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Introduction
Table of Contents
The Tiber River…
Legend tells us that Rome was founded by a brother who, along with his twin, was sentenced to death as an infant. They were put into a basket in the river to be drowned. However, since it was flooded at the time, they were not washed downstream, but instead gently deposited to the entrance of a she-wolf’s cave, who raised them until they were men. Even though this is probably a mythological beginning for the city, there are grains of truth that speak to the strong ties between the city of Rome and the Tiber River. For more information go here.
It is now a forgotten piece of the city, running down to 30 m below the ground height of the heart of the city. Despite its neglect today, the river used to be a source of prosperity, and more often than they would like, despair in regards to the violent floods it could create. One might ask, “How can a city become so successful, even though it is victim to floods every few years?” This report will explain the hydraulic flood plane that Rome is nestled within, the results of the floods, and how they tried to mitigate the issues due to flooding, then and now. Regardless of how, it is irrefutable that the river has shaped and influenced the lives of citizens of Rome from 700 BC to modern times.
Geography and History of the River
The Tiber’s ancient Path
Rome was founded on one of the “Seven Hills of Rome” which are more or less large plateaus. The plateaus were created by erosion of tributaries of the Tiber River. The materials of the hill are generally a soft tuff rock, easily broken down. The result is high plateaus to build homesteads and barriers, but an easily accessible river with means of communication and transportation. The historian Livy writes, “…the river is advantageous since along it are brought food stuffs from inland… but is not exposed to the dangers of enemy fleets.” (Livy 4.4.9.2) Today, some of the main streets of Rome are actually where these tributaries used to run. See Figure 1.
The tributaries ran between a few of the more prominent hills and eventually have been paved over to be some of the larger roadways in the city. The Aquare Sallustinaea ran between the Pincian and Quirinal hills. This was later paved over to become the Via del Tritone, Barberini, and Vittorio Veneto (Heiken, 2005). Another tributary from the Tiber River flowed over the marshes in the floodplains, mainly between the Capitoline and Palentine Hills. This ancient tributary and a few others are still the paths Romans travel today. Figure 2 shows the basin of the Tiber River.
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| Figure 1: Ancient Tributaries of the Tiber | Figure 2: Drainage Basin of the Tiber (Aldrete,2007) |
Flooding and Commerce
The Tiber River is prone to flooding. The records of these floods are not as accurate as we would like, but there are about 33 noted floods between the years 414 B.C. and 398 A.D. (Aldrete, 2007). The river is 250 miles long. It passes through the Tuscan, Umbrian, and Lazio regions, covering an area of 6,623 miles square. It has 42 tributaries feeding it. The Tiber Basin has a backbone of mountains and is surrounded on two sides by seas, which puts it in a very vulnerable flooding position (Heiken, 2005).
The Tiber River floods because the river swells with excess rainwater and it overflows its banks. The soils under-laying the drainage basin are baked by the hot Mediterranean climate during the dry season, which makes them less receptive to water. They will absorb as much rainwater as they are able, but at a certain point they become saturated. When this saturation level occurs any other water on top of the soil will run off of the soil and into the nearest stream or river. The Anio and Nera Rivers drain into the Tiber, as well the 42 other tributaries. The rainy season comes and fills these extremities, which drain directly into the Tiber river. The river fills and swells with the excess water and it eventually overflows, submerging surrounding and low-lying areas. The surface runoff has also been increased in the basin due to the fact that there is a city there. Cities are full of impervious surfaces that used to absorb rainwater, instead of directing it straight into the river. The runoff from impervious surfaces, such as roofs, roads, or sidewalks, can flow very quickly down narrow streets. Since the force of water is proportional to the square of its velocity (see Bernoulli’s equation), this increased velocity is very damaging to the city.
Another way to consider the extent of the flooding is to look at the rainfall data versus the outflow measurements. See Table 1. A map of the drainage basin where rainfall data was collected is in Figure 2. The Ripetta Station is located in Rome.
