The rising tide of development in downtown Washington is about to break over a barrier reef that has blocked out business for nearly a decade-the porno district along 14th Street, NW.

Today 14th Street's sleazy sex shops, running north from H Street NW, are considered the most obvious roadblock to the spread of redevelopment astwasd into the old downtown.

But optimistic developers contend economics will eventually accomplish what law enforcement has failed to do - drive out the peep shows "book stores" and other fronts for the sale of sex material.

The pron industry moved into 14th Street after the 1968 riots, when the sexual revolution overtook the urban rebellion. Stores were vacant, rents cheap and the neighborhood had been abandoned by the middle class.

As memories of the riots faded - removing that barrier to development - the sexual fantasy shops flourished, creating new blockades. Net only did the sex shops scare away legitimate business, but the lucrative incomes from the booming porn palaces provided rentals that other businesses could not match.

With income pouring in, there was less incentive for landlords to sell out to speculators assembling, sites for eventual redevelopment explained city planner J. Kirkwood White.

As a result the new buildings creeping toward downtown from the West End were delayed and diverted, because, as developer Chip Akridge puts it "people don't want to look out their front windows and see that kind of thing."

Calling the 14th Street porno district "a very major impediment to development" in downtown, Akridge says the red light district has forced the path of development southward, toward 15th Street and Pennslyvania Avenues, NW. Akridge's firm, the John Akridge Company, is one of three Press Building site, a few blocks down the 14th Street, under auspicies of the Pennsylvania Avenue Development Commission.

nographic blockage is only temporary. "Economic pressure will force them out," he said "Once redevelopment starts, they will have to move."

New construction probably will leapfog over the 14th Street barrier - lured by the convention center and the Redevelopment Land Agency project at 12th and 13th and G Streets NW.

Eventually, however, both White and Akridge expect the sex shops to move eastward into the Sixth and Seventh Street NW corridors.

Where the porn shops will go will be influenced by recently enacted zoning regulations that were designed to prevent creation of additional porno neighborhoods.

"Creation of a new red light district is impossible," under the present D.C. zoning law, said White. Rejecting the-combat zone" approach to controlling sexually oriented businesses - setting aside designated areas for them - the city opted for what is known as "the Detroit approach" - diversification.

Porno shops, massage parlors and the like are not permitted to open within 300 feet of each other or within 600 feet of a church, public building or apartment building, or in any residential or residential-commercial zone.

Another sign of downtown progress NW, where the Pennsylvania Avenue is underway at 13th and E Streets, Development Corp. is beginning the first phase of construction of Western plaza.

Natural gas lines are being moved now, sewer moving comes next, and in September the traffic islands on Pennsylvania Avenue between 13th and 15th Streets, NW, will be torn out and electrical ducts moved.

Then traffic will be rerouted from Pennsylvania onto what is now E Street, to jog around the plaza, which was planned by Pierre L'Enfant, but never built.