ATTACHMENT to Contract

Scope of Work and Project Schedule

Tasks – A1

Task A: Literature Review of Similar Restoration Projects

Given the complexity of both the ongoing physical processes in the slough and the scale of restoration that will be required to reverse the active marsh degrading processes, a review of comparable sites can help inform and guide the Elkhorn Slough Tidal Wetland Project. More importantly, the direct experience of the consultant team in analyzing and implementing management plans on a wide array of large scale estuarine and wetland projects will be essential in crafting the optimal management approach using the project tools. Therefore, many of the projects we will site in the literature review will be prior PWA and HTH projects. In addition our coastal geomorphologists and team biologists have extensive experience in the Gulf Coast (Louisiana) and the UK where comparable types and scales of erosion are occurring. These will provide a valuable addition to reference systems along coastal California and the Pacific Northwest.

The literature review will include the following categories:

1. The response of major slough channels to altered tidal exchange: PWA has conducted a variety of projects on major slough channels where the tidal prism has either been increased (leading to erosion, as at Elkhorn Slough) or decreased (resulting in channel aggradation). In the literature review, we will depict how a combination of hydrodynamic modeling and geomorphic prediction tools were used to predict the equilibrium channel condition in the largest San Francisco Bay wetland restoration projects (Sonoma Baylands, Warm Springs Marsh, and Cooley Landing Marsh).

2. Tidal Wetland Erosion: We will document projects and locations on the west coast where wetland erosion has occurred. A comparable form of wetland erosion is currently occurring in the Marin wetlands near Larkspur. We have been monitoring both edge erosion (where the marsh edge has retreated 450 ft over the past 150 years) and interior marsh erosion (more recent) which is strikingly similar to that occurring in the north side Elkhorn wetlands. In addition, our team staff (especially John Bourgeois, HTH), will provide both direct project experience, research and literature review from the Louisiana coastal wetlands where sediment starvation and inundation have resulted in the loss of millions of acres of tidal wetlands. Literature on erosion mechanisms, modeling studies, and solution approaches developed there will be included. We have ongoing research relationships with two key Louisiana researchers, Dr. Denise Reed and Dr Eric Webb (formerly of HTH) who are leading efforts to halt erosion and restore the Gulf Wetlands. These experts provide valuable insights for Elkhorn Slough Tidal Wetland Project.

Tasks – A1

Tasks

Three of PWA’s senior coastal geomorphologists (Dr. Steven Crooks, Dr. David Brew, and Jeremy Lowe,) have research and work experience with comparable problems in the extensive tidal salt marshes bordering the English coastline. Over a 15 year periods the estuaries along the southeast coast of England have lost between 10% and 55% of their salt marsh habitat. The mechanisms of loss include bank retreat in wave exposed areas, but the majority of these marshes are found in back estuarine settings protected from wave energy. Internal erosion, as pannes and sloughs enlarge and vegetation thins to be displaced by mudflat is widespread and pervasive. The loss of these highly valued marshes has been the subject of a considerable amount of research by Dr. Crooks of PWA. The factors identified by Dr Crooks include many of the same factors at Elkhorn Slough: increasing rate of relative sea-level rise, low sediment availability, human impacts on sediment transport pathways (ebb currents dominate the system causing a net export of sediment), and increasingly poor drainage of marsh soils. Dr Crooks will contribute the results of his own research, restoration methods being tested in Europe, and input from other renowned British marsh geomorphologists (Dr Allen Pye, Dr Jonathon French, Dr. Jon Pethick, Dr David Stoddard.)

3. Tidal Inlet prediction and management: There is extensive literature, with

excellent west coast applications, on the behavior of tidal inlets. However, most of this literature was previously generated for application to harbor inlets. Bob Battalion, PWA’s senior coastal engineer, has compiled an extensive library of these studies for application to prior PWA projects. However, while this data will be valuable in understanding the impacts of potential projects on the Moss Landing Harbor Entrance, it is more complex to apply to Alternative B (potential to recreate a new slough entrance directly to Monterey Bay, north of the harbor entrance. In the mid-1980’s PWA extended the prior work on harbor entrances (developed by Professors O’Brien and Johnson at UC Berkeley) to tidal estuaries with direct ocean connections. This work was developed in conjunction with a major wetland restoration project at the Tijuana Estuary, where inlet closure had become a significant problem. This work included a compilation of both wave data and tidal prism data from all of the major tidal inlets along the west coast. The categorization of data into those systems that are open, closed or intermittent represents the largest compilation of such data currently available.

4. Restoration of subsided tidal wetland systems: Prior experience and literature on restoring subsided wetlands (comparable to Parson’s Slough wetlands) will guide their future restoration. Our restoration of the Sonoma Baylands site in north San Francisco Bay involved the placement of several million cubic yards of dredge material to raise the marsh surface (about 2 meters) to an elevation where natural sedimentation and revegetation processes could be restored. This remains the largest and most successful subsided wetland restoration project on the west coast and a valuable guide to possible fill placement at the Parson’s slough wetlands, and possibly help raise the north side wetlands.

In addition to our experience with restored sites, we are currently the prime

Tasks – A2

consultant (with HTH Associates) developing the restoration plan for the South Bay Salt Ponds, involving the restoration of over 15,000 acres of subsided former tidal marshes in south San Francisco Bay. This project includes extensive literature review on the relationship between sediment supply and the restoration of subsided wetlands.

5. Management and restoration of eroding slough channels: The goal of the current project is not simply problem understanding; it is the development of the most implementable, cost effective and sustainable system with the least adverse impact. This will require first controlling the erosion in the primary slough channel, then implementing a program to reclaim the wetlands. Information on similar projects to control the main slough erosion problem is essential to the successful management of the interior and adjacent wetlands. In Oakland, we are currently designing the plan to reconnect Lake Merritt (formerly, a major tidal wetland) with San Francisco Bay. The plan must control the size and depth of the connecting channel to protect adjacent infrastructure and the BART (subway) tunnel, which passes under the slough channel. By controlling the range of tidal exchange, and preventing erosion with concrete sills, we will maintain adequate tidal exchange to support improved wetlands will controlling erosion in the main slough channel.

The literature review will be based on a combination of our own extensive experience, scientific literature review, reports from comparable analysis and restoration projects, and discussion with other experts throughout the world. A memorandum summarizing findings from the literature review will provide valuable background information that will help refine the work program for subsequent tasks, and provide guidance on the optimal solutions.

