South Fork SHaRP Plan

4. Chapter 4: Physical and Land-Use Context for

Aquatic Habitat in the SFER

Introduction Attributes of the South Fork Eel River Successful aquatic habitat restoration requires an understanding of both the natural  Mediterranean climate characterized by processes that define habitat potential under dry summers and wet winters unimpaired conditions as well as the effects  Principle communities: Garberville- of anthropogenic disturbance. Considering Redway, Laytonville, Branscomb how riverscapes once supported and (headwaters), Miranda, Weott (confluence steelhead life histories, what changes have of SFER and mainstem Eel) occurred, and how they limit these species helps us determine what conditions are  Anadromous salmonids: Steelhead, Coho attainable within existing geomorphic Salmon and Chinook Salmon constraints. Evaluating the historical context  Watershed statistics: of land-form and land use was fundamental  Eel River basin size: 3,684 square miles to the Collaborative’s thought process as we  SFER sub-basin size: 690 square miles identified limiting factors and restoration  Mainstem length: 105 miles treatments. The South Fork Eel River  Total length of stream: 683 miles Watershed Assessment (SFER WA) conducted by the Department of  when brought together, resulted in a more Fish and Wildlife and Pacific States Marine comprehensive understanding of the Fisheries Commission (CDFW 2014) served planning area. In this chapter, we summarize as a basis for the sub-basin setting. the geophysical processes of the SFER sub- Throughout the SFER SHaRP planning basin that we considered throughout the process, Collaborative members (including SFER SHaRP planning effort, explore representatives of a Native American tribe, historic and current land use patterns, and government agencies, non-governmental consider potential interactions in the context organizations (NGOs), landowners and of salmon recovery. universities) contributed relevant information and personal experience that,

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Figure 4-1. Location of the South Fork Eel River sub-basin within the Eel River Basin.

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regime (Patterson et al. 2020) with ecosystem Hydrologic and Geomorphic process provides a framework for assessing Processes how different flow management scenarios The SFER Basin exhibits a seasonally may result in ecologic change (Lane et al. dynamic hydrology and diverse geology. 2017). Functional flow periods in the SFER These characteristics, combined with are exemplified by the following variable micro-climates, give rise to variation characteristics: short but important fall flow in land form, plant communities, land use, events that initiate the wet season, elevated and the resulting habitats that influence winter base flows punctuated by extreme salmonid distribution and abundance across peaks, followed by a period of spring the basin. recession, and finally dry season low flows through the summer (Yarnell et al. 2020) Prolonged winter rains and foggy to dry (Figure 4-2). As flow regimes have shaped summer conditions are characteristic of the salmonid ecology over evolutionary climate in the SFER basin. The rainy season, timescales, each of these periods have which generally begins in late October and important implications for critical salmonid lasts through April, accounts for 90 percent life history events. The onset of fall of the mean annual runoff in the SFER sub- precipitation and its wet-season initiation basin (Monroe et al. 1974). The dry season trigger upstream movement of adults from typically lasts from May through September. the estuary to mainstem staging areas while The western sub-watersheds of the SFER are cooling temperatures and altering water strongly influenced by the coastal marine quality. Winter base flows, punctuated by layer and are defined by morning fog and storm events, result in moderate increases in overcast conditions, whereas the inland . This allows access to and eastern sub-watersheds become very hot and occupation of spawning grounds. These peak dry as the year progresses. This spatial and winter flows also mobilize substrate, form seasonal pattern of rainfall and runoff results channel features that provide habitat for in ecological challenges and opportunities salmon, and prepare spawning gravels for that have shaped the life histories of aquatic future cohorts (Lane et al. 2018). The spring organisms. recession is understood to be a critical period for fry re-distribution and parr growth, while The concept of functional flow periods is to the summer low-flow period can constrain partition the natural flow regime into juvenile salmon growth and distribution as elements that support important ecosystem temperatures reach annual maxima and processes for a broad range of native taxa and channels may dry, limiting both habitat for assemblages (Yarnell et al. 2020). The rearing fish and aquatic invertebrate food linkage of quantifiable measures of flow production.