Table 1. Rainfall and Drainage Data for the Tiber River (Aldrete, 2007)
| Month | Rainfall(mm) from 1921-1990 |
Drainage(m^3/s) as measured at the Ripetta Station |
| January | 83.02 | 316.2 |
| February | 90.52 | 356.7 |
| March | 81.25 | 312.1 |
| April | 83.62 | 259.5 |
| May | 80.27 | 228.1 |
| June | 63.42 | 174.0 |
| July | 35.52 | 139.7 |
| August | 49.22 | 128.4 |
| September | 85.9 | 148.8 |
| October | 110.9 | 178.7 |
| November | 129.27 | 254.5 |
| December | 105.13 | 306.8 |
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| Figure 3: Tiber River Delta, with Ostia |
It is easy to see that the peak rainfall occurs in November, while the minimum is in July. The river, however, isn’t flowing at its maximum capability until Feburary, while its slowest drainage occurs in August. The drainage for the light rainfall corresponds well, but the heavy rainfall clogs the river for a few months before it can flow out at a fast enough rate. Floods usually grow rapidly, yet drain slowly.
The mouth of the river is where sediment that has taken a journey along the river will most often be deposited. These deposit will eventually build up and thus extend the land. This area of deposit and growth is known as a delta. The delta of the Tiber River is now so large that you need a map to see it. Today, the delta covers an area of 58 square miles above sea level and 193 square miles below sea level(Aldrete,2007). The area occupied by the Fiumiccini Airport used to be the Port of Claudius, a major commercial port of Rome. This port was created by Emporer Claudius in 54 A.D. and extended by Trajan in 110 A.D. to become the largest man made harbor in the world at the time (Aldrete, 2007). The port of Ostia Antiqua was also an influential port and served to help make Rome into a formidable trader and naval power. After the fall of the Roman Empire, the port cities also lost much of their trade, and citizens were forced to abandon them. Seeing Figure 3 below, one could imagine the extents of this city. It would have been bustling with trade as up to 100,000 citizens lived their daily lives.
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| Figure 4: Ostia Antiqua, Ancient Roman Port City |
There has been some extensive research done in the 20th century on the flooding of the Tiber, by Aiessandroni and Renedia. They have done a thorough analysis on the Tiber basin in correspondence to rainfall. According to their research the river overflows when there are about 90 days of frequent rains, thus saturating the soil. Then, in the following ten days, there are large daily rains that cause a high surface runoff to occur.
The flood of 1937 was notable because it was one of the first times rainfall data was collected in the basin, and then corresponded to the levels of the flood. It rained eight inches in the mountains and basin, which resulted in a flood of 32 inches above ground level, with a flow of 2800 cubic meters per second.
Summary: Functions of the River
How it Helped
As mentioned above, the river played a critical role in the decision for the location of Rome. It became a fruitful trading route, helped move large quantities of goods, such as stones of tuff or travertine, into the city for the creation of infrastructure. Also, before the aqueducts came into creation, it provided a source of reliable and clean water for the citizens. The periodic flooding of the river also helped invigorate the surrounding marshlands, depositing new soil for crops, which animals could then graze on.
How it Hurt
The floods could also have devastating consequences. They could be violent, destroying bridges, homes, and field, in an instant, not to mention the casualties they caused. A particularly heavy flood could leave the city underwater for days at a time, submerging the most popular gathering grounds including the Pantheon, Piazza Navona, and Castel S’Angelo.
Floods
Quantity and Coverage
Table 2. Flooding Data (Aldrete, 2007).