Tasks – A3

Task B: Develop Alternative Conceptual Designs

In this task, PWA design staff will refine the identified large-scale alternatives to a level that can be adequately analyzed and modeled in Tasks C, D, E and F. The preferred approach (one or two) will then be further refined and developed in Task G to preliminary design level.

The key element of Task B is developing the alternatives to a level that demonstrates feasibility and is suitable for tidal inlet assessment, hydrodynamic model testing, morphological assessment, and future habitat characterization. The alternatives include:

Option 1: No ActionOption 2: Restore historic conditionsOption 3: Decrease the size of the opening under Highway 1Option 4: Decrease the tidal prism by muting Parsons Slough/other wetlandsOption 5: New alternative developed by PWA

It is important to recognize that PWA has previously analyzed and modeled all four of these options at a preliminary level in our 1992 study. In that study, we obtained bathymetric maps of the pre-harbor opening to the north to characterize historic conditions. We used available data to model existing conditions at the time (no action; Option 1) and used our understanding of the slough problems to identify options 3 and 4, and conduct preliminary testing of them. In the current study, we will incorporate the more detailed bathymetry now available to refine these options to the required level:

1. Option 1. No Action: The “no action” alternative is important for several reasons. It is important to understand how the project site will evolve and what the equilibrium conditions will be when it does stabilize. These will provide an important comparison with the other options for final decision-making of the preferred approach. In addition, the no action alternative is required by CEQA to demonstrate purpose and need and to compare potential impacts of the other options.

2. Option 2. Historic Mouth Conditions: Opening a new mouth to the north will provide a comparable wave and littoral sediment climate to conditions that existed prior to the new harbor mouth opening in 1947. This will require closure of the existing (at the Highway 1 Bridge), construction of a new Highway 1 bridge to the north, and excavation of a new slough mouth through the beach. PWA has the detailed bathymetry available to determine the mouth conditions for the pre-1947 configuration. However, it should be recognized that the current slough conditions produce a tidal prism significantly larger than the historic slough bathymetry. As a result, the initial equilibrium conditions of the new mouth/tidal inlet would be larger than historic conditions. We would use the tidal inlet analyses and our own database of tidal marsh outlet geometry to predict this initial condition. Over time, as sediment deposition (or active placement of material to fill eroded parts of the slough and constriction of the tidal prism from Parsons Slough) occurs the new mouth will be

Tasks – B1

expected to gradually decrease to a smaller size, likely close to the pre-1947 conditions. In addition to the new mouth and closure of the existing channel at Highway 1, the preliminary design will calculate the appropriate channel excavation required to connect the existing channel to the new mouth.

3. Option 3. Decreased mouth opening under Highway 1: In 1992, PWA Project Manager Jeffrey Haltiner teamed with Robert Battalio (with M&N at that time) to develop a preliminary design for a barrier at Highway 1 that would mimic the tidal damping effects of the historic shoaling mouth at the Bay. Different barrier heights were tested to determine the height of the barrier needed to reduce the erosive shear stress at various locations up the slough. Mr. Battalio and his team will refine this concept for use in the current model study. Determining the barrier dimensions sufficient to reduce slough erosion will require a trial and error method using the hydrodynamic model developed in Task D. Therefore, an initial barrier height will be estimated, and subsequently refined.

4. Option 4. Reduce the tidal prism in Parsons Slough: Our prior work demonstrated that the 1984 opening of Parsons Slough added up to 40-percent additional tidal prism to the total tidal exchange at the mouth. At that time we recommended reducing the size of Parson’s slough at the Railroad Bridge, as this provides a stable location to construct the required structure. We will evaluate the size of opening required to dampen the tidal exchange to that characteristic of a restored (mature) marsh in Parsons Slough. We have extensive data on the natural morphology of tidal marshes that provides a relationship between an equilibrium marsh and the tidal prism. Creating an opening of that size will immediately reduce the erosive effects in Elkhorn Slough, while providing adequate tidal exchange to support a restored marsh. Use of fill material would greatly accelerate the restoration of Parsons Slough, considering the limited sediment supply currently available.

The task deliverable will include sketches, dimensions of openings, sizes of structures and a description of assumptions made to characterize each of the options. In addition, the PWA team will work with the client team to determine if there are any other feasible options that should be considered, or refinement of the current options that would improve their function or implementation.

Tasks – B2

Task C: Predict Inlet Dynamics

There are two tidal inlets of concern in this project: The existing one at the current harbor mouth, and the potential future one at a more northerly (historic) location. The potential functioning and stability of each of these is essential in assessing a potential alternative. It is important to recognize that while the area of interest for Elkhorn Slough tidal processes under current conditions is the Highway 1 Bridge, the actual tidal inlet is at the harbor mouth and this controls conditions in the Elkhorn Slough, as well as internal harbor processes (dredging, flow etc).

The ability of an inlet to remain open is primarily a function of the amount of sediment deposited near its mouth due to wave-induced sand transport, and the scouring effect of tidal currents. Since the proposed restoration alternatives will affect the tidal prism (reduce scour potential) and/or relocate the inlet mouth (increase wave exposure), these actions have the potential to alter the inlet behavior. The goal of a new opening would be to recreate the shallow historical opening that produced the muted tidal regime pre-1947. However, it would be important for the new Elkhorn Slough mouth to maintain a continuously open connection to Monterey Bay. The changes in tidal prism could also affect the littoral sediment budget and result in greater need for navigation dredging at Moss Landing Harbor.

Inlet Stability and SizeWe propose to apply standard engineering methods, adjusted to account for known historical conditions at Elkhorn Slough, to characterize the inlet stability for the proposed restoration alternative. Results from this analysis will provide input for hydrodynamic modeling (e.g., specification inlet size)

Johnson (1973) noted that the dominant factor in controlling inlet stability is the relative balance between opposing wave forces and tidal processes, and he proposed a simplified approach of comparing the average annual wave power with the potential tidal prism. PWA will apply this method by adjusting offshore wave power using published data (Mohammad, 1989; Coastal Data Information Program) to account for refraction and shoaling of surface gravity waves across Monterey Bay. Professor Ed Thornton of the Naval Postgraduate School will provide guidance on the application of these refraction coefficients. We will compare the incident wave power at the mouth location to the tidal prism of the Elkhorn Slough prior to human alternation. This will provide a closure threshold based on historical conditions, which we can compare to values from other California inlets of known stability (Johnson 1973). This method and derivatives have been used successfully in the past for Bolinas Lagoon and other inlets on the open California coast (Williams & Cuff,1994; Goodwin, 1996), with refinements for local wave conditions (DeTemple and others, 1999; DeTemple, 1999) and near-instantaneous time series analysis (PWA, 2001; PWA, 2004; Battalio and others, in press). The cited work included corrections to the original data set by Johnson (1973). [Note: PWA has recently revised the original data presented in Johnson (1973) to correct a systematic error in the wave power computations (PWA, unpublished data).