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Figure 4-2. Dimensionless reference hydrograph for the South Fork Eel River at Miranda based on discharge records from 1951-1981, highlighting functional flow periods of the annual hydrograph. (Lane et al. Functional Flows Calculator v2.31 https://eflows.ucdavis.edu/ Accessed: 8 June 2020). Combinations of flow and geomorphic 2018). The western and eastern portions of attributes generate hydraulic patterns that the basin sit upon two distinct accreted belts support distinct life histories, and largely of the Franciscan Complex, leading to dictate the timing and spatial distribution of different water holding capacities of the life history events for salmon and steelhead. critical zone, timing of spring recession Where and how animals fulfill life history stream discharge and dry season stream base requirements is largely controlled by the flow. The eastern sub-watersheds are intersection of seasonal hydraulics and the characterized by critical zones that have shape and composition of the river corridor poorer water holding capacities than the and channel. Temporal water cycles are mélange geology in the western portion of the mediated through the critical zones—the SFER (Hahm et al. 2019). vertical extent of the Earth where water is received, stored, and released to support The combination of geologic and hydrologic surface flows or vegetation. Critical zones forces have sculpted a diversity of channel extend from the top of vegetation canopies forms in the SFER. Guillon et al. (2019) down to the top of unweathered bedrock, classified seven geomorphic archetypal where water becomes immobile on channel types within the SFER based on ecological time scales (Rempe and Dietrich watershed contributing area, valley form and

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South Fork Eel River SHaRP Plan slope, bankfull width-to-depth statistics, and side selected by the SHaRP substrate size distributions in an effort to process contain the majority of the gravel- categorize channels into morphological types cobble, bed undulating channel type which is that display distinct fluvial patterns (Figure characterized by gravel and coble substrates, 4-3). The seven focus areas selected through high depth variability with pool-riffle the SHaRP process for further planning occur sequences, and include forced bed structures exclusively in confined valley forms (Figure (Guillon et al. 2019) that are responsive to 4-3 and Figure 4-4). It is notable that the west large wood.

Figure 4-3. South Fork Eel River archetypal channel types classified by Guillon et al. (2019).

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Figure 4-4. The seven sub-watersheds shown in red were selected for further restoration planning using SHaRP and subsequently described as focus areas.

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Watershed History and Human (HCRCD 2002). Conflict between Native Americans and settlers between 1855 and impacts2 1865 resulted in the extirpation of a substantial population of people living in the Time Immemorial to mid-19th century basin. The number of settlers increased Native American tribes have inhabited the rapidly, and during this period nearly all Eel River watershed for at least 5,000 to public lands were conveyed to private 10,000 years (USBLM et al. 1996). ownership. Indians and Athabascan people, including Beginning in the early 1900s, settler aboriginal groups of Wailaki, Sinkyone and homesteads slowly began to transition to Cahto tribes occupied the SFER. They lived ranches as agriculture became one of the in small semi-sedentary villages, moving primary economic activities in the region. throughout the basin to take advantage of Many ranches consisted of thousands of acres seasonally available resources. Natural of converted pasture, most of it used for resources, such as large and small game, intensive sheep-grazing. The land conversion plants, and fish (salmon, steelhead, sturgeon, from forest to pasture affected the landscape and lamprey) were plentiful throughout the by compacting soil and forever changing the basin, and the population density within the vegetation type and soil pH on vast tracts of SFER Basin equaled or exceeded the density land. seen in other North American agricultural societies (USBLM et al. 1996). Even with The tanbark industry was the first large-scale this comparatively high density of people, forest management practice in the SFER, their cumulative impact on the fisheries beginning in the early 1900s and ending in resources and the environment was relatively the 1950s with the development of synthetic small (Yoshiyama and Moyle 2010). Based tannins (JMWM 2000). Peak production of on the earliest photographs, there is support natural tannin occurred between 1900 and however, for the hypothesis that Native 1920. Tanoak bark was peeled from trees and Americans managed forest structure through transported out of the area or sent to a plant the use of fire in the headwaters of the SFER in Briceland where the bark was converted to (Dr. Sharon Edell, personal communication, tannin extract. Stripped tanoak trees were left SHaRP Expert Panel, December 2020). on the ground, and nearly all of the tanoak trees in the sub-basin were harvested during European arrival and settlement this time (HCRCD 2002).

