Landscapes of Change author Roxi Thoren takes a look at the making of Buffalo Bayou, an award-winning park providing recreational opportunities as well as flood control and ecological restoration.
In the middle of downtown Houston, an alligator is floating down a bayou, lazily drifting in the muddy current. A group of park visitors excitedly points out its snout, the ridges on its back. On any given day, Houstonians can see three kinds of turtles, heron, osprey, songbirds, a colony of 150,000 bats, and even the reclusive alligator sunning on the silty banks in the middle of the fourth-largest city in the United States. This is an astonishing reversal for a bayou that until fairly recently was inhospitable to people as well as animals—a foul, polluted channel filled with trash.
Buffalo Bayou, apparently named for the bison that once roamed this landscape, is Houston’s generative force. The city was developed in 1836 at the confluence of Buffalo and White Oak bayous, and the urban grid was laid out parallel to a reach of Buffalo Bayou. The waterway served as the city’s primary transportation and shipping infrastructure, and by the early twentieth century, the channel had been dredged from 9 feet (2.7 meters) deep to 25 feet (7.6 meters) deep to allow oceangoing boats access to the port. But while urban access to water was good for transport, it was a problem in storms: the tidal bayou, waterway for a 102-square-mile (264-square-kilometer) watershed, was prone to flooding. Following devastating floods in 1929 and 1935, the Army Corps of Engineers designed a flood-control plan for the bayou. By the 1960s, the Corps had built an upstream dam and reservoir to control inflow to the bayou and had channelized White Oak Bayou, removing riparian vegetation and straightening its meanders. Concerned by White Oak Bayou’s transformation into a concrete channel, Houstonians rallied to protect Buffalo Bayou and to preserve the urban ecosystem.
A 2002 master plan by Thompson Design Group set the framework for hybrid improvement to the floodwater infrastructure that also improved the bayou’s ecological function. The master plan refocused the city around the bayou, provided access for recreation and social events, and used the green infrastructure as a catalyst for economic development. The plan conceptually divided the bayou into three zones—a downtown sector flanked by more expansive, meandering, and wild east and west sectors. The plan envisioned green fingers reaching into downtown Houston, pedestrian areas that would include street plantings to provide visibility and access to the bayou and also to slow, clean, and cool storm water before it entered the bayou.
Buffalo Bayou Promenade reclaims the downtown sector, serving as an ecological and urban amenity. Before the project, the bayou was largely inaccessible to Houstonians, with limited entry points and steep 20-to-30-foot (6-to-9-meter) banks. It felt unsafe, with limited visibility into the bayou. About 40 percent of the promenade is covered by freeway infrastructure—on-ramps, bridges, overpasses—which creates shaded nooks that added to the sense of danger. It was also inhospitable to wildlife. Trash collected in the bayou, trapped against bridge piers and among overgrown invasive shrubs. Fast-moving floodwater eroded the banks, and the silt removed from the banks clogged the water. The bayou had the worst water quality of any Texas stream or river and was nearly intolerable to aquatic species. To restore the bayou’s ecological function and turn it into an attractive urban park would require considerable ingenuity.
SWA Group faced extreme challenges at Buffalo Bayou: steep slopes, eroded banks, overhead infrastructure, invasive plants, limited access, and extremely poor water quality. The promenade at first glance is a successful urban park, 23 acres (9.3 hectares) of open space and jogging and biking trails, with beautiful planting, lush shade, and lovely views of the bayou and the skyline. But the promenade is more than just a park; it also functions as a flood control mechanism, an ecological restoration, and an urban amenity. It is part of a growing movement in landscape infrastructure benefiting from hybrid cultural and ecological spaces. Rather than addressing flooding with a narrow, straight, steep channel that moves water quickly out of an urban center, landscape infrastructures disperse and slow water, spreading storm water both spatially and temporally. Wenk Associates’ Shop Creek in Denver was an early example of using wetlands and stream meanders to slow water, wetlands to filter sediment and pollution, and deep pools to settle sediment out of the creek’s water. The approach is becoming more common, but Buffalo Bayou Promenade is one of the largest and most urban examples of a hybrid flood control and ecological restoration project.
By using landscape solutions to reduce flooding, SWA Group also restored the ecological function of the bayou and gave Houstonians access to the waterway. The designers regraded the steep banks, removing nearly 31,000 cubic yards (23,700 cubic meters) of soil. This significantly increases storm water storage capacity and provides access to the park as well as views into the bayou from the surrounding buildings, streets, and freeways. The erosional banks of the bayou were stabilized with gabions filled with reused crushed concrete; 14,000 tons of concrete were salvaged from demolition projects and used to fill the metal mesh cages. Water can flow through the gabions, creating a complex edge between water and land that disperses the energy of both storm water and the waterway, helping to reduce erosion throughout the bayou.
Invasive plants were removed, and native and naturalized plants that can withstand flooding were selected for the riparian edge. In floods, the extensive planted edge helps to filter trash and sediment from the water, and like the gabion edges, the plantings disperse some of the energy of the water, helping to limit erosion. The designers selected plants that could stabilize the banks with deep roots and lateral rhizomes, such as Mexican petunia. And throughout, planting was designed to create a beautiful park and to assist in wayfinding. Ferns, Mexican petunia, and Louisiana iris add beauty to the park, and perennial plantings at the access points form gateways into the park and help to orient visitors.
Connecting Houston to its bayou is one of the signal achievements of the project. The 1.4 miles (2.3 kilometers) of trails within the promenade connect to 20 miles (32 kilometers) of trails throughout the bayou and link downtown Houston to the larger urban context. Twelve new entrances connect the downtown street grid to the promenade with ramps that provide access for bikes and strollers. Several of the trails end at the water with boat launches, making canoeing and kayaking the bayou possible. Four of the entrances are marked by new art pieces, and all have iconic decorative planting, forming enticing gateways to the bayou. Signage helps visitors find their way and also educates them about the bayou ecosystem.
And “moon phase” lighting subtly connects visitors to natural cycles while also providing a sense of safety in the park. Lights on the underside and columns of the freeway slowly change color over the month, brightening to white at the full moon and fading to indigo at the new moon. Having darker lights during the darker skies minimizes light pollution, which can severely impact nocturnal insects and migratory birds. The lighting, along with open views into and out of the park, and open planting, has improved the sense of safety along the bayou. Along with an extensive program of events, this is bringing more people back to the water’s edge, where they can reconnect with the plants and animals of the bayou and with its rhythms of flooding and calm.
By improving and revealing an existing ecosystem, Buffalo Bayou Promenade gives Houstonians extraordinary connections to an urban wild: a bayou that floods and recedes, the migratory patterns of indifferent animals, the horror of predator and prey, and the beauty of songbirds.