The smell of rot rises from the drain holes and sidewalks on 40th Road in Flushing, Queens, after rainstorms. Flooding on this narrow street, packed with Chinese bakeries and restaurants, is often blamed on the neighborhood eateries, whose discarded fat and grease causes backups in the sewer system.

With intense rainstorms this summer overflowing sewers and immobilizing the subway system, some officials are seeking to crack down on restaurants that illegally dump their excess grease down city drain holes, where it hardens to block pipes and increases flooding incidents around the city.

The City Council’s environmental protection committee plans to convene a hearing this month to examine why the city’s subways and sewers were overwhelmed twice in one month by rain.

The chairman of the committee, Council Member James Gennaro of Queens, said it would examine how the city is enforcing laws that require eateries to collect their grease in traps to keep it out of sewers, where it creates backups that flood entire blocks and subway stations.

“There’s overall inadequacy generally,” Mr. Gennaro said. “Grease is a big contributor. We don’t have to create new laws because it’s already illegal. Now it’s an enforcement issue.”

Some lawmakers, however, said the city too often blames grease for the sewer system’s larger structural problems. “City officials use grease as a scapegoat for flooding when really what we need are infrastructure changes,” Council Member David Yassky of Brooklyn said. “Someone will always raise the issue of restaurants dumping grease, but it’s more of a red herring than not.”

The heavy rainstorm that shut down almost every subway line earlier this month would likely have flooded the sewer system regardless of the city’s grease problem, city officials said.

With real estate at a premium in New York City, restaurants often do not have room for larger grease traps, which strain fat and oils from wastewater, industry experts said.

Companies pick up the sludge and drive it to processors in the suburbs. When grease traps are filled, the water and the oils both overflow and leak onto streets and into sewers, where they cause backups. While restaurants in New Jersey have banks that can hold up to 5,000 gallons of grease, in Manhattan, grease traps generally hold between five and 100 gallons of grease.

“Grease can clog up a main line and create problems all up and down a block because it comes back up in people’s basements,” the vice president of the New York State Restaurant Association, Charles Hunt, said.

“It builds up like cholesterol in the body,” the president of Trap-Zap Environmental Systems, a grease trap-cleaning company, Robert Belle, said. “In certain neighborhoods, the grease gets thick like cement and you can actually walk on top of it.”

The Department of Environmental Protection last year issued 2,795 summonses to restaurants that did not have grease traps, or whose traps were dirty enough to be in violation of the law. The city performed 900 initial restaurant inspections and 2,724 follow up inspections, a spokesman for the department said.

Since the city began its grease education and enforcement initiative in 2000, 18,156 new grease traps have been installed at restaurants, and 15,400 violations have been issued.

Fines for failing to maintain grease traps can climb to $1,500 after multiple notices have been issued. Neighborhoods such as Flushing and Chinatown with high concentrations of Asian restaurants often have the most grease-related flooding issues, industry experts said.

“New immigrants from China and Vietnam are not very well educated, and garbage is really a problem,” the director of New York’s Greater Chinatown Community Association, Edward Fang, said. The city now distributes Chinese- and Korean-language information packets on grease disposal.

Council Member John Liu, who represents Flushing, said the charge against Asian eateries clogging pipes is unsubstantiated. “There is a perception among some people that Chinese food is greasy,” Mr. Liu said. “There’s lots of grease in plenty of other kinds of food, and there’s plenty of Chinese food that is lean and healthy. I’ve asked the city for comparisons with buildup in sewers in other areas, and I have gotten zilch.”

The city’s Department of Environmental Protection, which maintains the sewer system, often gets complaints from people who witness restaurant workers illegally pouring grease down a catch basin, but the department cannot issues summonses if its own inspectors do not catch someone in the act, officials said.

The owner of a gyro restaurant on Cedar Street in Lower Manhattan, Abdul Marhraoui, said he empties his grease traps into garbage bags, which he then stacks on the street corner at Broadway. By midday Thursday, the corner had a half-dozen bags waiting for pickup, filled with grease and discarded green peppers that oozed into the sewers.

“Even if you completely eliminated the grease dumping, you’d still be left with a big, big problem,” Mr. Yassky said.