumps that expel it from the inside of the building. Public buildings are similarly protected and access to many of them is guaranteed even during high floods, by the installation of wooden walking planks260. Quantifying the damage that floods do to buildings and stores may be difficult, but the expenditure related to the local prevention of flooding building-by-building and business-by-business should be somewhat easier to calculate, by inventorying and estimating the cost of all the measures that have been put in place to either protect private and public property from floods or to make them accessible during floods. Moreover, in addition to tallying the cost of preventive measures, one could also account for all of the restorations and repairs that were caused by particularly severe floods. It may be rather difficult to do so, however, unless the government was involved in disbursing emergency relief funds for such activities and thus records were kept of the repair costs incurred. As discussed above, City Knowledge would help us with such difficult estimates, by telling us where all the buildings are with respect to the flood lines. A map of all stores that was produced in 2001261 shows that 2,862 shops (out of 4,263) would get flooded by a 130 cm tide. Together, these two figures, about the number of flooded buildings and number of flooded shops, represent a necessary place to start in an estimate of flood damage to private and public property. Since permits are necessary to install local barriers or to raise the ground floors by adding a step or two to the entrance, an estimate of the overall citywide cost of localized flood prevention measures would be possible if a system was put in place to geographically archive permits that affect the external built environment. The City Knowledge framework recommends that such mechanisms for capturing administrative transactions be put in place to guarantee that the information systems are maintained upto- date as piecemeal changes to the urban fabric are allowed through the permitting process. Together with Dr. Pypaert (UNESCO) I have been actively promoting such a self-sustaining system, by bringing together data from the former Assessorato all’Urbanistica, that keeps track of zoning and land use; the Legge Speciale department, that is in charge of disbursing restoration funds, based on specific work estimates; the Edilizia Privata department, which administers permits; and the Soprintendenza, which updates the “vincoli” that restrict modifications to registered historic properties262. All these organizations provide information for the benefit of the Commissione di Salvaguardia. This institution has the final word on all major modifications to buildings in the historic city and would greatly benefit from such contextual knowledge at its fingertips when making important decisions263. Being one of the institutions with a representative in the Salvaguardia commission, UNESCO had a vested interest in bringing about such a confluence of information from all of these sources, but so do all Venetians, who are in the end affected by the permanent changes that are approved by this regulatory body. Dealing with this aspect of flooding would have been much easier if the data collected by a myriad organizations were already coordinated and interconnected. If that was the case, we would not only be able to know exactly what effects a flood would have on the piani terra, but we could also begin to estimate the cost of local flood protection by tallying up the permits to install miniature flood gates at one’s doorstep or to raise the entrance one step higher, etc. The first lesson for City Knowledge we glean from this section is that each organization that is in charge of some aspect of building construction, restoration, preservation or permitting should get its house in order first and foremost, as Dr. Pypaert and I have been trying to propose, so far unsuccessfully264. If the various departments listed above had operational information systems in place within the boundaries of their respective informational jurisdictions265, changes to the city of Venice would happen more cogently, thanks to the ability of these agencies to deliberate about permit applications while having all of the appropriate contextual information in front of them. By serving their own interests, these organizations would make their own job easier and would provide a better service to the citizens that foot their bills. The other lesson, which repeats a refrain that already appeared in previous sections is that after the public agencies have independently taken care of their own affairs, they can coordinate with each other to provide value-added benefits to each other and to the city, such as, in this case, the ability to estimate costs incurred for the local protection from high tides.