| Table 2. Flooding Data | |
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| Date | Source |
| 414 BC | Livy 4.49.2-3 |
| 363 BC | Livy 7.3.2 |
| 241 BC | Augustine, De Civitate Dei 3.18; Orosius 4.11.6 |
| 215 BC | Livy 24.9.6 |
| 203 BC | Livy 30.26.5 |
| 202 BC | Livy 30.38.10-12 |
| 193 BC | Livy 35.9.2-3 |
| 192 BC | Livy 35.21.5-6 |
| 189 BC | Livy 38.28.4 |
| 181 BC | Plutarch, Numa 22.4 |
| 156 BC | Iulius Obsequens 16 |
| 60 BC | Cassius Dio 37.58.3-4 |
| 54 BC | Cassius Dio 39.61.1-2; Cicero, Ad Quintum fraterm 3.7.1 |
| 44 BC | Horace, Carmina 1.2.1-20 |
| 32 BC | Cassius Dio 50.8.3 |
| 27 BC | Cassius Dio 53.20.1 |
| 23 BC | Cassius Dio 53.33.5 |
| 22 BC | Cassius Dio 54.1 |
| 13 BC | Cassius Dio 54.25.2 |
| AD 5 | Cassiodorus Chonicon 604: Cassius Dio 55.22.3 |
| AD 12 | Cassius Dio 58.26.5 |
| AD 15 | Tacitus, Annales 1.76 |
| AD 36 | Cassius Dio 58.26.5 |
| AD 69 | Plutarch, Otho 4.5 |
| Reign of Nerva | Sexus Aurelius Victor, Epitome 13 |
| Reign of Trajan | Pliny, Epistuale 8.17 |
| Reign of Hadrian | SHA, Hadrian 21.6 |
| AD 147 | SHA, Antoninus Pius 9.3 |
| Ad 162 | SHA, Marcus Aurelius 8 |
| AD 217 | Cassius Dio 79.25.5 |
| AD 253 | Sextus Aurelius Victor, De Caesaribus 32 |
| AD 371 | Ammianus Marcellinus 29.6.17-18 |
| AD 398 | Claudian, De Bello Gildonicio 41-43 |
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| Figure 5: Piazza Navona during 1870 Flood |
Aldrete provides an explanatory passage for each of the previous dates, and explains why he thinks each was a flood. He needs to provide an explanation for his claim because records from this time are very vague, and most don’t mention the word, “flood”. Instead, they are described as quickly flowing water, or just give descriptions about certain monuments being underwater. The data from this time period is unreliable. In ancient Rome, the flooding was just apart of life; it came, it did some damage, you moved on and repaired. For example, in 13 BC the General Balbus won a triumph, and to celebrate himself he also opened the Balbus Theater. He hoped to parade around the city with Emporor Augustus in attendance. However, when the day of the inauguration for his theater and his triumph came, the city flooded, turning the theater into a temporary swimming pool (Aldrete, 2007).
The flooding of the river reached large portions of the city, including many popular destinations inlcuding Piazza Navona(See Figure 5), Campo de Fiori, the Ghetto, Church of Santa Maria Sopra Minerva, the Pantheon, St. Peter’s Square, and Castel S’Angelo. The earliest quantifiable data comes from marble flood markers, the oldest dating back to 1277. Today, hundreds are scattered around the banks of the Tiber. These are small plaques, located outside of ancient ports and churches in order to mark the height of water during floods. A good example is from one of the worst floods in Santa Maria Sopra Minerva, Piazza di Minerva(see figure 6). The water reached 18.95 meters above sea level on December 24, 1530, Christmas Eve (Aldrete, 2007). This is the second highest recorded flood. The highest flood occurred in December of 1578, when the water reached 19.56 meters above sea level.
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| Figure 6: Flood Marker |
A marble column was erected at the port of Ripetta(see map above) in 1704 in order to better measure flood heights and get a better standard. This column was used to mark heights of floods, but it wasn’t until 1821 when the hydrometer of Ripetta was installed and daily observations of the Tiber river were recorded. This is now where flow rates are recorded for floods.Flow rates are measured in volume per unit time, normally cubic meters per second. The flow is calculated by multiplying the cross sectional area of a stream of water by its velocity. The velocity should ideally be an average, but water flowing in the middle of the stream may be faster than the water flowing on the edges (due to friction) so it is averaged as best as possible.
As we have seen, the river could make things quite inconvenient for citizens, however, it didn’t halt daily life. The floods that lasted anywhere from a few hours to 5 days (Aldrete, 2007). People could get around by boat in these times, or wait on top of their homes. The floods could take out bridges and cropland, but Romans were always able to rebuild. The historian Livy claims the first bridge was the Pons Sublicious. It was built just south of Tiber Island, where the flow was slowest and the piles for the bridge would not be washed away. The bridge was destroyed five times due to flooding, and each time it was rebuilt (Taylor, 2002).
