| Abstract | | Located on the western edge of the Santa Rosa Plain in Sonoma County, California, the Laguna
de Santa Rosa (Laguna) is the largest tributary to the Russian River and the second largest
freshwater wetland complex in northern California. One of the major tributaries to the Laguna,
Mark West Creek, flows west across the Santa Rosa Plain and connects with the Laguna just east
of Forestville.1 Together these freshwater systems provide habitat for a wide range of fish and
wildlife species, including the federally endangered coho salmon (Oncorhynchus kisutch) and
federally threatened steelhead trout (O. mykiss; Fawcett et al. 1990, CDFG 2004, Good et al.
2005, NMFS 2010). In addition, the Laguna functions as an important regulator of flood flows
on the Russian River by acting as a natural reservoir for storm runoff (Curtis et al. 2013). In
2010 the Laguna de Santa Rosa Wetland Complex was designated a Wetland of International
Importance by the Ramsar Convention on Wetlands (Ramsar 2014).
Over the past century and a half, the hydrology of the Laguna de Santa Rosa watershed has
been altered by a variety land use changes, including urbanization, agricultural development,
draining and filling of wetlands, and channelization of streams. These changes have impacted
the function of the Laguna and Mark West Creek and contributed to a range of contemporary
management problems, including habitat degradation, impaired water quality, altered
sediment dynamics, salmonid stranding, flooding, and trash accumulation (Honton and Sears
2006, Sloop et al. 2007, Potter and Hiatt 2009, Curtis et al. 2013). In the downstream portion
of the watershed (herein referred to as the lower Laguna region), major changes in the historical
channel alignment of lower Mark West Creek have altered flow and sediment dynamics
in both Mark West Creek and the Laguna.
Pinpointing the timing and location of historical changes in channel alignment will help managers
seeking to improve the ecological, hydrologic, and geomorphic functioning of the lower
Laguna region. Understanding the nature and context of these changes will help direct a path
toward future restoration efforts. To address this need, we collected, compiled, and synthesized
a wide range of historical documents in order to reconstruct 1) the channel alignment of lower
Mark West Creek, lower Laguna de Santa Rosa, and surrounding tributaries during the mid-
19th century, and 2) the major changes to channel alignment over the past 150 years. Despite
the major land use changes that have impacted the ecological functioning of streams and
wetlands within the region, many remnants of the historical landscape still exist, and many of
the physical controls that shaped the landscape in the past continue to operate today. Thus,
examining the historical landscape and the processes that sustained it can not only reveal the
underlying causes of contemporary management challenges, but can also improve our ability
to predict the outcome of proposed management efforts and to design successful, integrated
strategies for stream restoration, flood protection, sediment management, and other watershed
concerns. This research was conducted as part of the Laguna de Santa Rosa Historical Ecology Initiative, a broader suite of ongoing historical ecology studies intended to improve
our understanding of past landscape patterns and processes throughout
the region and to support an array of interlinked management activities.
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