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Freshwater Ecosystem Conservation: Perspectives from the Floodplain

Convergence on the Cosumnes River

Joshua H. Viers, Jeffrey F. Mount, Peter B. Moyle, James F. Quinn, Ingrid B. Hogle*

Cosumnes Research GroupUniversity of California, Davis

I am here representing the Cosumnes Research Group, a consortium of researchers studying floodplain restoration efforts at the Cosumnes River Preserve in California’s Central Valley, about half way between San Francisco and Lake Tahoe.

19th Annual Meeting of the Society for Conservation Biology

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Advancing Floodplain Conservation

• Principles of Floodplain Ecology • Principles of Freshwater Conservation• Freshwater Conservation in California• California Bay-Delta Authority• Cosumnes Research Group

Our research aims to advance floodplain conservation by increasing scientific understanding of riverine/floodplain ecology through the case study of the Cosumnes River Preserve.


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Floodplain Ecology & BiodiversityWard and Tockner Freshwater Biology (2001; 46:807-819)

• Functional Diversity• Structural Diversity• Species Diversity

Ward and Tockner advocate defining river ecology in terms of broad-concept biodiversity, which encompassesFunctional DiversityStructural DiversitySpecies DiversityThey advocate that river conservation should focus on re-establishing diverse river functions, including processes of ecological succession and hydrologic connectivity between surface and subsurface waters.


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Photo credit: www.rainforests.net/pictures.htm

Functional Diversity in a Riverine Ecosystem

• Fluvial dynamics• River Continuum Concept

Vannote, Minshall, et al. Canadian Journal of Fisheries and Aquatic Sciences (1980; 37: 130-137)

– Diversity of stream conditions from upstream to downstream• Flood pulse

Junk, Bayley & Sparks Proceedings of the International Large River Symposium (1989; p. 110-127)

– Importance of overbank inundation to floodplain productivity• Natural Flow Regime

Poff, Allan, et al. BioScience (1997; 47:769-784)

– Restoration of natural flow regimes important to entire ecosystem

• Flow pulse Tockner, Malard, et al. Hydrological Processes (2000; 14(16-17): 2861-2883)

– Importance of hydrologic dynamics at less than bankfull flows

They emphasize the importance of fluvial dynamics as a central component of ecological processes in river systems, and expand on a history of research into fluvial dynamics.

This history includes the River Continuum Concept, which provided a framework for stream ecology based on the gradient of physical characteristics changing from upstream to downstream reaches of permanent rivers.

The authors of the Flood Pulse concept complemented the River Continuum Concept by providing an ecological framework for the study of floodplains, with their characteristic seasonal nature.

In the Natural Flow Regime concept, Poff and others identify natural flow regimes as ..., and call for research on how restoring specific components of the flow regime will benefit the entire ecosystem.

Tockner added to the theory of floodplain-river ecology by adding the Flow Pulse concept, which points out that expansion and contraction of floodplains can result from hydrologic factors other than overbank flow.


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Structural Diversity

Landscape Dynamics– Aquatic/Terrestrial Transition Zone

Junk, Bayley & Sparks Proceedings of the International Large River Symposium (1989; p. 110-127)

– Ecological Succession


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Species Diversity• Hierarchical Scales• Alpha, Beta, Gamma Diversity


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Freshwater Conservation Targets*• Distinct communities, habitats and species

assemblages• Large expanses of intact habitats and

intact native biotas• Keystone species,

habitats, phenomena, processes

• Imperiled species

FRESHWATER CONSERVATION PLANNING Working Group (Washington, DC; 2004)

Striped Bass (Morone saxalitis) – Cosumnes River

Photo: Carson Jeffres

All groups recognize the need to apply freshwater-specific approaches to conservation planning for freshwaters, though the basic principles (e.g. representation, viability) are generic to conservation planning. There is a trend toward greater incorporation of coarse-filter targets. Fine-filter targets remain important, but data are often lacking.

Target: - Distinct communities, and habitats, such as floodplains, which require temporal connectivity (IS THIS WHAT YOU MEANT?)- Species assemblages such as, in our area, chinook salmon and Sacramento splittail, depend on these highly productive riverine floodplains- Conservation efforts should target large expanses of intact habitats and intact native biotas, using, whenever possible, a consortia approach to combining lands, and sharing rights and management responsibilities. Our study site, for example, is cooperatively owned and managed by seven entities including nonprofits such as The Nature Conservancy and Ducks Unlimited, state agencies such as the CA Department of Fish and Game, and federal agencies such as the US Fish & Wildlife Service.

