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Hydrology, Geomorphology and Vegetation - Feedback Loops & Implications for Restoration. A case study of Dry Creek, CA

Dry Creek, a major tributary to the Russian River in Sonoma County, is home to native threatened and endangered fish, and has remained a system of interest for ongoing regional endangered species recovery planning. Dry Creek’s current hydrology is regulated by Warm Springs Dam (WSD) and unregulated tributaries which enter Dry Creek below WSD. The geomorphic nature of lower Dry Creek is a result of the interaction between local geology, watershed characteristics, hydrology, and vegetation; the legacy of channel evolution and response to land management changes; and the ongoing influence of flow management. A primary control on geomorphology has been the feedback between regulated hydrology and vegetation, where elevated summer baseflow and reduced winter high flows have resulted in vigorous growth of riparian vegetation. Prolific vegetation establishment in the overbank regions have sequestered alluvial surfaces and sediment sources, resulting in narrowing and channelization of the main channel. Elevated baseflows, in combination with curtailed flood hydrology, supports the dense riparian communities currently present, which in turn, have reduced habitat forming processes that create habitats such as alcoves, backwaters, and side channels.

Restoring Riparian Landscapes to Achieve Multiple Ecosystem Services in the Sacramento Valley: Insights After 25-Years at Kachituli Oxbow

Riparian landscape transformation in the Great Central Valley of California has been intense. Conversion of disturbed riparian landscapes to native vegetation and wetlands to provide multiple ecosystem services, including preservation and enhancement of plant and animal biodiversity, has increased opportunities for long-term carbon (C) sequestration and enhanced biovalues associated with wetland functions. The Kachituli Oxbow, part of a 250-acre mature oak woodland/native grassland and functioning wetland preserve in western Yolo County was the largest mitigation-related restoration project in the western US when it was permitted and built in the late 1980’s/early 1990’s. Formerly planted to tomatoes, hops, and walnuts, it is now a superb teaching laboratory and research site.

Kachituli is suitable for field studies of a mature self-sustaining de novo ecosystem, with opportunities for evaluating the multiple ecosystem services it now provides. Our recent studies include:

Using the California Rapid Assessment Method (CRAM) to Quantify Riverine Riparian Condition in Santa Clara County Watersheds

The Santa Clara Valley Water District’s (District) Safe, Clean Water and Natural Flood Protection Program includes a priority project to assess stream ecosystem conditions at a watershed scale to make informed landscape-based asset management decisions. The District collaborated with the San Francisco Estuary Institute (SFEI) to conduct watershed-wide stream and riparian condition surveys throughout Santa Clara County in order to characterize and track the distribution, abundance, and condition of its creeks, rivers, riparian, and wetland habitats. Employing the U.S. EPA’s 3-level monitoring and assessment framework, the District has implemented a watershed approach to monitoring and tracking ecological stream conditions. The overall ecological condition of the District’s streams, wetlands, and adjacent riparian areas were assessed using the California Rapid Assessment Method (CRAM), a Generalized Random Tessellation Stratified (GRTS) survey design, and other GIS-based riparian analysis tools. Within each watershed, a GIS-based Riparian Zone Estimation Tool (RipZET) was run to estimate the amount and distribution of riparian areas based on vegetation and hillslope processes.

Assessing ecological benefits of river and floodplain restoration using targeted processes, habitats, species, and stressors

Restoring the natural vegetation and ecosystem processes of floodplains provides multiple ecological benefits, including habitat for numerous species with varied needs. A synthesis of these benefits would improve upon raw tabulations of changes in land cover and better inform the development and comparison of restoration concepts. To provide such a synthesis for the Central Valley Flood Protection Plan’s Basin-Wide Feasibility Studies, we used ecosystem processes, habitats (ecosystems), species, and stressors that are targets of the Central Valley Flood System Conservation Strategy. For target habitats, changes were synthesized into units of “functional acres” that were based on the area restored, the targeted processes and stressors affecting that area, and one to several additional attributes of the restored vegetation. For target species, benefits were measured by associating predicted restoration outcomes to species conservation needs. Results showed that adding natural vegetation to a site increased its functional value generally in proportion to the amount of acreage added, but value varied based on the extent to which a site could accommodate additional hydrogeomorphic processes, such as increased floodplain inundation and meander potential in riparian areas.

Development of a quantification methodology for greenhouse-gas benefits associated with riparian forest restoration and conservation

California’s cap-and-trade program regulating greenhouse gas (GHG) emitters receives revenue from the auction of emissions allowances that, by law, can only be spent on reducing GHG emissions. In order to award these Climate Investments funds to projects that reduce emissions or sequester CO2, state agencies must hae a method for estimating the size of a project’s GHG benefit. This talk describes the development of a quantitative methodology for carbon accounting in riparian forest restoration and conservation to be used by the California Department of Conservation (DOC) . The effort faced a scientific challenge and a policy challenge. On the science side, there were few published data relevant to predicting carbon accumulation in riparian forest stands, and timber models proved inadequate to the task. On the policy side, the challenge was to ensure that funded projects would not maximize carbon sequestration at the expense of other co-benefits (e.g., wildlife corridors, fish passage, erosion control, water quality). We used a mostly unpublished dataset of riparian forest inventory plots of known age to parameterize growth models for live tree biomass over 100 years. We then used these values to estimate accumulation of carbon other ecosystem pools. Results were grouped into look-up tables for carbon sequestration in various riparian forest types and coded into an online estimation tool, CREEC.

