The Los Angeles River Tunnels are a water drainage tunnel system connected to the Los Angeles River. When water gets too high in the river, due to rainstorms or floods, the water is diverted through the tunnel system in the concrete walls of the man-made river and is drained out in various points throughout the city to prevent flooding of the river and nearby areas. There are various access points to the tunnel system throughout the course of the L.A. River and can be found throughout the Warehouse District of Downtown, Los Angeles and the Boyle Heights area.
The Los Angeles River Tunnels is a location in L.A. Noire and is primarily featured in the final case of the game, the Arson case A Different Kind of War. It is the location of the game's final shootout, in which the D.A.'s Investigator Jack Kelso and LAPD Detective Cole Phelps engage in a gun battle with a bunch of crooked cops in pursuit of the insane former U.S. Marine, Ira Hogeboom, who has taken shelter in the tunnel system with Elsa Lichtmann as his hostage. A map of the tunnel system is found in Ira's home. During the course of the shootout, a heavy rainstorm begins to fill the tunnel system with water to it's maximum capacity, in which the water begins to surge in places and overfill the tunnels. Ultimately, the surging water causes the death of Phelps in the tunnel system, after he boosts Jack and Elsa to safety through an access grate above.