This article is first published in the FT Climate Graphic: Explained newsletter
This week we turned our attention to a challenging — and expensive — problem: new housing in areas that are especially vulnerable to climate disasters, including hurricanes, wildfires and extreme heat.
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Developers in the US are increasingly building into more high risk areas, an FT analysis found, amounting to about 4mn more single-family homes in high risk places in about a decade. The percentage of new homes built in these areas every year has also gradually risen, from 39 per cent in 2014 to 57 per cent in 2023.
To help illustrate the rapid growth in high-risk areas, I had the benefit of access to building data from CoreLogic, the property information services company which collaborated with the FT on the project.
Working with CoreLogic, I identified a few places that 1) had experienced double-digit housing growth within the last decade and 2) were in areas considered high risk for climate catastrophes.
Out of the list, the cities of Katy, Texas, just west of Houston, and Calimesa, California, in the greater LA area, stood out. Both represented a common US trend: the movement of people from large cities (Houston and LA) to suburbs or nearby towns, often in search of space and affordable homes.
The US housing shortage and affordability crisis is one of the reasons why limiting risky development has been difficult.
Using CoreLogic footprint building footprint data, which also tracks the year of construction, I was able to map the building of single-family homes. The data came in the form of CSV (comma separated values) files, making it easy to upload to Qgis, the open-source geographic information software we use at the FT for mapping.
To highlight the most recent construction, and show how both places have grown over the past decade, colouring the homes according to the year they were built made it immediately clear.
For Calimesa, and part of neighbouring town Beaumont, I added an additional layer to show the official “fire hazard severity zones” which are designated by the California fire and forest protection department based on vegetation, winds and other relevant factors. This showed how the two cities are hemmed in by areas the government considers high risk.
[Nerd note: I was able the download the information on the fire hazard zones through ArcGIS, which allows the export of the layer in geoJSON, the format for encoding a variety of geographic data structures, before porting it into Qgis. The severity of the risk zones range from moderate to very high, but I simplified it and eliminated more clutter from the map.
Finally, to give the map a bit more texture, I added some under-saturated satellite imagery to the background, a nice suggestion by my colleague Jana Tauschinski. This was done by pulling in satellite image raster tiles from the spatial data software ESRI into Qgis which also let me quickly add in roads for the two cities via an OpenStreetMap plugin.]
Building and retrofitting houses to be more resilient — such as installing fortified roofing or impact-resistant windows — is the easy part.
The hard part will be the massive realignment of existing incentives, from developers maximising short-term returns to local governments, who rely heavily on property taxes and believe they can lean on bailouts from the federal government whenever disasters strike.
As Craig Fugate, a former administrator of the US’s federal emergency management agency said: “Until you reach the pain point where behaviour will change, it’s easier to kick the can down the road.”
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