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This geoarchaeological analysis illustrates the extreme consequences that occur when protection measures related to coastal sites and associated environmental conditions are overlooked. Two ancient Greek cities, Herakleion and Eastern Canopus, originally occupied low-lying delta coastal areas along the Canopic channel of the Nile. Both were unprotected against flooding, earthquake, tsunami, and consequent subsidence. These sites, recently discovered in Abu Qir Bay on the northwestern margin of Egypt's Nile delta, were lowered a total of 8 m during the past 2500 yr, and now lie at water depths of 5-7 m. The two cities were located along the delta coast at river mouths that flooded annually, and man-made structures were built directly on underconsolidated sediment prone to geohazards. Processes leading to their submergence are interpreted on the basis of integrated archaeological, physiographic, geological (including cores), and geophysical (side-scan sonar, nuclear resonance magnetometer, high-resolution seismic) information. Gradual subsidence due to relative sealevel rise (eustatic rise, land lowering by sediment compaction) accounted for 4-5 m of submergence. Episodic failure during floods and earthquakes by loading and sediment remobilization of the water-saturated substrate upon which the cities were situated likely caused the additional 3-4 m of subsidence. Without foundations, pilings, dikes, or other protection measures, it is not surprising that the sites, over the long term, were damaged and subsided completely into the bay. Ancient cities discussed here cause us to reflect on present-day site selection and construction practices in modern deltaic and associated wetland settings, and potential challenges related to substrate failure and other coastal hazards.

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