The Layers of Rome
When a flood occurs, water isn’t the only thing being swept through the streets of a city. Floods carry dirt, mud, silt, and any other debris it may have picked up along the way. This means that a flood will require a great clean up effort to restore things to their previous state. Much of the time it is possible to clear away the debris; however, if a building has been abandoned, or even torn down by the flood, and all you have left is a deep layer of silt…. Romans would probably call that a good foundation. They would fill in the rest of the building with more dirt, or even trash, and start construction on a brand new building on top. Occasionally you can see pieces of incorporated ruins in the new buildings. In fact, almost all of the city is sitting on 5 to 10 meters of fill (16.4 ft-32.8 ft) (Heiken, 2007). The area known as Historical Rome is still pretty well preserved, as we can see by the ancient buildings. These have been excavated and thus the area has a smaller layer of fill, only 2-5 meters, or 6.6-16 feet of debris. The alluvial plain, around Trastevere and Pigna has a higher debris level, around 5 to 10 meters, 16-33 feet. However, the areas where the tributaries used to flow have the most, between 10-15 meters of fill. This wasn’t all silt left from flooding, it was also man-made debris, junk that people wanted to get rid of in order to build on top of it. The most comical example of this is the Monte Testaccio Hill. This is a 36 meter tall hill of debris, mostly broken clay pots that couldn’t be reused or recycled. It was/is an ancient dump. Most of the hill consists of amphorae, or terra cotta jugs, that were used to import oil. There is also broken roof tiles, some pavement, chunks from old oil lamps, and pozzolan concrete (Heiken, 2007). While this hill was not created by buildup of sediment from the river, it shows that people were quite willing to dispose of their trash in the earth beneath them and then build on top of it.
The layers of Rome weren’t solely built by silt from the river, although that was a major factor. They were also created from the debris mankind used to fill in half-destroyed buildings. The debris and extra garbage that got piled high eventually just became the new ground level for the city. See the description of the Roman Forum below.
Romans would have had to excavate by hand, which would have been a long, arduous process, one they would only have to repeat the next time it flooded. As an example of the intense muck they would have needed to sift through, the city of Florence had an extremely debilitating flood in 1966. Florence was covered in 600,000 tons of mud, reaching almost three feet high in some locations (Aldrete, 2007). The mud and silt washed into the city would have been a labor-intensive problem. It was easier to built on top of what was existing and hopefully above some of the flooding as well. The Colosseum was built in part on tuff and hard rock, then also partly on sediments that had been deposited by the river. These sediments are not as stable as the rocks, which is likely why it was so prone to damage from earthquakes (Heiken, 2005).
Basilica of San Clemente
One of the best examples of this debris layer is the Church of San Clemente, or the Church of Saint Clement. This church has been re-purposed, and reconstructed at higher elevations for the past two millenia. We know this today because the church has been excavated to reveal the lower floors. Each reconstruction follows the same contours of the building beneath it closely, or a jumble of buildings as an eclectic foundation. It is interesting to look inside of the current building at ground level and to notice the seemingly awkward arches supporting the base of the wall. Arches are normally higher, distributing weight more efficiently. The reason you can only see the top of the arch is because they rest of it originates in the building beneath, and when building the Basilica they decided not to raise the ground level again, but to reuse the church beneath (See Figure 6). The most recent renovation was carried out by Pope Clemente XI, which redecorated the inside of the Basilica and added an additional outdoor courtyard(Gilmartin, 1974).
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| Figure 7: Arches of San Clemente | Figure 8:Vaulted ceilings of lower church in San Clemente |
The Basilica is the top most layer of this site, built sometime in the the 12th century (Osborne, 1981). One layer down is
still a place of Christian worship built for the martyred Saint Clement around 300 A.D. This is the first time this building was used for Christianity. When the Basilica was being created the church beneath was quite old and in need of renovation. Therefore, the architects chose to fill in the old church, and make the walls a solid foundation for the Basilica. Both the space in the lower church and the Basilica have high ceilings. The ceiling in the lower church has barrel vaulted ceilings, and the Basilica has a more simple but higher beam on post ceiling (See figure 7). There is a beautiful painting of a Byzantine Empress in the lower church. When the building was being excavated they uncovered the painting after the fresco on top of it, Madonna and Child, disintegrated when exposed to air. It lasted so long because it was perfectly preserved behind the layer of fill within the building.
