Table of Contents Consolidated Report on Peer Reviews... Pages 2-17 Executive Summary. Page 2 Introduction... Page 5 Physical and Environmental Data Page 5 Numerical Modeling. Page 7 Coastal Engineering. Page 10 Review of CTC s Draft Final IMP Report. Page 12 Appendices of Peer Review Reports Applied Technology and Management, Inc A Coastal Planning and Engineering, Inc.. B Coastal Research Associates C Coastal Resources and Capital Management Services April 28, 2009
EXECUTIVE SUMMARY CONSOLIDATED REPORT ON PEER REVIEWS Sarasota County contracted with Coastal Planning and Engineering (CPE), Applied Technology Management (ATM) and Coastal Research Associates (CRA) to perform Peer Review services of the available Inlet Management Plan (IMP) for Big Sarasota and New Pass body of work created by Coastal Technologies Corporation (CTC). In general, the peer reviewers were assigned 3 tasks including 1) baseline review of existing data, 2) detailed evaluation of each IMP discipline area, and 3) providing a comprehensive final report of their findings. Task 1 included an initial review of 12 existing IMP data sets and reports, researching and reviewing any additional data deemed necessary, initial identification of problematic data and participation in a work coordination meeting with County staff and all peer review consultants. Task 2 included the detailed review and separate reports for each disciple area including physical and environmental data, numerical modeling, geotechnical data and coastal engineering. Task 3 involved the summation of the peer review findings in Tasks 1 and 2 with an appendix including the separate reports developed in Task 2. Physical And Environmental Data The physical and environmental data consists of extensive beach profile survey from Longboat Key to Siesta Key, cross sections of the Big Sarasota and New Pass inlet systems, aerial photography, water level elevations, current measurements and sediment sampling. In general, the reviewers consider the baseline data a sufficient basis for this study which meets acceptable standard engineering practices in type and procedures. The reviewers consider this data as detailed and comprehensive and should be used as the basis for further work within the system. CRA stated, we are not aware of any additional relevant data that have not been incorporated this IMP effort. However, the reviewers do point out some non-fatal technical deficiencies with the data that should be addressed before or during the design phase of any specific project related to the IMP. Numerical Modeling Hydrodynamic, wave refraction and sediment transport modeling of the inlet systems was performed as tools to predict future response of the system given a specific set of alternative project types that could be incorporated through future design. The specific alternatives are thoroughly described in CTC s IMP report dated 2008. April 2009 Page 2 of 17
Hydrodynamic Modeling (ADCIRC): ATM and CRA were in general agreement that the ADCIRC program, methodology of application and results generated were sufficiently used as a tool for screening (CRA) of the various project alternative options presented by CTC. CPE concluded that the ADCIRC modeling conducted did provide reasonable results but that ADCIRC was not appropriate for evaluating the alternative options for this project due to its limitations when considering the physics of waves, wave-current interactions and water level variations aside from astronomical tides. Their basis was that using a model (ADCIRC) not capable of including wave induced processes provides inaccurate results when considering alternatives which include bathymetric changes. CRA s review determined that the need for additional numerical modeling would be limited to that needed for specific designs. In additional to ATM and CRA s agreement with the modeling efforts and CPE s disagreement with the model used, other technical items were identified as those which are areas of deficiency or improvement. Wave Refraction Modeling (WABED) & Sediment Transport Modeling (M2D Beta): Wave refraction and sediment transport modeling were added to CTC s scope of work during the progress of developing the IMP. The US Army Corps of Engineers (USACE) authorized Sarasota County to utilize a beta or test version of their revised M2D sediment transport model for this effort. The County directed CTC to use the M2D model for evaluating the identified alternatives for Big Sarasota Pass. The USACE was to complete modeling efforts for New Pass which has not yet been completed as of the date of this report. While the USACE provided this model with the understanding it had been calibrated for use within the Big Sarasota Pass and New Pass system, CTC found many technical deficiencies. CTC spent a considerable amount of effort with the USACE resolving the major technical deficiencies to produce the provided results. The reviewers concluded that CTC s results made sense from a general analytical evaluation and were reasonable for use in screening the proposed alternatives. CRA stated that Predicted changes should represent an upper limit due to the most energetic of 20 year data being used. However, the technical deficiencies forced an inconsistent application of the effort for evaluating alternatives and precluded reviewers from fully supporting the results and they do not support reliance on the information as a decision making tool for the IMP. The reviewers also emphasize that sediment transport modeling is a difficult task and there is no existing tool which can currently provide results without a considerable margin of error. The reviewers do give credit to CTC s efforts recognizing the difficulty of their work and the current state of this science and technology. April 2009 Page 3 of 17
