River-Lab

Actively incising Lower Tassajara Creek in Dublin, California, was restored as a compound channel in 1999-2000 to mitigate incision and provide flood conveyance capacity to reduce flood risk to an adjacent greenfield residential development. The project benefitted from a wide floodplain corridor set aside during development, allowing a rough vegetated overbank channel with a design capacity to carry the 100-year flood. Several years of cross-sectional channel surveys conducted under an informal monitoring program from 2000 to 2006 indicated that active incision was largely attenuated following the restoration, with some minor incision still evident and low-flow channel complexity just beginning to develop. This research evaluates Lower Tassajara Creek 20 years after its restoration, investigating ongoing channel evolution, incision and aggradation, and floodplain reconnection, and discussing channel conditions in the context of the catchment land use history. I repeated and overlayed a series of cross-section surveys to detect channel incision and overbank deposition, documented field observations of channel condition, and cross-referenced against LiDAR terrain data to detect depositional landforms on the floodplain. I also developed a one-dimensional hydraulic model to better understand current flood conveyance capacity, using channel roughness back-calculated using measured high water marks from a recent storm. Preliminary results suggest overbank deposition has occurred in some locations, particularly in the upper reaches, while shallow slopes and fine sediment in the low flow channel throughout the project indicate a depositional environment. While active incision appears to have halted, entrenched conditions persist in the reach with a deeper low-flow channel sized to carry the 5-year flow. There may be opportunities to improve floodplain connection by adding woody debris to push more frequent flows out of the low flow channel, but additional hydraulic model validation and testing will be required to determine where flood conveyance capacity is sufficient to support such an intervention.

Vegetation restoration projects throughout the American Southwest have yielded positive outcomes for degraded desert streams, including the Mojave River restoration at Afton Canyon in the Eastern Mojave Desert (Egan, 1999; 2016; Bunn et al., 2003). Although rare, beaver translocation has demonstrated success as a passive desert river restoration strategy at the Price and San Rafael Rivers in eastern Utah and the San Pedro River in Arizona (Soykan et al., 2009; Doden, 2021; Sandbach, 2023). The success of translocated beaver populations is determined by mortality rate and site fidelity, as dictated by habitat quality (Colleen & Gibson, 2000; McKinstry & Anderson, 2002; Petro et al., 2015; Morris et al., 2021; Bilby & Moseby, 2023). In deserts, beaver habitat is restricted to riparian forests (Rutherford, 1964; Bee et al., 1981; Welch et al., 1993). The restoration project at Afton Canyon has facilitated the return of native willow and cottonwood populations and beaver sightings have increased (Egan, 1999; 2016; MDRCD, 2022). It is likely that a combination of natural beaver recolonization and translocation would facilitate further habitat restoration.

River restoration projects can be designed to cultivate a diversity of human interactions with the riverscape, alongside the fulfillment of traditional biophysical objectives. The Salinas River is a major river in an agricultural valley in California, where restoration projects could address annual concerns of winter flooding while facilitating more human interactions throughout the riverscape. We conducted a study to investigate (i) who currently interacts with the river, (ii) where the sites of these interactions are, and (iii) how we can restore them for ecological and socio-cultural benefits. We combined site visits and evaluations, informal interviews, and GIS analyses to answer our questions. We find the Salinas River largely disconnected from public life, out of view and physical access. Nonetheless, there is a desire to connect with the water and riverfronts. Among the five sites we evaluated, Arroyo Seco is a well-frequented public area with amenities and ease of access to the banks and streams. The other sites require illicit passage through private property, but vary with regards to visual and physical accessibility, and site conditions, such as quantity of trash. Nonetheless, all sites inspire visions for restoration projects. such as floodable parks and linear riverfront parks, to yield biophysical and socio-cultural benefits .

Our post-project monitoring research focuses on a natural beaver dam on French Creek in the Scott River Watershed in Siskiyou County, CA. The dam exists on a stretch of the creek with several beaver dam analogues (BDAs), which have been implemented by the Scott River Watershed Council in the hopes of combatting incision in the system and recruiting beaver to maintain the structures. French Creek in particular is an important spawning ground for the threatened coho salmon, so the impacts of the dam on fine sediment are of particular interest. Since the installment of the BDAs on French Creek, a beaver family has colonized the site and built a natural beaver dam. In 2021, high flows led to a breach in this dam. Scott River Watershed Council (Council) developed plans to fortify it using similar techniques used in the nearby BDAs. These plans will be implemented in November 2023, one week after this survey.

This dam breach presented the unique opportunity to analyze the surrounding area before its reconstruction, providing both post-breach and pre-reconstruction information on beaver presence, groundwater levels, channel morphology, and sediment grain size. We found evidence of continued beaver activity at the site. Groundwater levels were lower compared to pre-breach data from 2020. Sediment grain size was bimodal directly below the breached dam as compared to an upstream site with imported gravels, potentially indicating a release of fine sediment during the breach. Given the impact of fine sediment on salmon spawning, these fluxes of sediment should be carefully studied and managed. Comparable cross-section data did not exist for the studied reach, so we cannot draw conclusions about the impact of the breach on these metrics, though they may be used going forward to assess the influence of the artificial dam repair.