The first Euro-Americans came to the SFER Early logging activity in the mid-19th and in the 1850s. Trappers were the first to arrive, early 20th century resulted in the removal of followed by homesteaders and ranchers after all accessible old growth redwood along the the passage of the Homestead Act in 1862

2 Portions of the content of this section is drawn from SFER WA, CDFW (2014).

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South Fork Eel River SHaRP Plan creek mouths throughout the Subbasin. Due rather than leave it standing (O’Hara and to the long distance between the harvest areas Stockton 2012); subsequently the late 1950s and larger mills near Fortuna and Humboldt and early 1960s experienced peak timber Bay, many trees were used for split products harvest. such as railroad ties, shingles, and grape stakes. These split products were produced at Forest practice regulation sites where trees were felled, then transported Timber harvest continued relatively out of the basin more easily than whole logs unregulated until the implementation of the (O’Hara and Stockton 2012). 1973 Z’Berg-Nejedly Forest Practice Act. Intensified logging This legislation established a politically appointed Board of Forestry (BOF) whose Prior to World War II, Douglas-fir was mandate was the control over forest practices considered unmerchantable timber, but after and forest resources in California. The Act the war, nearly all Douglas-fir in the requires that Timber Harvest Plans (THP) be watershed was harvested in an effort to keep prepared by a Registered Professional up with the post-war building boom (BLM et Foresters (RPF) and include regeneration of al. 1996). Mechanized road building, log forested sites. In 1993 the BOF adopted rules skidding and additional transportation requiring sustained yield planning, with options allowed harvesters to access remote requirements that all forest landowners areas with steep terrain, which resulted in an develop at least 15% late-seral-stage forests increase in logging operations throughout the on their ownership. Although timber harvest basin. Roads, skid trails, and landings were levels have declined recently; the timber often located in creeks so logs could be easily industry is still an important component of skidded downhill, and instream log ponds the economy and harvest rates vary with were constructed to preserve and transport individual ownership, resource management logs further downstream. During this time, objectives and timber product market forces. extensive damage to streams and poor road building techniques combined with unstable Floods geology led to increased sedimentation in Floods are natural periodic occurrences that streams throughout the sub-basin (JMWM play a major role in formation of channels 2000). and have sculpted aquatic organisms over Improvements in timber harvest techniques evolutionary time scales. The effect of the and equipment led to increased harvest floods of 1955 and 1964 in the SFER must, efficiency. This new ability to harvest timber however, be considered in the context of the was coupled with a financial incentive to human impacts with which they coincided. harvest quickly: in 1956, the Humboldt During the larger and more devastating County Supervisors levied a tax on standing December 1964 flood, the maximum mean timber. As a result, most landowners were daily flow at Miranda was 161,000 Cubic forced to harvest timber for financial reasons Feet/Second (CFS) and the maximum peak flow was 199,000 CFS on December 22