Damage to Palaces, Churches, and Convents

Some of the buildings which are part of Venice’s more prestigious architectural heritage, such as palaces, churches and convents, are also touched by high tides. Being more important than others, they have received more attention from public authorities and from philanthropic organizations such as the socalled “private committees”. Venice owes much of its fame to its aqueous forma urbis and to the art and architecture it contains. In 1987, the whole city was inducted by UNESCO into the list of World Heritage Sites as a treasure that belongs to all humanity; the first city to receive such an honor in its entirety. When it comes to damage due to floods, the parts of Venice’s heritage that stand to suffer the most are palaces and churches, which tend to have ground floors containing more elaborate craftsmanship and more precious materials. Right after the 1966 flood, UNESCO funded the creation of catalogues of Venetian Palaces, Churches and Convents. In the three decades since then, these catalogues have proved invaluable as a knowledgebase supporting the relentless efforts for the restoration of the priceless treasures of art and architecture first inventoried in the late 1960’s. Starting in 1999, teams of WPI students began the task of revisiting and computerizing the UNESCO catalogs266. These efforts allow us to say, for instance, that out of the 383 palazzi in Venice, 308 get wet with a 130cm tide (top map at left), as do 46 out of 59 convents (center map). Similarly, we can identify all of the churches that would get flooded with the same 130cm tide. Out of a total of 113 churches in Venice (including Giudecca), 86 are affected by this acqua alta (bottom map). Nevertheless, in order to convert the knowledge of what gets wet at the various tide levels into a more useful estimate of the damage incurred by these artifacts when they get flooded, it is necessary to know a lot more about what’s inside these historic buildings. Starting in 2002, we began recording the tombstones, inscriptions and artifacts that are embedded in church floors267 (see photo at left). In addition to being frequently at lower elevations due to the age of the original foundation, churches have the added handicap of being vulnerable to flooding through their floors, which are riddled with tombstones. The underground cavities where the entombments took place are a conduit through which high tides can quickly reach the artifacts on the floor’s surface. This process is abetted by the high permeability of the bottoms of the tombs, which were constructed in such a way as to purposely allow tide waters into them, so that the mortal remains could be rapidly washed away and the tomb could be promptly recycled and reused. The photo below clearly shows the huge gaps purposely left between the planks laid at the bottom of a tomb recently excavated under the church of San Samuele268. Once this additional city knowledge catalogue of church floor artifacts is finished (over 80% of the surveys have been completed), a more accurate assessment of the potential damage inflicted upon church floors by frequent floods will be possible. Arriving at a similar inventory for the ground floors of palaces and convents would also be useful in this regard. The overall impact of flooding on churches, convents and palaces can thus include a better estimate of the damage to their floors, but should also include the deleterious effects of salt water on any other artifact that may be touched by tidal waters in the interior of these historic structures. Appropriate monitoring of the decay by the Curia and Soprintendenza could help maintain these catalogues up-to-date and thus prevent catastrophic damage to these important artifacts.

This topic does not yield many new lessons, but is more of a “refresher course”. It reminded us of the permanent/dynamic dichotomy and it reaffirmed the usefulness and re-usability of systematic catalogs. Nowhere is the advantage of separating the “permanent” from the “dynamic” more clear than when dealing with cultural heritage. These historic artifacts have been around for centuries and such ancient relics only change by subtraction, not by addition. No new artifacts are ever added, yet some may disappear or dissolve to dust. Cataloguing historic assets is therefore a finite process, but monitoring their state of conservation is not. The biggest lesson we learnt with these and similar projects is that it really pays to be thorough and complete when cataloguing antique artifacts. In this day and age, such a process could indeed be done once and for all. The key to avoid duplication of effort in the future is to disseminate the results widely and openly. Today’s internet technologies can help eliminate redundancy as long as people are amenable to sharing their inventories freely and willingly. The avoidance of duplication should free up some time that can be put instead into periodic checks of the conditions of these objects to detect degenerative processes that may lead to their complete loss.

Damage to Other Cultural Heritage

After the flood of 1966, most, if not all, precious paintings in Venice have been moved up and out of the reach of even the highest high tides. Practically all damage to heritage would now be limited to fixed and immovable structures, such as floors, bases, pedestals, columns, steps and other artifacts within a 2-meter band from ground level (which translates to over 3 meters above sea level)269. With the exception of our aforementioned recent work on church floors270, there are no systematic assessments of the artistic or historic heritage contained in this “danger zone” in the entire city. Common sense suggests that everything that could be moved away from this perilous band should have been already moved, though it is quite possible that some artwork might still be in a vulnerable location to this day. Estimating just how many works of art still remain within the “danger band” is arduous at best, whereas a fully-developed (utopian?) City Knowledge system could provide the answer to this enigma in a few seconds. Under such a system, the various authorities in charge of heritage collections (like the municipal, provincial and regional governments, the Curia, the Soprintendenze, the Archivio di Stato and the two main libraries – Querini and Marciana) would have already catalogued all of the objects that they are respectively in charge of, namely the buildings, properties, church floor artifacts, paintings, mosaics, manuscripts, parchments, books etc..

The information contained in the Venice archives and in the historic libraries would be even better protected if electronic transcriptions of the manuscripts were produced using the Emergent Transcription Assistant System271 (left) and the Ultraviolet Scanner272 that we have been concurrently developing at WPI273. With some foresight, these computerized catalogues could have included a field for the height of the artifact from the floor, which in turn would allow us to simply select all objects whose distance from the floor was less than 2 m. 270

As partial demonstration of the benefits of having city knowledge systems in place, it has been possible to select, from the 2,930 pieces of outdoor sculpture that have been catalogued over the last decade (figure at left), the ones within 2 meters of ground level274. This search instantly reports that 69 artworks are on public display at a height of 2m or less.

