Tools to quantify urban stormwater load reduction from SEZ restoration actions
SNPLMA Research Proposal: Round 11
Theme 2C. Quantifying the effects of actions to reduce sediment loads using Stream Environment Zones (SEZs)
October 27, 2010
Principal Investigator:
Nicole Beck, PhD, 2NDNATURE LLC, nbeck@2ndnaturellc.com
500 Seabright Ave, Suite 205
Santa Cruz CA 95062 Tel: 831.426.9119 Fax: 831.426.7092
Research Collaborators: Brent Wolfe, Northwest Hydraulic Consultants; bwolfe@nhcweb.com
Matt Kiesse, River Run, mkiesse@hughes.net
Catherine Rihimaki, Drew University, criihimaki@drew.edu
Jeremy Sokulsky, Environmental Incentives jsokulsky@enviroincentives.com
Grant Contact:
Krista McDonald, 2NDNATURE LLC, krista@2ndnaturellc.com, p 831.426.9119
Total Funding Requested: $329,601.01
Total Cost Share:
$65,000 - 90,000
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Santa Cruz, California 95062
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Proposal: Tahoe Research Supported by SNPLMA Round 11 Theme 2c: Quantifying the effects of actions to reduce sediment loads using Stream Environment Zones (SEZs) p. 1 II. Proposal Narrative A. ABSTRACT This research will develop a Tahoe Basin‐wide estimate of the potential load reductions from two types of stream environment zone (SEZ) improvements: 1) improving floodplain connectivity through stream restoration of perennial systems, and 2) increasing the function of SEZs that receive direct urban stormwater to retain water and intercept pollutants before entering perennial streams. Collectively, these estimates will provide a comparable load reduction opportunity analysis of the feasible pollutant load reductions achievable via functional stream and SEZ restoration actions in the Tahoe Basin. Basin‐wide estimates will be conducted using the integration of outputs derived from a spatially explicit USGS modeling platform (SPARROW), the Pollutant Load Reduction Model (nhc et al. 2009) and the Stream Load Reduction Tool (2NDNATURE 2010). SPARROW will be employed for the Tahoe Basin, calibrated and validated using the wide array of existing land use, hydrologic and water quality data from a selection of watersheds. The estimation methods will be validated to the extent possible on site‐specific stream and SEZ test sites, and used to inform a methodology to provide researchers and stormwater engineers with a consistent and relatively accurate method to estimate the pollutant load reductions from specific SEZ improvement projects. Available research will be analyzed to evaluate the feasibility and validity of approximating the urban derived pollutant loading to the upstream boundary of a stream restoration project, as well as the urban pollutant fraction retained. This research builds on existing models, datasets and past and ongoing SNPLMA‐funded efforts by the 2NDNATURE team, leverages existing datasets, methods and models in a manner consistent with the TMDL Pollutant Reduction Opportunity analysis (LRWQCB and NDEP 2008), and is directly applicable to the Lake Clarity Crediting Program (LRWQCB and NDEP 2009). B. JUSTIFICATION STATEMENT Resource managers need tools to quantify the water quality benefits of SEZ restoration efforts in a manner comparable and consistent with the stormwater quality load reduction tools that have been developed to support the Lake Tahoe TMDL (LRWQCB and NDEP 2010) and Crediting Program (LRWQCB and NDEP 2009). It is assumed that SEZ restorations may result in substantial removal of urban pollutants of concern, particularly fine sediment particles (FSP < 16µm), yet the Crediting Program cannot comprehensively account for SEZ pollutant reductions without such tools. The priority management needs with respect to how Tahoe Basin SEZ restoration can contribute to the TMDL goals are listed below. The 2NDNATURE proposed research will begin to address each of these needs by incorporating best available data and information, leveraging existing models and methods, and building upon existing research. Priority management needs: 1) A reasonable Basin‐wide estimate of the potentially achievable total load reductions from intensive SEZ functional restoration that is comparable and augments the Pollutant Reduction Opportunity analysis conducted for Phase II of the TMDL (2NDNATURE and nhc, 2010a; see Table 1). 2) A reliable methodology to estimate the pollutant load reductions achieved by routing of an urban catchment outfall to an intercepting SEZ. An intercepting SEZ is defined as a peripheral edge of a meadow or other undisturbed land that meets the TRPA definition of an SEZ and is hydrologically connected to and accepts stormwater runoff from an urban catchment. 3) A reliable methodology to estimate the average annual pollutant load delivered to and reduced by site specific stream restoration projects that accept a mix of urban and non‐urban pollutants. In order to provide an accurate quantification of the actual pollutant load reduction of a specific SEZ restoration effort, many years of high resolution data upstream and downstream of the restoration actions would be required both pre‐ and post‐ restoration. However, this data is costly, time consuming and difficult to obtain reliably. In lieu of extensive site‐
specific data collection, the research team believes that existing research and datasets can be integrated with key geomorphic and physical characteristics of an SEZ or stream reach and associated floodplain to provide a methodology from which managers can obtain a reasonable estimate of the water quality benefits of routing stormwater to SEZs or stream 2NDNATURE, LLC
