Hurricane Ida and Queens basements: what the flooding showed

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What happened

The Health Department’s account is stark. Rain fell faster than it could drain away. About nine inches fell, and in some areas record-breaking rainfall of 3.5 inches an hour came down, exceeding the city’s sewer capacity of 1.75 inches an hour. The National Weather Service issued its first-ever flash flood emergency warning for New York City.

Fourteen people died from causes related to Ida, the Health Department reports. Most of them, 71 percent or ten deaths, drowned in unregulated, illegal basement apartments. (Other city offices have given a count of 13; this article uses the Health Department’s figure.)

How Ida differed from Sandy

Superstorm Sandy in 2012 was a coastal flood. The Health Department counts 52 injury deaths in the city, most along the coasts in zones where an evacuation had been ordered: 44 percent on Staten Island, 25 percent in Queens and 23 percent in Brooklyn. At least a third of those who drowned at home were found in a basement or lived in a basement apartment.

Ida was a rain flood. The Health Department’s key point is that, unlike Sandy’s mostly coastal flooding, rainfall flooding can happen anywhere in the city. Low-lying areas and basement apartments are at higher risk. Evacuation zones, which are drawn for storm surge, do not tell you whether your basement will fill in a cloudburst.

Why basements filled

NYC’s Department of Environmental Protection names four kinds of flooding, and Ida brought several at once. Sewer backups happen when heavy rain exceeds pipe capacity, causing overflows from manholes, catch basins and basement sewer connections. Street flooding happens when catch basins are blocked. Groundwater flooding comes through foundation cracks or a leaking floor drain when the ground is saturated. When rain falls at twice the rate the sewers can carry, the lowest openings, the basement drains and the doors at the bottom of outside steps, are where the water goes.

What owners can do

• Disconnect downspouts. DEP says it is mandatory for homeowners to make sure downspouts are disconnected from the city’s sanitary sewer, redirecting water at least 6 feet from the foundation. Connected downspouts can cause sewer backups in basements.
• Ask about a backwater valve. FloodHelpNY lists gate, ball and flapper types and says a plumber or engineer can tell you which, if any, suits your home.
• Report clogged catch basins to 311 before storms. DEP cleans and maintains 150,000 of them.
• Read DEP’s guide, Rainfall Ready: A Homeowner’s Guide, published in 12 languages.
• Think about flood insurance early. FloodSmart says most homeowners insurance does not cover flood damage, and a flood policy generally takes effect 30 days after purchase. Check your own policy or ask your agent.

Basement apartments

Ida’s deaths make the point about basement apartments without any need for emphasis. If someone lives in a basement in your house, they need a way out that works when water is coming in, and a plan for when heavy rain is forecast. The NYC Department of Buildings can vacate a building for conditions posing imminent danger, and says owners of illegal apartments can be fined up to $25,000. FloodHelpNY notes that filling in a basement requires an engineer and a DOB permit.

After the next one

When a basement floods, the order is the same: safety first, with power switched off only from a dry place; then stop what you can, photograph everything, and start drying within 24 to 48 hours, as the EPA advises, to prevent mold. Treat water that came up through a drain as sewage, which the IICRC S500 counts as Category 3 water. The details are on flood cleanup in Queens, sewage cleanup and basement waterproofing.

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