The concrete channel that carries the slow trickle of the Tijuana River along the U.S.-Mexico border fence is known as "El Bordo."
Hundreds, possibly thousands of people — mostly migrants deported from the U.S. —live on the edge of the canal, in little lean-tos or in holes dug into piles of sand.
On Monday morning, a team of federal, state and municipal officers swarmed the canal, arrested 90 people, evicted hundreds more, destroyed their lean-tos and filled in their holes.
Juan Carlos Garcia Perez says the officers arrived suddenly. Some people, including himself, ran away, but others were roused from their holes and taken into custody.
"They started destroying everything, knocking things down, throwing clothes around," he said.
After the raid, a group called Angels Without Borders showed up with tents. It helped some of the migrants set up a camp in a barren plaza near the canal.
"We're going to stay here demanding the Tijuana government to stop the oppression and the raids of the migrants that are living in El Bordo," said Hugo Castro, who was coordinating the camp.
City officials have struggled with how to handle the population that lives in the Tijuana River canal. Many have drug habits. Most were deported from the U.S., and therefore have no family ties in Tijuana.
The police chief and other city officials blame the migrants for much of the city's crime, and also for a public health threat posed by sharing of needles in the canal.
San Diego State University professor and Tijuana human rights advocate Victor Clark Alfaro has been observing the canal for years, and said police raids are common, but not like this one.
"This one had the goal of cleaning up the canal once and for all," Clark said, to finally put an end to what has become a major social problem in Tijuana.
Tijuana officials were not available for interviews, but after Monday's raid, the police department issued a statement saying the raid was meant to protect the migrants living in the canal and to prevent crime. It also said the federal government will invest more than three million dollars for social programs to solve the problem of deported migrants in the canal and in nearby zones, though details remain scarce.
Some projects are already underway to keep people away from canal. In the last month the government erected a steel fence down the center of the four-lane highway that separates the canal from downtown Tijuana. It makes it harder to get to the canal, and it looks like a smaller version of the U.S. government's border fence that towers on the other side of the canal.
The irony isn't lost on Pedro Castillo, who was kicked out of the canal Monday.
"They built another wall!" he said. "It's like they've deported us again! What are we supposed to do?"
The first thing Hermez Ramirez Camacho did when he was released from jail Tuesday afternoon after 36 hours was head straight for the canal.
He found his little shack had been destroyed, but he didn't care. What he was really after was his guitar. He'd left it behind in the haste of his arrest.
Ramirez is 51, tall, skinny and with a wrinkled face. He's known as the canal's unofficial musician. He earns money going from bar to bar playing songs.
"It's my pay check. It's what feeds me. Music is what's helped me survive," he said.
When he returned to the canal, it was gone. He asked around desperately, with no luck, until he found a man who said he'd saved it. He charged Ramirez 40 pesos, about three dollars, to get it back. It had a big crack in it, but it still had a full sound.
Like many of the migrants who were lingering at the makeshift camp nearby, Ramirez had already re-built his little shack in the canal.
Within a day of the police raid, many people were already back, erecting posts and tarps and digging new holes in the sand.