The next layer down consists of multiple Roman buildings. There are two main buildings, with an alley or passage running between them. One of these buildings was a place of worship for a Mithraic cult worshiping the God Mithras, and the other likely housed apartment-style homes. There is still a spring that is visible in the rooms of the Mithraic worshipers, likely a holy symbol as it was pure spring water. This level also includes a large rectangular courtyard. The outlines of the courtyard are almost directly beneath the current basilica, only slightly larger. Once they had filled in this courtyard in order to build the church on top, the foundation was quite solid. If we go even a bit deeper, there was another layer, buildings burned in the fire of 64. Those are the layers of the building, created because when it came time to redecorate, the ground level had risen around it, turning the site into a low point prone to flooding.
The Roman Forum: The Temple of Antoninus Pius and Faustina
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| Figure 9: Raised green door on the Temple for Anoninus and Faustina |
The Roman Forum is probably the most obvious example of the layers in the city. The Form has been excavated and is now a large tourist destination. One of the best examples in the Forum is the Temple of Antonius Pius and Faustina. The Temple was built in 141 A.D. (Fulford 1994). As you can see from Figure 9, the green door is well above the ground level. There is another door right at ground level, obscured by the stairs. The temple has gone through many uses over the years, but what is clear is the fact that the elevation of the ground rose, covering some of the building, and necessitating a new ground level door. The building had to be excavated, and when it was the green door was at ground level. Some of the stairs on the entrance side were taken and used in St. Peter’s Basilica (Fulford, 1994).
The roman forum was created in an attempt to raise a large portion of ground area. People could easily fill in one house worth of debris to raise the ground level. However, larger areas of land needed a concentrated effort of planning and tons of fill. The Roman forum is estimated to have over 10,000 cubic meters of fill, raising the ground level from six or seven meters above sea level to nine (Aldrete, 2007). Since this was naturally such a low lying level, any rainy season would likely turn the ground into a swampy marsh, that were certainly not as pleasant for folks to walk through. Immediately following the rise in ground level, the first gravel paving was put in place in the forum (Aldrete, 2007).
Ostia Antiqua
The final example I will cite is Ostia Antiqua. Earlier in this website Ostia is described as an ancient bustling port, emphasising the functionality of the river. It was also one of many areas covered by sediment and silt from the river. As a consequence of being buried beneath meters of mud, it is extremely well preserved. The river would bring all of the excess dirt and silt from upstream and deposit it at the then-mouth of the river. The Tiber used to end its riverbound journey and empty into the Thyrrean Sea at Ostia(Refer back to Figure 3: the delta of the Tiber). The mouth of the river, or the delta, is very prone to debris and silt build up. When the city was abandoned after the fall of the Roman Empire, the debris built up quickly, and covered most of the city. The harbor located near the city would probably have needed to be dredged; data from 1873 to 1878 showed an accumulated debris level from the river at around 10.6 metric tons. The river is quite far away now, about 1.86 miles, from the city, due to sediment deposit. For more information refer to my earlier section Flooding and Commerce above.
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| Figure 10: View of the Tiber | Figure 11: View of the Tiber |
Taming the Tiber
It was truly hazardous during the flooding season because floods could be quite violent and left wreckage in their wake. Homes could be destroyed, and livestock was a frequent casualty. Also, when the flooding was at its worst, citizens would be cut off from their usual gathering places such as markets or piazzas. If they couldn’t’ go to markets, they couldn’t get their food. They needed a plan to stop the ever forceful river from killing their livestock and destroying their homes. Ways to do this include, but are not limited to, reservoirs, channel improvement and stabilization, levees, and flood-ways (Aldrete, 2007). Reservoirs are created from damming a river, they are the excess water trapped behind a large wall in order to release water at normal rates. Channel improvement and stabilization comprises of dredging a river, removing the excess or large debris, changing the shape or path of the river, and creating stronger riverbanks. A levee is a large barrier, made of earth or some other material, along the embankments of a river. Romans were actually quite equipped to create dams, however they did not build any in Italy (Aldrete, 2007). So what did they do?
