The equivalent of the Richter scale for wet-season floods was based on anticipated frequency, and in the world of rushing water the Big One was a hundred-year flood. The massive earthen Hanson Dam was almost two miles long, meant to keep a hundred-year flood sweeping down out of the Tujunga Canyons from obliterating the whole northeast Valley. On the safe side of the dam there was a manicured golf course for the rich, but on the inner, danger side they’d left a couple thousand acres of wild chaparral, boulders, dirt parking lot, and the kind of rough parkland that the city offers up to its working poor. He cruised slowly down the winding access roads. Here and there dusty pads off to the side held a handful of cars and Latino families cooking at portable barbecues or playing soccer. Art Castro drove a big silver Lexus but Jack Liffey guessed he’d have some sort of beat-up agency panel van for surveillances like this. The Lexus would stand out here like a gorilla in church. He smiled, thinking of his woeful Concord with its flapping plastic, which would fit right in.