New York and New Jersey residents, just coming to grips with the enormous costs of repairing homes damaged or destroyed by Hurricane Sandy, will soon face another financial blow: soaring flood insurance rates and heightened standards for rebuilding that threaten to make seaside living, once and for all, a luxury only the wealthy can afford.

Homeowners in storm-damaged coastal areas who had flood insurance — and many more who did not, but will now be required to — will face premium increases of as much as 20 percent or 25 percent per year beginning in January, under legislation enacted in July to shore up the debt-ridden National Flood Insurance Program. The yearly increases will add hundreds, even thousands, of dollars to homeowners’ annual bills.

The higher premiums, coupled with expensive requirements for homes being rebuilt within newly mapped flood hazard zones, which will take into account the storm’s vast reach, pose a serious threat to middle-class and lower-income enclaves. In Queens, on Staten Island, on Long Island and at the Jersey Shore, many families have clung fast to a modest coastal lifestyle, often passing bungalows or small Victorian homes down through generations, even as development turned other places into playgrounds for the well-to-do.

While many homeowners are beginning to rebuild without any thought to future costs, the changes could propel a demographic shift along the Northeast Coast, even in places spared by the storm, according to federal officials, insurance industry executives and regional development experts. Ronald Schiffman, a former member of the New York City Planning Commission, said that barring intervention by Congress or the states, there would be “a massive displacement of low-income families from their historic communities.”