A ditch runs through it

AMERICANS TEND to learn geography by combat. Who knew from Fallouja? The Mekong Delta? Kosovo? No one, until our guys went in there bearing arms.

So it’s no surprise that even locals don’t know where the once mighty Los Angeles River is. In the war Los Angeles waged against nature, the river was taken prisoner a long, long time ago.

Still, it is a very real river, and one of these days it may be freed from its POW status. Beginning Saturday -- don’t let your eyes glaze over like a pair of Krispy Kremes here -- the public gets a turn at the microphone at a series of official hearings for ideas on how to rehab this insulted and vandalized waterway. I do wonder how city officials expect people to come up with ideas for fixing a river that they hardly even know is there -- a once natural river demoted to a concrete flood channel, and thence to a joke, a myth, an urban legend.

I wrote a book about the river, and when I started, I thought I would be writing nonfiction. I did, but I also wrote a murder mystery -- who tried to kill the Los Angeles River, and why?

The river measures 51 miles from source (the Canoga Park High School football field) to mouth (the Long Beach Harbor). That makes it arguably the only thing, apart from disasters, that unites Los Angeles from the mountains to the sea. Its watershed is bigger than the island of Maui, and until the late 1930s -- only one lifetime ago -- it was, second to the Pacific Ocean, the dominant natural feature on the landscape.

A part-time river most of the year, it has always run full time through central Los Angeles, which is why the Gabrielinos and then the Spaniards and the Yankees built their settlements there. Until a flood changed its course in 1825, it turned west below downtown and ran more or less along the Santa Monica Freeway route, creating a great, green, grassy plain. It spread water so wide -- and deep -- that Angelenos could dig their own backyard wells. Lake Machado, where Reggie the gator still cavorts, is a remnant of that system. So was Sleepy Lagoon, the swimming hole where a young Latino’s murder in 1942 triggered a notoriously racist trial.

In an agrarian landscape, its seasonal overflows and occasional floods, like the Nile’s, were a blessing. And even in a town of 10,000 or 20,000 people, floods weren’t much of a problem. But boosterism and movies brought millions here, and the power brokers’ plans -- for the city and their own bank accounts -- did not allow for a capricious river that might not have enough water for a megalopolis and whose penchant for flooding could keep too much choice real estate off the market.

So in 1913, the moguls built themselves a reliable, Stepford river: the Los Angeles Aqueduct, piping in Owens Valley water. The aqueduct turned the real river into a Betty Broderick ex-wife waterway -- scorned, superfluous and dangerous. It flooded, defiantly, in 1914, 1934 and, as the last straw, 1938. How bad was the ’38 flood? So bad that they postponed the Oscars for a week. When Ronald Reagan was shot, they only postponed the Oscars for a day, and he was an actor.

The next step was “taming” the river, confining it to a concrete straitjacket, a flood-control channel. But the trade-offs were expensive, which explains the remorseful rethinking of here and now. A paved river freed up more land for development, but that meant more paving, and rain that once replenished the water table now washed into catch-basins and concrete diversions and was flushed into the ocean, dumping away enough water each year to keep thousands of families in showers and washing-machine loads -- water L.A. now buys from somewhere else.

Now, about those hearings. Why should Los Angeles be outdone by Reno, San Antonio and Denver, whose urban rivers manage to be safe and charming -- an asset in every sense? In L.A., the park-poorest big city in the nation, the river’s fenced-off bed and banks contain more acreage than Central Park.

So let’s hear those ideas. Inflatable dams to make little lakes for paddle-boaters and kayakers. Pocket parks. Marshlands to purify the water naturally, and to refill the thirsty water table. A living science museum where city kids can watch minnows and frogs. Make riverside property desirable, not risible. Make the river a kind of inland beach. Give it back to the people who need it most.

There are those who say they’ll consider the river restored when steelhead trout swim upstream again from the ocean. I’ll consider it restored when, like the Seine in Paris, which is also paved in places, moviemakers use it as the background for a romantic stroll featuring a future Cary Grant and Audrey Hepburn, not just another chase sequence in “Terminator 12.”