Equilibrium cross-sectional area of the restored inlet will be assessed using tidal prism and cross-sectional area relationships. Jarrett (1976) examined the earlier work of O’Brien

Tasks – C1

(1931), and established tidal prism-inlet area relationships for systems with jetties (one or two) or without jetties along the Pacific, Atlantic or Gulf Coasts. Considerable scatter in the data suggest these simplified tools do not account for all of the relevant processes. Therefore, we propose to evaluate the uncertainty associated with estimates of inlet area by calculating lower and upper bounds of inlet area using the published 95% confidence intervals (Jarrett, 1973). Model runs will then be executed to characterize the effect of the variable inlet size on tidal hydraulics (water levels, velocity, and bed shear stress) along Elkhorn Slough. We will then check the assumed inlet cross-section using the method of Escoffier (1940) using Corps of Engineers’ modeling tools (Seabergh et al, 1997) to assess the equilibrium of the sandy inlet.

Changes to Littoral Processes and Sediment BudgetAlthough the jetties of Moss Landing Harbor direct most of the longshore sediment transport into the submarine Monterey Canyon, a portion of the littoral sediments is swept through the inlet by flood tides and deposited in the harbor. Maintenance dredging is required to provide navigable depths, but ebb tidal currents remove some of these littoral sediments from the harbor through scour. The proposed restoration alternatives may affect the rate and pattern of sedimentation in Moss Landing Harbor, potentially resulting in more frequent dredging requirements.

An understanding of the littoral sediment budget, including the net and gross longshore sediment transport rates, will be necessary to describe inlet dynamics and shoreline adjustments. This is especially true if the historic location of the inlet mouth is restored, as described in Option 2. Unless accounted for in the design, restoration of the historic inlet may interrupt the delivery of beach sands downcoast of the inlet and potentially result in temporary beach retreat downcoast of the inlet. Over the longer term, modification to the wave field in the vicinity of the restored inlet may result in permanent changes to shoreline orientation.

PWA will assess the effects of restoration actions on Moss Landing Harbor by estimating the cross-sectional area on its new equilibrium inlet using the tidal prism relationships of Jarrett (1973). The reduced area of the equilibrium area will provide a relative measure of changes in shoaling potential within Moss Landing Harbor. We propose to characterize changes to the sediment budget by reviewing published estimates of longshore sediment transport, dredging records at Moss Landing Harbor, and information provided by Dr. Thornton. Delivery terms in the sediment budget (inputs) will be compared against the expected size of ebb- and flood-tide bars using available guidance (Walton and Adams, 1976).

An understanding of the littoral sediment budget will also inform the design. Inlet stability is party affected by the directionality of littoral sand transport (Bruun, 1966, 1978). For example, inlets with a relatively low tidal prism subject to high net-to-gross longshore sand transport ratios may migrate. An example of this is Crissy Field Inlet in the San Francisco, which migrates seasonally due to changing wave conditions (PWA, 2004), while the design included coastal structures to limit migration and enhance scouring power of the tidal prism. The existing jetties at Moss Landing may have affected northward sand transport along the shore north of the inlet, and hence may result in different inlet morphology than existed historically. Possibly implication for the restored inlet at Elkhorn Slough may include a single jetty upcoast of the mouth, if inlet migration were deemed undesirable.

Tasks – C2

A Note on the Application of Empirically-Based MethodsThe most recent inlet stability assessment at Elkhorn Slough consisted of an Escoffier analysis at the Highway 1 crossing and the mouth of Parsons Slough (Sea Engineering Inc., 2005). We believe the Escoffier analysis – like other engineering and empirical geomorphic methods intended to assess inlet size and stability – are more appropriately applied at locations there wave processes are significant (i.e., at the Moss Landing Inlet or the historic “throat” of the old Salinas River Inlet). Application of these methods should also consider the nature of the sediment, since many of these empirical relationships are based on systems dominated by beach sands, which have markedly different erosion characteristics than cohesive mud.

Tasks – C3

Task D: Modeling Of Hydrodynamic Processes

Elkhorn Slough has been responding to land-use changes over nearly a century. The physical processes governing those changes occur at multiple time scales: hydrodynamic processes (tidal exchange) are continuous, and modeling of that process must also be done on a time-step of seconds. The geomorphic change in an estuary becomes evident over a period of years and decades. Geomorphic methods that describe that process provide an important complement to the short-term modeling.

Based on our experience, planning of large-scale restoration projects is best supported by technical analyses that are founded on a solid “conceptual model”, and combine multiple approaches. In Tasks D and E, we describe how we will integrate conceptual modeling, computer-based simulation, and geomorphic analyses to characterize the hydrodynamic, sediment (erosion and deposition) and geomorphic processes in the Slough to support the evaluation of restoration alternatives at Elkhorn Slough.

Model Evaluation and SelectionSeveral past models have been developed to characterize the tidal hydrodynamics of Elkhorn Slough. In 1992, PWA applied a one-dimensional model (ESTFLO) to characterize the effects of human alterations on the slough hydraulic functioning (PWA, 1992). More recently, Stanford University has developed a three-dimensional model (TRIM) to characterize existing circulation patterns in the slough (Monismith et al, 2005). In response to issues of ownership and future support, Stanford is currently developing a new in-house program (SUNTANS) that will be used in future studies.

Selection of the preferred hydrodynamic model to characterize the physical processes occurring in Elkhorn Slough is a key decision both for the current project and for longer-term slough management and other research studies. There are a variety of suitable models available and each offers certain benefits and constraints. These include technical issues such as: how the model grids are established; runtime of the simulations; ease of including complex hydraulic structures; ability to add-on modules for sediment movement, water quality, temperature; and clarity/simplicity and usefulness of input and output (display/graphics) functions. Other issues include the expected longevity and support of the model supplier, initial and upgrade costs, propriety nature of the model, model review (open source code), and input by the US Army COE.

