Hurricane Katrina scattered about half New Orleans' pre-storm population of 465,000 and destroyed some 275,000 of its homes. One year later, few have been rebuilt, leaving the New Orleans diaspora unable to return.

Housing is a fundamental social need; its lack contributes to cascading social failures, from poverty and crime to failing schools and health care systems. For example, New Orleans' hospital and clinic space is still severely curtailed. Up to 75 percent of health care professionals left after Katrina, and though they are trickling back, the majority can't return without somewhere to live.

So what's delaying rebuilding? Though bureaucratic red tape is a factor, it's not the biggest.

True, the federally funded and Louisiana-administered $7.5 billion Road Home housing-aid program has failed to disburse any money yet. Congress didn't approve it until May, and there are other bureaucratic hurdles to clear, including title searches.

And yes, municipal bureaucratic delays are significant. May 2006 city elections meant no mandate for any rebuilding plan was possible before then.

Meanwhile, many of the 39 percent of New Orleanians who own homes are broke, bankrupt or absent since Katrina. City government can't trespass on derelict properties without owners present. And city staffing is often insufficient to adjudicate the ones whose owners are there - many municipal employees are themselves unable to return.

Also, since New Orleans' pre-storm low-income population was high, the challenge is not simply rebuilding. It's building affordable housing, while owners naturally want high prices.

Yet, none of these contributing factors explains the rebuilding delay. The primary explanation is the inherent difficulty of the task itself.

As relief professionals know, intractable rebuilding problems are endemic to disaster areas everywhere. Rebuilding housing is the highest priority for kick-starting disaster recovery anywhere in the world, but it's also the toughest, requiring the most capital and involving complex property rights issues.

In post-tsunami India and Sri Lanka, where families lack written title to land they worked for generations, with whom should rebuilders deal? In Honduras after 1998's Hurricane Mitch, my organization, Episcopal Relief and Development, or ERD, working with the local diocese, finally bought land outright to get clear title and begin building.

It's not so different in New Orleans, which is filled with old, damaged properties whose deeds are outdated or destroyed or were never written down. Absent owners, not to mention Louisiana's French heritage and unique Napoleonic civil law practices, complicate property rights questions. Even for adjudicated lots that the city donates to nongovernmental organization rebuilding projects, title searches take months and thousands of dollars. Then the real expenses and challenges begin.

One promising approach to meeting them is private partnerships. ERD and the Episcopal Diocese of Louisiana have partnered with a local bank to build affordable homes on 50-plus adjudicated lots awarded by the city. The partnership, Jericho Road Llc, takes ownership of the lots, obtains clear title, then leverages donor funds with bank financing.

As building proceeds, the project identifies and trains low-income clients to qualify for the financing. A pilot program on five of the 50 lots is already under way, but the partnership envisions 500 affordable new homes - and new homeowners - in central New Orleans within five years.

Other nongovernmental organizations - among them the Association of Community Organizations for Reform Now, Habitat for Humanity and Baptist and Catholic charities - build housing on adjudicated lots from the city without private partners. But nongovernmental organization-private partnerships offer some distinct advantages. The financing confers instant clout and credibility upon the organizations, helping them find market efficiencies amid the maze of hoops that can quickly absorb funding and staff time.

And while for-profit ventures use deep pockets to dispatch obstacles and get projects built, they may not focus on affordable housing. Nongovernmental organization-private partnerships can do both.

Perhaps most important, the partnership model is replicable and scalable. The more partnerships succeed in qualifying clients and completing projects, the more lots they can attract, and the more financing they can leverage for more affordable home building and home buying on a larger scale.

Such innovations may do more than surmount obstacles to rebuilding New Orleans. By leveraging funding, training new homeowners and building affordable housing - and on a potentially wide scale - they may also help restructure the city's pre-storm patterns of poverty.

Copyright 2006 Newsday Inc.