San Antonio River Tunnel is part of the San Antonio Channel Improvement flood protection project. The purpose of this tunnel is to provide protection from a 100-year flood event and provide rain runoff underneath the city leading to the San Antonio River. The project was initiated in 1987 and construction for the tunnel started in September 1993. This project was a coordinated effort between the United States Army Corps of Engineers and the San Antonio River Authority. The Corps bid on the project on behalf of the River Authority at an overall cost of 111 million dollars The tunnel became operational in August 1996 and was completed in 1999. The tunnel is 140 feet below the ground surface, 24 feet in diameter, and 3.1 miles long.

The future productivity of the San Antonio River Tunnel is great. Urban development in the watersheds above Olmos Dam has led to larger, more frequent floods in the San Antonio area. A recent example illustrates the tunnel's practical usefulness. San Antonio endured tremendous rains and flooding in 1998. The tunnel diverted much of the rain runoff, thus preventing the downtown district from being submerged in an estimated 6 feet of water. Thus, it has been proposed that the tunnel has already paid for itself regarding the damage prevention from this episode.

Not only will the tunnel lessen flood risk in San Antonio, but the city is currently focused on ecosystem restoration, which will reduce erosion and create an environment more suitable for recreation and wildlife. Restorative efforts include planting of trees and vegetation and the creation of wildlife habitat areas. These collaborative efforts will likely further lessen the risk of flood in San Antonio in the future.

In summary, the San Antonio River Tunnel is a recent addition to the city that has already proven its effectiveness. Furthermore, the tunnel will remain a benefit to the city along with the implementation of adjunctive flood control efforts.