Given the importance of the model selection to create a multi-use tool that is appropriate for this study, use by collaborative researchers, and use/support into the future, we recommend inclusion of the client team and particularly the Modeling Advisory Team (plus the US Army COE) in the final model selection. Therefore, we have added a “model selection” step to the list of tasks and project sequence. This step will not add cost or time to the project process, but will allow appropriate consideration and client participation in a project work product that is critically important.

In this section, we provide a preliminary discussion of the models we consider appropriate, discuss some of the above issues, and make a preliminary recommendation for a preferred model. This recommendation will be discussed with the client and stakeholder team and

Tasks – D1

finalized early in the project process. The following sections then describe model application, results, and linkages with other tasks. Both the modeling tasks and these linkages can be applied using any of the models discussed below, and are not limited by our initial model recommendation.

While we recommend development of a 3-d model for this study, many of the key processes can be adequately described by 1- and 2-d simulations for certain situations. This allows faster model setup and runs, testing of more alternatives and refinements, etc. Therefore, the model should be suitably flexible to allow operation in any one of these scales, depending on the specific requirements of the management question. It is important to recognize that in prior studies, most of the understanding of historical change and management guidance (including preliminary identification and assessment of three of the management options now recommended) has been based on PWA’s 1992 1-d model. This demonstrates the importance of selecting the appropriate modeling tool and scale (not modeling complexity or academic interests), and focusing attention on answering the important management questions.

Several models are available to simulate three-dimensional tidal flow in Elkhorn Slough, including:

DELFT3D from DELFT|WL TRIM3D from Vincenzo Casulli (University of Trento, Italy) MIKE3D from the Danish Hydraulic Institute (DHI) CH3D-WES from the USCE Waterways Experiment Station EFDC from TetraTech

The PWA team members have used a wide range of numerical models in support of restoration projects, including four of the above models. We recently completed a very similar model selection process on the highly-visible and complex Ballona Wetlands Restoration Modeling Project in Los Angeles, identifying appropriate models, selection criteria, and usability by various user groups and needs (including the US Army COE, water quality modelers, etc). The importance and success of this collaborative process instead of an a priori decision has confirmed the validity of this approach.

The table below provides an initial list of selection criteria and our preliminary evaluation of each of the models. Other models may also be considered by PWA and the MAT.

Tasks – D2

Preliminary Model Selection Criteria and Evaluation

DELF

T

TRIM

3D

MIK

E

CH3D

EFDC

1. Wetting & drying H H H H H2. Ability to resolve complex bathymetry H L L H L3. Flow control structures (e.g., culverts, weirs) H L H L L4. Future Extension (e.g., particle tracking ,

sediment transport, water quality) H L H L H

5. Long-term and responsive software support H L H L L6. Commercial (C), Proprietary (P) or Free (F) C P C P F7. Use by others H L H L L

Based on recent experience with DELFT|WL software, our initial recommendation is to apply DELFT3D to Elkhorn Slough. However, the final model selection will be made collaboratively with the Reserve and Modeling Advisory Team. The model will be selected within the first three weeks of the contract start date.

Model Construction and CalibrationIn addition to Dr. Haltiner and Dr. Goodwin’s development of the 1992 PWA numerical model, two PWA Team members (Professor Monismith and Gaurav Misra) were key participants in the Stanford data collection and model development described by Monismith et al. (2005). Their involvement provides valuable institutional knowledge to the development, calibration and application of the hydrodynamic model.

During model construction, we will construct a computational grid which extends from the head of the estuary into Monterey Bay (pass the jetties at Moss Landing Harbor) to allow characterization of the tidal exchange between the ocean, harbor and slough. In order to account for the full tidal range and tidal prism conveyed by through Elkhorn Slough, the grid will extend through the upstream areas of the slough as well as Parsons Slough. A curvilinear, channel-following grid will provide effective characterization of the different physical zones within Elkhorn Slough – channels, mudflats, and tidal marsh. Using 5-10m grid resolution will allow the inclusion of third-, second-, and some first-order marsh channels. These channels strongly influence the phase and magnitude of flow through the inter-tidal zone; their inclusion allows a better description of potential erosive forces along the mudflats. Specific characteristics of the grid development will likely be constrained by the availability of bathymetric data. PWA will use bathymetric data along the main slough channel acquired by CSUMB ca. 2002, and more recently acquired LiDAR of the intertidal mudflat and marshes.

PWA will use measured water levels and tidal current velocities collected by Stanford during the September 2002 and April 2003 monitoring programs for model calibration and

Tasks – D1

validation, respectively. Model parameters used previously at Elkhorn Slough will serve as a starting point for the calibration. Sensitivity of model results due to variation in model parameters will be documented as part of the calibration process. This will provide a characterize how water level, current velocities and bed shear stress vary with changes to changes to input parameters.

Application to Restoration AlternativesPWA will apply the calibrated model to the ‘no action’ alternative and up to five restoration scenarios at three instances in time: years 0, 10 and 50. The fee estimate also includes five additional runs to characterize circulation during a range of expected future conditions and address specific issues related to the proposed restoration alternatives. In each of the model runs, we will select a representative tidal period as the input parameter (driving force) that contains a combination of neap, spring and average tidal conditions to be representative of the annual tidal cycle. The allocation of model runs and what constitutes a “run” will be jointly decided by PWA and the MAT/TWP Coordinator (some runs are quick for sensitivity and fine tuning an alternative, some are more rigorous and require a full spring-neap tidal cycle, etc., and others are informed by earlier runs and will produce results worth carrying through for further geomorphic/habitat analysis).

Hydrodynamic modeling of the slough-inlet-marsh system will allow us to quantify changes in the tidal inundation over the marsh plain and tidal current velocities along the slough channel. We will compare model results from the ‘action alternatives’ against those simulated under existing and historical conditions to assess the effectiveness of the proposed restoration actions in modifying the physical mechanisms that, to a large extent, control the loss of marsh habitat. Specifically, we will quantify the following characteristics of the tidal hydraulics along Elkhorn Slough:

Water level (elevation-inundation frequency; tidal range and elevations) Distribution and frequency analysis of peak tidal current velocities Distribution and frequency analysis of bed shear stress Tidal prism

Recent work performed by PWA for the South Bay Salt Ponds Restoration Project involved characterizing long-term geomorphic change from the results of short-term hydrodynamic modeling. PWA developed an approach combining model results with statistical tools and qualitative experience with geomorphic development in order to predict changes for a 50-year time horizon. In a tidal marsh estuary like Elkhorn Slough, model results can only provide quantitative results regarding dominant hydrodynamic processes (velocity, bed shear stress, etc). Predicting long-term change requires an understanding of sedimentary and marsh evolution processes that are often difficult to capture in a hydrodynamic model. By utilizing the available research regarding marsh processes and the available geomorphic expertise, our approach allows for a back-and-forth analysis; model results are used to guide qualitative predictions, which can then be tested using the model. This process results in a very thorough consideration of the physical processes that may influence the evolution of Elkhorn Slough.