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South Fork Eel River SHaRP Plan while just four days before the event the watershed processes on a somewhat different SFER discharge was near baseflow at 1,180 trajectory. Suspended sediment CFS. concentrations declined to pre-flood levels within about 5 years (Lisle 1990). Channel Prior to the 1964 flood, the SFER had just beds in most tributaries scoured to stable experienced an intense period of accelerated levels in years following the 1964 flood, and logging, where poor road construction, are currently at or above pre-flood elevations. tractor logging and skid trails combined with During channel-bed degradation, some largely denuded riparian and upland forests channel geometries recovered to pre-flood generated a catastrophic event for aquatic arrangements with reestablishment of pre- habitats. This event unraveled the vulnerable flood channel widths. (Lisle 1982). Channels hillslopes, washing massive amounts of in many alluvial reaches have incised into sediment into channels. During the 1964 flood deposits, however, leaving a narrower flood, it is estimated 105 million tons of channel bounded by new riparian vegetation suspended sediment were transported past now disconnected from its associated Scotia, near the mouth of the Eel River, . The colonizing riparian during a 3-day period, compared to 85 vegetation has largely locked in low-flow million tons transported during the previous channel margins. The resulting riparian 8 years (Brown and Ritter 1971). Many community is also drastically altered from millions of tons of gravel and logging slash the historic redwood late seral stage to was transported into stream channels. primarily red alder and willow. In response to Channel capacity was thus impaired, forcing the massive loss of aquatic habitat associated water laterally and eroding streambanks with the floods, a large effort to clear debris which caused large streamside mass wasting jams and restore fish passage to upper events. The result of this sedimentation was spawning reaches ensued. Through highly aggraded, wide, shallow stream much of the 1970’s through 1980’s, the first channels. Much of the riparian forest that had concerted restoration efforts in the SFER been logged was laid bare. A large volume of focused on clearing the large volume of wood the sediment from tributaries deposited at from channels (R. Gienger personal tributary mouths, disconnecting them from communication, SHaRP Expert Panel the mainstem. As the waters receded the meeting, September 2019). While many of tributaries cut through the gravel leaving the large debris jam barriers necessitated unpaired terraces and knickpoints at clearing for fish passage, it is now recognized ecologically important hydrologic junctions that this effort was too vigorous. Much of the (Sloan et al. 2001). Large quantities of large wood that we now understand to play a logging slash clogged tributary channels, beneficial role in maintaining channel form, storing large volumes of sediment and aquatic habitat, and sediment regulation was creating barriers to upstream fish passage. completely removed. In the years that Watershed process and channel form have ensued, the lack of large wood in tributaries experienced considerable recovery, setting to the SFER has been deleterious to channel

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South Fork Eel River SHaRP Plan sediment maintenance and retention, illicit operations to proliferate with little especially in large wood forced channel regulation. By 2002-2007, large-scale types, and has resulted in reduced or growing operations or “mega grows” started simplified aquatic habitat formation in much showing up on the landscape. of the basin. Simultaneously, financing was readily available to anyone, regardless of their Subdivision and accelerated land-use financial stability, who wanted to buy real through the green rush estate. By 2010, it was estimated that nearly 80% of the nation’s cannabis came from By the late 1960s, aside from preserved State California and most of that from the Emerald Parks groves, most of the merchantable Triangle within the heart of the Eel River timber had been removed from the basin (Mathis 2020). The cannabis industry northwestern SFER basin. Land developers (permitted and unpermitted production) bought up large tracts of land, subdivided the nearly doubled in area under cultivation from smaller parcels (40-80 acres), and sold them 2012-2016 in Northern California (Butsic et to “new settlers”, also known as “back-to- al. 2018). the-landers”. Significant changes to the watershed from these activities included the The quantity and magnitude of stream development of roads to access every parcel, diversions associated with this expansion was an increase in the number of water voluminous, increasing water temperatures, diversions, and collectively an increase in the reducing flow at critical times for fish rearing total amount of water diverted from streams and migration, and altering water chemistry in the basin to supply additional residences. across the entire basin. The unregulated road building and grading was once again Many of these “back-to-the-landers” also impacting stream channels with excessive started cultivating marijuana, and these fine sediments. operations slowly expanded in both size and number. Development of this underground In 2015, the Governor approved the Medical industry beginning in the 1970’s provided an Cannabis Regulation and Safety Act and by economic boost throughout the sub-basin November 8, 2016, the voters of California (JMWM 2000). Illegal marijuana cultivation passed Proposition 64 -the Medicinal and proliferated through the 1980’s and 1990’s, Adult-Use Cannabis Regulation and Safety and the illicit nature of the industry resulted Act. This legislation required any person in unregulated development of water wishing to commercially cultivate cannabis resources, land clearing and grading and lawfully in California and obtain a license additional road building. from the California Department of Food and Agriculture. The regulatory framework California’s Proposition 215 ballot passed in accompanying this legislation came with November of 1996, opening the industry to environmental protections including water legal cultivation for medical use with limits development, land development in to size of operations. These regulations accordance with state and county ordinances, proved hard to enforce and spurred the quasi-

