The Hidden Engineering Behind Texas's Top Tourist Attraction
I am on location in downtown San Antonio, Texas, where crews have just finished setting up this massive 650-ton crane. The counterweights are on. The outriggers are down. And the jib, an extension for the crane's telescoping boom, is being rigged up. This is the famous San Antonio River Walk, a city park below street level that winds around the downtown district. It’s one of the biggest tourist attractions in the state, connecting shops, restaurants, theaters, and Spanish missions (the most famous of them being the Alamo). Every year, millions of people come to see the sights, learn some history, and maybe even take a tour boat on the water. It’s easy to enjoy the scenery without considering how it all works. But, how many rivers do you know that stay at an ideal, constant level, just below the banks year-round? One of the critical structures that make it all possible is due for some new gates, and it’s going to be a pretty interesting challenge to replace them without draining the whole river in the process. I’ve partnered up with the City of San Antonio and the San Antonio River Authority to document the entire process so you can see behind the scenes of one of my favorite places. I’m Grady, and this is Practical Engineering.
After a catastrophic flood in 1921 took more than 50 lives in San Antonio, the city took drastic measures to try and protect the downtown area from future storms. Back when my first book came out, I took a little tour of some of those measures, one historical - Olmos Dam - and one more modern - the flood diversion tunnel that runs below the city. But another of those projects eventually turned into one of San Antonio’s crown jewels. A major bend in the river, right in the heart of downtown, was cut off, creating a more direct path for floodwaters to drain out. But rather than fill in the old meander, the city decided to keep it, recognizing its value as a park. Gates were installed at both connections, allowing the bend to be isolated from the rest of the river. Later a dam was built downstream on the San Antonio River with two floodgates. During normal flows, these gates control the level upstream on the river, maintaining a constant elevation for the Great Bend and the cutoff. If a flood comes, these gates can be shut to maintain a constant level in the bend, and these gates can be opened to let the floodwaters pass downstream.
