Flood Control: The Show Must Go On
Flood Control: The Show Must Go On
This article by Ray Drexler PE originally appeared in the March/April 2023 issue of Storm Water Solutions.
The celebrated Alley Theatre, located in downtown Houston, is A 61,000-square foot 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. The storm 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 Hurricane Harvey, the theater was protected against water infiltration pathways that had devastated the basement with 14 feet of water during Tropical Storm Allison in 2001,” said Benjamin Dow, project engineer and senior associate in Walter P Moore’s Diagnostics Group. “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 that were discovered but did not contribute to damage related to Hurricane Harvey. It was determined that up to 6 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 rain load, freeing the floodwater to rush in. This led to the theater quickly flooding to a depth of 17 feet.
“Essentially, the basement level of our building that includes a 300-seat theatre, dressing rooms, laundry, storage, and electrical was inundated with water,” said Brandon Kahn, general manager of the Alley Theatre. “There was approximately $15 million worth of damage caused by the flooding. The biggest deficiency was the utility access holes in the driveway at the front of our building and the CenterPoint hatch. We did not have any protection against water filling in the CenterPoint vault.”
The assessment was 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 flood proofing that now protects the structure for a 500-year flood plain, plus two feet.
Flood Protection System
The flood mitigation project was challenging because of the building’s constraints, both on the interior and exterior. The latter was the location of the theater in Houston’s densely packed downtown area.
Dealing with these constraints, Walter P Moore’s engineers developed multiple flood protection solutions to protect the theater. These solutions did not compromise the building’s architectural significance, interior floor plan 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,” Dow said. “Notably, creative uses for existing technologies—for example, employing fiber-reinforced polymer (FRP) strengthening to resist potential floodwaters in lieu 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 usable area—layout and square footage—which could not be structurally altered. Additionally, the plain glass panels in the lobby atrium were replaced with floodgrade alternatives. These flood protection innovations were implemented to achieve the goal of barely visible flood barriers that could protect the building beyond the devastating power and pathways of future hurricanes.
“We were able to hide everything so most patrons would not even notice there was a flood protection system,” said Jared Wood, partner, Studio RED Architects. “We changed out the glass, which did not change the look, to new glass that could handle water loads, we hid gates in the sidewalk, and built walk off matts into the surface to hide them. We also changed the regular people doors to flood doors. Where FRP had to be added to strengthen walls, we found ways to hide it behind finishes.”
Furthermore, the team reviewed other technologies that could also be retrofit into the building’s makeup. They identified several additional, different systems that could be employed at various places within the theater.
Read the full article in the March/April 2023 issue of Storm Water Solutions.
Download Walter P Moore's flood protection paper An Introduction to Flood Protection: What Owners Need to Know to Protect Their Properties.
Ray Drexler, PE is a principal and senior project manager in Walter P Moore’s Diagnostics Group.
Image: (C) Bill Salt