Alley Theatre Undergoes Successful Flood Mitigation Process

29 November 2022
Image courtesy of Bill Salt


Houston’s Alley Theatre, located in downtown Houston, is a 61,000-sf structure that opened in 1968 and is home to a cutting-edge artistic production company. Since the company’s founding in 1949, it has grown into one of the most prestigious non-profit theaters in the United States and serves as a cornerstone of the Houston arts scene.

During the mid-2010s, the Alley was completely renovated. However, disaster struck in 2017 when Hurricane Harvey dumped the greatest rainfall event in recorded U.S. history on the Greater Houston area and inundated the theater with 17 feet of floodwater. The floodwaters settled in the theater’s stage area as well as the basement level, ruining nearly 100,000 prop pieces—many of which dated back to the company’s founding—causing nearly $18 million in damages. Furthermore, the theater’s electrical room, which sources and controls power for the entire building, was completely destroyed.

At the time of the hurricane, the theater was protected against water infiltration pathways that had devastated the basement with 14 feet of water during Tropical Storm Allison in 2001. The flood protection system mainly secured the connection tunnels to a nearby underground parking structure.

However when the theater’s staff realized this flood protection system had not been breached, they could not determine how 17 feet of water from Hurricane Harvey had filled the basement. As a result, Walter P Moore was asked by the theater to deploy an emergency assessment team to identify the flood vulnerabilities within the theater.

The assessment revealed the failures that led to the basement flooding as well as other flood vulnerabilities found that did not contribute to damage related to Hurricane Harvey. It was determined that up to six feet of floodwater entered the theater through the pedestrian doors and emergency stairwells at the ground level. However, the largest contributing factor to the basement flooding from Hurricane Harvey was due to an existing electrical vault, which shares a portion of wall that separates the vault from the theater’s electrical room and prop/set storage area. The electrical vault had several vents that opened directly to the sidewalk at the ground level above.

When Harvey spilled massive amounts of rain onto downtown Houston, the streets started to back up with water and any open drain was completely inundated. As the electrical vault filled with water, the wall separating Alley’s basement buckled under the rain load, freeing the floodwater to rush in. This led to the theater quickly flooding to a depth of 17 ft.

The assessment was also important for the theater staff to understand the flood-related deficiencies and how they could be prevented. The assessment would eventually grow to include designs and installation of several additional layers of floodproofing that now protects the structure past a 1,000-year storm potential.

Flood Protection System

The flood mitigation project was challenging because of the building’s constraints—both on the interior and exterior. The latter being the location of the theater in Houston’s densely packed downtown area. Relying on creativity and technical skill, Walter P Moore’s diagnostics engineers developed multiple flood protection solutions to protect the theater. These solutions did not compromise the building’s architectural significance, interior floorplan and storage capacity, or its structural relationship with adjacent towers and parking garages.

To meet the client’s vision for the flood protection system, the existing structure was retrofitted with a new flood protection scheme. Notably, creative uses for existing technologies—for example, employing fiber-reinforced polymer (FRP) strengthening to resist potential floodwaters in place of constructing new reinforced concrete walls in the basement’s electrical room and prop storage areas—were installed. FRP strengthening did not impact the building’s architecture or useable area (layout and square footage), which could not be structurally altered.

Additionally, the plain glass panels in the lobby atrium were replaced with flood-grade alternatives. These flood protection innovations were implemented to achieve the goal of “barely-there” flood barriers that will protect the building well beyond the devasting power and pathways of future hurricanes.

Furthermore, the team reviewed other technologies that could also be retrofit into the building’s makeup. They identified several different systems in addition to those mentioned above that could be employed at various places within the theater. These included:

Flood doors that look like ordinary doors at the emergency stairwells and exits

A 10 x 12-ft steel panel flood gate at the stage door and loading docks

Flip-up flood gates at the glass lobby entrance that look like floor plates and engage with the rising floodwater

A tracked, vertical lift door at the loading dock

An awning-like flood door between the basement electrical room and the electrical vault that allowed for emergency egress from the electrical vault during normal operating conditions

A redesigned, subgrade venting system with flood louvers for the electrical vault

A new steel support structure along the reconstructed basement electrical vault wall that failed in Harvey

Retaining Alley’s architect, Studio RED, the Walter P Moore team led the design phase and construction administration for all flood protection enhancements. Upon completion of the project in the fall of 2020, an owner’s operating manual was created. The manual outlines flood protection locations, usage, maintenance, and manufacturer information to ensure the theater’s current and future maintenance staff understood how to protect the Alley Theatre safely and successfully from flooding that may occur in the future.

Learn more about flood protection in Walter P Moore’s paper An Introduction to Flood Protection: What Owners Need to Know to Protect Their Properties.

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