The Roman Sewer, a marvel to this day
The first method of taming the river centered around drainage. Rome is on a flood plain, which means it has many areas of the city at, or even below, the river level during a flood. This was particularly a problem in areas that were lower than the flooding level, but were surrounded by higher land. In cases like that the floodwaters could exceed the higher ring of land and then be trapped in the bowl, dispersing only through evaporation or absorption into the ground. The early landscape of Rome was more akin to marshland in these areas, which is unfortunate because it it also happened to be some of the larger gathering places, such as the Roman Forum, the Velabrum (area connecting the Roman Forum to the Tiber River) or the Forum Boarium. Cores taken from the Velabrum show about four meters of sediment deposits from the Tiber(Ammerman, 2000). These cores also indicated a seasonal marshland, probably during the rainy wet season. Draining out this area would help with commerce by allowing it to be an area for permanent structures to be built (Aldrete, 2007).
This all leads us to the creation of one of the world’s greatest engineering marvels: The Cloaca Maxima, or the drainage and sewer system of Rome. This construction was started by Tarquinius Pricius, the fifth king of Rome (Livy). The project began somewhere around the 600 BC to be an open canal, and then around 100 BC covering was added as the city built up around and on top of it (Pliny). This is the first major public works project in Rome. The drain is set between the Quirinal and the Esquiline hills and it is 1,600 meters long(Aldrete, 2007). It does not take a straightforward path at all, and probably started with extra smaller canals funneling water into the main one, which were all eventually paved over and enclosed. The Cloaca has survived to this day, its exit into the Tiber River is still visible today next to the Ponte Rotto bridge. The drain outlet is 4.5 meters wide and 3.3 meters tall (Aldrete, 2007). The image below (Figure 9) shows that outlet point; it is the arch behind the path, quite overgrown and obscured in today’s time.
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| Figure 12: Cloaca Maxima Outlet | Figure 13: Main drains from ancient Rome |
There were other drains in the city as well, certianly one around the Circus Maximus, and likely one that ran through the Campus Martius, as well as drains for the Travastere neighborhood and the Vatican. The exact locations of these are only theorized locations on the map above (Figure 13) except for the Cloaca Maxima which still has flowing water through it. There are seven ancient sewers in all.
It is worth noting that these drains were meant to divert excess water due to flooding or heavy rains. They were not originally intended for human debris. People began tossing their waste into the river, affecting the quality of the water tremendously and reducing the capacity of the river. There was an estimated 100,000 pounds being moved through the sewer every day by the imperial period (Gowers, 1995). This became more of an issue during flooding (although the increased debris made it quite difficult to navigate the low water during the dry season especially), when the drains would get backed up and even reverse their flow back up into the city. Walking through the excrement and carcasses caused diseases to spread like wildfire (Aldrete, 2007). The drains are meant to drain, and they didn’t have a way to stop water from going in or out. All in all, these drains were incredibly durable, staying up through earthquakes and the force of water for over 1000 years, and they were a success for their intended purpose, draining the low lying areas of Rome.
Who has a Plan?
Julius Cesar
Cesar apparently had many ideas for the city, including some bold hydraulic ideas for controlling the flooding (Suetonius). One of his suggestions was to drain the Pomptine marshes, drain a lake, and cut a canal across an isthmus thus creating a safe harbor by Ostia. This project would have created utilized the marshland for extra passage, while draining away the excess water. It would have also have created a safe way for large ships to deliver good straight to the city. This plan ended up being too extravagant and was not therefore implemented. Cesar also suggested an entire diversion tactic, creating a new path for the river. It would begin just north of the city, by the Mulvian Bridge, then through the Vatican hills via a man made channel, and connecting back to its original path south of the city. This plan didn’t work out because the locations ended up being less than desirable (Aldrete, 2007).
Ateius and Arruntius
A destructive flood in 15 AD heightened the concern for a solution to the flooding. So Tiberius selected five senators to be in charge of preventing flooding and ensuring safe flowing waters of the Tiber. Two of these senators took this charge to heart; Ateius Capito and Lucius Arruntius. They proposed diverting one of the larger tributaries, the Chiani, away from the Tiber and into the Arno River. Additionally, they wanted to split the Nera River and dam the spillway from a lake that fed it. The problems associated with this were not directed at Rome, but the towns that would have been affected because of the diverted water. As inventive as their plan was it was ultimately dismissed by the Senate. (Aldrete, 2007).
