Buffalo Bayou Park

Challenge

• Reconnect Houston residents to their primary hydrologic system while preserving the cultural significance of the bayous.
• Mitigate physical, economic, and social damage caused by seasonal and catastrophic flooding events and reduce cleanup costs.
• Simplify and streamline ongoing maintenance.
• Restore ecologies and systems, curb site erosion, and mitigate pollution within a major urban corridor.
• Increase access to the outdoors and recreational opportunities for adjacent neighborhoods.
• Accommodate opportunities for active and passive recreation.
• Educate the public on flood protection and set a precedent for future development of riparian corridors and waterfront redevelopment in Houston.
• Catalyze economic revitalization of areas adjacent to the park.

• Through the coupling of hydrologic engineering and landscape adaptability, the park was designed as a resilient system able to withstand the forces of the bayou while protecting a significant investment in public amenities. All site furnishings, plantings, and walkways were selected and sited to withstand the natural, periodic flooding of the bayou.
• Through channel stabilization techniques and the U.S. Army Corps of Engineers’ HEC hydrologic modelling system, the park design implements principles of fluvial geomorphology to reintroduce greater sinuosity into the channel. This enables Buffalo Bayou to function in a more natural way within a restrictive urban context while preserving its cultural significance and natural beauty. Additionally, this allows the Bayou to function more effectively within its greater hydrologic system, consisting of 106 miles of open waterways served by a 102-square-mile watershed.
• The concrete columns of the four new pedestrian and bike bridges crossing the bayou have a hydrodynamic profile that minimizes turbulence of water moving through the channel during flood events. Bridge spans are made of corten steel and engineered to withstand impacts of logs and the occasional vehicle that gets washed down the bayou. Stairs and rails are also robustly engineered to withstand submersion and debris impacts.
• Light poles are constructed of concrete to withstand the impacts of floating debris, and high water switches can cut off power to the system during flood events.
• Hardscape items such as concrete retaining walls are sited parallel to water flow to prevent turbulence, impact from debris, and silt deposition as much as possible. The lowest footpath is located at 12 ft above the water level, which is the level that was deemed close enough to the water for visual and physical connection yet high enough (based on historic hydrograph high water event frequencies) to minimize the need for silt removal after flood events.
• To allow for quick recovery after a deluge, maintenance routes are routed to enable heavy equipment to access specially designed silt benches for silt removal several times a year. The silt benches are located on the inside bends of the channel geometry so that silt will naturally collect at locations of slower water velocity, which facilitates maintenance of the park by creating known locations for these deposits.
• Approximately 50% of the mowed turf previously used as informal event space was replaced with riparian woodlands and naturalized meadows to stabilize the landscape, improve and provide new habitat, add aesthetic value, and minimize maintenance costs. This includes the planting of 14,000 trees, including baldcypress (Taxodium distichum), American sycamore (Platanus occidentalis), and loblolly pine (Pinus taeda). The planting strategy also helps to curb bank erosion and water pollution.
• The park’s over 15 miles of pedestrian trails and bike paths allow for active recreation and increased access. In addition to parking and drop-off locations, multi-modal connectivity is fostered through bike share facilities as well as a network of pedestrian bridges, enhanced at-grade crossings, and underpass trail connections. The four pedestrian bridges crossing the bayou and numerous gateways along the park’s periphery provide numerous points of access to the park, improving accessibility for the surrounding neighborhoods. 
• Spaces for recreation and gathering include large event lawns, amphitheaters, an expansive dog park, a seating circle, protected gardens, the Joe Jamail Skatepark, a nature playground and picnic pavilion, and multiple flexible-use plazas.
• A number of overlooks and viewing areas provide specific vantage points for pedestrians including the Downtown Skyline Overlook, the Crosby Outfall and Overlook, the Memorial Heights Overlook, the Waugh Drive Bridge Bat Colony Viewing Area, and the Cemetery Overlook. The Waugh Drive Bridge Bat Colony Viewing Area allows visitors to observe the approximately 250,000 nonmigratory Mexican free-tailed bats that live in and under the Waugh bridge. Special considerations were implemented during construction to minimize disturbance to the colony.
• Water Works, a massive 87,500-sf underground installation art venue, reuses and reimagines a historic City water storage facility called the Cistern. The roof of the Cistern hosts the Downtown Skyline Pavilion and the Sky Lawn and Performance Stage, which include a flexible performance lawn, multi-use plaza, visitor center, restroom facilities, and bike rentals. A large lawn at Eleanor Tinsley Park provides space for seasonal events such as concerts and festivals.
• To the west, the Lost Lake garden and restaurant features a water garden, indoor dining, kayak rentals, and park offices, offering visitors a place of refuge during Houston’s hot summer months.
• Iconic, site-specific art pieces are found throughout the park. Blue LED lighting along trails and under bridge crossings is timed with lunar cycle to connect park users to the longer time scales of nature. The lights turn blue during the moon’s dark phases (new moon) and then back to white with the transition to a full moon. The blue lighting starts at Allen’s Landing and then gradually expands outward with each lunar cycle until the whole trail system is lit blue at the new moon.

