Flooding of the Tiber: Notes

Hey guys! It's Consul Lisa! I went to the lecture on the Flooding of the Tiber tonight on behalf of all of us at Classics Club! These are the notes I took : )

- floods and civilization go hand in hand

- civilizations arose on flood plains, near rivers

- easy to build on, good for irrigation, fertile, good for farming

- attractive but dangerous (Katrina, 19th/20th century floods in China wiped out a lot of the population in just 3 floods)

- Rome along Tiber River, right below Tiber island

- natural place for trade

- between hills: low valleys and plains

- before: valleys were marshes and swamps

- Rome was at the most flood prone stretch of the Tiber River (awesome...)

- Rome continuously occupied 3700 years

- flood marker plaques on the walls (showed the heights of the different floods)

- earliest plaque in 1277

- hydrometer next to a church near Tiber River, record of floods from 1495 on

- before 1200 there were no plaques to record flood heights, but there were literary records and geological evidence

- 44 accounts of 33 floods, 18 famous names (Cicero, Cassius...etc.)

- Tiber River: 400 km from Apennines all the way to Ostia where it empties out

- Tiber riverbed changed very little (now it still looks like it did in antiquity)

Characteristics of Floods in Rome

Seasonality:

- Fall/Spring rainy seasons + snowfall from Apennines (75% of floods take place in these months)

Duration:

- Major Flood: 7-9 days

- Minor Flood: 3-5 days

- above is true for all floods (modern and ancient)

* 1789: Pantheon flooded!

Tiber Classification:

- Ordinary level: 5-7 m above sea level

- Elevated level: 7-10 m above sea level

- Ordinary flood: 10-13 m above sea level

Frequency:

- Minor flood: 1 every 5 years

- Major flood: 1 every 19 years

- all ancient romans would experience 2 or 3 major floods in their lifetime

How far did they reach?

- ground levels in rome much higher now than in antiquity

- Campus Martius, Forum Boarium, Emporium, Transtiberium, Valley of the Circus, Forum Romanum: would have been affected by flood (in major flood, the 7 hills would become like islands)

Floods and different types of buildings

Roman Forum

- political heart

- squarely in the flood plain (would be completely flooded)

Forum Boarium

- early economic heart

- in flood plain (would flood all the way halfway up the columns)

- would have been very first place to be flooded

Coliseum, Flavian Amphitheater, Circus Maximus

- all in flood zone

- did they just not care?

- every building seems to have been built without considering flooding

- except for bathhouses (all were moved to just out of the flood zone, except for the first 2 that were built)

- bathhouses have more vulnerabilities to floods than other buildings

Domestic

- wealthiest romans could afford private homes (the domus)

- 790 domus

- 1400 apartments

- wealthy could choose where they wanted to live

- most of them (85%) were on hilltops (out of flood zone)

- this wasn't all because of floods, but it was a nice bonus to be out of danger of flooding

Anti-flood strategies

- not one single strategy

Fill: Raise the ground levels

- putting tons of dirt down to raise the ground level to make it higher so water doesn't come in (Forum Romanum)

- Campus Martius

Drains/Sewers:

- "The Great Drain" (Cloaca Maxima)

- built before they built the city (to drain the marsh)

- storm drain (quickly carries away flood water)

Divert: Canal Schemes

- cut off tributaries

- early empire: in the end they decided not to cut off the tributaries and do nothing

- because to cut off the tributaries would be to "lessen the majesty of Father Tiber" (Tiber River was considered a god)

Contain: Embankments

- most common way

- if they had, city would have been safe

- some were built, but not continuous or high up enough (only for unloading boats)

- 1870 flood: finally decided to build embankments (18 m above sea level)

Why didn't the Romans do more to prevent floods?

- they had the technology

- study of vulnerability to flooding

- they were either very resistant to floods, or got rid of them really quickly

Topography:

- hilly and flat

- no matter where you were, you were near higher ground (low mortality rate during floods, different from other places)

Construction Methods:

- horizontal pressure from flood against walls (ancient walls were super thick, could resist this pressure)

- today this would be a problem, walls are super thin

- floods undermine foundation

- roman foundation=hole with concrete, resisted floods

- in all accounts of floods, not one record of important buildings being damaged

Elite Housing Distribution:

- lived on hills (only poor lived near the river)

- the floods would get rid of poor bad housing, make room for more wealthy housing

Food Storage:

- down by river (could be bad for grain: mold...etc)

- but no sources of famine (only after major floods not minor)

- built really resistant warehouses

- only one door, tiny windows, thick thick walls

- kept thieves out, kept water out too, grain was kept dry

Water Supply System:

- after a flood, people need to be supplied with fresh water (could be a big problem)

- aqueducts! (solution, get water from far away: above the start of the flood)

- Roman temples built on podiums (height of podium was according to height that floods could reach)

- libraries too

- this way all the valuable items were safe

*ROME = SUPERIOR*