The Merced River below Vernal Fall.

When rivers run wild

The San Joaquin River slips past Antioch with the stealth of a mother past her sleeping child’s bedroom door. Beneath the grey surface where bass boats hover, the current is slow. A breeze raises ridges like wrinkles on a bed sheet, not high enough along the bank to hinder a heron’s solemn search for dinner.

But the river is not what it seems. Far upstream in the high places of the world it’s a different parent: a stepmother out of mythology, majestic and terrible.

In those high places the river is renewed in a million moments at once, when single drops of melted snow merge with others to form steep trickles that meander down to junctions with other trickles. They find their way to concave avenues like bowling balls find gutters. In a reverse delta spanning mountains, ten thousand rivulets reduce to a thousand streams reduce to a hundred creeks reduce to a dozen rivers reduce to one.

Trace the San Joaquin upstream from Contra Costa County and you take a snaking journey southeast for more than a hundred miles through Central Valley before hooking east toward Fresno and up into Sierra National Forest. Halfway up that journey, 25 miles south of Modesto, the river is joined by one of its tributaries. Follow that tributary upstream to an elevation of 4,000 feet and you find a valley enclosed by soaring walls of granite plumed with waterfalls and streaked by tumbling creeks.

The tributary is called Merced. The valley is known as Yosemite. It’s here that the Sierra’s winter melt is most vividly dramatized.

The Merced’s tributaries are unlike any other: two of the world’s 10 tallest waterfalls – Sentinel and Yosemite, the latter being the tallest in North America – and their retinue, no less magnificent, with names like Bridalveil, Ribbon, Illilouette, Vernal, Nevada and Snow Creek. Right now they’re not so much waterfalls as water cannons. A survey conducted in April showed the Merced-sector snowpack at 91% of average, but don’t let down your guard. Today, May 2, the Merced discharge at Yosemite’s Pohono Bridge was clocked at a rollicking 1,300 cubic feet per second. Toe-dipping not recommended.

In 1806, an expedition led by Gabriel Moraga came upon a river after a long, hot and dusty journey. To express his gratitude, Moraga named the river El Rio de Nuestra Señora de la Merced – River of Our Lady of Mercy. In the spring of 2016, there’s nothing merciful about the Merced. If our snowborn rivers are awe-inspiring, they’re also deadly.

On July 19, 2011, 21-year-old Ramina Badal of Manteca, 22-year-old Hormiz David of Modesto and 27-year-old Ninos Yacoub of Turlock climbed Yosemite’s Mist Trail to the rim of Vernal Fall. Witnesses reported that Badal, in an attempt to get her picture taken against the spectacular backdrop, hopped the guardrail and entered the shallow but swift water at the river’s edge. Several hikers at the scene yelled out warnings. To their horror they watched Badal lose her footing and get pulled by the current toward Vernal’s broad launching ramp. David and Yacoub rushed over the guardrail but were too late to save her – or themselves. All three were swept over the rim, fell 317 feet shrouded in a frigid curtain of cataract, and slammed onto the boulders at Vernal’s base.

The Merced and Cathedral Spires west of Pohono Bridge.

A river suffused with winter melt is more than a match for us humans. The shock of icy water and grip of hypothermia rob the body of strength and muscle coordination. The mind becomes confused and panic sets in. Aiding and abetting in the assault are the river’s heavy volume and powerful currents, which can carry a victim miles downstream before rescue can be attempted.

You needn’t pull a crazy stunt to be claimed by the river. Recreational boaters, skiers, swimmers, campers and hikers – all minding their own business – can be vulnerable to a sudden infusion of cold, fast and heavy water.

In May of 2006, the Truckee River was flowing at four times its volume of the previous year. On May 1, 20-year-old Edward Wilt of Sun Valley and three friends waded to a small island along the Truckee near Painted Rock east of Reno. From there, Wilt and one of his friends jumped into the river, apparently for the fun of it. His friend made it out. Wilt’s remains were found three weeks later near Wadsworth.

It was May 21, 2006, a day before Wilt’s body was hauled out of the Truckee. I was at the source, standing on the edge of a rock as big as a room overhanging the Merced in Yosemite Valley, just west of Pohono Bridge. Tons of river per second thundered past. Sensing Merced’s mass reach out and drag me toward it like a maelstrom drags a doomed ship into its vortex, I got low fast, cross-legged, desperate to drop my center of gravity and dispel the fantasy of falling.

The river was a different creature out of mythology that day: not an angry stepmother but a beast trapped in the cage of its banks, infuriated by my lack of respect, leaping at me and slamming against my granite perch. Two feet to my right the rock dropped away a mere 10 feet to the water. In Yosemite, you can fall to your death from impressive elevations. All I needed was 10 feet.

It was a memorable day; should I fall, the Merced’s biting embrace would be my last memory. I hoisted myself onto all fours and crabbed my way to the middle of the rock. The river, catching the scent of other prey, snarled on by.