A House elections subcommittee today developed a reapportionment proposal that could avert what many had feared would be a pitched battle between legislators from Northern Virginia and Tidewater during a special session next week.

The proposal, hammered out in a long and arduous meeting, would add two members to the 10-member House delegation of rapidly growing Fairfax County -- but instead of transferring one of the added slots from the Norfolk area, the panel chose to lift it instead from the rural area surrounding Roanoke.

Nothern Virginians hailed the decision as a victory of mathematical logic over politics, and expressed optimism that the proposal could win the approval of the legislature. "Gee, that's great," and Sen. Clive DuVal (D-Fairfax), one of the suburban Washington politicians who 10 years ago unsuccessfully fought the efforts of the powerful Tidewater delegation to gain another House seat at the expense of his region.

"I think it just proved too difficult for them to move it [the disputed delegate seat] down to the other parts of the state . . . I don't think they had any greater love of Northern Virginia than usual."

The second seat that Fairfax would gain presumably would be the one now shared by Arlington and Alexandria, which have lost population.

While yesterday's proposal eases the possibility of a conflict between the state's most populous regions, it seems to increase the possibility of intense bargaining over the shape of the House's districts during the special session. b

If approved by the full General Assembly, the plan may also increase the chance that the state will go into court to defend its reapportionment plans. Recent federal court decisions have held that the Constitution's one-man, one-vote concept requires that a state's electoral districts should not differ from one another by more than approximately 16 percent in population, but the panel's preliminary plan shows a deviation of more than 22 percent.

Hardest hit by the subcommittee's decision were House Finance Chairman Archibald Campbell (D-Wythe) and Del. C. Jefferson Stafford (R-Craig), who were placed in the same single-member district, and Dels. Lacey Putney (I-Franklin), James D. Davis (D-Franklin), and S. Vance Wilkins Jr. (R-Amherst), who were all placed in the same two-member district.

"That's a dirty damn thing for the Democratic committee to do," groused Campbell, who only recently had announced his decision to run for a ninth term. "That's the thing that I was trying to avoid, and they told me they weren't going to do it."

Subcommittee members apparently were more concerned about the threat of a united Northern Virginia vote against the state reapportionment plan, which must be in place before this fall's House elections. "We've got to have 51 votes [to pass any redistricting plan]," Del. Claude D. Anderson (D-Appomattox) told a colleague during today's meeting. "You get 20 with this plan right here., You lose 20 if you only give [Fairfax] 11 delegates."

Bargaining over Fairfax's request for 12 delegates began almost at the outset of yesterday's meeting, as the panel sifted through requests from Southwest Virginia, Southside and Tidewater. By the time the subcommittee had progressed as far north as Fauquier County, it had backed itself into a plan that would have called for 101 members in the Virginia House of Delegates, or one more than is allowed by law. Subsequent mathematical juggling produced the final plan.

Newport News Del. Theodore V. Morrison Jr., a Democrat, set the pattern for yesterday's discussion when he told the committee he would accept nothing less than the current allocation of three delegates for Newport News, which has lost 9.3 percent of its population since 1970. "There is no reason for Newport News to be denied a delegate," he said.

Northern Virginians long have been arguing that Fairfax County's recent population growth entitles it to 12 seats, but Del. John D. Gray (D-Hampton), chairman of the full House Privileges and Elections Committee, had proposed combining Falls Church and Arlington into one House district, with the effect of dropping Fairfax's delegation to 11 members.