Houston's stock of older, more affordable housing units are disproportionally prone to being of only average quality and are situated in areas that are at high risk for flooding.

That may prove a major problem for low-income Houstonians given the vast majority of affordable housing in the area consists of what's known as naturally occurring affordable housing, or NOAH.

Those units, which receive no public funding and are typically aging apartment buildings, are in desperate need of efforts to preserve their affordability, according to the Kinder Institute for Urban Research at Rice University. Unlike subsidized housing, which will receive funding for a period of time, NOAH risks becoming unaffordable when land values increase or when landlords renovate the property, according to Kinder Institute analysis of 2021 research.

About 40% of the 314,000 NOAH units in the metro are clustered around southwest Harris County, while subsidized housing is scattered around the city. Nearly a quarter of NOAH homes are in either a 100-year or 500-year flood plain, which means they have a high likelihood of flooding.

The Kinder Institute argues that, in order to decrease the flooding risk at those units, properties will have to be removed or the property will have to be elevated. But either of those options will result in higher costs for residents or the need for them to find new housing entirely.

"All other things being equal—if the county had two NOAH properties of the same quality, same size and same proximity to transit—it would be less costly to maintain a NOAH property outside a flood risk area," author John Park, a research fellow at the Kinder Institute, said in the report.

New city of Houston requirements call for NOAH properties to be removed from flood plains or to implement higher base flood elevations, with specific city of Houston plans in place to remove certain properties by 2030.

"To that end, financial and administrative incentives (e.g., tax incentives, reduced parking requirements, expedited permit processing, etc.) should be encouraged for qualifying affordable housing development projects outside the flood plains, while other measures, such as green infrastructure and flood resilience projects, could help protect NOAH that remains in the flood plains," the report stated.

As for the buildings themselves, quality ratings from the Harris County Appraisal District tend to rate them "average" compared to "superior/excellent" or "low/very low/poor," but that rating only examines the exterior of buildings, not interiors, plumbing or HVAC.

The Kinder Institute states that 180,000 Houston-area NOAH units may soon need substantial repair, and the older units that tend to be NOAH are more likely to need upkeep to keep them viable in the future.

"Much more data is needed about NOAH structures beyond the county’s assessment," the report states. "The uncertainty about maintenance needs does lead to a serious concern about housing preservation efforts."