Emperor Augustus
During his reign, Emperor Augustus decided to dredge the river’s channel as well as removing large obstacles (Aldrete, 2007). Clearing away the rubbish helped increase the capacity of the river. People who dump their garbage directly into the river didn’t account for the flow of the river at the time, let alone the health hazards that created. The river goes through seasonal flooding, as has been discussed in excessive detail above, but it also has a very dry season where the water runs slowly and is shallow. This is the summer season, especially late summer, and when people dumped their garbage into the river at this time it was more likely to clog the river. Ships attempting to navigate the river were inconvenienced as well, if not stopped altogether. Excessive debris started accumulating and eventually the river bed became full of trash that raised the riverbed and made flooding more likely. The dredging of the river helped reduce the riverbed height and clear away the debris.
Embankments
The ultimate solution for the Tiber river was and still is the embankments. During the Republic a few tuff and travertine embankments were built, with walkways above and a few flights of stairs to get below. They were mainly used as a method to further commerce, not necessarily for flooding. The walls weren’t high enough to offer real protection, and they weren’t continuous either. They were there for ships to tie up to, so it was all right if there was a gap in the embankments. This, however, made it nearly impossible to provide any protection from flooding. The embankment protection was built up by the second century A.D. and they reached five meters. The current embankments today reach ten or eleven meters (Heiken 2005).
Walking along the river you can easily the wall height increasing, then decreasing again as you move further along. This seems to be an attempt to control flooding at the most susceptible spot, right at the heart of the city. There is also a waterfall drop, to slow the river, cause turbulence, and give floods less power. As mentioned earlier, water’s energy is proportional to its velocity squared, so the slowing down the water actually decreases the energy quite a bit.
What is ironic about the river today is that it sits so far below the street level, that you could almost forget about it. The streets along the river and the bridges that cross it are bustling and there are beautiful sycamore trees that arch over the embankments beautifully (There aren’t many places for trees to easily take root in Rome, because so much of the ground is fill and debris). Yet for all of the traffic and foliage it provides, it is neglected. Walking along at the base of the river, it looks abandoned and overgrown. The city has tried to perk up the area, but with annual flooding only temporary exhibits can exist. The remains of old informational signs are half filled with debris and are hopelessly cracked. What once played such a pivotal role in both the good and bad aspects of life is now a broken mess.
The river has such a huge potential for fun, and it has an incredibly deep history, it is a shame to see that go to waste. There is an exciting summer market fair that they set up each summer, with shops and food set up in white tents around the river. Also, about a decade ago, Tom Rankin and friends decided to put modern art up along the walls, which are covered with vines and spray paint. They cleaned up a bit of the Tiber, right near Tiber Island, and were able to make the area more welcoming and exciting.
Conclusion
Rome was situated in one of the most geographically undesirable locations along the Tiber River. Their unfortunate situation caused them to be unusually prone to flooding. Their particular type of flooding, flooding due to high rains over a large drainage basin that funneled into their small channel of a river, was devastating to their homes and livestock. As time went on, these floods left more and more debris, silt, and mud in their wake. It simply became easier to flatten out the rubble and build on top of it, instead of trying to excavate an area that was sure to be flooded next year as well. There is plenty of evidence of how many layers have been developed in Rome. The most famous probably being the Roman Forum, and the most interesting (in my opinion) the Basilica of San Clemente. Flooding was also a dirty business in terms of health. Floods that carry animal carcasses are most likely infested with some sort of disease. It became a necessity to build above the flood level. This wasn’t truly possible until the ports of Rome were no longer Rome’s main source of sustenance. Before, the city had vast ports that were a main source of trade and prosperity, so they couldn’t eliminate their access to the river, the way they can today. The river is buried so far beneath the city that it is easy to forget about it. I think the necessity to escape the floods was what drove them to take such drastic measures. The river truly shaped the city, and it was an integral part of their society, but now it lies alone beneath the hustle and bustle.
References
Aldrete, Gregory S. Floods of the Tiber in Ancient Rome. Baltimore: Johns Hopkins UP, 2007. Print.
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Tristan Songer
Cameron Stuart
Josie Noone
Cecilia Bailey
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