The report, released in March, notes that current floodplain regulations, which require structures in the 100-year floodplain to be elevated 1 ft above the 100-year flood elevation, weren’t effective. Of the homes that were compliant with the city’s 100-year floodplain ordinance, 38% flooded, according to studies. The city only minimally regulates the 500-year floodplain, where 33% of homes flooded. The department recommends extending regulations to the 500-year floodplain.

Houston Public Works’ analysis found that 19% of the structures located in areas outside the floodplains, including single-family and multifamily homes and commercial buildings, also flooded.

If all of Houston’s homes had been built to 2 ft above the 500-year flood elevation, 84% of the homes that flooded during Hurricane Harvey would have been spared, the agency found.

Costs to elevate new structures to the new levels could range between $11,000 and $32,000 per structure, according to the analysis. The proposed changes would be based on FEMA floodplain maps. Harris County’s current map dates from 2007 and is incrementally updated on a regular basis. A countywide remap has begun, but will take several more years.

In a related move, city of Houston Chief Resilience Officer Stephen Costello presented 13 flood relief projects to the city council on March 21 that will compete for $500 million in Federal Emergency Management Agency (FEMA) relief funding. The projects would cost more than $700 million and include work such as the addition of flood gates at Lake Houston. Officials are also considering a major project that would require drilling huge tunnels under the city to drain stormwater. Black & Veatch opened a tunneling center in Houston and have been pushing tunnels as a partial solution to flooding. County commissioners were expected to vote on proceeding with a feasibility study on March 27.