Similarly, one could also include in the 2-metre band all 232 wellheads from the wellhead catalogue (bottom of page), since they all sit at ground level, as do all 22 historic flagpole holders that dot the city (left). More specifically, with the same 130 cm flood used as an example, 122 of the 232 wellheads would get wet (detail below). Fortunately, though, most of the 4.500+ pieces of public art and street furniture that have been inventoried in the calli and campi of the city are outside the 2m danger-zone.

Once again, the availability of a City Knowledge system would make many of these preliminary assessments instantly possible, as long as each institution in charge of artistic treasures had developed its own catalogue according to the aforementioned informational jurisdictions. It is also obvious that a disaster relief agency, such as the Italian Protezione Civile, would greatly benefit from a distributed, yet interconnected City Knowledge system that was able to direct emergency crews to the exact locations where works of art were in danger of being flooded during an acqua alta275. The key here is not to focus on creating a centralized know-it-all system, but to foster the emergence of a distributed network of smaller (and more manageable and maintainable) systems, through a process that I chose to call “middle-out276”, to differentiate it from “top-down” or “bottom-up”, both of which have demonstrated severe shortcomings. It may be that the information could be actually housed in a single server somewhere277, but each different agency will be managing the data updates independently, without an overarching entity mediating the data management. Data input, on the other hand, could be farmed out to a central agency (like an MIS department) to achieve some cost-savings, especially when specific skills are required, such as for GIS mapping. It is important to remember, however, that the goal of an efficient City Knowledge system is to outsource most data input to “customers” or contractors in order to basically get it done for free, or at least to minimize the costs of in-house data input. 275

Damage to Canal Walls

n concluding this brief excursus into the various points of contact between waters and stones in Venice, this section discusses what is perhaps the most critical interface between these two fundamental elements: canal walls. This section illustrates how a systematic and methodical approach to the accumulation of urban information can yield “deep knowledge” about the causal nexus between phenomena. Back in 1998, Babic et al., using the accumulated storehouse of knowledge on traffic, wall damage and bathymetries, concluded that the root cause of wall damage is lack of dredging, which is only later compounded and exponentially accelerated by traffic and wakes278.” Based on this knowledge, in the year 1999 a further study was conducted279 to quantify the relative and absolute contributions for a variety of possible sediment sources, including the debris produced by crumbling masonry, to the accumulation of sediment at the bottom of canals. This study led to the proposal for a Sedimentation Model to predict the rate and location of mud accumulation at the bottom of canals, which would allow a more effective and efficient scheduled maintenance before more wall damage was generated by the clogging of sewer outlets.

In 2002, the concept of a “moto ondoso index” was developed, that translates levels of boat traffic (i.e. number of boats) to levels of “wakeloading” (how much wake energy is discharged in the canal), which helps to better correlate traffic to damage280. More recently, WPI students281 designed and successfully tested an instrument that maps the locations where motorboats discharge energy into the canals when maneuvering to make turns, or otherwise stopping abruptly by shifting into reverse when an approaching boat threatens a collision, or even when moving back and forth near a dock to tie up the boat and unload people or cargo. This custom device is equipped with a differential GPS, a triaxial accelerometer and an RPM meter and will produce the first ever map of “turbulent discharges” in the inner canal network, further facilitating the prediction of future damage along canal walls.

The application of city knowledge principles has paid off dramatically in another project related to moto ondoso entitled Re-Engineering the City of Venice’s Cargo System283. The project has demonstrated the plausibility of “plan-demanding” knowledge as a consequence of “plan-ready” information, in opposition to the traditional modus operandi of “plan-demanded” data collection. Here, work on the optimization of canal closures284, which produced plan-ready information on the amount of cargo delivered to each Venetian island, has led directly to the spontaneous emergence of the need to develop a plan (hence the term “plandemanding”) to restructure the way deliveries are conducted in Venice. The 2001 award-winning project was conducted with and for the former Consorzio Trasportatori Veneziani Riuniti (a group representing about 70% of all cargo boat drivers in 2001) and resulted in a proposal to redistribute merchandise “by destination” instead of “by product”. We estimated cargo demand by inventorying all shops and stores in Venice and by surveying representative samples of each typology of commercial establishment to quantify the number of parcels delivered to each store of that type everywhere in the city.

This effort led to the aggregate depiction of the total demand of dry (yellow) and refrigerated (blue) cargo for each island in the city.

The research also proposed the creation of a cargo warehouse (interscambio merci) in the Tronchetto area to allow for the sorting of the merchandise arriving by truck. We envisioned that the city would be divided into 16 zones with commensurate delivery demands. The warehouse would mirror such a division, reserving a loading bay for each zone.

In the end, it was possible to estimate the total number of boats (for dry and refrigerated goods) that would be necessary to deliver all necessary merchandise to all the stores in each zone. Boat drivers were repeatedly engaged in public meetings as well as surveyed and interviewed during the development of this plan. This participatory process created consensus over a plan that would make all licensed drivers shareholders of a single, large logistics and distribution company delivering most of the goods in the city. Boat drivers would be able to deliver to their destination dock at a set time and without interference from other cargo boats. Vacations and sick days would now be possible without the fear of losing clients. The great majority of boat drivers that participated in the public meetings found the benefits of such a system advantageous. Presently, the municipality of Venice is moving forward with the actual implementation of this plan. This proposal will reduce cargo-generated moto ondoso by a substantial amount while preserving non-seasonal jobs. Point-to-point cargo journeys will be reduced to one or two per boat, instead of the dozen or more segments traveled each day under the current system. A reduction of the order of 90% of the wall damage induced by cargo boats is therefore not implausible285. In the summer and Autumn of 2001, the proposal was presented to the Mayor and the Vice Mayor who espoused it. The project, which is currently well on its way to being realized, was a triumph of City Knowledge principles, demonstrating the “plan-demanding” potential that such an approach entails. A plan-demanded study dedicated to minimizing disruption to deliveries during canal closings for maintenance and dredging operations led to the accumulation of enough plan-ready information about the inefficiencies of the system of deliveries “by product” to spur the inception of a follow-up study to explore the boat-drivers’ perspective on the revolutionary approach of deliveries “by destination” that was proposed. The project went full-circle, from plan-demanded to plandemanding. Although we have “deep knowledge” that tells us that timely dredging is more important than reducing wake-loading, nevertheless, whatever damage motor boat wakes do induce upon the canal walls will be reduced by a fraction that is proportional to the wake-loading that the number of cargo boat transits being eliminated would have caused as a percent of the total wake-loading induced by all boat types in each canal segment.

This section manifests the ultimate power of City Knowledge, i.e. the ability to create wholes that are bigger than the sum of their parts. Here is the ammunition for the “value-added” argument that should provide the final clinching proof about the efficiency, effectiveness and efficacy of City Knowledge. The efficiency of City Knowledge is demonstrated here by the lack of redundancy in the datasets and the smooth collation of information needed for the plan-demanded study, which mirrored the idealized situation of non-overlapping informational jurisdictions envisioned by the City Knowledge approach. Of course, the fact that the VPC functioned as a single overarching entity and not as a distributed cadre of informationproducers may be taken as evidence of the possible primacy of the centralized approach versus an emergent decentralized one. The fact is that the data that were used in these examples came from a variety of sources, administrative, academic, municipal, as well as our own data collection. The upkeep of the fundamental datasets for each one of the aspects we dealt with in this example could be easily attributed to one agency or another, based on informational jurisdictions. We could measure the “operational effectiveness” of the example discussed in this section according to Budić’s indicators286. She selected a sample of GIS practitioners in 125 county and municipal governments in four south-eastern states. According to that sample, our Cargo Project would be very appreciated by 63.6% of GIS professionals because of the instant accessibility and availability of the data we used to arrive at our reengineering proposal. Validating the accuracy of the data would make 27.3% additional users very happy. A well-crafted City Knowledge system should therefore be very effective operationally. As far as “decision-making effectiveness”, the plan-demanded example discussed herein should have made clear the power of the GIS tools to communicate the information pertaining to the cargo delivery system. This alone would have been highly desirable to half of the sample of GIS practitioners surveyed in Budić’s study. It could also be argued that the example discussed herein showcased both the ability to aid in the identification of conflicts and also in the confidence in the analyses that produced our radically re-designed delivery system, making it even more effective for decision makers.

The efficacy of our framework in terms of the measurable consequences of our proposals in the “real world” cannot be quantified quite yet since the proposed delivery system has not been put in place as of this writing. Measures of efficacy may include the financial benefits or quality-oflife gains of the citizens of Venice after the inauguration of the system.

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