Damage Control

Page 4 of 9

The basic blueprint for a storm-water management scheme like the Pate Plan is straightforward enough: Improve the channel to increase its capacity to convey the upstream runoff and dig a hole to detain any excess before it reaches flood-prone areas downstream. The difficult part is calculating how much storm water will be generated by a development, how quickly it will run off, how much bigger to make the channel and how deep to dig the detention pond.

Since no engineer can anticipate every condition -- and everything from a small pile of dirt to a new parking lot can skew the calculations -- the Pate Plan was based on "reasonable" assumptions. Pate began with the '83 flood hazard survey of White Oak Bayou, which analyzed the existing land conditions, or hydraulics, inside a 110-square-mile diagonal from downtown to the intersection of Highway 290 and Huffmeister. Using computer programs developed by the Army Corps of Engineers' Hydrological Engineering Center, or HEC, the impact of the watershed's hydraulics on the bayou's water levels, or hydrology, was determined to identify the White Oak's 100-year floodplain.

Pate updated those assumptions, first by determining how 15,000 acres of new development would reduce the natural hydraulic efficiency of the watershed, then by calculating how the $66 million regional plan would alleviate the subsequent hydrologic impacts. Pate concluded that with channel improvements and storm-water detention, the flows of the White Oak would be completely contained within the channel during a 100-year storm. Among the assumptions reached by Pate: The 160-acre detention pond at Fairbanks-North Houston Road would reduce peak flows in the area of Woodland Trails West and Woodland Oaks by nearly 105,000 gallons per second -- more than enough to allow 2,500 acres of new development to begin immediately.

This was, of course, what the developers had hoped Pate would say when they hired the firm -- not that who paid for the new HEC analysis would have made much difference. If the flood control district had initiated the White Oak regional plan, the agency would have hired a local engineering consultant to do the analysis, notwithstanding that the consultant also would be in line for design contracts when the vanquished floodplain was developed.

This is the "fatal flaw" in Harris County's oversight of floodplain development, says Jim Blackburn. In a speech called "Place, Spirituality and Activism," delivered October 11 at the Rothko Chapel, Blackburn likened the political contributions of engineering consultants to the bribery schemes in a "third-world country." He then proceeded, in detail, to list more than $600,000 in recent political contributions to county commissioners from engineers, developers, architects and contractors who make their living off new development.

For his lawsuit against the flood control district, Blackburn secured the services of Larry Dunbar, a hydrologist who has become something of a black sheep in the local engineering community. After years of taking the stand as an expert witness on behalf of developers and engineering consultants, Dunbar became an attorney and started using his experience on the other side of the aisle. Though he is careful not to disparage the entire profession, Dunbar says there are engineers who set aside their responsibility to the public in favor of their immediate benefactors.

"Their job is to walk the client as far up to the line as the client is willing to go," Dunbar says. "The established ones are very good at it. They know how far is too far and where to tweak the data that's put into the models. Then there are a whole bunch that really don't know what they're doing."

Precision would seem to be in the public's best interests, but county plan reviewers rarely challenge the assumptions of other engineers. The county's chief engineer, Steve Fitzgerald, says this deference is partly a matter of limits imposed on county resources and partly because there's no reason to suspect the models are manipulated to ensure a predetermined outcome.

"I reviewed plans for a long time, and I have heard those contentions before, and of course it is possible and it probably does happen," Fitzgerald says. "But just based on my experience, it is very rare that a professional engineer would do something like that."

When he first became an engineer in the 1970s, Fitzgerald recalls, the corps' computer models relied on punch-card data and "antiquated" topographical maps. These primitive tools increased the potential for error, as well as the time it took to do the modeling for an entire watershed. Indeed, before construction could begin on the first phase of Pate's interim plan -- the expansion of the White Oak's main channel -- the latest assumptions were washed away.

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Brian Wallstin