Petaluma watershed’s roots run deep

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A recently-released historical study of the Petaluma River could give ecologists, scientists, land-users and local policy-makers a powerful new tool in mapping the future of the Petaluma watershed. A broad, exhaustively thorough picture of what the watershed once looked like — including what lived and grew there, and how the complex system of waterways functioned 150-plus years ago — the finalized report is a detailed look at the significant alterations and modifications made by Euro-American settlers of the 1800s, and generations of land-users and city-builders since then.

The study, say its authors and funders, is a potentially invaluable resource that contains vital information that will be of use in upcoming restoration efforts and other local watershed projects.

A joint project of the San Francisco Estuary Institute (SFEI) and the Sonoma Resource Conservation District, the report is titled “The Petaluma Valley Historical Hydrology and Ecology Study.” Its primary authors are Emily Clark, a historical ecologist with SFEI’s Resilient Landscapes Program, and Sean Baumgarten, an Associate Environmental Scientist with SFEI.

Bankrolled in 2015 by a $365,000 grant from the U.S. Environmental Protection Agency, Baumgarten and Clark, working with a local team of researchers, sought out, collected and examined two centuries of historical material that included archival documents, maps and charts, government reports, personal diaries (16 of them, dating from 1868-1884), oral histories, photographs, newspaper articles, Mexican land-grant agreements and more.

The materials – culled from collections across the Bay Area, including the Sonoma State University library, the Petaluma Regional Library’s History Room, the Petaluma Historical Library and Museum, and the Sonoma County Surveyor’s office - were used to reconstruct an ecological and hydrological representation of local wetlands, concentrating on the watershed’s historical form and function. The scope of the work includes wetland, riparian and aquatic habitats, and stream channels throughout the watershed, with specific focus on natural and man-made landscape change over the years.

On April 17, as a requirement of the EPA’s grant, the SFEI presented a free community event titled “A Slough of Change,” drawing more than 100 people to the Petaluma Community Center.

According to Jared Vollmer, of Petaluma, who served as the EPA’s grant manager on the project, the team’s first step was to visit the County surveyor’s office. There in the basement they discovered a cache of old school district maps, with original drawings, including drawings of Petaluma.

“It was so amazing to see all of these creeks and streets the way they were 150 years ago,” Vollmer said. “Who knew that at one point they tried to start a new town down by where the Rocky Memorial Dog Park is? Working on this project, there were so many discoveries to make, so many questions to answer, all looking at what we have to do — based on our past. Where did Petaluma’s extensive wetland go? Is some of it still here? And what are our opportunities to bring some of that back?”

“This study is a long time coming,” said Scott Dusterhoff, of Petaluma, a senior scientist and geomorphologist at SFEI, a regional non-profit science organization. Headquartered in Richmond, SFEI focuses its work on finding ways to help California ecosystems become healthier. “One of the ways we do that is by doing these kinds of in-depth studies, to figure out how these landscapes used to look, and how these landscapes used to work, before widespread settlement and development in the early 1800s.”

With such information, he explained, scientists now have a functional starting point from which to determine what management action can be brought to the state’s watersheds, to possibly bring back important elements of those watersheds that have been lost. Such elements include habitats that have been diminished or destroyed, along with geomorphological features that help with flood control and ground water recharge.

“This study is going to help us with all of that,” Dusterhoff said.

The report comes as the Petaluma Wetlands last month were added to an international list of environmentally critical wetlands in need of protection. It also coincides with the first release of funds from Measure AA the 2016 parcel tax that will provide $2.6 million to Petaluma’s Point Blue Conservation Science, for local wetland restoration over the next five years.

It is likely that the new SFEI historical study will become a significant resource in the carrying out of several of those projects.

“One of the main objectives of our study,” said co-author Emily Clark, “was to produce a historical map of what the Petaluma Valley looked like in the past. It shows a diverse and excessive array of wetland aquatic habitats and channels in the Valley in the 19th century.”

According to the map, the Petaluma watershed, at that time, was vast, covering over 27,000 acres of tidal and non-tidal wetlands. The historical wetlands supported a number of plant and animals species, including large quantity of steelhead, San Pablo Song Sparrows, the Salt Marsh Harvest Mouse, and various pronghorn and elk. One striking take-away from the map is how twisting and sinuous the river was 150 years ago, a bedeviling characteristic to 19th century ship captains that was persistently reengineered and straightened over the decades.

“We found a great early quote,” Clark noted. “’The windings were bewildering, more than doubling the distance.’ Another great quote likened the river to ‘An everlasting corkscrew.’ So, as this study makes clear, a lot has changed here over the last 150 to 200 years.”

The report is available for free download at and can also be purchased in book form on Amazon, with arrangements now in the works to make the printed report available at Copperfield’s Books in Petaluma.

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