New base flood zones for many residents along the back bays will include the dreaded word velocity, which means those residents may have to spend significantly more money for flood insurance.

Those homeowners in the new velocity zones, including much of the Mystic Islands section of Little Egg Harbor Township, also may have to renovate or rebuild their houses to meet more stringent building codes if their properties suffered damage during Sandy that equals at least 50 percent of the building’s value.

The new advisory flood maps released this morning are being provided as a guide to homeowners and municipalities as part of the recovery process from Hurricane Sandy.

The maps are intended to act as guidance, but municipalities can vote to incorporate the data into zoning codes. Brigantine Mayor Phil Guenther said Friday that the city likely will begin revising codes next week.

Among the most significant changes are for houses along or near bays, including Little Egg Harbor, the West Atlantic City section of Egg Harbor Township and the bayside areas of Ventnor and Margate.

For example, the flood elevation on maps released in 2006 designatured the Mystic Islands a high risk flood area, but houses only needed to have their main floors raised to 8 feet. The new advisory maps now have those areas in a velocity zone, which is the highest risk area. That means builders must plan for 3-foot waves on top of the floodwaters. Houses also will need to be built to a 12-foot elevation, a four-foot difference.

In West Atlantic City, the entire area is listed as an A flood zone and houses needed to be at elevation 9. The new advisory maps list nearly all of West Atlantic City, except for a few areas several houses in from the water, as a velocity zone with a base elevation of 12. Those areas not included in the velocity zone now have elevations of 10 feet.