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Proposal: Tahoe Research Supported by SNPLMA Round 11 Theme 2c: Quantifying the effects of actions to reduce sediment loads using Stream Environment Zones (SEZs) p. 2 restoration efforts. In order for these methods to be useful to managers, the estimates and outputs of the pollutant load reductions should be consistent with the existing pollutant reduction estimation tools that support the Crediting Program. The 2NDNATURE team provides this synergy with our collective expertise in fluvial restoration actions that continue to occur in the Tahoe Basin (2NDNATURE 2010b), our past and current research to align data collection with method development to quantify fine sediment load reductions from SEZ/stream restoration efforts (2NDANTURE 2006a, 2NDNATURE 2010a), and our intimate involvement in the development and adaptive management of the Tahoe TMDL stormwater tools and associated Crediting Program (LRWQCB and NDEP 2009, nhc et al. 2009, 2NDNATURE et al. 2010b, 2NDNATURE et al. 2009). C. BACKGROUND AND PROBLEM STATEMENT The Lake Tahoe TMDL segregates potential sources of the pollutants of concern impairing Lake Clarity (fine sediment particles (FSP) <16µm, total nitrogen and total phosphorus) into 5 source category groups (urban/groundwater, atmospheric, forested upland, stream channel erosion, and shoreline erosion). The Lake Tahoe TMDL Technical Report (LRWQCB and NDEP 2010) estimates that urban areas are responsible for approximately 72% and streams are responsible for 8%, of the average annual FSP loading to Lake Tahoe. In an effort to define achievable future load reductions and a general lake clarity restoration strategy, the TMDL identified and quantified the pollutant control opportunities from each of the source category groups using a series of assumptions and available existing data. The Pollutant Reduction Opportunities Report (LRWQCB and NDEP 2008) quantified the Basin‐wide potential load reduction opportunities and associated costs for each source category group and results are summarized in Table 1. The results of these analyses indicated significant load reductions from urban areas are achievable and are a feasible means to reduce pollutant loads (33% basin‐wide fine sediment particles in the next 15 years, and 66% long‐term) necessary to restore lake clarity. The urban load reduction estimates in Table 1 are based on a significant increase in current urban water quality improvement efforts. These pollutant load reduction strategies include pollutant source controls (PSC) to reduce the amount of FSP generated on and available for transport from roads, commercial and residential lands; increased hydrologic source controls (HSC) to reduce stormwater volume generation including residential BMP implementation; and increased spatial distribution and effectiveness of centralized stormwater treatment BMPs (SWT). Currently, the Crediting Program (LRWQCB and NDEP 2009) limits jurisdictional credit awards to water quality improvement actions that treat stormwater from urban areas. These previous TMDL analyses made a simplifying assumption to separate urban loading and stream systems. Thus, all urban loading reaching surface waters is assumed to reach the lake. While it is appropriate for the TMDL Technical Report source analysis to separate and isolate stream bank channel erosion from other sources, the Pollutant Reduction Opportunity analysis misses the load reduction potential from intercepting SEZ and stream restoration actions that are known to increase water and sediment retention. The proposed 2NDNATURE team research will fill the information gap by providing a comparable estimate of the load reduction benefits and relative costs of intercepting and retaining pollutants via functional SEZs throughout the Tahoe Basin (see Table 1). SEZs appear to provide significant opportunity to supplement load reductions from urban source control and treatment systems. Typical centralized stormwater treatment BMPs (SWTs) that are constructed to accept and treat stormwater from public and private lands (e.g., dry basins, wet basins, cartridge filters, bed filters, etc.) usually do not exceed 1 acre in size, nor do treatment volume capacities typically exceed 1.5 acre‐
feet of water. Additionally, the remaining public land required to construct new SWTs in urban areas is limited, thus increasing the cost of future SWT implementation. In contrast, SEZs can be a few to hundreds of acres in size, require less continued maintenance than urban stormwater treatment structures to maintain water quality performance, and result in improvements to a number of Beneficial Uses and TRPA thresholds, including habitat, recreational, aquatic and wildlife resources. The 2NDNATURE team is currently developing a data‐validated methodology (i.e., SLRT) to quantify the pollutant load reductions achieved by the Trout Creek restoration project with SNPLMA Round 9 research funding (2NDNATURE 2010a). The SLRT end product will include 3 potential methodologies at varying levels of rigor and required datasets to estimate the average annual total and fine sediment load reductions associated with stream restoration efforts. However, there are three areas where the SLRT methodology would need to be expanded to meet the broader needs of managers to estimate load reductions of any SEZ interception and/or restoration project. 2NDNATURE, LLC
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Proposal: Tahoe Research Supported by SNPLMA Round 11 Theme 2c: Quantifying the effects of actions to reduce sediment loads using Stream Environment Zones (SEZs) p. 3 First, the Trout Creek restoration contains the greatest amount of applicable geomorphic, water quality and hydrologic data of any likely stream reach in the Tahoe Basin. The SLRT methods at the completion of the Round 9 research (expected Fall 2011) will not include a recommended and consistent approach to estimate the hydrology and pollutant loading to the upstream boundary of a stream restoration reach where an adequate long‐term dataset does not currently exist. A method to apply available datasets within the Tahoe Basin to estimate the volume and pollutant loading to the upstream boundary of a stream restoration project is a critical component and would be defined using the SNPLMA Round 11 resources requested herein. This would allow the development of a complete methodology to estimate the average annual load reductions of any stream restoration project in the Tahoe Basin applicable to the TMDL. Second, the SLRT input and modeling parameters will be developed and calibrated using high resolution water quality data from Trout Creek, a 97‐acre SEZ restoration effort, however, the inputs and computations are hypothesized to be directly applicable to any scale fluvial system. Using the SNPLMA Round 11 resources, the SLRT methodology will be refined and scaled for testing on smaller scale SEZs that accept 100% urban runoff to provide a recommended method to quantify urban load reductions from SEZs in these instances. Data obtained during this research will be used to provide preliminary testing, but it