HISTORICAL CHANGE ANALYSIS IN LIVERMORE-AMADOR VALLEY: IMPLICATIONS FOR LANDSCAPE-SCALE MANAGEMENT STRATEGIES Sean Baumgarten, Julie Beagle, and Robin Grossinger • San Francisco Estuary Institute, Richmond, CA. ABSTRACT CHANGE OVER TIME CONCEPTUAL MODELS CONCLUSIONS Urbanization and hydromodification in Livermore-Amador Valley (the Valley) over the last 150 years have created a highly altered Valley Freshwater Marsh Past, present, and future conceptual models of Arroyo Mocho. The three oblique views This study provides a first step towards developing a landscape-scale stream network and given rise to a variety of stream management challenges, including sedimentation, channel incision, and Pond 1800 1940 2010 represent conceptual depictions of the stream 1) during the historical period, 2) under strategy for addressing stream management challenges in instream and riparian habitat loss. This study applied recent historical ecology research to investigate potential landscape-scale Wet Meadow Willow Thicket present-day conditions, and 3) projected into the future based on potential management Livermore-Amador Valley. Although urbanization has irrevocably management strategies for two streams within the Valley: Arroyo Mocho and Arroyo las Positas. Explorations of historical landscape Alkali Meadow strategies identified in the case studies. Below the oblique view graphics are conceptual transformed the Valley and modified many hydrologic processes, key patterns and processes were used to identify underlying causes of management challenges, create conceptual models showing Alkali Sink Scrub-Vernal Pool Complex gradients of key physical and ecological parameters: seasonality of water flow, type of water physical controls on landscape functioning, such as sediment supply and physical and ecological controls for each system, and develop landscape-scale management and restoration strategies. To increase the Alkali Playa Complex Arroyo las Positas transport (recharge or transport, or both), sediment dynamics, and state of riparian habitat. topographic gradients, are relatively intact. By harnessing these physical Arroyo las Positas Arroyo las Positas resilience of the stream network, recommended management actions include restoration of braided stream morphology, increased Riparian mapped in 1800s was characterized as Sparsely Vegetated Braided controls to promote watershed functions such as sediment storage, flood floodplain creation and connectivity, preservation of remaining alkali wetlands, and implementation of Low Impact Development Channel Sycamore Alluvial Woodland control, and wildlife habitat, managers can reduce costs while promoting (LID) strategies within a watershed framework. Riparian mapped in 1940s and 2010 was characterized as Livermore Livermore the long term ecological resilience of the stream network. Mapped Riparian Zone (1940, 2010) Arroyo Mocho Arroyo Mocho Arroyo Mocho Impervious Surface HISTORICAL c1800 Gravel mining pond The following table summarizes recommended management strategies, Arroyo del Valle Arroyo del Valle INTRODUCTION Stream channel Arroyo del Valle and the watershed functions they support, for different reaches of Channels mapped for the 1800s time period Land and water use changes in are further characterized as: Arroyo Mocho and Arroyo las Positas: Intermittent/Ephemeral Stream s San Ramon Livermore-Amador Valley (the Valley) over Perennial Stream Change over time of wetland and riparian habitat, stream configurations, gravel mining locations, and extent of impervious surfaces between 1800, 1940, and 2010. Ephemeral Undened/ SAN RAMON VALLEY DIABLO RANGE the past 150 years have impaired the Valley Freshwater Marsh Overow Channel South San Ramon Creek Pond ability of the stream network to provide d ass R t P e v ltamon A A e r Wet Meadow o m Brushy Peak Tributary r Stream Reach Intervention Functions e SPRINGTOWN v i valued watershed functions such as L Frick Lake N ALKALI SINK Willow Thicket 680 Increased sediment deposition and Alamo Creek Altamont580 Creek groundwater recharge and high-quality Restore braiding where 1. Southeast in channel storage, sycamore alluvial Alkali Meadow ALTAMONT HLLS HISTORICAL c1850 land is available Collier Creek Cayetano Creek Tassajara wildlife habitat. Along Arroyo Mocho, the SELECTED CASE STUDIES woodland Creek Cottonwood Creek Alkali Sink Scrub-Vernal Pool Complex Dublin 580 las CASE STUDY 1: ARROYO MOCHO SOUTHEAST INTERMITTENT PERENNIAL INTERMITTENT PERENNIAL Arroyo las Positas Increased sediment deposition and 580 AMADOR VALLEY Arroyo Patterson Pass Rd construction of flood control channels has Alkali Playa Complex Positas Flow Type Redesign Holmes Street in channel storage in parks, de- SPRINGTOWN Current Management Problems 2. Holmes Street to Livermore