Flood fix helped in recent storm

It was 11 years ago that a wide swath of northern Petaluma was submerged in a New Year’s Eve flood caused when five inches of rain fell over the area in a 24-hour period.|

It was 11 years ago that a wide swath of northern Petaluma was submerged in a New Year’s Eve flood caused when five inches of rain fell over the area in a 24-hour period. The deluge caused $56 million in damage to homes and businesses in town and took an incalculable emotional toll on victims.

Last Sunday’s storm, while only mildly destructive by comparison, was a reminder that heavily saturated soil, incessant and heavy rainfall and a high tide can still close roads, flood homes and threaten public safety around town.

Petaluma has historically flooded because it lies at the bottom of a vast watershed where dozens of streams flow in from the hills, through town and into the Petaluma River. After two destructive floods in central Petaluma in the 1980s, a $43 million federally-funded flood control project was initiated. The project, completed last year, was constructed primarily to protect the oft-flooded Payran neighborhood and the city’s downtown core.

But no single flood fix is foolproof. Following the 2006 flood, work began to prevent flooding in northern Petaluma. Among the projects credited with alleviating more extensive flooding in the north end of town is a river terracing project between Industrial Drive and the Petaluma River that has increased the carrying capacity of the river during major storms.

An ongoing stream maintenance program has also been undertaken, with the city and county water agency crews working to clear stream beds of silt, invasive plants and debris like old mattresses. Such efforts helped allow flood waters to flow south unobstructed during the most recent storms.

In central Petaluma, regular dredging of the river is needed to remove silt that builds up after winter storms. The Army Corps of Engineers had regularly dredged the Petaluma River every four years to ensure its navigability. But the last time it did so was in 2006 when emergency dredging was completed by FEMA following the flood. The lack of dredging has increased the risk of flooding downtown since a channel choked with silt cannot effectively and safely move floodwaters down to the bay.

With global warming threatening to increase the likelihood of flooding here in years to come, enhanced efforts to control floodwaters in the northern part of the city and more regular dredging of the Petaluma River should be a continued priority for local, state and federal elected officials.

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