is likely that long‐term datasets will be necessary to validate and test these methods over time. The method development to estimate intercepting SEZ pollutant load reduction benefit would include the integration of PLRM hydrologic and water quality outputs as inputs to the upstream boundary of the SEZ in question. The final problem is that Tahoe Basin managers have a desire for a consistent methodology to determine the urban derived pollutant loads delivered to, and retained by, restored steam reaches and their associated floodplains. The 2NDNATURE team under this grant will conduct isolated statistical analyses on targeted watersheds with the most comprehensive water quality datasets using SPARROW and PLRM models to determine if watershed attributes may be powerful predictors of relative pollutant loading. However, the existing fine sediment particle or appropriate proxy data in Tahoe Basin stream systems is severely limited and makes our confidence in the results for FSP (the primary pollutant of concern) or the ability to validate other potential methods to separate urban and non urban loading relatively low. Similarly, the ability to differentiate SEZ removal capabilities for urban and non‐urban pollutants is significantly challenging given available data. However, based on existing datasets and knowledge gained from the research herein, the research team will provide a feasibility assessment as well as our impression of the necessary data required to provide a reasonable method to managers in the future. D. GOAL, OBJECTIVES, HYPOTHESES Goal 1. Develop a Tahoe Basin‐wide estimate of pollutant load reduction potential from stream and SEZ restoration that will augment the Pollutant Reduction Opportunity analysis completed for the TMDL. Goal 2. Provide a load reduction estimation approach to quantify load reductions from specific SEZs restoration projects of all potential sizes in the Tahoe Basin given available data and models. Objective 1. Refine and provide preliminary testing of the application of the SLRT parameters to estimate the urban pollutant load reductions of a small‐scale SEZ that accepts 100% urban runoff, and integrate with PLRM outputs to create an intercepting SEZ load reduction module. Objective 2. Evaluate the statistical power of watershed attributes to predict pollutant loading to specific stream locations using existing spatial, hydrologic and water quality data. Hypothesis 1. Spatially explicit modeling tools can improve the power and application of existing datasets and inform a watershed‐based approach to quantify the pollutant load reductions as a result of SEZ functional improvements at all scales. Hypothesis 2. The SLRT methodology is directly applicable and can be refined to provide reasonable and defensible estimates of pollutant load reductions achieved for all potential scales of SEZs that exist in the Tahoe Basin. 2NDNATURE, LLC
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Proposal: Tahoe Research Supported by SNPLMA Round 11 Theme 2c: Quantifying the effects of actions to reduce sediment loads using Stream Environment Zones (SEZs) p. 4 E. APPROACH, METHODOLOGY AND LOCATION OF RESEARCH LOCATION OF RESEARCH The potentially achievable load reduction estimate as a result of extensive SEZ restoration will be completed on the Tahoe Basin scale and directly comparable to other Phase II TMDL estimates (LRWQCB and NDEP 2010; see Table 1). Tangible SEZ examples will be used to develop, test and refine the specific SEZ pollutant load reduction methodology. Building upon past and current fluvial research efforts by the 2NDNATURE team, two site‐scale examples of stream restoration projects will be characterized and the load reduction potential as a result of past or planned restoration efforts will be quantified using the methods developed. Potential sites include a segment of the planned restoration by CA State Parks on the Upper Truckee River Golf Course Reach, or segments of the completed Cookhouse Meadow, Third Creek, or other completed restoration efforts where adequate and available pre‐project geomorphic and physical datasets exist. Two or three intercepting SEZ sites currently accepting direct runoff from urban catchment outlets will also be analyzed. These intercepting sites will be selected to collectively represent a range of existing functionality. APPROACH The SNPLMA Round 11 resources will be used to provide 1) a basin‐scale SEZ Pollutant Reduction Opportunity analysis should wide‐spread feasible SEZ functional restoration actions be implemented and 2) develop an approach to estimate the annual average pollutant load reductions from the expected scales of SEZ restoration efforts conducted in the Tahoe Basin. The Basin‐scale analysis will rely upon existing sub‐basin loading estimates from the Lake Tahoe Watershed Model, available spatially explicit datasets, and past and ongoing research on the link between SEZ function and expected load reductions. The Basin‐scale SEZ pollutant load reduction opportunity analysis will require a number of simplifying assumptions and larger scale analyses, similar to the urban/groundwater source category group approach to Phase II of the TMDL (LRWQCB and NDEP 2010). Cost estimates will be generated to provide a comparable cost/benefit analysis of extensive functional SEZ restoration in the Tahoe Basin. All assumptions and methods will be documented and the results will be directly comparable to the estimates provided in Table 1. The development of a reasonable, repeatable and reliable toolbox that quantify project‐specific stream and SEZ restoration water quality benefits on an average annual basis will be based on past and ongoing research of existing datasets in combination with the key attributes of functional stream/meadow/SEZ systems. Figure 1 summarizes potential integration of existing tools and models. The recommended methodology will include an approach to estimate hydrology and pollutant loads at the upstream boundary of the SEZ/stream reach of interest. Should the upstream boundary be an urban catchment outfall, the methodology will recommend the use of PLRM to obtain hydrology and pollutant loading. If the catchment is mixed land use SPARROW outputs may be used to inform methods to estimate hydrology and pollutant loading in the instances where local long‐term datasets may not exist (see Figure 1). Typical SEZ restoration includes geomorphic modifications to oversized channels within an SEZ to increase the likelihood of inundating floodplain areas adjacent to the stream channel, allowing deposition of sediment on the floodplain and decreasing in‐channel shear stress that drives sediment generation via channel erosion. The SLRT approach models these geomorphic and physical concepts and we believe it is potentially applicable on all SEZ scales. The research team will refine and apply the SLRT parameters and approach such that a preliminary methodology will be developed to provide site‐specific estimates of pollutant load reductions for all potential sizes of SEZs encountered in the Tahoe Basin (Figure 1). METHODOLOGY The three technical components to the proposed research are discussed below. Spatially explicit model development. The research team will apply the USGS SPARROW (SPAtially Referenced Regressions On Watershed Attributes) model (http://water.usgs.gov/nawqa/sparrow/) and test if SPARROW can be sufficiently calibrated regionally using these existing data sources to provide reliable regressions between watershed attributes and pollutant loading. SPARROW integrates monitoring data with land use and other watershed attributes in a hybrid process‐
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Proposal: Tahoe Research Supported by SNPLMA Round 11 Theme 2c: Quantifying the effects of actions to reduce sediment loads using Stream Environment Zones (SEZs) p. 5 based and statistical modeling approach for a spatially explicit estimation of pollutant sources and contaminant transport. The platform provides an ideal opportunity to apply the extensive USGS Lake Tahoe Interagency Monitoring Program (LTIMP) stream hydrology and water quality dataset, existing stream FSP and turbidity water quality data (2NDNATURE 2010a, S. Andrews, pers. comm.), existing digital elevation and stream spatial data, the TRPA and TMDL land use spatial data, the USFS/TRPA existing SEZ GIS layers or maps, etc. SPARROW preserves the connectivity of a stream network and prioritizes watershed attributes that are expected to influence downslope water quality to provide simulations on annual time scales. It can calculate loading at any point on the landscape, allowing the users to investigate linkages between pollutant loads and watershed attributes such as land use type, land use relative condition, soil type, slope, proximity to stream, and land management changes. SPARROW is substantially less complex than more deterministic, process‐based models such as LSPC C++ (Lake Tahoe Watershed Model), SWMM or other high resolution hydrologic routing platforms that may require substantial subjective decisions on the part of the user during model calibration. The non‐linear parameter estimation procedure employed by the model uses relationships between measured water quality data and hydrogeologic properties (e.g., precipitation, topography, vegetation, soils, water routing) and ensures that the calibrated model will not be more complex than can be supported by the data available. This provides an objective statistical approach for evaluating alternative hypotheses about priority contaminant sources and controlling transport processes over large spatial scales in watersheds (Schwartz et al. 2006). We believe less complex modeling approaches, such as SPARROW, that focus on the most sensitive parameters have a strong advantage for applications intended for use by natural resource managers since the parameters are physically interpretable and predictive uncertainty can be quantified. The outputs are not expected to replace the estimates or value of the other existing models (notably the Lake Tahoe Watershed Model or PLRM) by any means. Rather, it may complement the others by filling in gaps where they are lacking (i.e., usability, spatial scalability, etc.). The outputs from SPARROW will be compared to other modeling estimates of sediment species loading on both catchment and Tahoe Basin scale to evaluate consistency and reasonableness of results. Given the limited amount of FSP data obtained at USGS gage sites relative to the extensive hydrology and TSS datasets, available FSP and turbidity data from relatively recent monitoring of SEZ systems will be used as proxies for FSP by defining empirical relationships between the pollutants (Figure 2). Quantifying SEZ potential load reduction opportunity; Basin Scale. The Basin‐wide estimate will include all scales of potential SEZs within the Tahoe Basin. The effort required to develop and implement the SPARROW model on the Tahoe Basin scale is not expected to require significant resources since the majority of necessary spatial, hydrologic and water quality data already exist, with the exception of a well‐accepted SEZ GIS layer. Existing SEZ GIS layers for the Tahoe Basin will be obtained from local agencies and augmented with aerial photography as necessary and all assumptions of mapping will be documented. The condition of the each SEZ polygon will be characterized as functional, moderate or degraded as of 2004 based on any existing condition assessments; the personal knowledge of team members; the inventory of Tahoe Basin SEZ restoration projects completed as of 2009 (2NDNATURE 2010b: Appendix A); interviews with Tahoe Basin SEZ restoration practitioners at USFS LTBMU, CA State Parks, CTC; and the existing or future inventory of SEZ conditions conducted by TRPA and SFEI (US EPA 104(b)(3) grant), etc. The SEZ pollutant load reduction opportunity analysis will be focused on SEZs with a high likelihood of accepting some fraction of urban runoff, based on watershed proximity of land uses and digital elevation models. Non‐urbanized areas of watersheds will likely not be evaluated in any specific detail in the Basin analysis. Assumptions regarding SEZ load contribution for SEZ condition categories per unit area of SEZ will be made using preliminary research from 2NDNATURE (2NDNATURE 2010a), UC Davis’ Steven Andrews and other sources. The load contributions will include the load reduction potential given assumptions regarding geomorphic form and floodplain characteristics of each SEZ condition category. The achievable conditions will include extensive, yet feasible, functional restoration of Tahoe SEZs. Based on the limitations of available water quality data, estimates will be made constrained to TSS