Moto ondoso

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Moto Ondoso in Venice

Venetian Canal

What is Moto Ondoso?

Moto ondoso is an Italian term commonly used to refer to the damage caused by wakes. Moto ondoso is a topic of considerable concern in Venice as the wakes created by the various boats traveling through the city's canals cause continual erosion to foundations of the canal-facing buildings located throughout the city. Thus, moto ondoso is an example of one of the negative impacts of boat traffic in Venice. While most cities in the modern world have primary concerns of traffic impacts resulting from pollution, moto ondoso imposes a demanding and immediate threat that has the potential to compromise areas of the city's structural integrity if left ignored and untreated.

Rowboats and sailboats have plied the canals of Venice ever since the fall of the Roman Empire, but motorboats have only plagued the city since World War II. Therefore, with the advent of new means of transportation, the canal walls experience constant force of boat wakes, whose waves continue to erode and damage. In the few decades since their widespread popularity growth in the 1960s, motorboats have become one of the major problems Venice is facing today.

The Hydrodynamics of Moto Ondoso

Boat wakes are primarily created by the boat propellers that cause turbulence in the water. The size of the wake depends on different factors such as the speed of the boat, the size of the boat's propellers, the power of the boat engine, the shape of the boat's hull, the depth of the channel being traversed, and the boat's load. Thus, with all these factors, it is difficult to pinpoint a specific wake size to a specific speed. However, a relative scale can be useful, of which there are 3 categories.

Displacement Speed

This is the boat's lowest range of speeds, in which the boat is level with the water and there is minimal wake created by the boat.

Transition Speed

This occurs when the boat is accelerating on the water and typically the bow of the boat is high off the water, creating the highest amount of wakes.

Planning Speed

This occurs after the transition speed, where the boat returns to the water level and creates less wakes than the transition speed, but more wakes than the displacement speed. However, Venetian boats cannot achieve this speed.

Energy in Boat Wakes

As boat wakes are created by the propellers, energy is created. However, since the canals are small in width and depth, there is not enough room for the energy to disperse. A study in 1996 used a combination of kinetic and potential energy to determine the total energy caused by boat wakes, based on amplitude and wavelength of the wave deriving the formula,

E = 1/8(Gamma)(H^2)(L)(sinσ)

where,

E=total engery released into the water by the boat (kg*m)
Gamma= density of the water in the Venetian lagoon(1024 kg/m^3)
H= the amplitude of the wave (m)
L= the wavelength (m)
σ= the angle made between a perpendicular line from the rear of the boat and the leading edge of the wave.

Wake Amplitude Chart caused by a Motoscafo Taxi (generally, the higher the wave amplitude of the boat wake, the higher the velocity of the wake and thus more energy generated)

Necessity of Water Transportation

Uses of Water Transportation

Since Venice is primarily surrounded by water, water transportation is a complete necessity and integral to the Venetian inhabitants. Such dependence on water travel leads to great amounts of water traffic. In fact, according to the traffic distribution chart, the greatest amount of traffic stems from taxi/public use, followed closely by cargo use.

Boat traffic in Venice not only generates the same congestion problems that gridlock most mainland cities, but it is simultaneously a much more insidious phenomenon than its land cousin. Unlike the comparably innocuous automobile, boats have the ability to physically erode the foundations of buildings near their paths of travel. This destruction of buildings and canal walls presents dangerous consequences if not immediately prepared. Thus, there is a constant need for repair, coming from taxpayers, which increases the cost of living in Venice. Therefore, the passage of cars on a street cannot dismantle a city block piece by piece the way turbulence and boat wakes do when vessels travel the inner canals.

Boat wakes

Despite the exodus of Venetians away from their city of birth, boat traffic continues to increase in order to cater to the needs of an ever-growing tourist industry. According to our calculations, traffic has almost doubled in the past 25 years; population declined by 50% in the same period. People who live along the canals are literally watching their dwellings crumble under the incessant pounding of boat waves. In desperation, many property owners have begun a public protest against the daily assault on their homes. “Stop Moto Ondoso” (loosely translatable as “Stop Making Waves”) is a frequently-uttered phrase that even tourists have begun to recognize after seeing displayed in windows the city over.

Aggravating Moto Ondoso

Certain factors can cause greater amounts of boat wakes and force against the canal walls

Few Primary Routes

The moto ondoso problem is particularly bad along the primary arteries. In fact, despite the apparent intricacy of the web of canals, the entire water network can be schematically simplified to just a few primary routes where most of the boat traffic is concentrated. Although there are 367 segments and 182 inner canals in the city (for a total of 47.5 kilometers of waterways), the number of main thoroughfares can be counted on the fingers of two hands.

Sewage

Moto ondoso can be aggravated further by clogged sewer outlets, boat collisions, and biological and chemical agents such as sulfuric acid, pollution, and algae, which thus increase the rate of canal wall erosion. Sewage enters the canals underwater through a system of pipes. When silt deposits in front of sewage pipes develop, it can cause clogs in the sewage system. When clogging occurs, the sewage backs up and bursts the pipes, causing sewerage to seep into the surrounding mortar, contributing to the weakening of the canal walls. The picture demonstrates canal damage due to sewage

Canal Damage due to Sewage

Congestion

The Venetian dependence on the canals is vital; not only do the canals transport people and goods, but they also play a major role in the waste disposal system of Venice. The canals divide Venice into more than 100 islands, all of which need to be accessible by boat such as garbage collection and ambulances. Also, since Venice’s economy is dependent on tourism, the use of the canals for sightseeing and tourist transportation is essential. This along with the large number of boats and inefficient motion of various boats causes congestion.

Effects on Canal Wall Damage

As can be observed in the map of Venice, there are many canals intertwining the city's geography. This further cements the important relationship of canals to Venice. In the 1990's a large hole was discovered on one of the canal walls of Rio Novo. Although it seemed like a small hole, it was actually an outward manifestation of serious structural damage within the canal. The canal was shut down for repairs, directing traffic to Rio Cerris canal. However, the increased traffic and in turn the increased moto ondoso, caused irreparable damage to the canal and within two years, a building near Ponto Rosso collapsed. Seven years and seven billion euros later, the Rio Novo reopened.

Another area that was plagued by erosion problems was Galeazze Canal. In 1996, it was repaired for the first time, followed by installation of metal sheets along the canal wall two years later. Then in 1999, the entire canal was closed off to traffic due to tremendous amounts of repair needed. Other places affected by moto ondoso included the Ca' Foscari building, Rio della Maddalen, San Moise, San Lorenzo, and the Rio di Noal, among many others.

Methods of Perservation

There are currently two methods of preserving canal walls affected by Moto Ondoso. Firstly, a restorative method is underway. Some plans include reforming the damaged bottom of the canal. Secondly, preventative measures are utilized in stopping any further damage by the waves. These include boat traffic and speed limit regulations, allowing for the police to control the speed of passing boats and the amount of congestion in an area.

Reason for Debate

There are differing opinions on what is the actual cause of canal wall damage. One group, the Pax in Aqua(Peace in the Water), believe that the actual cause of canal damage is Moto Ondoso and boat turbulence, and are working to raise public awareness of this problem, through funding for sponsored programs; however, another group, Insula, believes canal damage has nothing to do with moto ondoso and can be controlled by improving the wall material and shape of the wall.