Advancing Riparian and River Restoration in a Time of Uncertainty: Natural Disturbances and Human Induced Stressors Including Drought, Climate Change, Bore Beetle, Fire

Restoration as a practice is built on the principle of change, with a primary goal of maximizing ecological processes to facilitate self-sustaining dynamic systems. Natural disturbances such as fire, drought, and flood play an important role in riparian ecosystems with many dominant species evolving aspects of their life history to complement such disturbances. However, natural disturbances have been modified by human actions with increased fire frequency/intensity, modified hydrology (e.g., dams and flood conveyance), and climate change. In addition to natural disturbances many stressors brought on by direct human actions further complicate restoration and subsequent management of riparian ecosystems. In southern California invasive plant and wildlife species are one of the primary stressors plaguing riparian areas. We will utilize two large scale restoration projects currently in the planning phases to discuss a variety of current issues facing riparian restoration including the Polyphagous Shot Hole Borer (PSHB) beetle (Euwallacea sp.), water management (drought, dams, and conservation efforts), invasive plant species, and sensitive wildlife species. The first project is the Otay River Restoration Project, located in San Diego California, where mitigation is proposed for the mainstem river approximately 1 mile below Savage Dam.

Fire, Floodplains, and Fish. The Historic Ecology of the Lower Cosumnes River Watershed

For thousands of years, the California landscape (and riparian areas in particular) has been tended and its resources sustainably harvested by its inhabitants. Prior to Euro-American settlement, California Native Americans manipulated the natural resources, particularly plant resources, to meet long-term cultural needs. Our hypothesis is that the floodplain biodiversity and native fish productivity benefited from burning and other traditional management practices utilized by the Plains Miwok and other Native Californians for thousands of years. These practices may have enhanced floodplain rearing habitats, thereby increasing fish growth and reducing fish mortality. We support our argument with ethnographic data, traditional knowledge and archaeological fish faunal remains to reconstruct the landscape of the lower Cosumnes River watershed prior to Euro-American settlement and alteration. The historical reconstruction proposed here will illustrate, within the limitations of the data, how past indigenous traditional management practices influenced both vegetation patterns and probably fish species distributions in the Lower Cosumnes River watershed. These practices may have enhanced floodplain rearing habitats, thereby increasing fish growth and reducing fish mortality. Traditional resource management has been demonstrated to do the following:

High Quality Riparian Restoration at Pace and Scale (Rogue River)

The Freshwater Trust (TFT), a nonprofit river restoration organization, began working in the Rogue River Basin in Southern Oregon in 2012 by planting more than 5,000 native trees and shrubs on streamside property north of Medford. Since then, TFT’s efforts to reduce water temperature and restore native fish habitat have grown to 18 project sites. These early actions have helped build capacity and spur additional projects with local partners to fix the basin. Flowing from the foothills of Crater Lake to its estuary in Gold Beach, the Rogue is an ecologically diverse home to rare and endemic species. Such conditions make it the ideal watershed for large-scale targeted restoration. In five years, TFT has grown its Rogue restoration program to 15 miles (100 acres) of instream and nearstream projects, with similar growth expected in the future. Major projects include riparian restoration sites for the City of Medford to meet water temperature requirements of the Clean Water Act, and large wood structures for the Bureau of Reclamation to meet requirements of a biological opinion for fish habitat. To rapidly increase the pace, scale, and concentration of restoration efforts, TFT secured a range of large multi-year funding sources.

Large-scale, multi-benefit riparian restoration at Dos Rios Ranch, Stanislaus County, California

Dos Rios Ranch is a 2,100 acre property located at the confluence of the San Joaquin River and its largest tributary, the Tuolumne River in Stanislaus County, California. Adjacent to the San Joaquin River National Wildlife Refuge, Dos Rios Ranch is being developed as a landscape-scale model for floodplain restoration, threatened and endangered species recovery, transient floodwater storage, groundwater recharge, water supply, water quality, and recreational opportunities. In the first phase of restoration, River Partners planted over 130,000 native trees and shrubs in resilient plant communities that are adapted to climate change and provide high quality habitat. River Partners is close to obtaining the necessary permits to begin restoration on the balance of fields on the river side of a federal levee that bisects the property. In this next phases of restoration, River Partners will plant over 200,000 native trees and shrubs on flood prone farmland which has been in some form of agriculture for decades. Restoration of the floodplain will include areas of elevated flood refugia for terrestrial species in addition to ephemeral swales to increase seasonal inundation for salmonids. Plant communities will be designed to provide flood conveyance and resist the invasion of non-native species.