Text: Northern Autumn
Edited by Beiqiu
Construction took place in the flood-prone lowlands in the mid-1st century BC, and Roman residents participated in large-scale landscape improvement projects and flood control measures. The urbanization of Rome has given rise to new ecological challenges, including rapid sedimentation and churning floods. And the inhabitants of Rome used a series of adaptive strategies to cope with their unstable rivers.
Over the centuries, they have continued to mitigate the effects of riverbank flooding through strategic urban planning, land reclamation, flood protection construction, and bureaucratic oversight of the river's landscape. Despite the ability of the ancient Romans, they chose not to develop large-scale engineering projects to prevent floods altogether. Thus, the so-called Eternal City is seen as a resilient city, one that persevers in the face of ecological conditions and recurrent floods.
1. Advantages and challenges of the Roman river landscape
Rome's natural landscape is the product of a dynamic, high-energy environment that has been shaped by volcanic and river forces since the Pleistocene. Between 6 million and 0 million years ago, a series of volcanic eruptions produced huge volcaniclastic deposits that left plateaus in the Roman region.
This soft volcanic rock, known as tuff, was then eroded and deeply cut by the Tiber and its tributaries. These geological processes left the character of the later city: steep hills separated by low-lying valleys, in one of the most flood-prone sections of the Tiber.
This environment offered a variety of opportunities and challenges for the development of the Roman city. In addition to fresh water and arable land, as well as trade and communication networks, Rome's exceptional location along the Tiber River offered important ecological advantages, making the site particularly attractive for human habitation.
Later Romans, looking back at the achievements of their earliest ancestors, seem to have recognized that their landscape offered them many advantages. In the 1st century BC, the Roman statesman Cicero raved about the mythical founder of Rome. The creation of a city is something that must be done with the most diligent foresight, and Romulus chose a location with incredible opportunities.
The city can not only get what it needs from the sea, but also export the excess, and the city can not only import goods that are urgently needed for cultural life from the sea, but also receive goods transported by land.
It is important to remember that Cicero's meditations on the origins of Rome at the hands of a revered founder are purely speculative, influenced by mythological stories that have been circulating over the centuries. Although the cities of his time were very different from the settlements he imagined had existed some 700 years earlier, Cicero rightly concluded that Rome's position in the Tiber Valley and the wider Mediterranean region provided important economic opportunities for its inhabitants.
Proximity to the river, while advantageous, also means that the location is prone to flooding. When the Tiber River floods, which probably happens all year round during the rainy winter months, the valleys of Rome are submerged.
In the first few centuries of settlement at the Roman site, this seasonal flooding may not have caused major problems. Archaeologists have found traces of human settlement in Rome dating back to the Late Bronze Age (late 2nd century BC), and the available evidence suggests that this dwelling was relatively small and limited to a group of huts on the hills.
Although during the Late Bronze Age and Early Iron Age, the valley undoubtedly hosted various events, such as agriculture and animal husbandry, as well as harbours near the riverbank, there is no evidence of contemporary architectural infrastructure in the Lowlands.
Considering that the main building materials of that era were mud-based wattles and smears, the structures built in the floodplain were severely damaged every year. It can be assumed that either lowland activities do not require physical structures, or the inhabitants accept regular destruction and are ready to rebuild it using cheap and readily available materials.
When Rome was submerged, the inhabitants could temporarily dismiss their valley activities and quickly move to the safety of the hills. The later Romans, who themselves were familiar with the problem of floods, responded to it in this way: "When the river flooded, as often happened, they were Xi to cross the river by ferry at this time".
While this was undoubtedly an inconvenience, early floods could have caused minimal death and damage. This ecological situation, while defensible in a pre-urban environment, will become more problematic as settlements develop and begin to use lowland spaces in a more substantial way.
Paddle between the hills is impractical, and the valley may remain uninhabitable even after the floodwaters recede. The stagnant water left behind by receding floodwaters can breed mosquitoes, which can carry malaria. In order to build the city of Rome, residents were forced to alter their river landscape and make early urban investments that seemed aimed at mitigating the effects of flooding.
II. Early Flood Control in Rome
Archaeological records suggest that the 6th century BC was a period of transition: Rome evolved from disjointed hut settlements into a cohesive urban center. It is worth mentioning that as one of the earliest urban construction projects, the early inhabitants chose not to confine themselves to the relative safety of the hilltop, but chose to build in the river valley.
In fact, the first temple built in Rome was located directly on the banks of the Tiber near the river port. Excavations have revealed the temple's stone pulpit and associated altars, dating back to the early 6th century BC.
At the top of the stone pulpit will stand a temple building of thorns and smeared walls, topped by a tiled roof and lavish architectural decorations, including statues of Hercules and Minerva.
The temple is often associated with the cult of Fortuna, as the deity is associated with a later sanctuary on the same site. This lady of luck is undoubtedly the right person for the port environment, as sea travel and cross-cultural interaction in the ancient Mediterranean were often dangerous and unpredictable.
Although the banks of the Forum Boarium are essential for the movement of people and goods through the port, the area will be the first and most often flooded, making it a particularly vulnerable location for investment in this type of construction. Recent geoarchaeological surveys have revealed that the temple was strategically placed on a landscape that is significantly higher than the rest of the valley: the raised part of the riverbank that extends from the foot of the Capitoline hill.
