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When the remnants of Hurricane Ida reached New York this month, the severity of the storm shocked the city. Despite meteorologists’ warning of heavy rain and flooding, the speed with which the storm turned streets into fast-flowing – and deadly – rivers caught officials and residents off guard.

New York has taken steps to prepare for the extreme weather conditions brought on by climate change. Over the years, civic groups, environmental organizations and officials have raised alarms and called for action to avoid extreme storms, especially after Hurricane Sandy flooded much of the region.

But much of the post-Sandy work has focused on flooding caused by rising waters surrounding the city’s shores. The rains that Ida brought – and two other storms This summer, which has flooded parts of the region, poses a different kind of threat: heavy rainfall in a short time.

The storms revealed how New York City’s aging infrastructure, including the vital subway built for a different climate, needs significant improvements to adapt to the types of storms that climate scientists say will be both more frequent and more intense.

Currently, city planners, climate scientists, some local authorities and designers have a long list of design and engineering solutions that can help the city meet an urgent need. (Some say they’ve warned the city of excessive rainfall for years, citing past reports.)

Many experts, local elected officials and climate groups are now pressing even more strongly after a storm they hope will serve as a wake-up call. Here are some of their offerings.

Unclog drains and widen pipes. This is no easy task.

The most direct way to reduce flooding from precipitation is to evacuate precipitation more efficiently. But New York’s sewer pipes, some more than a century old, were built for a smaller city with a cooler climate that produces less downpours.

About 60 percent of the city is served by a combined sewer system that receives both domestic wastewater and street water. Other cities have separate pipes for these two sources.

During heavy storms, New York’s pipes often overflow and back up the system so the water can’t drain as quickly as it rains.

The city spends hundreds of millions of dollars a year renovating sewers, but the pace hasn’t kept up with changes in the weather. Projects are underway to separate combined sewers in several flood-prone areas off the Brooklyn coast and parts of Queens on Jamaica Bay.

Still, one of the most urgent fixes for the sewer system is the simplest: better maintenance of existing drains and catchments, underground holding pens for water that may become clogged with leaves, mud or garbage.

The city’s Department of Environmental Protection is responding to complaints about clogged drains, but officials say more staff are needed to proactively open blockages in sensitive areas. Other state and city agencies are responsible for some sewers, such as on highways.

Other measures to reduce litter blockages include more frequent street sweeping and placing containers on streetsides to prevent household and commercial garbage bags from being ripped or ripped by rats and thrown away.

Some steps to better protect the city against climate change carry significant price tags, but experts say the cost of inaction will be even higher.

“Here we are, rubbing our hands and saying it’s too expensive,” said geophysicist Klaus Jacob, who studies climate change and cities at Columbia University. “Well, it’s actually very expensive not to do the right things.”

Turn streets, parks and open spaces into sponges.

New York City has more than 6,000 miles of streets and 30,000 acres of land. parking lot – green spaces absorb countless gallons of rainwater, but asphalt drags it onto roads and sidewalks. During particularly strong storms, when water flows into homes, businesses and the subway.

Infrastructure and public space experts say the city needs to maximize surfaces to collect, absorb and slow down rainwater.

“The challenge for us is turning New York City into a sponge,” said Amy Chester, executive director of Rebuild by Design, a nonprofit that works to make infrastructure more resilient to storms and climate change.

Take the streets. Experts say the city needs to expand a green infrastructure program that includes: installing bioswalesor rain gardens — landscaped curbside areas planted with water-loving vegetation. Many cities across the country used them to help reduce street flooding.

Experts say New York needs to use more water-permeable materials for its streets and sidewalks, which it’s already starting to build in flood-prone areas. The city used Stormcrete, a more porous form of concrete, to rebuild sidewalks in parts of Southeast Queens, and added stone rather than mortar to the joints between pavers to reduce rainwater buildup in Brooklyn.

“These projects have weathered Tropical Storm Ida well, and we have plans for similar work,” said Christopher Browne, spokesman for the city’s Department of Transportation.

The agency will soon operate a new network of flood walls and gates, largely on city property, to protect roads and neighborhoods from flooding. These are being built as part of a citywide flood protection system in areas that can be activated before major storms, such as Manhattan’s Lower East Side.