Modeling of Tidal Creeks

Tasks – D2

In addition to scour along the slough channel and drowning of the marsh plain, increasing tidal creek width has contributed to the loss of marsh habitat (Van Dyke and Wasson, 2005). We propose to develop a focused numerical model of a limited domain and finer spatial resolution to demonstrate how interior marsh tidal current velocities have changed over time. The boundary conditions for this small-scale model will be extracted from simulations of water level in the system-wide model of Elkhorn Slough.

Information from these simulations will improve our understanding of how the hydraulics of tidal creek interacts with other influences affecting the wetland stability, described in the current conceptual model of wetland change. These include possible subsidence, baselevel lowering of the main channel, wave propagation, soil saturation, vegetative response, and other factors.

Relation to Other Technical AnalysesHydrodynamic modeling will be informed by, and provide input to, other technical analyses. For example, maps of bed shear stress along Elkhorn Slough produced from numerical simulation will be compared with historic rates of channel changes to inform our projections future slough scour and widening. Information will also pass in the opposite direction; projections of future morphology established in Task E will provide updates to the bathymetry files for hydrodynamic modeling at years 10 and 50.

Two-way transfer of information will also occur between the hydrodynamic modeling results and assessment of inlet stability. The inlet stability assessment will include an estimate of the size throat, which we will use to refine the bathymetric description of the connection between Elkhorn Slough and Monterey Bay. Changes to the size of the inlet throat and other changes to the morphology the system, including the presence of flood-tide shoals, may affect the effective tidal range and/or prism of Elkhorn Slough. Therefore, these parameters will be simulated by the numerical model and feed into the assessment of inlet closure potential.

Results from the hydrodynamic modeling also provide information for the prediction of the future habitat composition. Specifically, frequency analysis of model results will be used to develop into elevation-inundation curves for evaluation of how changes to the hydroperiod affect marsh vegetation.

PWA agrees to work with a Stanford modeling team (if they are hired through a separate contract) to evaluate how well the prediction of existing conditions compares between the two models and monitoring data.

Tasks – D3

Task E: Predict Future Morphological Scenarios

Prediction of morphologic evolution at Elkhorn Slough integrates the results of the hydrodynamic modeling with geomorphic assessment to predict future slough morphology and under each of the proposed restoration actions, including the “no action” alternative. Past human modifications to the landscape, such as the creation of a new tidal inlet and diversion of the old Salinas River, altered the physical processes that shape the inlet-slough-marsh system. Changes to natural processes continue to be affected by on-going maintenance dredging at Moss Landing Harbor. Placing these changes to natural processes into a geomorphic perspective will be essential to predict the future morphology of Elkhorn Slough.

As described below, PWA will combine the results from conceptual modeling, computer-based hydrodynamic simulation, and applied geomorphic tools to describe the evolutionary trajectory of Elkhorn Slough at distinct ‘snapshots’ along its evolutionary trajectory. This will occur for each of the restoration alternatives at years 0, 10 and 50. The conceptual model refined in Task 3 will be essential in guiding the analysis.

Refinement of a Conceptual Model A conceptual model is an explicit description, or ‘intellectual roadmap’, of cause-and-effect linkages that explains how we think important resources respond to changing ecologic processes, particularly those physical processes affected by human activity. A well-constructed conceptual model need not be complex. In fact, unnecessary complexity obscures key linkages between management actions and ecosystem response. A comprehensive conceptual model can focus the quantitative technical analyses on the critical processes and management questions and avoid time-consuming studies of less relevant issues. In some earlier restoration studies, the lack of such a model resulted in open-ended studies and the failure to address the critical Slough management questions.

Draft conceptual models developed during earlier stages in the TWP planning process graphically depict the linkages between land use changes (i.e. watershed development and creation of Moss Landing Harbor) and tidal marsh loss. We propose to quantify where possible the scale of the changes, develop short narratives to describe the most important of these cause-and-effect linkages, and add new linkages that describe how the proposed restoration actions may affect the future evolution of the inlet-slough-marsh system. The refined conceptual model will guide subsequent hydrodynamic modeling and geomorphic analysis – as well as alternative development and evaluation – by identifying the most important linkages between the proposed management actions and the response of tidal habitats.

Geomorphic PerspectiveElkhorn Slough is a part of a coastal system that includes an open inlet which provides exchange with coastal waters and sediment, and marshes along a relatively narrow elevation band where tidal inundation allows vegetation to grow. Hydrodynamic processes and sediment dynamics shape various geomorphic features within the inlet-slough-marsh system. Some of these morphologic changes can in-turn modify the physical forces.

Tasks – E1

Complex interactions between form and process may result in unexpected results, such as the positive feedback that has resulted in channel widening of Elkhorn Slough after construction of the Moss Landing Inlet (PWA, 1992).

PWA will apply our geomorphic understanding of the inlet-slough-system to understand changes observed over the past decades, and inform our assessment of how the proposed restoration alternatives may affect future evolution. This will include a detailed (and where feasible, quantitative) description of the key historic changes which transformed Elkhorn Slough from a low energy, frequently brackish or even freshwater, low-energy depositional system to a high-energy, saline, and erosive system after construction of the new ocean inlet in 1947. In addition to the construction of the Moss Landing Inlet, these changes include the 1909 re-routing of the Salinas River, which altered freshwater flow and sediment, and the likely functioning with the pre-1947 mouth. We will also consider how the expected changes to sediment delivery under each alternative may contribute to future evolution of Elkhorn Slough. PWA has recently applied these geomorphic principles and sediment budget analysis in the prediction of future evolution at Bolinas Lagoon and the development of a comprehensive, long-term lagoon management plan (PWA 2006).