This stretch of the river bank is protected at a much lower surface elsewhere in the valley, more than 5 meters above the floodplain immediately to the south, where ships arriving in Rome in prehistoric times may have been pulled ashore. Located on a nearly 2-meter-high podium on the banks of the high river, this 6th-century harbour temple is prominently positioned and at a height that protects it from the threat of flooding.
Not far from the banks of the river, a large-scale land reclamation project was carried out in the valley between the two main hills of Rome: the Capitoline and the Palatine. In order to support a growing population and permanent buildings, this flood-prone lowland problem needs to be addressed. Archaeological exploration in the valley has shown that up to 20,000 m3 of sediment was dumped into the low-lying basin, initially raising the ground by almost 2 m.
This monumental undertaking required the cooperation and labor of many and seemed to have been specifically designed to raise the ground from the threat of flooding, so that even if the Tiber overflowed its banks, there would be a land bridge between the Capitoline and the Palatine hills.
This investment in land reclamation provided valuable new space for the development of public institutions, including some of the earliest political and religious spaces in Rome. Eventually, this area will be known as the Roman Forum, the civic center of the city.
In conjunction with this reclamation, the Romans began to build an extensive drainage system. The first phase of this infrastructure, known as the Cloaca Maxima or Greatest Sewer, discharges water from the newly reclaimed Forum Romanum into the Tiber River, helping to speed up the post-flood drying process.
Although it originated in the open access of a tributary of the Tiber, eventually the cloaca was closed and buried under further landfills. This underground system is an advanced infrastructure even in its original form, which has been rebuilt, expanded, and maintained throughout the ancient period, so it helps to transport water and waste into the river. Even today, the ancient Chili cloaca estuary is still visible, as it terminates on the east bank of the Tiber.
When the first permanent structure was erected in the lowlands of Rome, the inhabitants employed a multifaceted strategy, so to speak, to adapt to the flooding conditions of the Tiber and to prevent at least some devastating consequences. In the early years of the city's history, various measures were taken to take advantage of the commanding heights of the landscape, the use of stone cattails to raise structures, land reclamation and canalization of the ground, drainage systems and tributaries, which will continue to be used for centuries to come.
As they urbanize, their landscapes change, exacerbating the problems they are trying to solve. As the city grew, the river changed, and as the river changed, the inhabitants were forced to adapt further.
3. River dynamics
The coring of the Roman valley shows that the landscape has changed radically with the early stages of major urban development. After centuries of relatively steady and slow sedimentation, the Tiber moved westward in the 6th century, and silt deposited by floods on the banks of the river began to accumulate rapidly along the riverside in the Forum Boarium area.
Geoarchaeological evidence suggests that a staggering 8.6 m of sediment was accumulated in the 5th century BC alone. The river sediment is close to the height of the Temple of Fortuna, so in just a few generations, the location that was once largely protected from the threat of flooding has become extremely vulnerable.
Changes in the hydrological regime of the river have also reshaped the valley's topography: the once low-lying river harbor banks have silted up and replaced them with wide, high-lying banks. The deposition of the Forum Boarium area lasted at least until the 3rd century BC, raising the ground level by 10 m in parts of the valley. Based on the currently available evidence, it is difficult to determine the reason for this change in the location and sedimentary behavior of the Tiber. Rivers are highly dynamic and sometimes unstable. They can move riverbeds, erode large tracts of land, and create new floodplains.
They are susceptible to climate change, precipitation fluctuations, and even small-scale changes in sediment or hydrological inputs and outputs. In addition to these natural forces, human activities can cause considerable instability in the riverine landscape. According to the archaeological record, the urbanization of Rome in the 6th century appears to have been both rapid and massive. In just a few generations, the Romans reclaimed part of the lowlands and invested in more than a dozen monumental buildings.
To support documented construction activity and a potentially growing urban population, wood will be used as a building material and its primary fuel source. Although much of the area around modern Rome is not currently densely forested, paleobotanical evidence suggests that central Italy was once densely forested before human settlement spread.
In addition to the impact on land, deforestation has a significant impact on river systems. As trees are cut down, sediment can easily erode from the slopes and wash into the river valley. Unfortunately, ancient pollen data is currently limited, making it difficult to track the chronology of local deforestation. Later anecdotes suggest that by the beginning of the first century AD, forests as far away as Pisa were being developed to meet Rome's demand for wood.
Although the evidence is not conclusive, it still highly suggests a link between urban growth, deforestation, and change in the Tiber River. The major river dynamics of this period not only triggered sedimentation, complicating operations around the river port, but also appeared to have led to an increase in the scale of flooding.
As the city grew and the valley ground rose, there was less room to accommodate floods. The available evidence suggests that flooding reached greater heights over time.
Coring surveys of the valley revealed the alluvial sediment characteristics of flood sediments dating back to the 6th century BC, 6 meters above sea level, which reached 3 meters by the 9th century BC. By the 1st century BC, historical records of the Roman flood showed that buildings at much higher elevations were threatened by the floods.
As the city grew, the flood challenge in Rome persisted, and in the face of changing conditions, initial mitigation efforts quickly became inadequate.