The District's heavily black neighborhoods east of the Anacostia River grew more segregated over the past two decades even as areas in the central city became more diverse, according to an Urban Institute study of census data released yesterday.

The study was presented at a forum of experts and community leaders, who said it raised important issues as city officials draft policies to fulfill Mayor Anthony A. Williams's goal of adding 100,000 residents in the next decade.

The city has lost population for decades, with the sharpest losses in the District's black neighborhoods east of Rock Creek Park. In recent years, the city's Hispanic and Asian populations have soared, and many have moved into downtown areas to replace African Americans.

According to the study of census data by Noah Sawyer and Peter A. Tatian, most of the city's 39 neighborhood clusters are at least "moderately" diverse. That is a change from 1980, when less than a third met that definition. The number of neighborhoods considered "highly" diverse quadrupled over two decades.

But those diverse neighborhoods mainly are in the middle of the city -- places such as Columbia Heights and Capitol Hill in Wards 1, 2 and 6. By contrast, places east of the Anacostia River declined in diversity, with areas that once were moderately integrated now markedly less so, the study said.

The segregated black neighborhoods east of the Anacostia River include some of the city's poorest blocks, experts said. The social isolation of those areas makes it difficult for residents to connect to jobs or role models, a pattern found in other older large cities.

Citywide, black-white segregation declined slightly since 1980. But 2000 Census data show that Hispanics have become more segregated as their numbers have grown.

A Washington Post study of housing patterns after the 2000 Census found a larger decline in black-white segregation across the country, compared with the District. But the study found a similar rise in Hispanic segregation.

Williams said this month that he wants to increase the city's population by bringing in all types of people, from black families with children who left for Prince George's County to well-off retirees. Experts say his chances for success hinge on improving the city's schools and lowering the crime rate.

Demographer George Grier said his survey of people who moved into the District in the mid- to late 1990s found that most whites moved to mainly white neighborhoods, and most blacks to mainly black neighborhoods.

The neighborhoods east of the river need to have more amenities, he said, if that pattern is to be broken.

Gentrification can help break up concentrations of poverty that lead to segregation by importing a greater mix of income levels into poorer neighborhoods, said James O. Gibson, a senior fellow at the Center for Social Policy. But he said that must be accompanied by greater access to affordable housing to give options to lower-income people who want to stay in the city.