Yet the city can do more by identifying how and where neighborhoods are flooded, and redesigning streets and other surfaces to divert rainwater into parking lots, schoolyards, parks, and even private containment tanks, until it goes to soil or drains into sewers. said Franco Montalto, a professor of civil and environmental engineering at Drexel University.

Professor Montalto, who is also a member of the climate change panel appointed by the mayor, said: “It’s like turning streets into urban streams to move water to places where people can safely lake their homes without flooding.”

adopting city, instructions has worked on projects to absorb and collect rainwater in parks and recreation areas, including basketball courts, and to help them recover from flooding, to ensure that public parks are designed and protected to be more flood resistant.

Since 2013, the Trust for Public Land, a conservation group, has partnered with the city to rebuild more than 40 playgrounds to absorb and collect rainwater. In total, these playgrounds now collect more than 23.5 million gallons of rainwater per year.

“This is a proverbial drop in the bucket given billions of gallons of rainwater a year, but we need more of these small-scale solutions because every little solution helps,” said Carter Strickland, New York state trust director.

Metro needs to plug leaks. But the MTA cannot do this alone.

After Hurricane Sandy destroyed the subway system when corrosive saltwater flooded tunnels and damaged important equipment, the Metropolitan Transportation Authority embarked on a major climate resilience study.

The agency has spent at least $2.6 billion to protect subway openings from flooding, replace pumps and strengthen tunnels under the East River.

These improvements have helped to some extent. Janno Lieber, acting head of the agency, noted that the tunnels that Sandy flooded remained dry or emptied quickly during Ida’s downpour.

However, the agency’s efforts have largely focused on stations and tunnels in coastal and low-lying areas. Storms like Ida have highlighted the need for a broader approach to mitigating climate-induced flooding; most of the flooded stations were at higher elevations.

Water has long plagued New York’s subway system. It was designed with the knowledge that it will almost always be wet: Tunnels through bedrock are surrounded by infiltrating groundwater.

Rainwater enters the subway mainly through stairs that pull riders underground and ventilation grilles that provide air circulation.

“The subway system cannot be made waterproof,” said Mr. Lieber. “It’s a hollow system.”

Mr. Lieber said the system can pump up to 14 million gallons of water even on dry days. But its capacity has been stifled by recent storms that have quickly drained several inches of rain in a matter of hours.

Most of the water that flooded the system overflowed from the city’s waters. sewer and drainage infrastructure and fixes that can help prevent water from flooding streets will also help prevent the subway system from flooding. They would also assist the subway pumping system, which sent excess water into the city’s sewers.

But many urban planning and transportation experts have encouraged an even more aggressive approach.

After a storm in July, the Regional Plan Association, an urban planning research and advocacy group, published an analysis that found that one-fifth of subway entrances, or more than 400 in total, could be affected by significant flooding in a storm. It rained 3.5 inches per hour. Ida poured 3.15 inches of rain over Central Park in an hour.

“The system has been tested from this,” said Robert Freudenberg, the association’s vice president for energy and environment. “And we found where the weak spots are.”

Sarah M. Kaufman, vice principal at the Rudin Center for Transportation at New York University, said the public transportation authority should do a better job of cleaning up the 418 miles of sewers and gutters.

A Report published last month It was found by the MTA’s inspector general that it would take 15 years to clean the entire system at the authority’s target rate for sewer cleaning — 150,000 linear feet per year. Officials said they would switch to cleaning sewers on a four-year cycle.

Ms. Kaufman also encouraged city and state officials to think on a larger scale and learn from them. other cities facing similar problems. He pointed to Tokyo, which is partially building its flood defenses. huge underground cisterns put floodgates at subway entrances and to catch the current.

Columbia geophysicist Dr. Jacob suggested it could overlook Taipei, Taiwan, where many subway entrances have been slightly elevated to prevent New York City street-level flooding. (Doing this on the New York subway accommodation for the disabled, an area where the system has traditionally lagged.)

Mr. Lieber said the system is investigating upgrading some inputs. Engineers were also looking for ways to efficiently close vents or cover grates through which water could spill. The transport authority has installed “flex gates,” watertight barriers, that it can place at stations in traditional flood zones to seal off some subway entrances.

Still, any engineering solution would be expensive for a system that is already facing financial burdens.