Review of the Lake Ontario-St. Lawrence River Studies (2006) / Chapter Skim
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3 Coastal Processes in the LOSLR Study: Flooding and Erosion Prediction System
3 Coastal Processes in the LOSLR Study: Flooding and Erosion Prediction System
Pages 63-88
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From page 63... ...
FEPS models wave and erosion physical processes of public concern: intermittent flooding, erosion of barrier beaches, sediment transport, and the economic damage associated with coastal processes along the LOSLR shoreline. The FEPS model and the field of coastal erosion and flood damage prediction remain partly in the domain of research and partly in engineering practice.
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From page 64... ...
DESCRIPTION AND ACCOMPLISHMENTS OF THE FEPS MODEL The FEPS is a modular software system developed by Baird & Associates, and the overall modeling framework is fundamentally sound. It links bathymetric, topographic, and land use data in a GIS platform with engineering models intended to characterize the physical processes involved in coastal erosion and flooding, including wave generation through loss of shoreline, damage to structures, and shore protection costs (Figure 3-1)
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From page 65... ...
Coastal Processes in the LOSLR Studies 65 at on-line 5. ailable Av 200 October (2005)
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From page 66... ...
This methodology was developed specifically for Lake Ontario. Erosion Modeling Erosion hazards were modeled as physical failures of shore protection structures and economic investment in future shore protection.
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From page 67... ...
An algorithm was developed to determine flood damage from inundation and damage from waves striking a building. The damages are quantified directly from the depth of inundation and the wave energy, respectively, using 4th order regression equations that relate the percentage of damage to flood elevation and to wave energy at the ground floor, respectively.
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From page 68... ...
Criterion 1: Empirical Foundations The FEPS models combine analyses of winds, waves, coastal erosion, shore protection, physical flood damages, and flood protection costs. Detailed databases were compiled at the county, township, reach, and parcel scales for the models (FEPS 7, pp.
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From page 69... ...
in the FEPS materials, and implications of using regression analysis for FEPS applications need further explanation and defense. BOX 3-1 Limitations of Regression Analysis for FEPS Applications Regression analyses are inexpensive, available, and straightforward, but they may not be well suited for use in the coastal and erosion analyses in the FEPS model and sub-models.
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From page 70... ...
The simple logarithmic relationship used to calculate coastal erosion has some curious characteristics that require explanation. The dimensional nature of constant "a" requires an explanation as constants in regression equations are normally dimensionless unless there is a more fundamental underlying relationship.
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From page 71... ...
For example, the wave damage to buildings is based on as little as one data set from the 1973 high lake level period. FEPS has compiled extensive datasets that have longterm value, but FEPS documentation does not fully discuss empirical weaknesses or data quality issues that affect application and interpretation of these datasets in the Shared Vision Model.
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From page 72... ...
It is common practice for a study of this magnitude and complexity to depend on rigorous independent scientific peer review of each component of the FEPS modeling. The independent review process may also suggest alternatives to the existing methods that could improve efficiency, costs, and time.
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From page 73... ...
For example, failure of shore protection structures is amenable to analysis using structural reliability methods (USACE, 2003, Voortman et al., 2002)
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From page 74... ...
Thus calibrating the recession regression equations Uncertainty in failure probability er Composite failure ailuf probability of ty ilib Mode 'c' Modal failure probabilities Mode 'b' Proba Mode 'a' Load applied to structure FIGURE 3-2 Form of result of structural reliability analysis of shore protection structure.
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From page 75... ...
Coastal Processes in the LOSLR Studies 75 .)
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From page 76... ...
The lack of specific treatment of uncertainties in the coastal recession regression model, especially parameters "a" and "b," make objective discrimination between the coastal impacts of regulation plan options impossible. INTEGRATION AND DISPLAY OF KEY INFORMATION The second charge in the statement of task focuses on the degree to which the FEPS models integrate and display coastal erosion and flooding information needed for a comprehensive evaluation and understanding of the tradeoffs for selecting among candidate regulation plans.
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From page 77... ...
The effects of coastal erosion and flooding should be incorporated as inputs to the environmental and economic models as well as the Shared Vision Model. Also, the FEPS modeling currently does not include an analysis of the potential effects of future water regulation deviations, analogous to the deviations that have occurred under Plan 1958D, on flooding and erosion damages under alternative hydroclimatic scenarios and water regulation plans.
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From page 78... ...
The temporal and spatial scales of inferences derived from the FEPS modeling endeavor are not currently explained in the FEPS documentation. Linking hourly wave data with quarter-monthly lake levels introduces issues of spatial and tempo ral resolution at the outset of the analysis.
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From page 79... ...
In fact, the important parameter for the erosion model is the lake level at the time of the storm, not an averaged value over a 1-week period. Connections between the SVM and FEPS models appear to give inadequate treatment to the spatial and temporal variation of lake water levels within the time step important for proper evaluation of flood damages.
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From page 80... ...
The FEPS review documents do not discuss these issues of spatial and temporal autocorrelation, or the effects of different storm sequences on shoreline evolution. The treatment of spatial and temporal scaling requires considerable additional effort to enable a comprehensive evaluation and understanding of flooding and erosion hazards associated with regulation plan options.
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From page 81... ...
The FEPS documentation should ultimately also be suitable for publication in the broader body of established scientific domains of coastal erosion, hydrodynamics, soil mechanics, structural reliability, economics, long-term policy and planning. Although superior to documentation of the SVM, FEPS documentation presented and reviewed here is deemed inadequate for external scientific review, and for the judgments and conclusions to be defensible in public decision-making.
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From page 82... ...
Effective scientific communication of FEPS model output requires a more thorough discussion of uncertainties associated with the flooding and erosion forecasts to enable a broad public understanding of tradeoffs among regulation alternatives. OVERALL APPROPRIATENESS AND SUFFICIENCY TO INFORM REGULATION PLAN OPTIONS The third charge of the statement of task is aimed at determining whether the IJC documents presented for review are appropriate and sufficient for use in selecting a water regulation plan option and determining impacts of changes in water levels.
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From page 83... ...
Typically, these interfaces would include dynamic feedback from other models to permit comprehensive modeling of the system. The FEPS study takes a broad approach to erosion and flood hazards of water level regulation of Lake Ontario and Upper St.
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From page 84... ...
Predictive capability would be expected to improve over time, and there is opportunity to refine the FEPS modeling process dynamically over time. A long-term monitoring program would help assess the reliability of the FEPS model predictions using water regulation outcomes.
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From page 85... ...
From the same perspective, the scientific robustness of the FEPS models remains to be demonstrated. It is clear from the documentation that the regression analysis approach to modeling coastal erosion and forecasting flood damages is considered by the FEPS authors to be less than ideal.
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From page 86... ...
n.d. Automated Lake wide Erosion Predic tions and Economic Damages on Lake Ontario .
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From page 87... ...
February 2004. Shore Protection Performance Indi cator: Methodology and Shared Vision Model Application.
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From page 88... ...
Lawrence River Studies.
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