HOUSTON — Voters in Houston and its surrounding county marked the anniversary of Hurricane Harvey coming ashore by approving the issuance of $2.5 billion in bonds to fund flood-control projects that might mitigate the damage caused by future storms.

With nearly all precincts reporting Saturday night, about 85 percent of voters approved the referendum. The bonds will fund projects that may include buyouts of homes in flood-prone areas, the expansion of local bayous and the construction of additional stormwater detention basins.

Harvey, which made landfall as a powerful Category 4 storm on Aug. 25, 2017, killed 68 people and caused an estimated $125 billion in damage in Texas. Thirty-six of the deaths were in the low-lying Houston area, where days of torrential rainfall and decades of unchecked development contributed to the flooding of more than 150,000 homes and 300,000 vehicles.

The bond referendum would help pay for projects to be chosen from a list of more than 230 proposals. Officials said the bond money would help supplement federal funds earmarked for flood mitigation after Harvey.

Passage of the measure means taxpayers in Harris County, which includes Houston, would see an average increase of $5 per year in their property taxes.

"Harris County residents have put their trust in the Flood Control District," district executive director Russ Poppe said in a statement after Saturday's vote. "We plan to work extremely hard and efficiently to turn the financial resources made available as a result of this election into the reality of reduced flooding risks."

Poppe also said the agenda for next week's Harris County Commissioners Court will include more than a dozen flood-control projects.

Houston, which is barely above sea level, has long been susceptible to flooding. A web of bayous and other watersheds that can overflow during heavy rainfall snake their way through Harris County. Flood maps show that more than 25 percent of Harris County is in the 100-year flood plain and more than 33 percent of the county is in the 500-year flood plain.

Structures in a 100-year flood plain have a 1 percent chance of flooding in any given year, while those in a 500-year flood plain have a 0.2 percent chance of flooding during any year. The Houston area has had three 500-year flood events since 2015. Many of the Houston area homes damaged during Harvey were not in designated flood plains.

The flooding from Harvey and damaging storms in the two preceding years has galvanized efforts to make the Houston area more resilient to future floods.

Since Harvey, the city and the county have approved rules requiring new homes and other buildings constructed in flood plains to be built higher off the ground to avoid flooding.

Houston Mayor Sylvester Turner said things like the bond referendum and the new building rules show that the area is serious about better protecting itself.

"As we develop going forward, we're going to have to do things differently," Turner said.

The bond referendum received bipartisan support and was endorsed by business and labor groups as well as religious and community advocacy organizations.

However, there were some community concerns about transparency and how the money would be used.

Keith Downey, president of the Kashmere Gardens Super Neighborhood, a local community group, said he would have liked more information about how some of the projects will benefit the city's low-income neighborhoods, many of which flooded during Harvey and have a history of repeated flooding.

"There are more questions than we have answers," Downey said as he stood next to Hunting Bayou, one of the waterways that swamped low-income neighborhoods during Harvey.

Officials have said they have been transparent about the bond proposal, holding 23 community meetings this summer to gather public input and ideas.