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South Fork Eel River SHaRP Plan and compliance with state fish and wildlife Southern Oregon-Northern California Coast regulations, among others. (SONCC) , only the SFER population of Coho Salmon is thought to Salmon and steelhead decline persist marginally above its depensation threshold (NMFS 2014). The Eel River watershed historically supported a significant number of salmon and The fish ladder installed at the former steelhead, with populations present in all Benbow Dam at river mile 40 on the South major tributaries (NMFS 2014). Yoshiyama Fork Eel River was operated from 1938 to and Moyle (2010) examined commercial 1976 capturing and counting passing fish. fishery and cannery records from as early as Data from the Benbow fish ladder arguably 1854 through 1921. Extrapolating these data provides the most robust information on to minimal population estimates, these population declines. The most precipitous authors estimated an average annual decline in the era of post-commercial river population of approximately 93,000 fish harvest occurred during a period when during this period with a peak roughly six- habitat conditions were significantly affected fold higher in 1877. Chinook Salmon by timber harvest activities and punctuated represented most of this commercial catch, as by the catastrophic floods of 1955 and 1964 the timing of river entry likely made them (Figure 4-5). These data show declines in highly vulnerable to the netting operations in populations of all three anadromous fish the lower river. The authors also noted, species from highs of 10,000-20,000 fish “given that the cannery records result in a immediately prior to the beginning of post- very conservative estimate of Chinook WWII tractor logging in 1945, to lows of less numbers, the records suggest that historic than 5,000 fish at the end of the time series in runs of Chinook Salmon probably ranged 1976. Coho Salmon, in particular, were between 100,000 and 800,000 fish per year, captured in precipitously low numbers in the declining to roughly 50,000-100,000 fish per last few years of ladder operation. year in the first half of the 20th century”. The winter and summer steelhead run (combined) Contemporary data collected from 2010 to likely numbered between 100,000 -150,000 2019 by the California Salmonid Monitoring adults per year during the late 1800s and early Program (CMP) indicate Coho Salmon 1900s. Coho Salmon numbers were less than populations have not recovered in the past 45 those of steelhead; nonetheless, historic years. Rather, populations appear to continue numbers probably ranged in the 50,000- to fluctuate around disparagingly low 100,000 fish per year (Yoshiyama and Moyle abundances that approach the critical 2010). population depensation levels outlined by NMFS (2014). Taking incomplete CMP It is estimated that by the turn of the 21st abundance data on steelhead and Chinook century, Coho Salmon were reduced to 6 - Salmon, together with anecdotal information 15% of abundance estimates from the 1940’s on these species, indicates these species also (CDFG 2004). Within the entire range of continue to fluctuate around critically low

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South Fork Eel River SHaRP Plan levels (Figure 4-5). Most recently, in 2018- Estimates produced with this technique 2019, California Trout partnered with the placed Chinook Salmon escapement in the CDFW and the California Conservation range of 3,150 to 4,500 fish, with slightly Corps to estimate Chinook Salmon entering lower steelhead estimates between 2,500- the South Fork Eel River using a sound 4,000 fish (Methany in prep). navigation ranging (SONAR) camera.

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Figure 4-5. Top Panel: Counts and smoothed trend line of adult salmonids at Benbow Dam (RM 40), SFER, 1938-1976. Shaded area indicates the period of increased post WWII tractor logging, and vertical lines indicate timing of major flood occurrences, and forest management legislation. Lower Panel: Number of salmonid redds (multiplied by 2.5 to scale redds to escapement) estimated by the California Monitoring Plan and smoothed trend line.