Coastal Engineering Based on predictive numerical modeling and analytical coastal engineering practice, the CTC team developed five alternative project conditions for each inlet in addition to the existing inlet conditions. With regard to these alternatives, the reviewers conducted specific tasks to review and report on the coastal engineering efficacy of CTC s work. Based on their review ATM and CRA conclude the recommended alternatives are reasonable and consistent with standard coastal engineering practices and there are no fatal or irreconcilable issues were noted within the review of all efforts to date (CRA). The estimated levels of uncertainty, inherent with the analysis taken, meet accepted standards and are directly related to the magnitude of each alternative effort. CPE offers guarded acceptance of the recommended alternatives basing their support on various criteria. The primary suggestions of additional measures which could be taken to mitigate hazards or unintended consequences were; to implement an active monitoring plan to baseline existing conditions; start with a small or test scale effort; monitor the effects of the work in comparison with baseline conditions; and continue with IMP implementation based on the outcome of monitoring results. It was also indicated that the regulatory process required for any specific project would thoroughly vet and incorporate additional measures which could be taken to mitigate hazards or unintended consequences. The sediment budget was well received by ATM and CPE and both suggest it should be the basis for future evolution of the management plan (ATM). CRA considers the information useful but suggests the sediment budget and sand redistribution should be further reviewed by at least 2 firms and then vetted by a panel of experts. Review of CTC s Draft Final IMP Report In association with the evaluation of the three subject areas listed above, the reviewers provided their comments on CTC s draft final report titled Comprehensive Inlet Management Program, Big Pass and New Pass Management Alternatives dated April 2008. Based on the IMP body of work, this report is intended to provide Sarasota County with a management plan which addresses all three objectives of the effort including a) controlling erosion on adjacent beaches; b) providing a sand management strategy, and c) facilitating safe navigation. The reviewer s evaluation of CTC s draft final report identified its sufficiency to serve as a framework for development of a comprehensive inlet management plan for both passes but it insufficiently utilized the project data to appropriately address all three objectives and provide a practical management plan. A specific weakness of the report is that it overemphasizes modeling which should be superseded by the goals (a, b and c) outlined above. Using the reviewer s comments and suggested revisions noted below, CTC intends to revise their draft report and provide the County with a final management plan inclusive of content which sufficiently addresses all objectives of the planning effort. April 2009 Page 4 of 17
CONSOLIDATED REPORT ON PEER REVIEWS INTRODUCTION Sarasota County contracted with Coastal Planning and Engineering (CPE), Applied Technology Management (ATM) and Coastal Research Associates (CRA) to perform Peer Review services of the available Inlet Management Plan (IMP) for Big Sarasota and New Pass body of work created by Coastal Technologies Corporation (CTC). In general, the peer reviewers were assigned 3 tasks including 1) baseline review of existing data, 2) detailed evaluation of each IMP discipline area, and 3) providing a comprehensive final report of their findings. Task 1 included an initial review of 12 existing IMP data sets and reports, researching and reviewing any additional data deemed necessary, initial identification of problematic data and participation in a work coordination meeting with County staff and all peer review consultants. Task 2 included the detailed review and separate reports for each disciple area including physical and environmental data, numerical modeling, geotechnical data and coastal engineering. Task 3 involved the summation of the peer review findings in Tasks 1 and 2 with an appendix including the separate reports developed in Task 2. The following consolidated report outlines the findings of the peer review consultants. PHYSICAL AND ENVIRONMENTAL DATA The physical and environmental data consists of extensive beach profile survey from Longboat Key to Siesta Key, cross sections of the Big Sarasota and New Pass inlet systems, aerial photography, water level elevations, current measurements and sediment sampling. In general, the reviewers consider the baseline data a sufficient basis for this study which meets acceptable standard engineering practices in type and procedures. There reviewers consider this data as detailed and comprehensive and should be used as the basis for further work within the system. CRA stated, we are not aware of any additional relevant data that have not been incorporated this IMP effort. However, the reviewers do point out some non-fatal technical deficiencies with the data that should be addressed before or during the design phase of any specific project related to the IMP. These deficiencies include: Lack of establishing a vertical datum for the water level recorders (ATM/CPE). April 2009 Page 5 of 17