and FSP achievable load reductions via extensive SEZ restoration. Watershed scale estimates will be calibrated on a selection of watersheds and other watersheds will be employed to validate model estimates. The areas of SEZ restoration and pollutant load reductions opportunities will be documented spatially and cost estimates will be developed, based on reasonable assumptions, to estimate the total annualized costs to achieve the estimated load reductions via intensive SEZ restoration. All methods, assumptions and limitations will be documented and the Basin‐wide evaluation will be a much broader scale analysis than the site‐specific SEZ load reduction methodology development described below. Methodology to estimate intercepting SEZ pollutant load reductions. The goal of a stream load reduction tool (2NDNATURE 2010a) is to create a repeatable yet cost‐effective methodology to estimate the average annual pollutant load at the downstream reach of a stream restoration project for both pre‐ and post‐restoration conditions. Water quality 2NDNATURE, LLC
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Proposal: Tahoe Research Supported by SNPLMA Round 11 Theme 2c: Quantifying the effects of actions to reduce sediment loads using Stream Environment Zones (SEZs) p. 6 effectiveness of a stream restoration project (defined as the expected pollutant load reduction as a result of restoration actions) can be assessed as a function of 1) the storage of pollutants that would otherwise have reached downstream areas (floodplain deposition) and 2) the reduction in pollutant generation via stability of the stream banks that would otherwise have eroded (Figure 3). Thus, the SLRT will allow for a load reduction estimate of a stream restoration effort by determining the expected difference in pollutant loading pre‐ and post‐restoration actions. The stream load reduction tool (2NDNATURE 2010a) integrates functional geomorphic and physical characteristics of a stream and associated meadow with sediment transport processes to estimate the pollutant load reduction as a result of specific site restoration actions. On‐going floodplain pollutant retention research on select Tahoe Basin streams suggests overbank flow events do provide FSP retention and concentration reductions via settling, adherence to vegetation, flocculation and stranding (S. Andrews, pers. comm., 2NDNATURE 2006, 2NDNATURE 2010a). The 2NDNATURE team is obtaining detailed site‐specific floodplain retention data and site constrained continuous sediment loading at the upstream and downstream boundary for Trout Creek for 2010 and 2011 snowmelt events in order to inform reasonable retention coefficients for pollutants that access the floodplain (Figure 4). The reduction in channel‐derived sediment as a result of restoration can be estimated using a number of methods that range in complexity and the amount of required data. Figure 5 summarizes the concepts associated with estimating channel sediment generation, and SLRT methodologies will lend from existing models implemented in the Tahoe Basin including Bank Stability and Toe Erosion Model (BSTEM), which calculates erosion rates for particular discharge conditions, and CONservational Channel Evolution and Pollutant Transport System (CONCEPTS), a data intensive channel erosion model. The SLRT development, implementation and analysis funded by SNPLMA Round 9 will be completed in Fall 2011. The outcome from the SLRT effort will be 3 empirically supported methodologies that have a range of complexity and data input requirements to estimate the average annual pollutant load reduction from a stream restoration project given available hydrologic and pollutant loading datasets. The more complex approaches will be used to validate estimates using the simple approaches. SLRT estimates the expected difference in pollutant loading pre‐ and post‐restoration actions based on changes to specific attributes of geomorphic form and floodplain characteristics that are key to achieving volume and pollutant retention. In the instance of an intercepting SEZ whose catchment is 100% urban, the average annual volume and pollutant loading will be generated using PLRM. The research team will use Round 11 funds to apply and scale these physical and geomorphic concepts to develop a methodology to estimate the load reductions achieved by routing an urban drainage outfall to an intercepting SEZ while preserving the geomorphic concepts applicable to smaller sized SEZ systems. The methodology will be applied to the 2‐3 example intercepting SEZ’s selected to demonstrate application and outputs. Cost‐effective site surveys, hydrologic and water quality data will be collected from the sites as necessary to test assumptions and provide preliminary validation of the applicability of SLRT to intercepting SEZs. The data collection will be scaled based on available resources. The SEZ pollutant load reduction estimates will be limited to total and fine sediment reductions, but future effort could augment these methods with nutrients as desired. F. RELATIONSHIP OF RESEARCH TO CURRENT EFFORTS As outlined in the approach, this proposed research will significantly leverage and utilize a wide array of existing datasets. In addition, the proposed research will inform and/or build upon the following Tahoe Basin efforts: • Stream Load Reduction Tool development (2NDNATURE 2010a) • Riparian Ecosystem Restoration Effectiveness Framework (2NDNATURE et al 2010b) • Methodology to Predict Total and Fine Sediment Load Reductions as a Result of Channel Restoration in Tahoe Streams (2NDNATURE et al 2010) • Pollutant Load Reduction Model (nhc et al. 2009) • Pollutant Load Reduction Opportunity Report (LRWQCB and NDEP 2008) • Lake Tahoe Total Daily Maximum Load (LRWQCB and NDEP 2010) • Lake Clarity Crediting Program (LRWQCB and NDEP 2009) • Lake Tahoe TMDL Accounting & Tracking Tool (ACOE 2009) G. ENGAGING MANAGERS A technical advisory committee (TAC) will be assembled and include stream restoration practitioners, jurisdictional stormwater managers, regulators and technical reviewers. The TAC will be called upon to review and comment on draft 2NDNATURE, LLC
