This is the story of how we helped the City of Houston visualize and communicate the impact of Hurricane Harvey. You may have already seen these maps on Harvey by the Numbers. This isn’t a story about designing the maps and choosing the colors (although that was a lot of fun). This is a story about the data.
Why do these maps exist?
Immediately after the storm, Houston Mayor Sylvester Turner wanted the public to have the best available information about their neighborhood. He recognized an opportunity to share the scope of the storm’s impact, and send a signal that the City was working hard to get back to normal.
But after a disaster like Hurricane Harvey, data arrives in bits and pieces. It takes months, even years, for the whole story to arrive. So as new and better data comes in, we keep updating the maps.
Hurricane Harvey Damage Map
The Hurricane Harvey damage map estimates the number of affected units by census block group:
At first, the only damage maps were FEMA estimates based on an inundation model. You can see that as a heatmap layer on the map above. These estimates only covered areas up to the 500 year floodplain, which wasn’t the whole story for Harvey. FEMA finalized their model on September 2, and that the extent of public estimates for weeks.
Meanwhile, the City of Houston Department of Neighborhoods drove around for several days and surveyed some of the hardest hit neighborhoods. This “windshield assessment” contained about 22,000 records and gave us our first look at property-level damage data.
During the weeks following the storm, data analysts at the city ranked, merged, and deduplicated several other datasets to form a comprehensive damage estimate. This estimate includes National Flood Insurance Program (NFIP) claims, FEMA individual assistance (IA) claims, and debris collection coordinates. It also includes a “unit estimate” methodology that takes into account the number of first floor units in affected multi-family properties.
At the City’s request, I added a poverty layer broken down by census tract.
Hurricane Harvey Response Map
The Hurricane Harvey response map shows 311 and 911 calls, placed during and immediately after the storm, and related to high water or flooding:
The city has direct access to these datasets, so it provided a good view of how flooding unfolded during the storm. However, it’s still only a partial view because the 311 and 911 systems faced unprecedented volume. There were plenty of people who couldn’t get through to 911, and they turned to Zello or Twitter or Facebook.
The 311/911 request details give us a good sense of the government response, but it still doesn’t tell the whole story.
Hurricane Harvey Debris Map
The Hurricane Harvey debris map shows where trash trucks picked up hurricane debris left on the curb. It’s broken into debris collection zones, which is apparently a unique set of boundaries specifically for trash pickup. The map highlights what zones has the most debris (measured in cubic yards). The numbers on the map tell you how many trucks were most recently dispatched to the zone:
This map continues to be updated from time to time with new data. At the time of this writing, we’ve had three months of debris pickup.
