Global mean sea level has risen nearly 9 inches since 1880, with over two inches of that over just the last 25 years. The rising water level is primarily due to two factors: additional water in the oceans coming from melting glaciers and ice sheets; and the thermal expansion of seawater as it warms. Climate models estimate that over the course of the century, global sea levels will rise at least a foot even if efforts to reduce greenhouse gas emissions are quite successful and, in the worst case, levels could rise as much as 8 feet.
Faced with this situation, the greatest concerns are, initially, increasing amounts of coastal flooding and erosion and, as things get worse, inundation of coastal regions making many places uninhabitable and creating millions of climate refugees.
Recently, computer modeling studies have focused on an additional imminent problem: the flooding of coastal wastewater infrastructure, which includes sewer lines and cesspools.
A new study by the University of Hawaii at Manoa is the first to provide direct evidence that tidally driven groundwater inundation of wastewater infrastructure is already occurring in urban Honolulu. The study shows that higher ocean water levels are leading to wastewater entering storm drains and the coastal ocean. The result is degradation of coastal water quality and ecological health.
The researchers used chemical tracers to detect groundwater discharge and wastewater present at multiple low-lying areas during spring tides. During high tides, storm drains become channels for untreated wastewater to flood streets and sidewalks.
People tend to think of sea-level rise as a future problem, but there are already serious effects going on today that are only going to get worse.
Photo, posted August 23, 2011, courtesy of Eric Tessmer via Flickr.