Below the skyscrapers and highway flyovers of this booming port city a water system winds, barely visible yet following the original logic of Houston's topography. These tributaries, called "bayous" in the South, have become the focus of an extensive planning effort that has repositioned a neglected corridor into a center of recreational and cultural life.

Like other bayous in Houston, the Buffalo Bayou was for decades considered little more than a sewer and water drainage system, best avoided by residents. It meanders approximately 30 feet below grade through the center of downtown, threaded between the maze of highway support columns and cutting across city blocks. As a principal drainage system for much of the city, it carries substantial amounts of water, but still occasionally becomes the site of major flooding.

In 1986, local leaders created the nonprofit Buffalo Bayou Partnership to oversee improvement projects and advocate for the area, but urgency crystallized in 2001, when tropical storm Allison hit Houston, causing record flooding in the downtown and becoming the costliest (nonhurricane) rain event in US history. With perfect timing, the "Buffalo Bayou and Beyond" plan was released in 2002, led by Boston-based Thompson Design Group. The planning effort, which still guides work today, anchors a paradigm shift in Houstonians' mental maps of their city.

The bayou was often inundated with trash, a result of Houston's street-water drainage system that collects runoff and debris and empties it into the creek. A bright pink Skimmer Boat (christened Mighty-Tidy) purchased in partnership with the Port of Houston Authority, helped manage the recurring litter while adding visibility. Through this boat — and other advocacy measures such as canoe races, dragon boat festivals, tree planting programs, and community service cleanups — attention turned to an area of the city that most locals didn't even know existed.

Much of the public funding for the Buffalo Bayou project was supplemented through foundation partnerships and private donations. Although not unique in American cities, it stands out in Houston, a city with many Fortune 500 oil and gas companies. The city's characteristically conservative political economy lends itself to a climate where large companies anticipate playing substantial philanthropic roles in city building. The robust private sector aid seems to enable a kind of unspoken commitment to keep government presence small in rebuilding affairs — hence, also in corporate affairs.

While land acquisition and cleanup efforts in the bayou system continue, some more highly visible park segments have been created downtown. In 2010, Houston-based landscape architects SWA Group designed and completed the first of these, called the Sabine Promenade. This 1.2-mile stretch has become a below-grade link, connecting parts of the downtown that were previously fragmented by highway ramps.

The design features of the Sabine Promenade follow clues from the infrastructure above. Instead of shielding users from the gritty character of the roadways, trails twist and bend around columns as needed to move continuously through the space. The result is a multisensory environment, amplified by the rumble of trucks and traffic above. What separates the Sabine Promenade from other contemporary open space investments is its ambition to take advantage of a degraded space, the kind found in almost any American city, then capitalize on the water course below. Such marginal spaces are seldom confronted or transformed. But in Houston — a city known for its free-for-all building environment with no traditional zoning laws — the bayou project serves as a new connective tissue. At local and regional scales, it provides a cohesive, environmentally forward gesture that recenters the haphazard.