Buffalo Bayou Park is a critical link within a regional system of bayous that when connected, increase the open space network by leveraging the City of Houston’s underutilized floodplains. Buffalo Bayou lies at the heart of this network upstream of downtown Houston, where the Allen brothers landed and founded the city in 1836. Most of the site was clear-cut as part of an Army Corps of Engineers channel straightening project in 1958; however, Buffalo Bayou was saved from being paved by the Bayou Preservation Association in the 1960s. The site was then converted to turf to serve as a drainage corridor, and it degraded over the following decades due to invasive vegetation and silt deposits.

The Buffalo Bayou Partnership, a non-profit organization, worked with the landscape architect to design the park, which opened in 2015 and attempted to restore some of the site’s original ecology. The park has been a catalyst for the Bayou Greenways 2020 initiative, launched by the City of Houston and the Houston Parks Board. The initiative will connect the major bayous by creating 150 miles of trails and bridges by 2020 and will provide access to this network to 1.5 million Houstonians living within 1.5 miles of the bayous. The history and development of Buffalo Bayou Park, spearheaded by the Buffalo Bayou Partnership and a number of public-private partnership endeavors, has greatly influenced the Bayou Greenways 2020 initiative by providing a precedent, and it will continue to play a critical role in the open space network that will serve the City of Houston.

A series of riparian bank stabilization techniques were considered during the design phase of Buffalo Bayou Park in order to control for bank erosion from fluctuating water levels throughout the course of each flood season. Where creating a 3:1 slope (or even a more conservative 4:1 slope) was not possible due to constrained right-of-way, the preferred method was to install gabion walls along the banks of the bayou in combination with a 2:1 slope of planting above to limit the amount of erosion during flood events. However, at $925.80 per linear foot (lf), installing gabion walls on both 2-mile-long banks was extremely cost-prohibitive. Instead, the design team stabilized the banks with vegetation at a 2:1 slope where wetland species would occupy the portion of the bank that would occasionally submerge, with a native grass mix above. Only a few locations were constructed with more aggressive stabilization techniques due to their high vulnerability for slope failure. Vegetated slope costs were $72.50 per lf, most of which was already included in the planting budget.

However, due to the known vulnerable nature of vegetated slopes without gabion walls, repairs were necessary after Hurricane Harvey. The cost of repair for 4,315 lf of slope failures at $748.50 per lf was $3,229,778. If this same linear footage of banks had been initially constructed with gabion walls, the cost would have been $3,994,827. While the repair costs for these vegetated slope failures totaled less than the cost to construct gabion walls in these locations, repetitive failures from future flooding events will cause this gap to shrink.

