Saying that low-lying and leveed areas of coastal cities are particularly vulnerable to sea level rise is axiomatic. However, planning for and imagining the consequences of predicted sea level rise is a difficult exercise for humans, as our species is prone to cognitive bias that can prevent us from accurately understanding reality and making change (e.g. “The Current Moment Bias,” or the “Status-quo Bias”).
When I was living in Baton Rouge, Louisiana pre-Katrina, I never imagined the destruction that hit southern Louisiana even though I was well aware that nearly half the land in New Orleans is situated below sea level. Like most people, I assumed the natural and man-made levees would continue to protect the city from the sea as they had done since the great flood of 1927 .
Living in southern Louisiana post-Katrina and hearing first hand stories of loss and destruction – walking the city and seeing blocks of homes without walls with sand and debris where dining and living rooms were – was a profoundly sad and galvanizing experience. Many urban designers around the globe expressed a desperate desire to provide a design solution to prevent similar future human and environmental tragedy.
The biggest value urban designers can provide is imagining of alternate ways of building, developing workable solutions and seeking political support/funding for implementation of the best ideas. To address flood vulnerability in a neighborhood slow to recover from the damage caused by Hurricane Katrina, I proposed a strategy of topography building utilizing sediment from routine navigational canal dredging. The project site is located adjacent to the industrial canal, and the 65,000 cubic yards of material needed to construct the entire lock would take the Army Corps of Engineers dredge ship Wheeler only eighteen days to dredge and deliver. Currently, the dredge material is dumped off the coastal shelf of the Gulf of Mexico, because it is the cheapest way to dispose of excess land.
What was difficult to imagine pre-Katrina is clear now: the destruction caused by levee breaks and tidal surge was exacerbated by the loss of protective land, the result of channelization, an inadequate levee system, and imprudent development in low lying areas. With this in mind, it is now more clear what can go wrong in our coastal cities as sea levels rise…except that the looming disaster is still an imagined alternate future, rather than a looming reality.