Flood and civilizations have always been companions. —Greg Aldrete, professor
Five years ago this summer, Cedar Rapids, Iowa, experienced a major flood event. Nearly 10 square miles, or 14% of the city's area, was inundated, including nine urban neighborhoods and its downtown core. In the years since, the city has been implementing its recovery plan. The plan—developed with thousands of hours of community input—includes a variety of response tactics, from property acquisitions and new flood infrastructure construction to updated emergency preparedness planning and improved stormwater management policy.
Unfortunately, Cedar Rapid is one of a number of places devastated in recent decades by water: the East Coast communities impacted by Superstorm Sandy, the Gulf Coast towns and cities ravaged by Hurricane Katrina, Asian countries hit by recent tsunamis, and Central European countries that experienced severe flooding in 2010. These events are occurring with ever greater frequency and severity.
Flooding in Cedar Rapids, 2008
The processes, outcomes, and implementation stories that emerge out of previous recovery planning are a critical resource for more recently impacted communities. The new academic network Disaster University, for example, was formed specifically to pool resources and think critically about what does and doesn't work in the days, years, and decades following a devastating natural disaster.
One inevitable and increasingly frustrating question emerges in all of these discussions, as it did recently in a New York Times article on the Cedar Rapids recovery. Why bother rebuilding in the floodplain? Why waste any more money or resource recovering something that will certainly flood again? The implied polemic—often framed as "rebuilding versus retreating"—is, in reality, much more complicated.
Why Rebuilding (Alone) Won't Work
The Earth is the Water Planet, and the only water planet we currently know. Human beings have become one of the most significant forces of misusing water. —Carol Franklin, Design for Flooding
One thing probably everyone can agree on: business as usual is no longer a viable position. For many generations, our cities have been built and adapted to co-exist with water in aggressively engineered ways. Rain that becomes stormwater is hustled off paved surfaces into drains and pipes, and then follows an intentionally accelerated course to our natural water bodies. The edges of rivers are leveed and walled—creating, in effect, a larger "pipe" for this run-off. Water is treated as a problem, one that needs to be moved quickly away.
Rebuilding in the floodplain, as an act of recreating what once was, presents the risk of flood again. And as extreme weather events occur more frequently and greater volumes of water accelerate through our engineered systems, this vulnerability to flood damage is even greater and with more potential severity.
In Cedar Rapids, the recovery plan recommended rebuilding efforts that would not simply replicate what was, but rather provide more effective and sustainable solutions. This included flood-proofing new and existing structures by raising mechanical systems and using water-friendly materials at low elevations. Another strategy was the promotion of integrated stormwater management—minimizing system stress by incorporating best management practices like bioswales, porous pavers, and pavement reduction.
Cedar Rapids framework plan
Why Retreat (Alone) Won't Work
We live in watersheds. More importantly, we live in estuaries. More than half the population of North America lives on coasts and estuaries...and that figure is rising. —Pierre Belangier, Urban Fabric lecture series
What appears to be a silver bullet is often a fallacy, as is the case with the call to retreat from our war with water. It dramatically oversimplifies an incredibly complex problem. Following a visit to Staten Island after Superstorm Sandy my colleagues Hope Stege and Laura Marett eloquently wrote:
Water is, in many ways, a driving factor of urbanism. It has determined the location of the world's largest and most successful cities, whether at natural harbors, critical points along major waterways, or sources of fresh water. But now, the same access to water that has been a locational advantage in the past makes cities increasingly vulnerable to a dangerous mix of storm impacts, man-made disasters, climate change, and rising sea levels.
Given the scale of the proposition, relocating the country's floodplain population does not seem logistically or economically possible. And, even if it were, it would come at the loss of nearly all of our economic and cultural centers.
In Cedar Rapids, the recovery plan calls for partial retreat, recommending city to acquire as many properties as possible within the most vulnerable 100-year floodplain. Since the flood, nearly 1,300 properties have been acquired. This minimizes risk for future damages and gives the river more room to breathe by introducing more open green space.
Cedar Rapids community meeting
A Truce: Layering Strategies
While it would be an overstatement to say that the great metropolis of ancient Rome lived in harmony with the Tiber, there existed at least a very uneasy truce; unlike today, when unruly rivers are viewed as objects to be tamed, the Romans were willing to cede a measure of independence to Father Tiber. —Greg Aldrete
We must start imagining what a truce with water would look like. For this, there are few examples in the modern world, but one significant ancient precedent.
Greg Aldrete's Floods of the Tiber in Ancient Rome describes five characteristics that helped to minimize flood impacts in Rome. First, Rome's distinct and varied topography offered a range of conditions—from the high, dry slopes of its famed Seven Hill to acres of low-lying marshland. Secondly, construction methods were aligned with elevation. Builders employed wood construction on high-and-dry sites and masonry construction in lower lying areas. Third, residential patterns placed the majority of the city's housing atop the city's higher topographic features. Fourth, food supplies were stored in fortress-like courtyard buildings that, though positioned close to the Tiber for ease of transport, could easily be flood-protected. Fifth, water supply in the city came from more distant sources, allowing potable water to continue un-impacted and uncontaminated by flood waters.
Aldrete interestingly concludes that "religious scruples" over altering the Tiber probably contributed to Ancient Rome's flood resilience. This attitude of embracing the Tiber's natural rhythms, coupled with these five critical characteristics, allowed the city to coexist with water. As a precedent for flood resilience, this urban framework is surprisingly relevant in the face of today's environmental challenges.
In Cedar Rapids, the new amphitheater is an example of layering strategies and embracing water. The river's edge, once steep and erodible, has been restored with a shallower slope lined with riparian vegetation. All of the vulnerable site elements (e.g. electricity) are housed on higher ground or in elevated positions. The landscape elements, from the stage to the seating, are designed for floodwaters to flow along and around them. The new levee is planted in native meadow grasses rather than mown lawn, providing biodiversity and greater potential for infiltration.
At the heart of the climate change and flood issue is our attitude toward nature. We need to make a fundamental shift in which the power of water is understood and respected. What would our cities look like if we started imagining water as a resource to be capitalized upon rather than a problem to be eliminated? From our truce we may create a more productive, harmonious future.