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.

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.

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.

A riparian vegetation simulation module (RVSM) was developed to predict spatially-explicit seed germination, seedling establishment, plant growth and mortality in response to riverine hydrological conditions. The RVSM was integrated into a hydraulic model HEC-RAS and a simplified groundwater model for simulating the interactions between flow and riparian vegetation. The HEC-RAS – RVSM system was applied to the Sacramento River reach to evaluate its capability. River hydraulics, groundwater level and five vegetation types of the study reach were simulated for an 8-year period from 1999 to 2007. The HEC-RAS flow and groundwater were calibrated using observed river stage and groundwater level data at two sites in 2005. Cottonwood seedling density and elevation collected at point bars of River mile (RM) 192.5 and RM183 in 2005 and 2006 were used to calibrate key parameters of vegetation simulation. Two sets of vegetation mapping dated in 1999 and 2007 were used to assign initial conditions and to evaluate the performance of vegetation model. Model results demonstrate that the HEC-RAS – RVSM system successfully reproduced the vegetation area increase of cottonwood, riparian shrub, invasive species and grass as well as the area decrease in mixed forest over the 8-year period.

To quantify the flow resistance for riparian vegetation of channels and floodplains, a large number of equations have been proposed in the past half century based on theoretical derivation or lab experiments. However, only few of them were applied to one-dimensional (1D) numerical modeling of river hydraulics and sediment transport. In this study, eleven methods to compute vegetation-induced roughness were gathered from the literature. The change of Manning’s n for vegetation with the increase of flow depth from zero to threefold of plant height was calculated and compared among these methods to check the feasibility of adding them into hydraulic model. Next, all the methods were incorporated into a 1D hydraulic model HEC-RAS to automatically compute dynamic Manning’s n for vegetation based on vegetation properties and flow conditions instead of using user-defined values. The enhanced HEC-RAS was applied to a reach of the San Joaquin River to compute spatially explicit and temporally dynamic roughness coefficients under six flow conditions using vegetation data from field survey and GIS vegetation mapping. The HEC-RAS model of this reach was calibrated with observed river stage profiles and hydrograph in 2011, and validated with observed hydrograph in 2017.

In 2002 the City of Laguna Niguel embarked on a journey to address the ongoing degradation of the City’s surface water quality through restoration of a degraded stream to native wetland, riparian, and upland habitats through the center of an urban area.  Through a State Proposition 13 grant, a State Coastal Conservancy grant, a State Urban Streams Restoration grant, a Federal Section 206 cost-share with the United States Army corps of Engineers, and partnerships with the local Homeowners Associations and the County of Orange, the City has successfully planned and installed over 2.5 miles of restoration along a semi-contiguous portion of Sulphur Creek located in the Aliso Creek Watershed. The restoration effort was divided into two projects referred to as Upper Sulphur Creek and Middle Sulphur Creek. Specific restoration goals identified during the planning process for both projects included (1) restoring hydrologic processes including water storage, stream stability, and energy dissipation; (2) restoring biogeochemical functions including nutrient cycling, nutrient availability, and sediment deposition; and (3) restoring biologic functions including native wetland and riparian vegetation, plant and animal movement and dispersal, biomass production, and native plant and animal diversity.