We have several flagship species at our Preserve which help guide management actions. These include the Sacramento Splittail and Chinook Salmon, which are threatened by non-native, invasive fish; the terrestrial Valley Elderberry Long-Horn Beetle, which requires intact riparian habitat for its host plant; and the Sandhill Cranes, which overwinter at the Preserve and which depend on seasonally flooded wetlands.

Keystone species, habitats, phenomena, processesSacramento splittail () – Swainson’s hawk () –Late-seral stage valley oak (Quercus lobata) with epiphytes (Vitis californica)Anadromous chinook (Oncorhynchus tschawytscha) spawning in California’s Central ValleyFloodplain connectivity in a sea of levees and agricultural lands (below sea level)- Imperiled speciesCentral Valley chinook


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Valley Elderberry Longhorned Beetle (Desmocerus californicus)Photo: Mary Gardner






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Sandhill Cranes, flying (Grus canadensis)






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Moyle’s 5 Tier Approach

1 – Species Level Preservation with ESA2 – Management Cluster3 – Aquatic Diversity Management Area 4 – Key Watersheds5 – Landscape Management

Moyle’s five tiered approach offers a systematic method for aquatic conservation. The approach advocates the use of the Endangered Species Act, or other equivalent species-based approach, for conservation of a single species at the mostdiscrete tier. Aquatic Diversity Management Areas, defined as water bodies that have as their top management priority the maintenance of local biodiversity, provide medium-term protection for aquatic biodiversity while a functional system of watershed and landscape level conservation is being developed.


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Statewide Landscape Scale Conservation Efforts

Sierra Nevada Ecosystem Project

Northwest Forest Plan

In Northern California, we have three examples of ecosystem-based, landscape-scale conservation efforts. The Northwest Forest Plan was initiated by President Clinton in 1993 to provide a scientific basis for forest management in the Pacific Northwest and northern California. The aquatic conservation chapter of this plan focused solely on salmonids as the target species. It used a conservation strategy of defining key watersheds and riparian reserves, and conducting watershed analysis and restoration.

The Sierra Nevada Ecosystem Project was initiated by the US congress to determine the ecological state of and provide conservation recommendations for the Sierra Nevada region of California. This project developed hierarchical conservation framework derived from the five tiered approach to aquatic conservation offered by Moyle and Yoshiyama (1992, 1994).


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http://calwater.ca.gov

California Bay-Delta Authority

A third statewide aquatic conservation effort is the California Bay-Delta Authority, which manages the omnibus CALFED Bay-Delta program in its mission to develop and implement a long-term comprehensive plan that will restore ecological health and improve water management for beneficial uses of the San Francisco Bay-Delta System.

CALFED has a specific programs to address its ecosystem restoration mandate.


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Quasi Governmental Approaches

25 state and federal agencies working cooperatively to improve the quality and reliability of California’s water supplies while restoring the Bay-Delta ecosystem(http://calwater.ca.gov/CBDA/)

California Bay-Delta Authority

Cosumnes River

The Cosumnes River watershed lies within the red circle here. As the only remaining un-dammed river draining the south slope of the Sierra Nevada, the Cosumnes River provides an opportunity to study a river with a semi-natural flow regime. The headwaters are a key watershed within the Sierra Nevada Ecosystem Project, and the lower watershed lies within the CALFED management area.


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Moyle, Crain, Whitener & Mount Environmental Biology of Fishes (2003; 68:143-162)

The Cosumnes River watershed extends from the headwaters in the Sierra Nevada to the sea level Central Valley. Here you can see the elevational division between the Sierra Nevada and Central Valley. The Cosumnes River Preserve is located right around here, in the Sacramento Valley, at the confluence of the Cosumnes and Mokulemne Rivers. The Preserve is in a unique location, receiving freshwater from snow melt upstream but also experiencing the tidal influence of the nearby San Francisco Bay Delta.


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Bay Delta River Hydromodification• Levees • Channelization• Dams • Water diversion

Changes in Floodwater• Magnitude• Timing• Duration• Frequency• Connectivity

Hydromodification of Sierra Nevada rivers, and most California, rivers include creation of levees, channelization, dams, and water diversion. These modifications result in major changes in the magnitude, timing, duration and frequency of floods, and often destroy connectivity between channels and historic floodplains.