This paper presents historical overviews and original ecological surveys on the North Fork of Strawberry Creek in Berkeley, California to better inform the Kingman Hall Creek Restoration Project. Analysis of geomorphologic changes in the North Fork of Strawberry Creek during urbanization reveals the legacy of alterations on contemporary ecology. Case studies varying in time, scale, and approach contextualize restoration efforts in the entire Strawberry Creek Watershed. The impacts of urbanization and culverting are evidenced by an ecological snapshot of current creek conditions between LBNL and the UC Berkeley Campus. Rod and level topographic surveys, ArcGIS permeability analysis, vegetation analysis, avian surveys, and macroinvertebrate counts conducted at three distinct locations along the North Fork provide a multipronged baseline survey of current conditions. Topographic surveys show a higher degree of incision below culverted stream sections. ArcGIS permeability analysis reveals a highly urbanized watershed, especially around the restoration project site. Vegetation analysis shows the prevalence of invasive species in urbanized riparian ecosystems. Avian surveys found the majority of birds in riparian areas of the North Fork to be generalist ground foragers. Finally, macroinvertebrate surveys found that the complexity and richness of benthic insects decrease after culverting, suggesting a need for further restoration work along the creek. Our surveys found that the impacts on stream health due to culverting and urbanization are beyond the scale of the Kingman Hall Creek Restoration Project. This paper is intended to provide a baseline for future research on the North Fork.

We researched indigenous-led river restoration in order to understand how this approach promotes long-term stewardship, a common challenge in the river restoration field. We were connected through the UC Berkeley community to the Pinoleville Pomo Nation in Mendocino County. We visited the Pinoleville Pomo Nation (PPN) to learn more about the restoration work they are conducting around Ackerman Creek, a tributary of the Russian River. They are incorporating cultural practices, long term monitoring, continuous maintenance, community outreach, invasive species mitigation, and native plantings into the restoration process. We then conducted a baseline survey of cross-sections and sketches, which may serve as a point of reference for gauging the impacts of future restoration activities. We learned that constraints to this stewardship approach come from limited jurisdiction of the tribe throughout the watershed, resulting in impacts from off-site factors such as dams and runoff. Even with built-in community engagement and synthesis of social connectivity and ecological health, the current on-site practices can not address upstream and downstream disturbances.

In 1996, the National Park Service (NPS) restored a 100-yard section of Lobos Creek in San Francisco. In this study, we evaluated the presence of invasive species within the Lobos Creek restoration project. The restoration site is not actively managed by any organization or volunteer group. Our research is unique in that it is a comparison between an unmanaged restoration site and an actively managed area along the same creek. Our project takes into account the historical land use changes within the area to provide context on how plant communities have been impacted. We found that the unmanaged Lobos Creek restoration site has reduced the presence of invasive species, in comparison to the managed and unrestored upstream portions of the creek.

The San Clemente Dam on the Carmel River was removed in 2015 . We analyzed the grain size distribution changes on the river on one site upstream and six sites downstream of the damsite, as part of an ongoing study monitoring a total of 10 sites since 2013 (East et al., 2023). Trends from this data indicate that the geomorphic changes observed downstream of the dam are predominantly dependent on high flows. This study contributes to field data collection and analyzes fresh pebble count data for 2023 from one control reach above the dam removal and six reaches downstream of the removal. Given that the Carmel River had a peak flow of 11,000 CFS during the 2022-2023 winter, pebble counts from 2023 offer the opportunity to continue studying the stream system’s geomorphic response to high flows. To study spawning gravel availability, we applied the criteria of Smith et al (2021), who used grains within 32mm and 90mm to study spawning gravel abundance, then calculated the average percent of spawning gravel at each reach. We used the same analysis method to assess changes in fines and cobbles, where in this study cobbles are more accurately the grains that are too large to be productive spawning gravel according to Smith et al. (2021)’s analysis. Fines are classified as grains less than 2mm from Wentworth (1922) and cobbles as sediment greater than 64 mm. However, for the purpose of this study, we have considered cobbles as grain sizes too large to contribute to the spawning gravel range of 32mm to 90 mm according to Smith et al. (2021). Therefore, we have calculated cobbles as greater than 90mm, but acknowledge that cobbles are defined as sediment greater than 64mm by Wentworth (1922). Downstream of the dam, the average percent spawning gravel increased in four of the six reaches, average percent fines decreased for four of the six reaches, and average percent cobble increased in two reaches, decreased in the three, and showed no change in two reaches. At the control reach site, the percent spawning gravel decreased slightly, the percent fines decreased, and the percent cobble increased significantly. We found that the high flows of the past year coincided with an average increase in sediment size across reaches downstream of the dam. While percent spawning gravel increased, we were not confident in drawing conclusions about the effect of this year’s high flows on spawning gravel.

The current interest in "multibenefit projects" that balance ecology, flood control, and social use in urban rivers makes developing sound theory and methods for social assessments of urban rivers a pressing concern. "Social connectivity" is one theoretical approach to assessing the relationship between the social use and physical condition of rivers. In this study we apply a social connectivity analysis to the American River Parkway in Sacramento, California. We combined observations of channel form with in person counts of users and activities, interviews with users, and reviews of planning documents to conduct a post project assessment of some of the major goals and use assumptions that informed the planning of the Parkway. We found that channel form and access to the river largely drove use patterns, many uses were quotidian and conventional but the largest user groups were there for special occasions, and that users viewed the Parkway positively but had low awareness of flood control and modifications to the hydrology. The results may be relevant to planners or researchers studying urban rivers and their use as public spaces.