converted many reaches from braided to PLEASANTON ALKALI SINK • Increased base flows from South Bay Aqueduct and Bridge, reconnect inactive creased sedimentation at Holmes Sparsely Vegetated Braided Channel MARSH d Arroyo Mocho Arroyo Mocho Madeiros Parkway Stanley Blv • Narrowing of creek corridor has led to reduced COMPLEX WATER RECHARGE WATER RECHARGE AND TRANSPORT WATER TRANSPORT side channels Street Bridge, increased diversity in Pleasanton LIVERMORE VALLE Y Arroyo Seco single-threaded, which has likely reduced urban runoff e Conned Riparian Woodland/Savanna F Arroyo v in-channel sediment storage oothill R Dry Creek A Water riparian habitat d del Valle e Arroyo del Valle r • Replacement of sycamore alluvial woodland with Sycamore Alluvial Woodland off-channel habitat and contributed to o Create channels to act as Sediment transport into gravel m • Loss of riparian habitat Arroyo Mocho r e willows and other pioneer species SEDIMENT STORAGE SEDIMENT STORAGE AND TRANSPORT SEDIMENT TRANSPORT v Arroyo de la i distributaries into gravel pits at high flows, reconnection of downstream sediment deposition. L Oak Savanna Laguna N 3. Distributaries CRESTA Sediment BLANCA MODERN pits, reconnect floodplain floodplains, re-introduction of native Grassland Artificial augmentation of base flows, Historical Conditions Future Potential HISTORICAL c1850 habitat to channel species SPARSE OAKS / HERBACEOUS SPARSE OAKS / SYCAMORES SYCAMORE ALLUVIAL WOODLAND coupled with urban development on the • High coarse sediment supply from watershed Preserve remaining vernal Important habitat for rare and en- Sinbad Creek Perennial Stream d DIAB • Restore braided channel where unfarmed land is os R Riparian Habitat allecit LO V R CASE STUDY 4 AN ositas 4. Springtown Sink pool habitat, implement dangered species, flood attenuation, GE yo las P • Primarily braided channel available or agricultural land becomes available, Intermittent Stream Stonybrook Creek surrounding floodplain, has resulted in an o 580 Arr LID strategies reduce channel incision 680 eek to increase sediment storage, reduce | Slough/Overow Channel 84 Sunol | Cr N | • Frequent flooding | 1 mile unnaturally narrow riparian corridor and | | Preserve remaining vernal Alameda Creek sedimentation problems downstream, and enhance | NILES | Distributary 1:85,000 | Alameda | Important habitat for rare and en- CANYON | | riparian habitat (see case studies 2 and 3) | 5. Arroyo las Positas pool habitat along Cayeta- encroachment by dense vegetation. • In-channel water and sediment storage (in contrast | CASE STUDY 5 | | Arroyo las Positas dangered species Spring | | | no Creek to water and sediment transport along Arroyo | | CONTRA COSTA | | Along Arroyo las Positas, channelization | las Positas) Decreased impacts of channel inci- and increases in impervious surface cover Livermore Create inset floodplains at sion (lowering adjacent floodplain), SAN Chain of Lakes • Riparian zone dominated by sycamore FRANCISCO strategic locations mimic wet meadows, LID functions; SAN have likely increased flow velocities and created an imbalance of water and sediment, leading to channel incision and downstream San STUDY alluvial woodland JOAQUIN Francisco AREA flood attenuation CASE STUDY 3 A MODERN Bay d rroyo Mo sedimentation. In addition, urban development has reduced and fragmented rare wetland habitats in the Springtown alkali sink. ALAMEDA Stanley Blv cho ALAMEDA Change Over Time CREEK Historical channel congura- SAN MATEO WATERSHED LIVERMORE VALLE Y • Agricultural expansion into riparian corridor tion over modern aerial photo. Today Arroyo Mocho is a Today, managers are exploring ways to balance the demand for flood control and reliable water supply with the need to protect CASE STUDY 2 single-threaded channel • Conversion from braided to single-threaded | through this reach. | | | ecosystem functions such as high-quality riparian and instream habitat. This study drew on findings from the recently-completed | A (NAIP 2009) | rr channel | | SANTA CLARA o | yo del V CASE STUDY | 1 | | | Alameda Creek Watershed Historical Ecology Study (Stanford et al. 2013) to analyze contemporary stream management challenges in | N alle | | 10 miles • Decreased sediment deposition | | | | | | | Livermore-Amador Valley and identify potential landscape-scale management strategies. Sustainable, long-term solutions to | watershed management problems require watershed-scale strategies that capitalize on underlying physical processes to restore target MODERN functions and enhance ecological resilience (Beechie et al. 2010). Analysis of historical landscape structure and function can reveal FUTURE persistent geologic, geomorphic, and hydrologic controls that in many cases continue to operate today, and therefore determine both CASE