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Proposal: Tahoe Research Supported by SNPLMA Round 11 Theme 2c: Quantifying the effects of actions to reduce sediment loads using Stream Environment Zones (SEZs) p. 7 products at 3 critical milestones of the project (see task descriptions below). The research team will compile and review existing datasets to refine our proposed Research Strategy to meet the two goals of this research. The TAC will be convened to review, comment and reach agreement on the most feasible approach and expected products based on the collective needs and available resources. The addition of Environmental Incentives (the lead developer of the Crediting Program (LRWQCB and NDEP 2009)) will ensure the manager’s technical needs related to the TMDL will be addressed from this research. H. DELIVERABLES/PRODUCTS Task 1 Deliverable: Data collection and data management for hydrologic modeling applications Task 1 includes the collection and management of any and all existing monitoring, land and SEZ condition, modeling and/or spatial datasets necessary to achieve the objectives of this research. These data will be compiled and managed to facilitate use in the SPARROW model, but will also be useful for any future spatial modeling applications. Any field data collection, SEZ surveys and other specific data collection necessary to meet the goals of this research will be completed given existing resources. Task 2 Deliverable: Research Strategy Following the compilation and evaluation of existing datasets, model outputs, maps, GIS, water quality data, etc. the research team will draft a detailed research strategy on how to best meet both the research goals and management needs given available resources. The TAC will be convened to collectively prioritize and approve the detailed research strategy to be implemented by the 2NDNATURE team. Task 3 Deliverable: Basin‐wide SEZ load reduction opportunity analysis Based on the approach and methodology outlined herein, the existing datasets and model platform will be used to generate reasonable estimates of the potential pollutant load reduction achievable by extensive restoration of SEZs in the Tahoe Basin. Cost estimates will be developed for the implementation of SEZ restoration and documented in the analysis to provide cost/benefit comparisons. All terms, methods, references and assumptions will be documented in detail. The final products will provide a comparable quantitative estimate to the existing Phase II PRO tiered estimates (LRWQCB and NDEP 2008) that will be scaled based on the spatial and feasible opportunities for SEZ restoration. The TAC will review and provide feedback on the draft analysis. Task 4. Deliverable: Technical Reporting of recommended methods Based on the approach and methodology outlined herein, the 2NDNATURE team will provide recommended methods to estimate: 1) Pollutant load reductions expected from stream restoration projects, 2) Load reduction benefits associated with the interception of urban stormwater outfalls to SEZs and 3) Additional load reduction benefits if a degraded intercepting SEZ is restored. The methods will include necessary site‐specific data collection and reporting metrics to document pre‐ and post‐restoration physical and geomorphic characteristics of a specific stream or SEZ. The methods will also include recommendations for utilizing available data to determine site hydrology and sediment loading for the upstream boundaries of stream restoration efforts where rich long‐term datasets may not be available. In the instance where the upstream boundary of an SEZ can be modeled using PLRM, the methods will include how PLRM outputs are used as inputs to quantify the SEZ load reduction benefit. The methods will be demonstrated using the selected example stream and SEZ sites. The technical document will summarize the existing data, methods, justification, assumptions as well as identify recommended next steps, limitations and priority data gaps. The TAC will review and provide feedback on the draft analysis. 2NDNATURE, LLC
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Proposal: Tahoe Research Supported by SNPLMA Round 11 Theme 2c: Quantifying the effects of actions to reduce sediment loads using Stream Environment Zones (SEZs) III. Schedule Milestone Task 1 Compile and manage existing data. Select and conduct field analysis of example SEZ sites as necessary. Task 2.1 Develop Research Strategy TAC Meeting #1: Review, prioritize and approve strategy Task 2.2 Draft Basin‐wide SEZ Pollutant Reduction Opportunity analysis TAC Meeting #2: Review Task 1 results and Draft of Task 2 Task 2.3 Final Basin‐wide SEZ load reduction opportunity analysis Task 3.1 Develop draft methodology to estimate the load reduction benefits of SEZ interception and/or stream restoration projects. Task 3.2 Draft Technical Report TAC Meeting #3: Review Draft of Task 3 Task 3.3 Final Technical Report End Date July 11 July 12 July 11 Oct 11 Nov 11 Nov 11 June 12 July 12 July 12 Aug 12 Nov 11 Oct 12 Oct 12 Jan 13 Feb 13 Feb 13 May 13 2NDNATURE, LLC
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p. 8 Proposal: Tahoe Research Supported by SNPLMA Round 11 Theme 2c: Quantifying the effects of actions to reduce sediment loads using Stream Environment Zones (SEZs) p. 9 IV. Literature cited/References 2NDNATURE. 2006a. CSLT Upper Truckee River Sediment Monitoring: Middle Reach (2002‐2005). Prepared for the City of South Lake Tahoe. March 2006. ftp://www.2ndnaturellc.com/2ndnature/2NDNATURE_Reports/Lake%20Tahoe/UTRSedimentStudy_FinalReport.pdf 2NDNATURE. 2006b. Detention Basin Treatment of Hydrocarbon Compounds in Urban Stormwater. Final Technical Report. Prepared for South Lake Tahoe Public Utility District. March 2006. ftp://www.2ndnaturellc.com/2ndnature/2NDNATURE_Reports/Lake%20Tahoe/Detention%20Basin%20Treatment%20of%2
0Hydrocarbon%20Compounds%20in%20Urban%20Stormwater%202006.pdf 2NDNATURE. 2008. Water Quality Performance Evaluation of Park Avenue Detention Basins; South Lake Tahoe,CA. Final Technical Report. Prepared for City of South Lake Tahoe Engineering Division. August 2008. ftp://www.2ndnaturellc.com/2ndnature/2NDNATURE_Reports/Lake%20Tahoe/Water%20Quality%20Performance%20Eval
uations%20of%20Park%20Ave%20Detention%20Basins%202008.pdf 2NDNATURE. 2010a. Quantification and Characterization of Trout Creek Restoration Effectiveness; Focused Development of a Stream Load Reduction Methodology (SLRT). Prepared for the USFS, Lake Tahoe Basin Management Unit. April 2010 ftp://www.2ndnaturellc.com/2ndnature/2NDNATURE_Reports/Lake%20Tahoe/SLRT_Trout%20ChPlan_Final%20April%202
