Imagine living in a city where the ground is slowly sinking under your feet. Now picture this city below sea level, surrounded by water, and kept dry by a system of surrounding walls (levees). This is normal life for residents of New Orleans, a city of over 350,000 people in the US state of Louisiana built on the original floodplain of the Mississippi River.
Previous studies showed that New Orleans is slowly sinking into the ground, increasing an already high flood risk from storms like Hurricane Katrina (Fig. 1). Is that really the case? And if so, at what rate is it sinking? We set out to answer these important questions by using improved radar technology. We further investigated to what extent natural or human processes contribute to the sinking of the city. Our results show that sinking is real and in some areas worse than previously measured. We also found that human actions – mainly pumping of ground and surface water – are worsening the situation.