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Mount and Twiss. San Francisco Estuary and Watershed Science (March 2005 Vol. 3, Issue 1, Article 5)

Levee Impact

Unplanned Levee Break 6/3/2004 Upper & Lower Jones Tract

Photo: DWR

This map shows the Preserve’s location in relation to the SF Bay Delta, and illustrates the elevation BELOW sea level of Bay Delta islands.


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Levee Evolution

Intentional levee breach, Cosumnes River Preserve

1995

Mount and Twiss. San Francisco Estuary and Watershed Science (March 2005 Vol. 3, Issue 1, Article 5)

At the end of the gold rush, agriculture became the major focus in California. The Central Valley islands provided very fertile, flat land which was easily converted to agricultural field by simple levee building. Microbial oxidation and loss of CO2 led to compaction of soils in these islands, erosion took it’s toll, and the islands are now below sea level, artificially maintained as island by an extensive levee system. These levees have became more difficult to maintain due to the increased water pressure exerted on them. Jeff Mount hypothesizes that increased sea level rise due to global climate change, and/or an earthquake in the area, could forever alter the system through levee failure and resulting salinization of areas which are now maintained as freshwater systems through the levee system.


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Restored Floodplain Cosumnes River Preserve

Sacramento County, California

Florsheim and Mount

Geomorphology (2002; 44: 67–94)

Accidental breaches in constructed levees promote sedimentation similar to that which occurred along the Mississippi and Missouri Rivers in 1993 (Gomez et al., 1997; Jacobson and Oberg, 1997; Schalk and Jacobson, 1997) or to that which occurred on the lower Cosumnes River in 1985 (Florsheim and Mount, 2002). Levees that blocked floods from the Sacramento River changed thehydrogeomorphology of the lowland flood basin, and the Cosumnes River is currently the dominant source of water and sediment to the adjacent floodplain. Since completion of the levee systems on the Sacramento and Cosumnes Rivers, floodplain flows that exist are likely to have significantly lower stages and shorter duration than during the pre-disturbance Holocene. Levee construction concentrated flow from multiple secondary channels and likely increased velocity and shear stress in the main channel leading to the incision upstream of the study area. Further, levees limit transport of sediment, water, and nutrients from the channel onto the adjacent floodplain, except during accidental breaches such as occurred at the Accidental Forest at the Cosumnes River Preserve (Florsheim and Mount, 2002). The loss of connectivity and reduction in the number of shallow water anastomosing channel segments reduced edge habitat and affected ecosystem diversity in the floodplain ecotone. Finally, these floodplain and channel changes were compounded by riparian vegetation denudation and agricultural leveling that subsequently dominated floodplain morphology.(Note: 1985 sandsplay was only 0.06% km2!)


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The Accidental Forest

Cottonwood (Populus fremontii)

(Hunter, Willet and others, 1999 Environmental Management)Although floodplain forests were the predominant floodplain vegetation prior to extensive settlement, only 3.3% of floodplain was covered by forest in the late 1980s. This remaining forest was fragmented into 2607 patches with an average area of 3.1 ha. Only 180 patches were >10 ha, with three patches >100 ha. Despite over two decades of conservation efforts, these forests are essentially unpreserved: Only 14.5% of extant forests are in public ownership or on land managed primarily for biological conservation.


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The Tall Forest


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The Triangle Floodplain

Florsheim and Mount Geomorphology (2002; 44: 67–94)

Intentional levee breach created the triangle floodplain in 1997. The center pond was excavated by the Army Corp of Engineers as an unrelated mitigation project.


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Point out spatial location of triangle floodplain in relation to accidental forest.


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Florsheim and Mount Geomorphology (2002; 44: 67–94)

We have been monitoring the flood pulse rate of discharge at which floodplain connectivity occurs on the restored floodplain.


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Breached Levees• Improve Floodplain Connectivity• Establish Heterogeneous Geomorphology & Habitat• Provide Invasion Opportunity

J.L. Florsheim and J.F. Mount. Geomorphology 44 (2002) 67–94

Breached LeveesImprove Floodplain ConnectivityEstablish Heterogeneous Geomorphology & HabitatProvide Invasion Opportunity


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D.S. Ahearn, J.H. Viers, & J.F. Mount (in prep)

Priming the productivity pump: Temporal trends in suspended algal biomass distribution across a restored floodplain

Influx of organic and inorganic materials (nutrients, sediments, etc.)