010.pdf 2NDNATURE. 2010b. Riparian Ecosystem Restoration Framework; Tracking the Benefits of Stream and Floodplain Restoration in the Lake Tahoe Basin. Prepared for the USFS, Lake Tahoe Basin Management Unit. January 2010 ftp://www.2ndnaturellc.com/2ndnature/2NDNATURE_Reports/Lake%20Tahoe/Riparian%20Ecosystem%20Restoration%20
Framework__FINAL.pdf 2NDNATURE and Northwest Hydraulic Consultants (nhc). 2010a. PLRM Refinement Monitoring: Phase II. Final Monitoring Plan. Prepared for USFS Lake Tahoe Basin Management Unit. July 2010. ftp://2ndnaturellc.com/2ndnature/2NDNATURE_Reports/Lake%20Tahoe/PLRMRefinement_FinalPhaseII_MonitoringPlan.p
df 2NDNATURE and nhc. 2010b. PLRM, Focused Stormwater Monitoring to Validate Water Quality Source Control and Treatment Assumptions. Final Technical Report. Prepared for US Army Corps of Engineers, Sacramento District. March 2010. ftp://2ndnaturellc.com/2ndnature/2NDNATURE_Reports/Lake%20Tahoe/PLRM%20Refinement_FinalPhaseI_TechnicalRepo
rt.pdf 2NDNATURE and nhc. 2011. PLRM Refinement Monitoring: Phase II. Final Technical Report. Prepared for USFS Lake Tahoe Basin Management Unit. Expected December 2011. 2NDNATURE, nhc and Environmental Incentives (EI). 2009. BMP Maintenance Rapid Assessment Methodology (BMP RAM) Technical Document and Users Manual. Lake Tahoe, CA. Prepared for the Army Corps of Engineers. September, 2009 http://www.swrcb.ca.gov/rwqcb6/water_issues/programs/tmdl/lake_tahoe/ 2NDNATURE, nhc, and EI. 2010a. Pilot catchment scale testing of Lake Tahoe stormwater tools. Funded by the Army Corps of Engineers. Contract awarded September 2010. 2NDNATURE, LLC
500 Seabright Avenue Suite 205 Santa Cruz CA 95062 p 831.426.9119 w 2ndnaturellc.com
Proposal: Tahoe Research Supported by SNPLMA Round 11 Theme 2c: Quantifying the effects of actions to reduce sediment loads using Stream Environment Zones (SEZs) p. 10 2NDNATURE, nhc and EI. 2010b. Road Rapid Assessment Methodology (Road RAM) Technical Document and Users Manual, Tahoe Basin. Prepared for the California Tahoe Conservancy and Nevada Division of Environmental Protection. Expected November 2010. 2NDNATURE, nhc, and EI 2011. Placer County Stormwater TMDL Strategy. Final Technical Report. Prepared for Army Corps of Engineers and Placer County. Expected March 2011 US Army Corps of Engineers (ACOE). 2009. Lake Tahoe TMDL Tracking Tool is the accounting database tool used by urban jurisdictions and program managers to submit, approve and track catchment load reductions and associated credit schedules. Version 1 of the TMDL Tracking Tool was released by 2NDNATURE and Environmental Incentives in October 2009 and funded by the Army Corps of Engineers. Lahontan Regional Water Quality Control Board (LRWQCB) and Nevada Division of Environmental Protection (NDEP). 2008. Lake Tahoe TMDL Pollutant Reduction Opportunity Report. March 2008 http://www.waterboards.ca.gov/lahontan/water_issues/programs/tmdl/lake_tahoe/docs/presentations/pro_report_v2.pd
f LRWQCB and NDEP. 2009. Lake Clarity Crediting Program Handbook. Developed by Environmental Incentives. September 2009. http://www.swrcb.ca.gov/rwqcb6/water_issues/programs/tmdl/lake_tahoe/index.shtml LRWQCB and NDEP. 2010. Tahoe Basin Total Maximum Daily Load, Technical Report. California and Nevada. June 2010. http://www.swrcb.ca.gov/rwqcb6/water_issues/programs/tmdl/lake_tahoe/index.shtml nhc, Geosyntec Consultants, and 2NDNATURE. 2009. PLRM Model Development Document. Prepared for Lake Tahoe Basin Stormwater Quality Improvement Committee. South Lake Tahoe. CA. A complete Users Manual as well as full source code and other supporting documents can be downloaded from www.tiims.org. Schwarz, G.E., Hoos, A.B., Alexander, R.B., and Smith, R.A., 2006, The SPARROW Surface Water‐Quality Model Theory, Applications and User Documentation: U.S. Geological Survey, Techniques and Methods 6–B3, 248 p. and CD –ROM.
2NDNATURE, LLC
500 Seabright Avenue Suite 205 Santa Cruz CA 95062 p 831.426.9119 w 2ndnaturellc.com
Source
Category
Group
particles/yr
MT/yr
Urban
3.48E+20
3102
Forest
4.10E+19
Stream
channels
Urban+
Forest+
Streams
AnnualLoad(FSP<16)1
Pollutantreduction
strategies2
AnnualReduction(FSP<16um)2
Totalcost
($millions)
Cost/benefit
($/gramFSP)
particles/yr
MT/yr
Pollutantsourcecontrol,
hydrologicsourcecontroland
stormwatertreatment
1.39E+20
1227
$6,000
$5
365
NonͲurbanTreatment
1.64E+18
15
$3,000
$200
1.70E+19
152
StreamChannelStabilization
3.40E+17
3
$100
$33
4.7E+20
>3600
SEZandstreamfloodplain
retention
Tobeestimatedbyproposed2NDNATUREteamresearch
TABLE 1. 1TMDL fine sediment particle (FSP < 16 um) annual loading estimates (LRWQCB and NDEP 2009)
from urban, forest and stream channel sources compared with the 2TMDL Phase II pollutant reduction opportunities estimates that are assumed to be achievable from these source category groups (LRWQCB and
NDEP 2008) based on a collection of implemented pollutant reduction strategies. These cost/benefit results
informed the current TMDL goals and Crediting Program focus on urban pollutant load reductions. The proposed 2NDNATURE research will provide comparable achievable load reduction estimates and relative costs
as a result of intensive SEZ and stream restoration.
TMDL POLLUTANT LOADING & REDUCTION OPPORTUNITY ESTIMATES
Table 1
Pre-SEZ Restoration
Stream reach
contributing area
from mixed land use
Degraded SEZ intercepting
urban runoff
SLRT method used to estimate
SEZ average annual pollutant load at
downstream boundary pre restoration
100% urban
catchment
LTIMP
monitoring
station
PLRM volume and pollutant
loading estimates from
contributing urban catchment
to intercepting SEZ
SPARROW informed methodology to generate volume and
pollutant loading estimates from contributing mixed land use
catchment to upstream boundary of stream reach to be
restored. Based on watershed attributes from mixed landuse catchments. Validated by LTIMP datasets
Post-SEZ Restoration
Stream reach
contributing area
from mixed land use
Functional
Intercepting
SEZ
SLRT method used to estimate
functional stream/SEZ average annual
pollutant load at downstream boundary
100% urban
catchment
LTIMP
monitoring
station
PLRM used to obtain
pollutant loading contribution
from urban catchment
SPARROW volume and pollutant
loading estimates at upstream
extent of large-scale catchment
based on watershed attributes from
mixed land-use catchments.
