Reconstructing the historical ecology of the Petaluma River watershed

Authors: Emily Clark*, San Francisco Estuary Institute, Sean Baumgarten, San Francisco Estuary Institute, Scott Dusterhoff, San Francisco Estuary Institute, Josh Collins, San Francisco Estuary Institute, Robin Grossinger, San Francisco Estuary Institute
Topics: Environmental Science, Land Use and Land Cover Change, Landscape
Keywords: Historical ecology, landscape change, restoration, wetlands, estuary, river
Session Type: Paper
Day: 4/13/2018
Start / End Time: 1:20 PM / 3:00 PM
Room: Jackson, Marriott, 5th Floor
Presentation File: No File Uploaded


This study reconstructs the historical hydrology of the Petaluma River watershed in Northern California. A large amount of historical data—including Mexican diseños, U.S. Coast Survey documents, landscape photos, soil maps, personal diaries, and oral histories— documents the early ecological and hydrological conditions within the watershed, but until now has not been synthesized comprehensively. An understanding of historical conditions can be used to identify and manage current physical controls, set restoration targets, and prioritize multi-benefit opportunities. Historical materials were collected from 21 California archives and 20 online databases. High-priority, spatially explicit data were synthesized using GIS to produce a map of wetland habitats and channel networks circa 1850. Narrative data and other non-spatial sources were evaluated for contextual information, and to establish a timeline of landscape change over the past two centuries. Historical evidence suggests that the watershed supported an interconnected network of mostly intermittent streams, mixed riparian forests, extensive freshwater wetlands, and complex tidal marshes. Significant landscape modifications—dredging and straightening the mainstem channel and diking and draining wetlands—began in the mid-19th century. To measure change over time, modern wetland habitats were mapped and crosswalked to the historical habitat types. A change analysis compared the wetland habitat area and channel length of the historical and modern watershed. Overall, wetland and aquatic habitat area has decreased by approximately 68% and channel length has increased by 50%. These findings will be used to prioritize restoration activities including enhancing flood protection, increasing groundwater recharge, improving sediment management, and restoring wildlife habitat.

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