Issues influencing the sustainability of the world’s coastal cities are assessed, reflecting the combination of impending sea level rise and storm surges, subsidence, and increasing growth in populations in coastal cities (using the so-called ‘low elevation coastal zone areas’). Geologic-time scales are utilized to draw parallels to characterize relevant historical occurrences that help to understand the context of projections of impending sea level rise issue to year 2100 being the range of 0.3 to 1 m. Given that Antarctica holds sufficient water to raise global sea levels by 58 m if the ice were to melt, this indicates that even a small percentage of melting of the polar ice caps, should this occur, will have enormous implications to the sustainability of coastal cities which are projected to hold 12.4 percent of the world’s population by 2060.
While issues of sea level rise are highly relevant, the implications of storm surges are shown to be much more critical than sea level rise alone. As well, the rates of land subsidence in coastal cities due to widespread groundwater withdrawals, are also shown to be extremely important in terms of implications to the projected challenges for protecting coastal cities, over the next decades. The result is the combination of predicted sea level rise and associated storm surges, plus subsidence, indicate that intensive efforts need to be focused on developing innovative measures and these must be promoted, to improve the sustainability of the world’s coastal cities. The resulting implications of the needs for innovation will involve growing needs for innovative engineering, and the spectrum of engineering disciplines, to protect coastal cities. Issues of water security will be amongst the very most important facing the world’s populations over the next century.