PWA will combine our understanding of these geomorphic processes at Elkhorn Slough with the results from hydrodynamic modeling to describe the effectiveness of the proposed restoration alternatives. As described below, we will combine geomorphically-derived tools with numerical simulations to predict the future main channel morphology, loss of marsh edge due to slough scour and expansion of tidal creeks, and ‘drowning’ of vegetation caused by changes in tidal inundation over the marsh plain. The method will be initially “calibrated” using the observed changes between 1947 and the present to establish the parameters of the predictive approach. The calibrated model and method will then be used to forecast future morphology under the restoration alternatives identified in Task B.

Main Slough Scour and Loss of Tidal Marsh EdgeTidal current velocities and bed shear stress simulated by the hydrodynamic model under historical and existing conditions will be related to past and contemporary rates of slough widening documented by PWA (1992), Dean (2003) and others. Simulated velocities and shear for pre-1947 conditions, when the slough channel was still depositional, will define an erosional “signature” (i.e., frequency plots of accumulated shear stress over a representative tidal period) and threshold values for dynamic stability, where erosion and deposition are balanced over the long term. Since each restoration action is aimed at reducing the tidal prism, these comparisons will provide upper and lower bounds to the range of channel-widening tidal currents and bed shear stress values. For each ‘snapshot’ in time, PWA will assess areas of erosion along the slough channel by comparing the simulated tidal hydraulics to the upper and lower bounds described above. Rates of channel widening along Elkhorn Slough from 1993-2001 (Dean 2003) will be adjusted based on an erosion “signature” established from the hydrodynamic model results.

While a number of the models discussed in the model selection task have sediment transport modules, the complexity of erosion/deposition of cohesive sediment is challenging. This is compounded by the interest in predicting the morphological change in the system over long-term time frames (up to 50 years). Given the uncertainties in the accuracy of modeling velocity, shear stress and erosion/deposition on a timestep of seconds, accumulating these predicted changes over decades will result in considerable uncertainty

Tasks – E2

and wide confidence limits. In response, we will combine the hydrodynamic approach above with empirical tools developed from tidal marshes in San Francisco Bay (Williams et al., 2002).

First, for a given alternative (Options 1-4 from Task B) and ‘snapshot’ (years 0, 10 and 50) we will compare the model-predicted shear stress and velocity “signatures” at various locations throughout the slough system with the pre-1947 (stable) “signatures”. If the shear stress for the alternative is greater than the baseline condition, we will adjust the slough morphology. This will be done by applying hydraulic geometry relationships between tidal prism and channel geometry using the modeled tidal prism to estimate the equilibrium channel size at various sections along Elkhorn Slough. We will compare the channel dimensions prescribed in the model and equilibrium dimensions predicted by hydraulic geometry to confirm the trends of erosion identified by inspection of bed shear stress. This comparison between results will provide an assessment of dynamic equilibrium. For year 50 simulations, the numerical model will run again to create a new shear stress signature. This process of adjusting the slough geometry and re-computing the expected shear stress regime will continue until the shear stress signature of the alternative matches that of the pre-1947 conditions. When that condition is achieved, the system will be assumed to be in dynamic equilibrium.

Expansion of Tidal Marsh CreeksThrough the use of GIS tools, Van Dyke and Wasson (2005) have documented how tidal creek widening has contributed to the loss of marsh area. We propose to assess how this process may change under restored conditions by combining numerical modeling and hydraulic geometry.

Simulated bed shear along two selected tidal creeks will examined for each restoration scenario. The simulated bed shear along the creeks will be compared to modeled values from a hypothetical equilibrium creek channel, which we will predict from hydraulic geometry, to assess if creek widening is expected to continue. Observed channel widths will also be compared against equilibrium widths estimated from hydraulic geometry.

Drowning of Marsh InteriorsModeled changes in the inundation characteristics of the marsh plain will be used to assess if past marsh drowning will continue. Changes in vegetation cover have varied over the past decades, with spatial differences in the marshes along Elkhorn Slough (Van Dyke and Wasson, 2005). We proposed to compare the modeled inundation-elevation characteristics with historical data to inform our projection of future change.

Because of the complexity of the marsh interior erosion process (as described in the conceptual model developed by the Science Team) it is likely that a wide range of factors is contributing to the wetland degradation. We will review all of the potential factors and available data to assess which individual parameters are likely the most important to control. This will include a review of detailed marsh topographic surveying (if conducted) to determine the amount of possible marsh subsidence (from the 1989 Earthquake), wave erosion, sediment starvation, etc. While the numerical model can provide valuable information on these processes (and the potential benefits of the management alternatives in reducing slough channel erosion and marsh inundation), the conceptual model scale analysis is also essential in describing and quantifying the larger array of erosive forces.

Tasks – E3

Task F: Prediction Of Tidal Habitat Composition

Research has shown that a number of variables control the distribution of plant species in coastal marshes. The most significant controls on tidal marsh composition include: depth and duration of flooding; surface water and soil salinity; accumulation of phytotoxins such as hydrogen sulfide; and soil mineral and organic matter content. Anthropogenic effects may affect marsh distribution by modifying these (e.g., changes in the tide range or nutrient loading form the watershed), or by physically removing vegetation through erosion. A thorough understand of marsh ecosystem processes is important in understanding the factors that affect wetland elevation and the vulnerability of marsh systems to factors such as changes in sediment dynamics and hydrology, as well as predicted sea level rise, in order to develop appropriate restoration designs. These processes include vertical accretion, marsh elevation change, and shallow subsidence. Over the long-term, marsh distribution is largely controlled by the sea-level rise relative to the delivery of marsh-building sediments from littoral and fluvial sources.

Based on current understanding, increased tidal scour and inundation are believed to be the primary factors controlling marsh loss at Elkhorn Slough, although changes in nutrient loading, root growth, groundwater levels, and tectonic events may also contribute to the observed marsh loss over the past decades. The marshes at Elkhorn Slough are unique in that they dominated by pickleweed, with cordgrass largely absent.  Presumably, this makes losses of vegetated marshes more sensitive to alterations of hydroperiod and sedimentation rates. Stewardship of the coastal wetlands at Elkhorn Slough requires an through understanding of the processes described above in order to adequately assess management options.

We propose to predict future habitat composition by using information generated in previous tasks (i.e., hydrodynamic modeling and geomorphic evolution) and considering the factors controlling marsh distribution. We shall provide predictions of changes to estuarine habitats (percent change and acreage of habitat types) and produce a map showing habitat distribution and changes for each selected large-scale restoration alternatives, including no-action, for each of the time periods specified. HTH has used this approach to describe future habitat change for other large-scale restoration projects, such as the South Bay Salt Pond Restoration Project (HTH 2005).

