The influence of a sophisticated water distribution system on urban development in Roman times is tested against the impact of Vesuvius volcanic activity, in particular the great eruption of AD 79, on all of the ancient cities of the Bay of Naples (Neapolis). Written accounts on urbanization outside of Rome are scarce and the archaeological record sketchy, especially during the tumultuous fifth and sixth centuries AD when Neapolis became the dominant city in the region. Here we show that isotopic ratios of lead measured on a well-dated sedimentary sequence from Neapolis' harbor covering the first six centuries CE have recorded how the AD 79 eruption was followed by a complete overhaul of Neapolis' water supply network. The Pb isotopic signatures of the sediments further reveal that the previously steady growth of Neapolis' water distribution system ceased during the collapse of the fifth century AD, although vital repairs to this critical infrastructure were still carried out in the aftermath of invasions and volcanic eruptions.AD 79 Somma-Vesuvius eruption | Pb isotopes | harbor geoarchaeology | Neapolis | paleo-pollution U rban centers have always been critically dependent on a stable water supply, and ancient cities relying on masonry aqueducts were particularly vulnerable to the disruption of their water distribution system by earthquakes and volcanic eruptions (1). The archaeological record of the major eruption of Vesuvius in AD 79 and its effect on the water supply of Naples, then known as Neapolis, and its neighboring cities illustrates well how efficiently the Roman world was able to mitigate the effects of major disasters on the daily life of its population.
Neapolis: Water Supply and VolcanismNeapolis and the surrounding region were supplied with water from the Aqua Augusta or Serino aqueduct, built during the reign of Augustus between 27 BC and AD 10 (2, 3). The Augusta was a regional network supplying eight or nine cities, as well as numerous villas, through multiple branches (Fig. 1A): Nola, possibly Pompeii, Acerrae, Atella, Neapolis, Puteoli, Cumae, Baiae, and Misenum (2, 4). The total length of the aqueduct, including its branches, was ∼140 km. The construction of this monumental hydraulic network helped meet a need to secure the water supply for the strategic region of Campania during a critical period: the establishment of the Principate (2). The aim of the Augusta was to provide water to naval harbors (first Portus Iulius and later Misenum) and the commercial harbor of Puteoli, one of the busiest centers of trade in the Roman Empire (5), as well as to cities, coloniae, and villas of influential individuals. At an unknown time between the fifth century BC and the Middle Ages, the Bolla aqueduct (Fig. 1A) was constructed to bring additional water to Neapolis (3).One of the challenges in maintaining the Augusta and, with it, the integrity of the water supply of the heavily settled area around Neapolis, was counteracting the slow movements of the ground associated with the activity of volcanic sy...