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History of Habitat Restoration need to organize and expedite watershed restoration to support recovery of these Restoration efforts throughout the SFER species, CDFW developed the Stream have been ongoing since the 1970s. Similar Habitat Restoration Manual (Flosi et al. to other areas in the region, early efforts were 1994). The manual provided guidance and a largely volunteer opportunistic, and primarily systematic approach to developing and addressed treating symptoms caused by implementing restoration projects. However, unregulated land use (CDFW 2014). While funding shortfalls limited the manual’s initial well intended, much of these efforts were not utilization. optimally designed. Restoration efforts have since evolved to include a systematic Landmark legislation passed in 1997, when approach for collecting and analyzing data, Senate Bill 271 provided an additional assessing watershed condition, and funding source for FRGP’s watershed identifying critical issues. This information planning, upslope erosion control, culminates in project designs that address organizational support, and monitoring habitat deficiencies and consider natural categories. Furthermore, the U.S. Congress watershed processes. established the Pacific Coastal Salmon Recovery Fund (PCSRF) in 2000 to reverse CDFW’s Fisheries Restoration Grant the declines of Pacific salmon and steelhead Program (FRGP) was established in 1981 and in California, Oregon, Washington, Idaho, has provided much of the funding for aquatic and Alaska. NMFS administers the program habitat restoration within the SFER and and has granted California millions of dollars across the North Coast. During the 1980s and through PCSRF since 2000, which CDFW early 1990s, limited funds were available for has allocated through FRGP. the program. Restorationists primarily pursued small-scale instream habitat While the FRGP has been a significant driver improvement and bank stabilization projects in funding and guiding restoration activities, that were spread across the watershed and other agency funding, private funds, and were limited in their overall effectiveness. numerous landowner contributions have Small cooperative fish rearing facilities and supported a diverse array of additional rearing pond operations were undertaken in restoration projects in the SFER. For several SFER tributaries but proved to be example, NMFS has funded SFER projects somewhat ineffective at producing salmonids since 2001 through its Community-based, (CDFW 2014). Open Rivers and Coastal Resiliency Programs. In addition, funds available As salmonid populations remained depressed through the Water Quality, Supply, and in the late 1980s and 1990s, restoration Infrastructure Improvement Act of 2014 organizations successfully petitioned state (commonly known as Proposition 1) has and federal agencies to list salmonid species supported restoration efforts throughout the under their respective Endangered Species SFER sub-basin. Acts. In response to species listing and the

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Role of Restoration and the SHaRP anthropogenic threats and stressors continue Process to affect surrounding areas. However, pool depth and pool shelter indices, overall, have As discussed, insufficient funding and not shown improvement, which indicates emerging watershed science shaped the sediment inputs are on-going and instream initial scale and scope of restoration efforts habitat complexity is still lacking. To date, from the 1960s to the 1990s. In the 2000s, about 8% of the 275 miles of tributaries in the diverse and increased funding sources SFER have been treated to improve instream allowed for expanded, more systematic complexity and a smaller percentage of restoration planning and project execution. upland habitat has been restored since 2004 Between 2004 and 2018, FRGP funded 112 (North Coast Salmon Project in prep). projects in the SFER and its tributaries, Scientific literature, including Roni et al. totaling over 14 million dollars (North Coast (2010) describe the need to treat a noticeably Salmon Project in prep). About 70 percent of higher percentage of a stream/watershed this funding supported three project types: before a population response can be detected. Upslope Watershed Restoration, Instream Considering the size of the SFER watershed, Habitat Restoration, and Fish Passage at it is evident that a significant amount of Stream Crossings. Upslope watershed restoration is still needed. restoration received nearly half (44%) of this funding, addressing the critical need to The SFER SHaRP process culminated in decommission numerous miles of old logging identification of the highest-priority roads. This large-scale road restoration projects in seven focus areas of decommissioning improved drainage and the sub-basin, as detailed in Chapters 5 reduced the sediment loads entering streams. through 11 of this plan. SHaRP restoration Such upslope work was essential to prevent planning utilized local expertise, advanced compromising the effectiveness of future knowledge in watershed sciences, and riparian and instream work. improved restoration techniques to collectively; identify current barriers needing The SFER WA compared habitat suitability fish passage modifications, incorporate indices from data collected in 1990 – 1999 to updated large wood loading target metrics values from 2000-2010 and determined that (Kier Associates and National Marine overall habitat suitability has increased in the Fisheries Service (NMFS) 2008) to advance northern and western portions of the large wood loading effectiveness, GIS watershed. While it is difficult to discern the mapping exercises to integrate potential for relative contribution of restoration actions, restoration of floodplain connectivity and improvements in environmental regulation, identify potential winter refugia (rearing and natural processes to this improvement, it habitat); and mapping of key road networks is noteworthy that some aspects of habitat and other significant sediment sources conditions, such as canopy cover, pool-tail requiring treatment to reduce sediment input. embeddedness, and percentage of pool habitat are improving given the fact