The projected habitat shifts may affect wildlife and plant species. Therefore, attention must be given to the ecological trade-offs as they relate to the needs of special estuarine conservation targets such as estuarine-dependent species, state- and federally-listed species, migratory species, and historically dominant species. 

Tasks – F1

Elevation and salinity as they relate to marsh plant distributions (H. T. Harvey 2005).

Tasks – F2

TidalFreshwater

Marsh

TidalBrackish

Marsh

TidalBrackish -Salt MarshTransition

TidalSalt Marsh

5.0

4.0

3.0

2.0

1.0

Scirpuscalifornicus

Scirpusmaritimus

Salicorniavirginica

0

5 10 15 20

Spartinafoliosa

Water Column Salinity (ppt)**

Elevation (feet,

NGVD 29)*

6.0

MTL (0.52)

MHHW (4.7)

Tidal Datum

(feet,

NGVD 29)

* Shows means of elevation limits. Island Pond Report (2456-01) Appendix B contains complete data.** Salinity data modeled (Gross, 2003). Elevation and habitat data is empirical.

MHW (4.1)

Typhaangustifolia

Task G: Create Designs of Large-Scale Restoration Alternatives

PWA will develop 10%-complete, conceptual project descriptions for two options identified by the Science Panel and Strategic Planning Team. The designs will be sufficiently detailed to identify key issues and elements that require further analysis and design, and to scope the associated engineering efforts. The designs will be documented in an Engineer’s Report, which will be included as an appendix to the project report.

The Engineer’s Report will, for each option, include brief written descriptions, drawings and engineer’s estimates. The project descriptions will reference and build upon descriptions developed in other Tasks, and document the engineering criteria used to detail the options to the 10% complete level. The descriptions will include geometry, materials, likely construction methods and other pertinent characteristics. Report figures will be reduced scale versions of the larger drawings listed below, and other sketches as appropriate to describe the project.

Drawings will be produced in AutoCAD and or GIS formats for use as report figures and as large size sheets (24” x 36” or larger). These drawings are expected to consist of the following:

Key Map – Elkhorn Slough Wetlands Map (re-use project map) Plan and Typical Sections – Tidal barrier, Vicinity of Highway 1 Bridge Plan and Typical Sections – New Tidal Inlet OR Tidal Barrier at Parsons Slough Up to 6 Plans and Typical Sections – Channel / Estuarine Fill

Due to the size of the project, plan drawings will be developed only where significant work is proposed, as listed above. The Key Map will locate the coverage of each plan and serve as the index for the overall drawing set. We anticipate that the Key Map will be the same or similar to the Elkhorn Slough Wetlands Map already available, as modified for use in other tasks. Other drawings will be generated on base maps developed from digital mapping information provided to us by the project sponsors, or otherwise readily available for our use. The drawings will not be adequate for construction.

An engineer’s estimate of likely construction quantities, methods, costs and schedule will be developed and included in the report. The estimates will be based on typical sections and general dimensions shown in the drawings and an assumed phasing and sequence. The estimates will therefore be approximate, and include a contingency.

A section of the Engineer’s Report will outline a workplan to complete the project design and implementation through construction. While provided within the context of engineering design and construction, the workplan will also include expected scientific and institutional Tasks identified by the team. Performance criteria for project elements will be outlined as part of the description of required engineering. The performance criteria will address expectations of function relative to ecologic conditions, operations and maintenance efforts, and adaptive management. For example, hydraulic structures need to have the desired effect on hydraulics immediately after construction and as the site evolves toward

Tasks – G1

equilibrium. In this case, geotechnical considerations such as settlement and the ability to adjust hydraulic function are examples of performance criteria to be included in the description of required engineering effort.

Tasks – G2

Work completed under Tasks A through F will be presented through various memoranda, which will later form chapters and appendices of the project report. Preliminary designs and descriptions of construction activity for the two most promising options chosen by the Reserve will be included in the project report as well. Final deliverables for each task will be made available to the TWP Coordinator for public distribution by the dates listed in the table below.

PWA will deliver draft and final copies of the project report. Up to 5 bound copies (depending on the product, draft documents may not need to be submitted in this format which will be determined by the TWP Coordinator) and a PDF version of the draft report will be distributed. Draft documents need to be sent two weeks before the review is to be completed and need to be provided in a format acceptable to reviewers (as determined by the TWP Coordinator). Hard copies of the interim products will be made available for the meetings as deemed appropriate by the TWP Coordinator. The TWP Coordinator will receive a document containing all comments, and if any review comments were not incorporated, a document explaining the reasoning. The TWP Coordinator has the final word about what will be accepted in the final documents. For the final report we will provide at least 5 bound copies, one un-bound copy, and a PDF version.

Schedule of DeliverablesTask Draft FinalD Model Selection Meeting – agenda & minutes Week of

12/4/06Week of 12/11/06

A Literature Review Memorandum 12/15/06 1/12/07D Summary of data acquisition for model development 12/22/07 1/12/07B Restoration Concepts Memorandum 1/19/07 2/16/07D/E Refined Conceptual Model & Typology Memorandum 1/19/07 2/16/07D 33% Report: Model Calibration Report

(grid construction [domain and resolution], runtimes, etc)1/26/07 n/a

D 100% Report: Model Calibration Report (calibration & validation results)

3/16/07 3/30/07

C/D/E/F 20% Report: The Future Evolution of Elkhorn Slough (No action only; chapters on hydrodynamics, inlet stability, morphology & habitat at years 0, 10 & 50)

6/8/07 n/a

C/D/E/F 50% Report: The Future Evolution of Elkhorn Slough (No action + 2 restoration concepts; chapters on hydrodynamics, inlet stability, morphology & habitat at years 0, 10 & 50)

7/27/07 n/a

C/D/E/F 100% Report: The Future Evolution of Elkhorn Slough (No action + 4 restoration concepts; chapters on hydrodynamics, inlet stability, morphology & habitat at years 0, 10 & 50)

9/28/07 10/26/07

G Conceptual Engineering Design 2/1/08 3/20/08ALL Final Project Report 2/21/08 3/20/08

Reporting & Schedule – 1

Reporting & Schedule

Model construction and calibration will be completed five months from the contract start date. Model application, morphological scenarios, and inlet dynamics tasks will be completed twelve months from the contract start date.

