Transportation planners say detention ponds and pumps will be part of a major freeway rebuild downtown and on the north side.

One year ago this week was the event we now just call "Harvey." The storm's record-breaking rainfall highlighted any and all weak spots.

One of those spots is Houston's freeways. They can flood even during a big thunderstorm, but should they be getting that much water?

I looked at one trouble spot, next to where TxDOT is planning a major redesign of I-45. That's Historic Hollywood Cemetery, a sprawling 55-acre property close to where 45 meets Main Street. I climbed into a golf cart with cemetery manager Tom Snyder.

"Well, we've been here since 1895," said Snyder. "And during that time this was probably a pretty far stretch from downtown Houston."

Curving roads take visitors through wooded glens and rolling hills, past well-tended grave sites that bear the names of generations of Houstonians.

At the back of the cemetery there's Little White Oak Bayou. On this day it was meandering peacefully behind a bank of trees. But Snyder said it can make a mess when it comes out of its banks.

"And it is not uncommon, when there are significant floods, that this entire area will be flooded, so that everything is totally under water," explained Snyder.

And that flooding also includes nearby I-45.

As part of the North Houston Highway Improvement Project, TxDOT wants to put a cap over a below-grade section near Main Street and place frontage roads on top. They also want to do the same thing with a portion that will go below ground near the George R. Brown Convention Center.

But after what we saw during Harvey, how will TxDOT keep the roadway dry, in particular the below-grade segments? We went to talk to District Engineer Quincy Allen.

"Especially with Harvey we have such a vivid memory of what a 500-plus year event can do to an area," said Allen.

And even lesser storms can cause a lot of flooding. Allen said they're considering several options.

"The things that we're looking at are detention ponds, bigger and better than we've had before," said Allen. "A detention pond helps us gather the water and hold it in a location that keeps from overwhelming the stream."

But what about parts of the freeway that will go underground? Allen says they’ll have to use pumps.

"And we're going to add a few on this project," added Allen. "It'll help us move the water out of areas like that and get them up in either detention ponds or headed downstream."

For a project of this magnitude planners need to worry about more than just the freeways. And that's where the Harris County Flood Control District comes in. Director of Operations Matthew Zeve said they're partnering in the work.

"We're trying to make sure that whatever project gets built has flood damage reduction benefits outside of the highway itself and helps other people with drainage issues as well," Zeve told News 88.7.

But with rainfall sometimes hard to predict, Zeve added you really can't guarantee there won't be any flooding at all in the future.

"The level of service that TxDOT would like to provide for these main lanes, is the one percent storm or the 100-year rainfall level of service, to keep those main lanes functioning during a storm of that magnitude," said Zeve.

Meanwhile back at Hollywood Cemetery, Tom Snyder said one thing that might help in the short term is some cleanup work on Little White Oak Bayou. That would help the water flow better on so it won't flood the freeway.

"There's too much vegetation, there's too much trash," said Snyder. "There's any number of issues that could be addressed that would improve the flow of water in that bayou area."

Construction on the downtown portion of the freeway project is expected to start around 2021. The section north of downtown hasn't been funded yet and it doesn't have a start date.



North Houston Highway Improvement Project (PDF)



North Houston Highway Improvement Project (Text)

