September 28, 2017

Beginning to Assess the Magnitude of Destroyed Housing After Maria

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The devastation caused by Hurricane Maria is becoming a humanitarian crisis in Puerto Rico and the U.S. Virgin Islands. While power has now been restored to a water production plant in the US Virgin Islands, the Pentagon is reporting that almost half of Puerto Rico’s residents have no potable water. Puerto Rico’s power grid is decimated, with 80 percent of long-distance transmission lines and all local distribution lines damaged. In parts of Puerto Rico, particularly remote areas that remain cut off, food and medical supplies have dwindled. The administration’s waiver of the Jones Act, which effectively required that US-flagged vessels be used to bring relief supplies, will increase the speed at which supplies can be brought to the islands, but huge hurdles still remain to get supplies from the ports to where they are desperately needed.

Compounding the physical and logistical challenges of relief and recovery is the extensive poverty in Puerto Rico. Homeowners in Puerto Rico have a median income of only $25,200, barely one-third of U.S. homeowners overall. Puerto Rican renters, with a median income of $11,300, have even less to draw upon. These individuals and families will have an even harder recovery if relief efforts don’t adequately address their needs. In the short term, this means quickly getting adequate necessities—water, food, medicine, and fuel—to the impacted areas and allocating funds to begin the longer process of recovery and rebuilding, all of which must be done with resilience in mind, to limit the damage to lives if another hurricane strikes the islands.

PR flooding.jpg

Individual scenes of devastated homes and communities have been making their way into the national consciousness, but now the scope of the terrible physical devastation is slowly coming into view. Imagery from the Copernicus Program’s Sentinel satellites, processed by the Dartmouth Flood Observatory, shows that flooding in Puerto Rico was concentrated along the coasts and several rivers. (Further flooding in Quebradillas and Isabela in the northwestern part of the island is possible should the Guajataca Dam fail.)

But focusing on flooding gives an incomplete picture of the destruction Maria caused, as damage proxy maps for eastern Puerto Rico created by NASA’s Advanced Rapid Imaging and Analysis (ARIA) team using the Sentinel data show very substantial damage in areas far beyond the flooding. FEMA has been combining these maps with building infrastructure data to identify concentrations of damage for the purpose of directing its Urban Search and Rescue teams.[1] While the maps provide a good sense of the widespread damage, they don’t allow for a true property-level analysis. 


Severity of damage ranges from yellow to red. Purple areas indicate census tracts with poverty rates above 50 percent. Source: NASA Damage Proxy Map; U.S. Census 2015 American Community Survey, 5-year Sample, Table S1701

Although we don’t yet have full damage estimates for Puerto Rico and the U.S. Virgin Islands, the extent of the destruction on the nearby island of Dominica—also hit by Maria—may provide a guide. Recently completed property-level assessments for Dominica by the Copernicus Emergency Management Service show 100 percent agricultural losses and 90 percent of houses damaged. Analyses of eight areas of interest on Dominica—coastal and inland—reveal that 60 percent of the affected homes were either destroyed or highly damaged. If we apply those ratios to the 1.56 million housing units in Puerto Rico and the 56,000 units in the U.S. Virgin Islands, we would have to replace roughly 860,000 homes—akin to rebuilding every housing unit in and around Indianapolis —without even taking into account houses that suffered only moderate or slight damage.

Even significantly smaller damage numbers would still prove challenging for Puerto Rico and the U.S. Virgin Islands. If we were to estimate that only 10 percent of the homes on the islands were left uninhabitable or even beyond repair, that would still mean over 150,000 homes would need to be rebuilt—more construction than Puerto Rico saw in the past decade. 

Replacing even 10 percent of the housing will require massive amounts of materials and labor, and as of now, it is not at all clear where the money for rebuilding will come from. While damage from wind, unlike that from flooding, is covered by standard homeowner’s insurance, it is estimated that only half of Puerto Rican homeowners were insured at all. When coupled with the island’s low incomes even prior to the hurricane, without adequate federal resources, repairs to damaged homes will likely proceed intermittently if at all. On the other hand, federal disaster recovery funds for rebuilding can be used to thoughtfully restore communities, making them more resilient and creating needed jobs in the process.


[1] The ARIA team uses before and after images at a 30 meter resolution to identify damage. They note that the methodology is less accurate in places with thicker vegetation or flooding. High-definition aerial photos from flights at altitudes of 2,500–5,000 feet are available, however, from NOAA’s Remote Sensing Division, but the coverage is primarily limited to coastal areas of Puerto Rico, St. Thomas and St. John; overflights of St. Croix have covered the entire island.

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