Reporting & Schedule – 1

PWA has the staff, organization and experience to manage large projects and team, insuring excellence in technical work, clear communications, and on-time/on-budget delivery of work products. Our project leadership team will handle all management tasks including staffing, client communications, budget tracking and invoicing, subconsultant coordination, project deliverables, and QAQC.

The PWA team will be led by Don Danmeier as the day-to-day project manager overseeing task, schedule and budget management and coordinating work among the technical disciplines. Jeffrey Haltiner will provide Principal-level project guidance and oversight as Project Director. Either Dr Haltiner or Dr Danmeier will always be available for communication with the client and immediate response.

The PWA Project Manager will conduct regular progress calls with both the client and subconsultant staff. The PWA Project Manager and TWP Coordinator will hold weekly or biweekly calls. The progress calls will provide an opportunity to discuss progress on active tasks and deliverables; identify any necessary changes to the project approach to meet the project objectives; discuss and resolve key issues; and identify items for follow-up. The PWA Project Manager will record the key items discussed, decisions, and action items. These notes will be filed in the PWA project file, and distributed to the TWP Coordinator as appropriate.

The PWA Project Manager conducts detailed monthly project and budget tracking during preparation of the monthly invoice. The tracking process includes comparing actual monthly expenditures to expected expenditures and remaining budget, at a task and subcontractor level of detail. The expected expenditures are based on task start and end dates and percent complete. Any significant deviations from expected progress are identified and resolved.

The PWA Project Manager will be responsible for ongoing client communications and coordination. We anticipate six formal meetings with Reserve staff throughout the duration of the project. These are a project start-up meeting, four interim meetings and a meeting to present final results. The interim meetings will provide progress updates, identify any necessary changes to the project approach to meet the project objectives and discuss and resolve key issues. We anticipate the Modeling Advisory Team will participate at these interim meetings. One week prior to interim meetings, the PWA Project Manager will provide an agenda that includes a short summary of activities to date (including percent completion of each task and a written description of progress made), a projection of the next quarter’s activities, a list of key decisions that need to be made at the meeting, and any materials that will be presented at the meeting (in order for the MAT and TWP Coordinator to properly prepare for the meeting). The agenda and read-ahead material will be made available to Tidal Wetland Project participants. More frequent informal meetings will be arranged as necessary between key participants for discussion of progress, project site visits, etc.

Project Management – 1

Project Management

Our QAQC program involves quality control checks at multiple levels: all calculations, model parameters, model results etc are peer-reviewed for accuracy by technical staff prior to submittal. In addition, senior staff (PM and PD) review all results for reasonableness, and the translation of these results into management guidance. All subconsultant reports are also reviewed by the PWA project leaders. Preliminary design work and cost estimates are reviewed by registered California Civil Engineers.

Project Management – 2

All of the analysis, modeling and prediction in Tasks C, D, E, and F is subject to varying levels of accuracy and uncertainty resulting from a combination of: data availability and accuracy; the capability of numerical models to simulate actual processes; conversion of short term modeling results into longer term morphological changes; conversion of morphological change into habitat response; future climatic and sea level conditions; and other factors. Identifying the types of uncertainty, determining the relative scale and importance of uncertainty in different processes, and particularly, recognizing how the types of uncertainty affect management decisions are crucial to selecting the preferred alternative. Therefore, we recommend that the following approach:

1. Characterize (and quantify where possible) the uncertainty in each of the key steps in Tasks C-F).

2. Identify those that are most important in determining impacts and assessing alternatives. Review the accuracy and sufficiency of available data. Recommend additional or future data collection as needed (for example, the availability of accurate topographic elevation data on both the eroding and more stable salt marshes is key to separating possible erosion from tectonic subsidence versus increased tidal elevations/drowning in response to the harbor opening).

3. Reducing uncertainty by maximizing use of calibration data (and validation periods where available), observed changes and input from key long-term stakeholders and scientists.

4. Using multiple methods to assess various processes (such as using both hydrodynamic and geomorphic methods to predict slough evolution).

5. Recommending management approaches that are most resilient to uncertainty and future changes.

6. Using an “adaptive management” approach to implementation (build experiments into initial steps and “learn as you go”). PWA recommended this approach in our 1992 work, which identified separate projects that could be implemented in a phases manner to reduce tidal prism (i.e., controlling tidal exchange in Parson’s slough, and other wetlands with controllable tidal connections such as the Azevedo and Blohm-Porter marshes)

In step 1 above, we recognize that uncertainties in the analysis process result from a number of factors, including:

Uncertainty in the model input parameters (e.g., elevation data over vegetated marsh and tidal creek channels, etc)

Uncertainty in the model predictions of hydrodynamics (e.g., sensitivity of results to specification of model parameters, resolution of all relevant processes, etc)

Uncertainty in the conversion of flow predictions to shear stress (e.g., influenced by assumed bed roughness and ability to resolve bathymetry)

Uncertainty in the conversion of shear stress to predicted erosion and sedimentation (e.g., spatially variability of physical properties of soil)

Budget – 1

Identifying and Managing Prediction Accuracy and Uncertainty

Uncertainty in the conversion of short-term sediment predictions to long-term geomorphic response. (e.g., errors in short-term model results may accumulate if simply extrapolated over the long-term)

Uncertainty in the prediction of future habitat to future morphology and tidal regime (e.g., role of biological processes, resilience of approach).

The use of normal statistic distributions to identify the model uncertainty from initial data uncertainty is not feasible because of the complexity and nonlinearity of the processes involved. In response, we will use a “sensitivity analysis” to quantify the key responses (i.e., predictions of erosion and sedimentation) to varying model parameters (e.g., bed roughness, et cetera). Results from the sensitivity runs will quantify how the uncertainty in model parameters translates to a range of predicted responses.

Use of the short term hydrodynamic model results to predict future morphology is also subject to significant uncertainty. We propose to address this by using two complementary methods:

Use of the numerical model to create appropriate “shear signatures” for various conditions (pre-1947, current, future with each alternative) and comparing these to identify equilibrium conditions.

Use of reference sites/equilibrium hydraulic geometry to predict future equilibrium results.

The difference between these methods also provides an estimate of prediction uncertainty. Use of similar approaches (sensitivity of results to a range of input parameters and geomorphic methods) will be used to identify uncertainty in the tidal inlet stability analysis.

Quantification of uncertainty combined with the selection of the most appropriate management responses (Items 5 & 6 above) that are resilient and where possible, can be adaptively implemented will provide the optimal selection of a preferred alternative.

Budget – 2