THE SENATE DISTRICT Committee, which for generations was an influential leader in the colonial cabinet that ran this city's local affairs from Capitol Hill, died of natural causes last week at the age of 160. It is survived by an overweight cousin, the House District Committee, and a newborn heir, the Senate Governmental Affairs Subcommittee on the District. In lieu of flowers or expressions of sympathy, the community should think a few kind thoughts about some of its useful work in the past - and take heart.

In recent years, the committee had been in semi-retirement, with many of its elected city government. But in the heyday of congressional control over the city's legislative affair, the Senate District Committee did a reputation as the most compassionate of the District's municipal foster parents. Decades before the House District Committee agreed even to let the city have its own elected school board, the SDC was voting its approval of full self-government here. Under the benign leadership of Sens Thomas F. Eagleton, chairman, and Charles McC. Mathias Jr., ranking minority member, the Senate committee finally was able to join with its House Counterpart, led by Chairman Charles C. Diggs Jr. and Republicans Ancher Nelsen and Gilbert Gude, to draw up a charter for the city in 1973.

With the burden of local lawmaking thus transferred to Washington's elected city council, the unrewarding work of the Senate committee was mercifully curtailed. So the new subcommittee should have no problems handling the estate. Meanwhile, the House District Committee is suffering from personnel obesity. As we noted in this space last August, this committee has more staff people attached to it than it did when the city charter took affect. Indeed, a General Accounting Office audit for 1975 showed more people on the HDC staff than there are working for the House Armed Services Committee or the Argriculture Committee or three other standing committees in the House tha presumably have more and better things to do.

If it's any comfort to District residents, not all of the HDC staffers are working on city affairs. Many of them do other business for Chairman Diggs in connection withhis notoriously extensive travels abroad, his press relations or anything else he chooses to use them for. Defenders of this curious arrangement argue that it's common pratice on Capitol Hill. Even so, that does not excuse it, and still less does it justify such excesses under the disguise of District of Columbia affairs. We have long supported a proposal made in the past by Mr. Gude to replace the House District Committee with a committee on urban and District of Columbia affairs. Such a unit could examine municipal fiscal nationally, the cost of public services, the effects of population shifts, federal-state-city responsibilities and so on. With more time devoted to problems of cities in general, such a committee would have less time to intervene in this city's municipal lawmaking - which is what we all assumed the framers of the city's charter had in mind.