coauthored with Jody Dean–

[Over com­ing weeks, the staff of City Atlas will be pre­sent­ing sum­maries, analy­sis, and pub­lic feed­back on the city’s mon­u­men­talSIRR report about rebuild­ing and resilience, which includes lessons learned from Hur­ri­cane Sandy and plans for the city in the face of new chal­lenges from a chang­ing climate.]

The cli­mate analy­sis sec­tion includes this photo, a reminder that NYC has flooded in the past. (Photo NYT)

Extreme events often prompt ques­tions that begin with “why?”  Why now? Why me? Why here? Due to the chaotic nature of the cli­mate sys­tem, there is no sim­ple answer to these ques­tions. Part of the answer, though, can be found by exam­in­ing past cli­mate trends and pro­jec­tions for the future. Extreme events like Sandy cause huge impacts, the most jar­ring being the loss of lives and the dis­place­ment of peo­ple from their homes. There are also mas­sive mon­e­tary costs asso­ci­ated with rebuild­ing. We will all bear the bur­den of these costs, through taxes and resource reallocation.

The Spe­cial Ini­tia­tive for Rebuild­ing and Resiliency (SIRR) report offers tar­geted sug­ges­tions for pol­i­cy­mak­ers regard­ing the devel­op­ment of more resilient sys­tems for New York, in order to make the impacts of extreme events and cli­mate change man­age­able rather than catastrophic.

In time and with the increased polit­i­cal grav­i­tas deliv­ered by this exten­sive report and ongo­ing dis­cus­sion around it, the con­ver­sa­tion can shift from “why did this hap­pen to us?” to “how can we adapt and rebuild respon­si­bly”? This refo­cused ques­tion allows us to move for­ward and is made pos­si­ble by under­stand­ing the chronic haz­ards faced by the city and the poten­tial impacts of extreme events, whose fre­quency and sever­ity are likely to increase with the chang­ing climate.

The full report includes a cli­mate analy­sis sec­tion (hi res pdf) that doc­u­ments the impact of his­toric extreme weather events and pro­vides a con­text for future cli­mate sce­nar­ios, along with the pro­jected costs. The SIRR uti­lizes cli­mate mod­els devel­oped for the forth­com­ing Inter­gov­ern­men­tal Panel on Cli­mate Change Fifth Assess­ment Report (IPCC AR5). The AR5 con­cludes that “long-term changes in cli­mate mean that when extreme weather events strike, they are likely to be increas­ingly severe and dam­ag­ing.” Despite the extreme and his­toric nature of the event, Sandy was not the first storm to cause sig­nif­i­cant dam­age. The time­line below illus­trates other coastal storm events with major impacts on New York City. As with Sandy, the effects of these storms were expe­ri­enced all along the East­ern Seaboard.

The vul­ner­a­bil­ity of the city to coastal storms is noth­ing new, but as pre­vi­ously noted, cli­mate change will exac­er­bate the sit­u­a­tion by wors­en­ing extreme events and chronic con­di­tions. As indi­cated in the IPCC AR5, over the past cen­tury sea lev­els in New York City have risen over a foot, while simul­ta­ne­ously tem­per­a­tures are increas­ing. The sci­en­tific con­sen­sus is that these trends will accel­er­ate and this is high­lighted in the New York City Panel on Cli­mate Change (NPCC) 2013 cli­mate pro­jec­tions, which were included in the SIRR report.

Source: NPCC

In addi­tion to these chronic haz­ards, another vul­ner­a­bil­ity high­lighted in the SIRR is the city’s use of out­dated Flood Insur­ance Rate Maps (FIRM’s), which show the per­cent­age of land that lies within the so-called “100-year” and “500-year” flood­plains. At the time that Sandy hit, the FIRM’s had not been updated since 1983, though in 2007 the City for­mally requested that FEMA update the maps to include the last 30 years of data. The lack of updated maps left the city with an inac­cu­rate view of the per­cent­age of land at risk for flood­ing and the areas that flooded dur­ing Sandy were sev­eral times larger than the flood­plains out­lined in the 1983 FIRM’s. The SIRR empha­sized the impor­tance of reg­u­larly updated maps to assist with adap­ta­tion and mit­i­ga­tion strate­gies for coastal flooding.

The cli­mate analy­sis sec­tion also explained the fre­quently mis­un­der­stood clas­si­fi­ca­tion of a “100-year” or “500-year” event. Clas­si­fy­ing an area as part of a “100-year flood­plain”  indi­cates that there is a 1 per­cent chance of a flood occur­ring in the area in a given year and that expe­ri­enc­ing a 100-year flood does not decrease the chance of a sec­ond 100-year flood occur­ring that same year or any year that fol­lows. Fol­low­ing these cal­cu­la­tions, Klaus Jacob writes in the June issue of Sci­en­tific Amer­i­can that, “the chance of what had been a one-in-100-year storm surge occur­ring in New York City will be one in 50 dur­ing any year in the 2020s, one in 15 dur­ing the 2050s and one in two by the 2080s.” The city is now work­ing again with the NPCC to develop more accu­rate “future flood maps” to assist with the rebuild­ing, plan­ning and adap­ta­tion efforts.

The cli­mate analy­sis sec­tion con­cludes with spe­cific, forward-looking ini­tia­tives for plan­ning along New York City’s 520 miles of coast­line, includ­ing a net­work of flood­walls, lev­ees and bulk­heads to pro­tect build­ings and inhab­i­tants. More than encour­ag­ing “emer­gency pre­pared­ness,” longer-term sce­nario plan­ning will be nec­es­sary in order to ade­quately safe­guard New York and its grow­ing pop­u­la­tion. Fur­ther, cli­mate projects need to be reg­u­larly updated in order to ade­quately inform deci­sion making.

Advo­cat­ing that we “plan ambi­tiously,” the SIRR report sug­gests that mit­i­ga­tion efforts require buy-in from pol­icy mak­ers, plan­ners and insur­ers and civil soci­ety. Cyn­thia Rosen­zweig, NPCC co-chair, makes the salient point that adap­ta­tion plans can­not suc­ceed “with­out tak­ing the voices of neigh­bor­hoods into account.” In order to best address ques­tions of “why me,” vul­ner­a­bil­ity must be ana­lyzed at mul­ti­ple lev­els and the result­ing plans backed by finan­cial invest­ment for address­ing the con­tin­ued threat of cli­mate change. Above all, the SIRR report empha­sizes that build­ing capac­ity for resilience requires accu­rate data to assess the poten­tial impacts and the tools and finan­cial resources avail­able to imple­ment solutions.

The full report can be found here, and is a mar­vel of lucid expla­na­tion: it’s a self-contained, bench­mark work that inte­grates cli­mate and urban plan­ning for the most pop­u­lous city in the world’s largest economy.

Addi­tional Reading:

–Coastal sub­si­dence also plays a role in NYC coastal vul­ner­a­bil­ity. Pro­vid­ing his­tor­i­cal analy­sis and vivid maps, Mark Fischetti’s Sci­en­tific Amer­i­can arti­cle explains how North Amer­i­can glac­ier retreat began over 20,000 years ago and lit­tle by lit­tle, has resulted in the east­ern U.S. land­mass sink­ing as the crust adjusts to the unloading.

–The ques­tion of whether or not rebuild­ing after nat­ural dis­as­ter has been hotly debated since Sandy. Tom Ash­brook tack­led this ques­tion in a Feb­ru­ary 2013 On Point Pod­cast.

– Our inter­view with Klaus Jacob, who also raises the ques­tion of rebuild­ing in areas that will become increas­ingly endan­gered over time.