What is underneath the streets of older major cities may not be enough to face new weather patterns and additional challenges cities face today. Here are some of the efforts from recent years in New York City:

New York had its first climate-related wake-up call nine years ago, when Hurricane Sandy brought a storm surge that flooded low-lying areas and, yes, subway stations. Since then, the city has spent almost $20 million on climate-proofing the city, according to the Mayor’s Office of Resiliency. But some of that funding went to solving a different problem than the one presented by Ida: water coming from the rivers. This week, all the wet stuff fell from the sky, threatening even areas above sea level…

Now, after years of updates, 60 percent of New York City has a combined sewer system, which uses a single pipe to carry both wastewater and stormwater to treatment plants. During heavy rainstorms, the system can get quickly overwhelmed. The detritus of city living—trash, plants, general gunk—clogs drains, further gumming up the works. “So if you get a really big kahuna like this, I don’t think it really has a shot at draining that out fast enough to avoid flooding,” says Farnham.

The city has worked to separate those combined sewer systems and to clear clogged drains, especially when storms threaten. It has raised and in some cases eliminated subway grates, which were built to allow fresh air to flow down to dank underground spaces but which now look like holes to let more water in. In some places, the MTA constructed flood-proof doors, which can close when the water gets too close.

More generally, cities like New York can create more green infrastructure to help with their water problems—basically, less pavement and more dirt. You might, for instance, create roadside green spaces where water can percolate before moving into stormwater drains, removing trash and pollution in the process. Los Angeles has been doing this to catch rainwater. “This is a long-term thing,” says Horodniceanu. Retrofitting cities to deal with what’s coming, and what’s already come, will take gobs of one of the scarcest resources of all: much more funding.

As cities expand and change, fixing the infrastructure already there to incorporate new technologies and grow the capacity is a difficult task. How disruptive will the efforts be? How much will it cost? It could be much easier in the long run to anticipate these issues way ahead of time and proactively make changes rather than only act after a major issue is exposed.

Water is particularly destructive as much of modern life depends on the fact that water will be excluded from the system. Residences, businesses, mass transit, electronics must be dry to function well. If there is an overwhelming storm or a breach of the water defenses, water can quickly wreak havoc both in the short-term and long-term. Cities require a lot of things to go right to properly go about their business but water can quickly disrupt this operation.

The recent events in New York City and New Orleans also remind me of the planning that can go into highways and parking lots: they can be constructed with peak use in mind. The parking lot needs to be large enough to handle the biggest crowds, hence the shopping mall parking lots that can handle Thanksgiving weekend shopping but are not fully used throughout the rest of the year. Or, the highway that needs more and more lanes to handle rush hour traffic while there are many hours when that capacity is not needed. Sewers need to handle really big storms or events. But, in each case, can the largest need be forecast correctly? Adding lanes to roads can increase the traffic. Right-sizing parking lots can be tricky. And planning for the rare storm is hard, particularly if conditions are changing. Similarly, people will not be happy in these cases if there is not enough capacity and there will be calls to fix the problem afterward.