A creek (once) ran through it


As Bay Area Creeks go, Alameda Creek is rather large. It drains a watershed of around 700 square miles the bulk of which lies east of Niles Canyon out toward Livermore, Altamont and points south. After the creek exits Niles Canyon it crosses six miles or so of alluvial plain then another two miles of what used to be marshland before discharging into San Francisco Bay proper. This lowland section of the creek was prone to flooding during Northern California’s wintertime rainy season. Streams of subtropical moisture, the “Pineapple Express,” can deliver impressive amounts of moisture during the Bay Area’s winter storms. Trenching studies in the alluvial plain have revealed layers of mud and gravel deposited by major floods that historically occurred every 50 to 100 years. Each major flood would inundate the flats between hill and marsh with floodwaters eventually reaching the bay through various outlets – historically Mt. Eden Creek, Old Alameda Creek, Coyote Hills Slough, and even Newark Slough. The marshes once reduced flooding by capacitance – absorbing the oncoming rush of water – and by keeping the marsh channels deep though tidal scouring. As marsh gave way to salt ponds these benefits were lost.

Patterson Creek vestige

The vestigial remnant of what was once Patterson Creek.

Early settlers in the East Bay took measures to protect their property against floods. They built on higher ground, raised their living quarters above the ground plane, and consstructed levees here and there. As time passed settlements became more expansive and flood control measures followed suite. The last major floods along Alameda Creek happened in the 1950s and they were impressive. The 1950s floods spurred the construction of major flood control channels along Old Alameda Creek and the Coyote Hills Slough. Unlike the sinuous marsh channels they replaced, the new flood control channels, completed in the early 1970s and 500 feet wide, are relatively straight shots from the flats to the bay.

Patterson Creek vestige

Looking over the remnant of Patterson Creek toward the Coyote Hills.

When you hike down the levees of the flood control channels you encounter cut-off remnants of the original creek beds among the adjacent salt ponds. I have recently visited two of these sites. Little snippets of the original Alameda Creek lie orphaned on either side of the current day Old Alameda Creek Flood Control Channel. I often stop to photographs a particularly interesting stretch adjacent to the ruins of the Alvarado Salt Works. Here there is a collapsed bridge that once spanned the creek (when it existed there). It now spans a smallish salt pond puddle. Along the former creek channel there are pilings for what was a major boat landing in the 19th century. In the current day the old creek channel fills with the winter rains and turns a dull green. During the summer it dries out and turns a bright yellow with dark red accents along the periphery.

The yellow color scheme is also found along remnants of Coyote Hills Slough one drainage south. This tidal slough once ran past the northern end of the Coyote Hills just south of Turk Island. Its southern fork, Patterson Creek, wound its way to a stretch of marsh on the eastern side of the Coyote Hills. These days the relatively straight Alameda Creek Flood Control Channel has replaced Coyote Hills Slough’s winding channels. On several occasions I have visited an interesting section of the old slough channel just south of Turk Island. Once you visualize what this ditch once was it gives you a sense of scale for the old marsh channels. Interestingly the border between Fremont, California and the neighboring Union City still follows this ditch. In the current day it too dries out to shallow pools in the summer to sport a bright yellow color and the texture of buckled gypsum.

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