Flood insurance is getting a huge overhaul. Here’s what it means in Hampton Roads.

When it comes to flooding, Hampton Roads residents are used to seeing numbers change.

Maps morph. Predictions for sea levels rise.

But for decades, the way national flood insurance has been calculated stayed the same. That changes Friday.

The Federal Emergency Management Agency is launching a new methodology for setting premium rates.

Dubbed Risk Rating 2.0, it bases prices less on general flood zones and more on a mix of factors including what a building looks like and how close it is to a variety of flooding sources.

The agency says it’s designed to be more equitable — people with more expensive homes will pay proportionally more, and vice versa.

But coastal communities will feel the changes most acutely, national experts have noted.

Here’s what you should know about the impact in Hampton Roads.

Why is it changing?

Since the National Flood Insurance Program was created a half-century ago, premiums have been based on relatively static measurements, FEMA says. They were focused on a property’s elevation within a flood map area.

Risk Rating 2.0 will incorporate more variables that can affect flooding, the agency says. Their website calls it a “transformational leap forward” by including more private-sector datasets and newer risk science.

Federal officials also say equity was a driving factor.

Policyholders with lower-valued homes currently pay more than their fair share, FEMA says. Home values weren’t spread as far apart when the program started as they are now, FEMA officials said on a recent call with media. That’s led to drastic under or overpayment even when buying the same insurance.

The new methodology factors in the cost of rebuilding a home to correct that problem.

Ben McFarlane, senior regional planner with the Hampton Roads Planning District Commission, said local officials have been monitoring changes in the works for years. Congress occasionally tried to overhaul the program, but usually backed off when it looked as if people would have to pay more, he said.

As a coastal community prone to flooding, Hampton Roads has a sizable concentration of flood insurance, he said.

“More people here are going to be seeing some sort of change than in many other regions around the country.”

How will new rates be calculated?

Not all of the data and models that FEMA uses are publicly available. Some are proprietary from private companies, McFarlane said. That means it will be difficult to precisely predict impact until premiums are rolled out under the new method.

But FEMA has revealed many of the new considerations built into the calculations. They include distance to a flooding source, building occupancy, construction and foundation type, drainage area, height of the first floor and more.

The general difference is including the specific aspects of a home rather than just its elevation within a flood zone.

Risk Rating 2.0 also accounts for a wider range of flood risk. The government previously relied on what’s known as a 1% or 100-year flood standard. That doesn’t mean flooding happens once every century, but rather that in a given year, there’s a 1% chance of flooding.

As data changes — due to climate change conditions, for example — the new models are supposed to reflect that increased risk, FEMA officials said. McFarlane said it’s all a step forward, but probably still doesn’t give property owners a true sense of their risk.

The NFIP doesn’t map flooding due to rainfall, for example, as when storms pass through Hampton Roads and overwhelm the stormwater infrastructure.

“That kind of risk is not very well addressed,” he said. “It’s hard to do.”

Will my premium go up — and when?

The good news: For about half of Hampton Roads policyholders, the answer is no. About 47% will see immediate decreases in their premiums, according to analysis from the planning commission.

For the other half, bad news. About 48% of policyholders will see increases of up to $10 per month. A small amount will see higher increases. By law, rates cannot go up by more than 18% per year.

For people with the biggest change, therefore, it could take years to reach the new rate. It’ll take about 5-10 years for most policies, according to FEMA, up to two decades for those with the most drastic change.

There’s additional relief in Hampton Roads.

Many localities participate in a program that rewards floodplain management efforts with discounts on flood insurance premiums, called the Community Rating System. Chesapeake, Virginia Beach, Norfolk, Portsmouth, Hampton and Poquoson, along with Gloucester, James City and York counties are in that system.

Risk Rating 2.0 launches Oct. 1 and will apply immediately to policies bought from that day forward.

If you already have flood insurance, the change doesn’t take effect until April.

Hampton Roads is likely underinsured

There are just over 71,000 national flood insurance policyholders across the 17 localities with which the planning commission works. McFarlane said his organization’s worked for years to encourage more residents to opt for it.

Most people with flood insurance buy it because it’s required, he said. It’s mandated for those with federally-backed mortgages who live in what are known as Special Flood Hazard Areas.

Many places that flood aren’t technically in such an area. About a third of claims that FEMA gets each year come from outside those high-risk areas. Plus, older homes that are paid off no longer have a mortgage requiring such insurance, McFarlane noted.

The commission has a website called GetFloodFluent.org where people can learn more, including a calculator to estimate cost.

The calculator will come down Friday, though, while officials figure out how to update it with the new method. For now, they don’t know exactly what to expect.

Katherine Hafner, 757-222-5208, katherine.hafner@pilotonline.com