Debris Accumulation in Ancient and Modern Cities

A study of 13 cities shows that, for at least 10,000 yr, debris has accumulated and raised average elevations of cities and towns at rates of 10 to 400 cm (0.3 to 13 ft) per century. Although short-term increases result from natural disasters and wars, most accumulation derives from normal peacetime activities. A rate of 140 cm (4.7 ft) was obtained for both Bronze Age Troy and 20th Century Manhattan; this value is approximately twice the median for the 13 cities. The 400-cm (13-ft) per century figure suggests there is a limiting rate above which it becomes easier to abandon the site. On the long-term basis, the only viable alternatives to accumulation are those based on recycling or continuous engineering control of all resources.