• The greatest overarching lesson has been that the bayou is ever-changing and unpredictable. The design team used historic hydrograph data to determine elevations to locate trails, gardens, and other site elements in anticipation of high water events and maintenance. After the park’s opening in 2015, three 500-year flood events took place in three consecutive years, which was unpredictable and unprecedented. Some slope failures and design adjustments were anticipated given the nature of a 160-acre site within a dynamic environment, which is why the park has an ongoing maintenance and repair budget for major storm events.
• Immediately post-Hurricane Harvey, the US Army Corps of Engineers released water at an atypically rapid rate from the Barker and Addicks reservoirs upstream to prevent them from failing (their failure would have sent a wall of water through downtown Houston). Normally, the reservoirs discharge at approximately 2,500 cfs after a storm event; under other “typical” flood conditions they may release up to 5,000 to 6,000 cfs. Post-Harvey, the discharge was released at 13,000 to 16,000 cfs over an extended period of time. This inundated the park with higher water levels than normal and subjected it to higher water flow velocities for longer periods of time, leading to some slope failures.
• It was almost impossible to predict the amount of silt that would be deposited in the park post-Harvey. This was directly related to how far north and south the bayou went over its banks, much farther than in previous flood events, which caused floodwaters to pick up sediment and silt from a much larger area (including areas that had not flooded before) and deposit them within the channel. In the end, 68 million lbs of sediment (3,400 truckloads) had to be removed from the park.
• As part of their work in developing the park, the Harris County Flood Control District (HCFCD) installed coir lifts and live staking at selected locations to control erosion and slope failure. As part of the landscape architect’s work, synthetic soil fibers were implemented on extreme slopes and slopes were planted with species that have deep rooting systems to control erosion and slope failure. These were implemented because one of the primary issues with inundation within the bayous is rapid drawdown which leads to slope failures. This means that the water level remains high for an extended period, saturating the soil and creating instability, and then when the water level drops quickly as the bayous empty, slopes can fail if they are not designed properly. Of 30 different species on slopes that became submerged, no species established well enough to withstand the effects of unstable slopes. Today, most of the lower bank elevations consist of muddy slopes because of this and have become the weak points in the resiliency of the bayou as a system during flood events.
• Because the site is essentially straitjacketed between Allen Parkway and Memorial Drive, it was difficult to stabilize some of the slopes where the right-of-way was very narrow. In locations where slopes are steeper than HCFCD requirements, there have been slope failures during major high water events because there was not enough funding for toe stabilization along the entire length of the project.
• Drainage wasn’t addressed adequately in the lower planting beds at Lost Lake, resulting in frequent submersion and plant failure. The significant amount of water coming down the slopes from both irrigation and precipitation was not well understood before construction. Most other planting locations in the park are on slopes, so water naturally drains across them into the bayou. At Lost Lake, the water stays trapped in the lower beds. 
• The planting plan was designed to a vegetation survey completed in 2010. In 2011, there was a severe drought (the driest year on record), which resulted in the loss of a fair number of large trees in the park. At that point, it would have been prohibitively expensive to re-survey as there were thousands of trees on site. Some of the proposed understory plantings had been designed for shade-tolerant locations; however, in areas where trees had died in the drought and been removed, the amount of sun exposure had changed. This resulted in additional plant mortality from the increased exposure.
• While the site utilities and overall electrical system within vaults have withstood flood impacts, light fixtures being underwater for an extended period during these events necessitated replacing a number of light bulbs.
• Mock-ups were completed prior to construction of light poles, rails, retaining walls, and all hardscaped surfaces in order to test their performance during flood events through simulated impacts. To date, these items have all withstood flood impacts.
• The dog park was already being used as an informal, unfenced dog park prior to park design and construction (official dog parks in the City of Houston are required to be fenced). It was an expansive grassy sloped area in the midst of an urban environment adjacent to the bayou where people would let their dogs run freely. It was also a location where the US Army Corps of Engineers realigned the bayou in the mid-20th century, so it was at a very low elevation and highly subject to inundation. Because of this, the team designed ponds at the low area for dogs to play in, with the ability to drain them into the bayou channel after high water events. However, the three 500-year storms caused this location to be underwater more frequently and the ponds filled up with silt, which necessitated an expensive effort to remove it in addition to long-term closure of the site. As a result, the dog park was rebuilt post-Hurricane Harvey to remove the large pond.
• The dog park was also a victim of its own success, apart from the flood events. Due to the sloped nature of the park, turf was used as a surfacing material instead of decomposed granite, which performs better with constant use. Many more people and dogs than anticipated used the park from its opening, which made it difficult for the turf to establish. This resulted in higher greater maintenance efforts and costs. Mulch is now used in place of turf to help reduce wear and tear; however, it easily washes away during flood events. Ultimately, the unconventional siting of the dog park due to the slope and prior informal public use, has greatly contributed to ongoing maintenance issues.

Site furnishings: Landscape Forms
Bollards: Creative Pipe
Pavers: ipc Building Products
Gravel retaining wall: Redi-Rock Clay
Pond liner: Cetco Lining Technologies
Water features and pumps: Greenscape Pumps and Crystal Fountains
Soil stabilization: Fiber Soils
Playground equipment: Natural Playgrounds Company
Granite water table: Meadows Mills, Inc.
Cast stone: Siteworks
Architectural cast stone playground mesh guardrail: Jakob Webnet
Irrigation: Hunter
Drainage: ADS
Sunshade: Ametco
Reinforced turf paving: NDS TUFFTRACK
Reinforced gravel paving: Gravel Pave 2
Trail light poles: Lonestar Prestress
Lighting: ELA, Neutex, Lumenpulse, Filix, Hydrel, Gardco, Bega, BK Lighting, Louis Poulsen

Project Team

Prime/Master Planning/Landscape Architecture: SWA Group
Architect (Park Structures): Page Architects
Horticultural/Specialty Landscape Architecture: Reed Hilderbrand
Civil Engineering: United Engineers
Structural Engineering: RDP Engineers
MEP Engineering: Hunt & Hunt Engineering, Corp.
Geotechnical: Aviles Engineers
Traffic Engineers: AIA Engineers
Lighting: L’Observatoire and artist Stephen Korns
Water Feature: Greenscape Pump Services
Irrigation Design: Sweeney & Associates
General Contractor: Millis Development & Construction, Inc.
Wayfinding: Marek Hill Design
Playground Consultants: Natural Learning Initiative. College of Design, NC State University
ADA Consultant: Advanced Design Solutions
Financing: Kinder Foundation, City of Houston, Houston Parks and Recreation Department, Harris County Flood Control District, Downtown Tax Increment Reinvestment Zone (TIRZ) #3, and private funds raised by Buffalo Bayou Partnership

Role of the Landscape Architect

The landscape architect administered comprehensive landscape architecture services for the design and construction of Buffalo Bayou Park, working closely with an extensive consultant team and leading coordination with multiple agencies. Site design, grading, and planting design; paving and plaza layout; and materials were completed and detailed by the landscape architect. The landscape architect had previously administered comprehensive landscape architecture services for the design and construction of Buffalo Bayou Promenade in 2005, a park segment from Sabine Street to Bagby Street within the overall master plan of Buffalo Bayou Park. The success of the Promenade served as a catalyst and proof-of-concept for the park.