The steady disappearance of adequate, affordable housing for thousands of poor and lower-income people in the District of Columbia was described vividly in reports released this week by Mayor Marion Barry.

The reports describe a pattern of rapidly rising prices for single-family homes that are far beyond the incomes of many city residents, the displacement of lower-income families in neighborhood after neighborhood, and a continuing problem with tens of thousands of substandard housing units.

The documents contain statistics that confirm the worst fears of many officials studying the city's housing crisis.

The problems are so severe that D.C. housing director Robert L. Moore said yesterday "it will take more than the four years of the Barry administration" to solve them.

"We're talking about maybe a 20-year planning frame," Moore said.

Some of the statistics are not new to housing experts, but they are being presented now as part of an effort to develop a housing policy for the city.

Among the factors outlined:

About 60,000 housing units - more than one of every five in the city - are substandard, with major housing code violations. They would require thousands of dollars in repairs to make them habitable. Thousands of other units are vacant and boarded.

Displacement of the poor is complete in some neighborhoods and spreading rapidly to others, including some communities east of the Anacostia River. Increasingly, Higher-income families are competing for a limited supply of homes in these neighborhoods.

More than 10,000 people are on the city's waiting list for public housing, with "waiting over five years for occupancy more the rule than the exception."

About 60,000 tenants and more than 14,000 homeowners need some form of housing assistance from the city because of substandard housing conditions or overcrowding, or because excessive portions of their income go for housing costs.

By 1985, there probably will be a shortage of 19,000 housing units that will be needed to meet the demands of more than 300,000 housholds.

Although home ownership in the city apparently is increasing, about two-thirds of the city's housing units in 1977 were rentals. This represents a substantial change from 1970, the reports said when about 82 percent of the city's housing was rental.

The reports portray a city with the lowest turnover in housing - rentals and sales - in the country, where those with low and moderate incomes are facing fierce competition for scarce housing resources from middle- and upper-income people seeking home ownership and investment opportunities.

Higher-income families are buying older, low-priced housing in the central city, forcing out lower-income residents, while rising construction costs and interest rates mean that the price of new housing has been and will continue to be high, the reports say. One map in the reports shows hundreds of blocks where sales prices of homes increased more than an average of $28,740 each from 1977 to 1978.

After months of study, the city found that displacement of poor and lower-income people is nearly complete in the neighborhoods of Capitol Hill, Dupont Circle, Adams Morgan and Mount Pleasant. Displacement is substantially under way in Logan Circle, portions of Shaw, Stanton Park and Lincoln Park, as well as scattered areas east of the Anacostia River.

Displacement is beginning to spread north from Shaw into Westminster and Columbia Heights, and northeast to Le Droit Park, Bloomingdale and Eckington, the city found.

Information about neighborhoods and sales activity came from a computerized system developed by the city's housing and planning departments. The system stores assessment, ownership, land use and zoning information for every parcel of land in the city, plus information about real estate sales and descriptions of buildings. Called the Municipal Automated Geographic Information System, it uses information gleaned from records kept by various public agencies and departments.

Much of the citywide information included in the draft policy is the result of work done by the D.C. Legislative Commission on Housing, which last year issued a much-publicized report that pointed to many of the city's most pressing housing problems and needs.

Mayor Barry said in an introductory statement to the reports that the problems faced by the city "are in a large measure characteristic of a building national crisis."

One objective stated in the draft housing policy is to adjust current rent control and condominium legislation so that low and moderate-income rental housing can be maintained. Conversions have skyrocketed recently as developers and landlords find converting more profitable than owning old, deteriorating apartment buildings.

Last year, the city approved 10,481 rental apartments as eligible for conversion, nearly 15 times the figure for 1977. The city found that most of those conversions were along Wisconsin, Massachussetts, and Connecticut Avenues, along 16th Street, in Foggy Bottom and the central portion of the city.

The report also lists as an objective the relaxing of rent control restrictions on new and existing so-called "luxury" housing. No definitions were included in the report.

The so-called "draft housing policy" can be picked up by the public at various libraries, housing department offices, and Project Area Committee offices around the city. It will be a form of working paper for discussion at a "housing summit" to take place all day on June 30 at the Friendship Learning Center at Livingston Road and South Capitol Street SE.

More than 500 civic and community leaders, representative of the real estate and banking industries, and city and federal officials have been invited to attend. CAPTION: Map, Status of Displacement, By Richard Furno - The Washington Post