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Resiliency in the Face of Climate subsequent juvenile rearing distribution. The Change timing of springtime downstream juvenile migration, however, appears relatively Over thousands of years, evolution has given invariant to local spring discharge regimes rise to a diverse set of life history patterns in (Kelson et al. 2018), but displays larger California salmon and steelhead. Relatively regional scale latitudinal gradients indicative short-term environmental variability leads to of adaptation to longer term climatic trends certain strategies having better success than (Spence et al. 2014). Near the southern end of others at different times and places (Bisson et distribution in North America, SFER salmon al. 2009). A diverse portfolio of life history and steelhead are at the critical edge of options serves to spread the risk of mortality genotypic adaptation and phenotypic across a population during cyclical periods of plasticity that allow population persistence climate anomaly or acute catastrophic events through periods of rapid climate change (Hilborn et al. 2003, Schindler et al. 2010, (Herbold et al. 2018). 2015) when portions of the landscape or periods within the life cycle become less Collaborative members recognized that productive. Climate variations include the climate change contributes to many of the cyclical but increasing severity of concerning habitat conditions and disrupted temperatures and drought (Robeson 2015) watershed processes identified in the seven (Figure 4-6), and multi-decadal patterns of focus sub-watersheds, however, it was ocean productivity (Mantua et al. 1997, beyond the scope and authority of the Mantua 2015). Catastrophic events include Collaborative to address the proximate causal wildfire, floods, earthquakes, and landslides factors of climate change (e.g. greenhouse that often occur in combination. gas emissions) through the SHaRP process. Rather, the Collaborative believes that One of the most serious threats to salmon and completion of the restoration treatments steelhead in the Eel River is changes to the identified in the following Chapters 5-11 will timing and location of rainfall in the basin, help to both directly address acute stressors and the availability and temperature of (e.g. water enhancement and conservation, surface waters. It is widely recognized that habitat complexity) as well as restore human induced global climate change is, in watershed processes (i.e. delivery and part, responsible for recent changes in distribution of sediments), which will climatic patterns (Williams et al. 2015, collectively contribute to an increased range Obama 2017) (Figure 4-6), and increased and diversity of habitats necessary to support human demand for water likely responsible a broad array of salmon life-histories. for more localized dry season deficits (Asarian and Walker 2016). Shifting patterns The concept that habitat diversity leads to in the onset of the wet season, and the resiliency is in contrast to restoration magnitude and timing of peak flows can approaches that attempt to engineer instream disrupt the timing and upstream distribution habitats to conform to an idealized condition of adult anadromous salmonid spawning and (Bisson et al. 2009). An idyllic but over-

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South Fork Eel River SHaRP Plan simplified version of what a salmon stream ‘should’ look like may result in the loss of the life-history diversity necessary to support populations through periods of change. Recovery of habitats in the SFER sub- watersheds alone cannot address the entire suite of diverse freshwater and estuarine habitats necessary to support the complex life-histories of salmon and steelhead in the SFER. Consequently, the next SHaRP planning areas of the main-stem SFER through the main-stem Eel River and estuary are necessary, and currently underway.

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Figure 4-6. Top panel displays the Mean August Air Temperature in Scotia, CA from 1930 to 2020. The middle panel displays the Annual Precipitation received by Mendocino County, CA from 1890-2019. The bottom panel displays the Palmer Hydrological Drought Index (PDHI) for North Coast Basins in California. The PDHI is a standardized index based on rainfall, temperature and soil water balance and is used as an index of longer-term drought that reduces surface and groundwater supply. The magnitude of PHDI indicates the severity of the departure from normal conditions. A PHDI value >4 represents very wet conditions, while a PHDI <-4 represents an extreme drought. Blue trend lines in the panels represent a LOESS (locally weighted scatterplot smoothing) trend line and the grey envelopes surrounding the trend line indicate the standard error. Sources: https://calclim.dri.edu/index.html Accessed: 21 January 2021.

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