Improved Floodplain Connectivity brings an influx of organic and inorganic materials (nutrients, sediments, and sometimes pumpkins!) into the Cosumnes River floodplain.


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Native Fish Thrive on Restored Floodplain

Non-native fishes in

river

Native fishes in

floodplain

Crain et al.

Use of the Cosumnes River floodplain by native and alien fishes was related to inflowing floodwaters and accompanying water temperatures. Our results suggests that floodplains were historically important habitats for rearing of native fishes, such as splittail, although their importance to river-spawning species, such as Sacramento sucker and prickly sculpin, and native species resident in sloughs, such as Sacramento blackfish, is poorly understood. At present, floodplains appear important for native fishes mainly early in the season (February– April) because warmer temperatures and lower flows later in the season favor alien species, especially those that are permanent residents in ponds, ditches, and sloughs on the floodplain. By summer, the only fishes appearing as larvae are alien fishes, especially inland silverside and centrarchids. However, some alien species, especially common carp, have spawning habits very similar to native species and also benefit from early season flooding. Another important observation is that larval fishes in the main floodplain were secondarily associated with flooded annual vegetation in 1999. This suggests that unforested fields of annual vegetation may be useful for larval rearing because of the abundance of food and cover. Larval fish use of forested habitats, however, has not yet been adequately studied. Presumably the historic floodplains of the Central Valley were a mosaic of forested and open habitats, so would have provided both habitats. Overall, our observations suggest that management of recreated floodplains, such as the Cosumnes River, should involve strong emphasis on (1) flooding in February– pril, with rapid draining thereafter; (2) reduction in permanent habitats that support resident alien fishes; and (3) maintenance of habitat mosaics that keep large expanses of annual vegetation available for flooding.


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Carson Jeffres et al. (unpublished manuscript)

Juvenile chinook (O. tschawytscha)

River raised chinook salmon

Floodplain raised chinook salmon

The implication is that likelihood of out migration, ocean rearing, and in migration success is positively correlated with size at out migration. Primary reasons for size difference is increased productivity on the floodplain, slower moving water (ability to prey), & ability to avoid predators in the shallows.


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Spatial temporal dynamics of ecosystem processing: deleterious effects (invasion) are perhaps more rapid

than desired ones (restoration)

Lepidium latifolium

We have been tracking the invasion of the perennial herbaceous plant Lepidium latifolium (perennial pepperweed) onto the floodplain. This species is a threat because it can quickly become a monoculture, preventing establishment of native plants on the floodplain. We are also tracking the success of passive and active riparian forest restoration. Restoration of these desired tree species, of course, takes place on a much slower time scale than invasion by non-native annuals and perennials.


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Ecosystem Restoration Monitoring

Collaborators studying the ecosystem impacts of floodplain restoration through the Cosumnes Research Group include the University of California, The Nature Conservancy, the Point Reyes Bird Observatory and others. This multidisciplinary, interdisciplinary research effort is only funded by the California Bay-Delta Authority through the end of this calendar year. But as we look back on our research efforts, it is clear that we have accomplished a lot. We have met our goal to define linkages between all of our various research topics ranging from birds to bats to floodplain morphology to fish, to explain the ecosystem impacts of restoring the flow regime in this experimental floodplain. Our results can be used to inform science-based management of floodplains throughout the Bay Delta area. We hope that the powers that be will see fit to continue funding science-based restoration and management of these mostly disappeared ecosystems.


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Collaborators studying the ecosystem impacts of floodplain restoration through the Cosumnes Research Group include the University of California, The Nature Conservancy, the Point Reyes Bird Observatory and others. This multidisciplinary, interdisciplinary research effort is only funded by the California Bay-Delta Authority through the end of this calendar year.But as we look back on our research efforts, it is clear that we have accomplished a lot. We have met our goal to define linkages between all of our various research topics ranging from birds to bats to floodplain morphology to fish, to explain the ecosystem impacts of restoring the flow regime in this experimental floodplain. Our results can be used to inform science-based management of floodplains throughout the Bay Delta area. We hope that the powers that be will see fit to continue funding science-based restoration and management of these mostly disappeared ecosystems.


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Acknowledgments

California Bay Delta Authority Ecological Restoration Program (Award # ERP-01-NO1)

John Muir Institute of the Environment, University of California, Davis; Cosumnes Research Group II

Information Center for the EnvironmentUniversity of California, Davis

Information Center for the Environment

Cosumnes Research Group


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