President Donald Trump. REUTERS: Kevin Lamarque Ten days before Hurricane Harvey descended upon Texas on Friday, wreaking havoc and causing widespread flooding, President Donald Trump signed an executive order revoking a set of regulations that would have made federally funded infrastructure less vulnerable to flooding.

The Obama-era rules, which had not yet gone into effect, would have required the federal government to take into account the risk of flooding and sea-level rise as a result of climate change when constructing new infrastructure and rebuilding after disasters.

Experts are predicting that Harvey — the most powerful storm to hit the US since 2004 — will cost Texas between $30 billion and $100 billion in damage.

And in the coming days, Congress will be called upon to send billions of federal dollars to help with the state's recovery and rebuilding efforts.

But because of Trump's rollback of President Barack Obama's Federal Flood Risk Management Standard, experts across the political spectrum say much of the federal money sent to Texas is likely to be wasted on construction that will insufficiently protect against the next storm.

"We will rebuild things that should not be rebuilt and ... in ways that are less safe and secure than they should be," Eli Lehrer, president of the conservative think tank R Street Institute in Washington, told Business Insider.

Shana Udvardy, a climate-preparedness specialist at the Union of Concerned Scientists, said it would be a "grave mistake" to rebuild in Texas without taking into consideration the increasing occurrence and severity of major storms. She added that the federal government would lag some 600 towns and cities that have already implemented requirements to build between 1 and 3 feet above the 100-year flood level.

Lehrer called Trump's decision to revoke the standards "the biggest step backwards that has ever been taken in flood-management policy" and said the move would waste taxpayer money, harm the environment, and cost lives.

He and others argue that Trump's decision was a politically motivated attempt to undo Obama's climate-change legacy.

"If the Obama administration had simply described this as a sensible taxpayer-protecting land-use measure, the regulations would still be in effect," Lehrer said.

And some Republican lawmakers have denounced the move.

"This executive order is not fiscally conservative," Rep. Carlos Curbelo, a Florida Republican, said in a statement. "It's irresponsible, and it will lead to taxpayer dollars being wasted on projects that may not be built to endure the flooding we are already seeing and know is only going to get worse."

The Obama administration estimated the regulations would increase building costs by 0.25% to 1.25% but save taxpayers significant money in the future. Studies have found that for every $1 spent on disaster mitigation, the government will save $4 on post-disaster aid.

Joel Scata, an attorney with the Natural Resources Defense Council, told Business Insider that the regulations were spurred partly by the enormous costs of the disaster-relief efforts following Hurricane Katrina in 2005 and Hurricane Sandy in 2012.

"This not only would have protected people and property from future flood events, but also was really meant to reduce the amount of disaster aid we spend on recovery," he said.

And while Trump justified the rollback as part of an attempt to streamline and speed up construction projects, Lehrer said the regulations' effect on the construction process would have been largely "subtle and inexpensive" and that an insignificant number of projects would have been abandoned because of increased costs.

Scata also said the rollback would most likely have a disproportionate effect on poor and vulnerable people and communities.

For example, because the Department of Housing and Urban Development will not be obliged to build more-resilient structures, those who live in public housing are likely to suffer the consequences. On top of that, about 5%, or 11,000, of the country's public-housing buildings are in the floodplain, according to a 2015 report from the department's inspector general.