Validated by LTIMP datasets
Intercepting SEZ restoration load reduction = (PLRM urban loading – SLRT pre SEZ restoration load) – (PLRM urban loading - SLRT post SEZ restoration load )
Stream restoration load reduction = (SPARROW loading – SLRT pre stream restoration load) – (SPARROW loading - SLRT post stream restoration load )
APPROACH TO ESTIMATING SITE-SPECIFIC SEZ LOAD REDUCTIONS
FIGURE 1
StreamSamplesͲ includesUTRandTroutͲ WY2010
70
MeasuredFSSP(<16um)conceentration(mg/L)
60
50
y=0.77x
R²=0.87
n=94
40
30
20
10
0
0
10
20
30
40
50
60
70
FieldTurbidity(ntu)
Field turbidity measured using a Hach 2100P portable turbidity meter. FSP concentrations are calculated by
the product of TSS concentration and % of TSS < 16µm as provided by the analytical laboratory.
2NDNATURE data sets generated from the following efforts:
• 2NDNATURE. 2008. Methodology to Predict Total and Fine Sediment Load Reductions as a Result of
Channel Restoration in Lake Tahoe Streams: Data Collection Sampling Plan, February 1, 2008. Funded by
Round 7 of SNPLMA Research Grant. Final report expected end of 2010.
• 2NDNATURE et al. 2010. Quantification and Characterization of Trout Creek Restoration Effectiveness; Focused Development of a Stream Load Reduction Methodology (SLRT) Final Characterization Plan. Funded
by Round 9 of SNPLMA Research Grant. Final report expected end of 2011.
FIELD TURBIDITY TO ANALYTICAL FSP CORRELATION PLOTS
FIGURE 2
Sediment Load IN
Sediment deposition
Stream
reach
2
Sediment deposition
1
1
Floodplain
Stream
2
Floodplain
Channel erosion
Channel erosion
Sediment Load OUT
1 Deposition pre-restoration
2 Additional deposition post-restoration
Simplest conceptual model: For a given stream reach, transfer of mass (water, sediment) is from the
stream to the floodplain and of mass (sediment) from the banks to the stream. The amount of sediment
sequestered on the floodplain or produced by channel erosion depends on factors that reflect the
physical and biogeochemical processes acting on the total and fine (<16 μm) sediment.
Channel and floodplain geometry
(cross-sections, roughness)
Water discharge
(USGS gages)
Water elevation and floodplain inundation
(HEC-RAS, HEC-geoRAS, stage recorders)
TSS and FSP concentrations
(USGS and others)
TSS and FSP load input to reach
(water quality mmts.)
Bank factors:
lithology, vegetation, height
(field observations)
Floodplain factors:
topo. complexity, vegetation, soils
(field observations)
TSS/FSP load generation from bank erosion within reach
(cross-sections)
Floodplain retention or bypass of TSS/FSP load
(water quality mmts., sediment pins, surveys)
TSS and FSP load output from reach
(water quality mmts.)
General structure of SLRT models: field measurements of water quality and channel and floodplain
characteristics (blue) constrain calculations of floodplain inundation, channel erosion, and floodplain
deposition (green). Information and/or data needed to validate and improve calculations are noted in
green boxes within parentheses. The difference between sediment load inputs and outputs represents
the water quality benefit of the reach. Comparison of the output pre- and post-restoration indicates the
net water quality benefits of the project.
from 2NDNATURE et. al. (2010)
SLRT CONCEPTUAL MODELING APPROACH
FIGURE 3
Frequency of occurrence (days)
TSS and FSP load (tonnes/day)
1
TSS
FSP
2
Water discharge (cfs)
Water discharge (cfs)
Floodplain area flooded (hectares)
Retention coefficient (Cr)
3
?
to be determined by stream and
floodplain measurements
4
post-restoration
pre-restoration
inundation
pre- and postrestoration
Water discharge (cfs)
inundation
post-restoration
only
no floodplain
inundation
Average annual sediment (TSS
and FSP) retained on
floodplain (tonnes/year)
Water discharge (cfs)
post-
pre-
Water discharge (cfs)
Floodplain deposition model: Deposition on the floodplain for total and fine sediment can be determined in the simplest
case using water quality (1) and water discharge data (2) to determine the amount of sediment transported during discharge
conditions with inundation post-project but not pre-project. The model can be made more complex by incorporating additional
data from floodplain measurements to determine a retention coefficient that estimates the fraction of TSS and FSP load retained
on the floodplain for different discharge conditions pre- and post-project (3). The retention coefficient is based on floodplain
factors such as vegetation height and density, floodplain area, and topographic complexity. The most complex case incorporates
a model of 2D flow to determine specific areas inundated for different discharge conditions (4). We hypothesize that the primary
water quality benefit from floodplain deposition occurs at intermediate discharge values between inundation post-project and
inundation pre- and post-project (bottom graph between red lines).
from 2NDNATURE et. al. (2010)
FLOODPLAIN DEPOSITION MODEL COMPONENTS FOR SLRT
FIGURE 4
Water depth (ft)
Elevation (ft)
pre-restoration
post-restoration
Frequency of occurrence (days)
2
1
post
-rest
oratio
n
pre-rest
oration
Water discharge (cfs)
Water discharge (cfs)
Distance (ft)
4
3
5
E2~k2τ
Sediment produced (TSS and fines)
by channel erosion
(amount per time)
E1~k1τ
pre-
post-
Water discharge (cfs)
Channel erosion model: Generation of total and fine sediment by erosion of the channel can be determined
in the simplest case using changes in average channel water depth for a given discharge (1) from lowering
bank heighs and/or raising bed elevation, and in channel gradient (shown as changes in the longitudinal
profile in 2) from increasing sinuosity. The intermediate-complexity case adds additional parameters to
consider the probability of particular water discharge occurrence (3) and to separately model vertical incision
and stream bank erosion (4). In the complex case, a 2D model (HEC-geoRAS or CONCEPTS) would calculate
vertical and horizontal erosion for multiple cross-sections, thereby producing 2D erosion results (5). The
cumulative water quality benefit is greatest at intermediate water discharge conditions (bottom graph).
from 2NDNATURE et. al. (2010)
CHANNEL EROSION MODEL COMPONENTS FOR SLRT
FIGURE 5