NBC – While Houston is now seeing flooding on an unprecedented scale, it turns out that flooding is not uncommon here.

In fact, it’s a long-standing problem.

In the nation’s fourth largest city….floods are a way of life…

In 2015…a Memorial Day flood racked up almost half a billion dollars in damages.

Last year….Houston led the u-s in flood-related deaths…mostly due to an April storm that claimed eight lives.

So *why* is the bayou city so vulnerable?

Not only is it low-lying….with many creeks and rivers…

The metro area’s development has exploded.

One study found the Houston area has added 25 percent more pavement over 15 years.

Replacing soil-rich wetlands that could absorb water….with concrete covered suburbia.

Houston is unique among major cities in that it has no formal zoning laws.

As for other regulations…new structures here are required to be built 12 inches above 100-year-flooding levels.

With the city’s population expected to grow by more than three million people over the next three decades…it’s a problem…that might only get deeper.