Lack of a quantitative analysis of the aerial photography which would demonstrate the inlet morphodynamics based on the time-series of aerials (ATM/CPE/CRA). Current and tide gauges were not deployed to adequately measure the vertical current profile in the Big Sarasota Pass channel (CPE). The Big Sarasota Pass current profiler was not located correctly (CPE). Observation of offshore water levels using a standard tide gauge would have been a good addition (CRA/CPE). Include clarification of the inaccuracies regarding 2 nd and 3 rd order control (CPE). A fence diagram for sediment data would be helpful (ATM). Some of the significant accumulations of shell hash material may be questionable for beach compatibility (ATM). An isopatch delineation the areas of beach compatible sand would be helpful (ATM). The sand used for nourishment of Longboat and Lido keys is different from the native material in the nearshore area and shoal systems in terms of composition, grain size and color. This may prove useful in the determination of sediment pathways and magnitude of transport within the littoral system. There are some historic discrepancies regarding grain size within the Big Pass ebb shoal associated with previous studies. This type of sediment mapping would help to address this discrepancy (ATM). Additional geotechnical data may need to be collected for any detailed design and regulatory permitting (ATM). Ebb shoal sand sources should have been characterized by grain sizes and identified at which beaches it would be compatible (CPE). The 2006 vibracore logs are lacking layer descriptions for 16/18 logs. No munsell colors were recorded. The 76 core samples provide an accurate representation of the upper portion of each core. There may be some missing samples from the bottom of most cores (CPE). Native and filled beach sample data was to be collected and analyzed as an effort to better understand how the beaches may have changed as a result of previous fill projects. This information was not provided (CPE). The number and depth of cores were not determined by statistical analysis (CRA). The source and variability of collected data incorporate inconsistency (CRA). The BPNP deltas were divided into subareas and potential volumes of beach quality sand. The report does not discuss the classification criteria for beach quality sand. The report should state whether FDEP criteria and guidelines were considered (CPE). Appendices of the geotechnical reports should include a legend and description indicating the lithologic symbols used in the logs (CPE). Additional consideration should be given to the northern boundary of the sediment budget Cell 1 because long term profile and fill placements extend beyond this boundary (ATM). Additional detail needed on hot spots (Longboat/Lido/Siesta) (ATM). Hindcasting is adequate for general planning purposes but is subject to potential error of +- 20%. A state of the art wave gauge deployed in the area of Siesta Key should be deployed to improve confidence in modeling (CRA). April 2009 Page 6 of 17
NUMERICAL MODELING Hydrodynamic, wave refraction and sediment transport modeling of the inlet systems was performed as tools to predict future response of the system given a specific set of alternative project types that could be incorporated through future design. The specific alternatives are thoroughly described in CTC s IMP report dated 2008. Hydrodynamic Modeling (ADCIRC): ATM and CRA were in general agreement that the ADCIRC program, methodology of application and results generated were sufficiently used as a tool for screening (CRA) of the various project alternative options presented by CTC. CPE did conclude that the ADCIRC modeling conducted did provide reasonable results but that ADCIRC was not appropriate for evaluating the alternative options for this project due to its limitations when considering the physics of waves, wave-current interactions and water level variations aside from astronomical tides. Their basis was that using a model (ADCIRC) not capable of including wave induced processes provides inaccurate results when considering alternatives which include bathymetric changes. CRA s review determined that the need for additional numerical modeling would be limited to that needed for specific designs. In additional to ATM and CRA s agreement with the modeling efforts and CPE s disagreement with the model used, the following technical items were identified as those which are areas of deficiency or improvement: Model calibration was reasonable but should have included water levels inside the bay to show the tidal wave was propagating correctly (ATM). ADCP current was measured across the inlet. Additional bin comparisons would have been good to represent the cross sectional distribution (ATM). Collection report emphasizes the benefit of the meters in getting the multiple bins but the information is not presented (ATM). Some inconsistency where the report states the importance of wind but it was not included as one of the modeled forcing boundaries (ATM). Additional discussion on the expected accuracy to the offshore forcing in relation to measured tides at the inlet would clarify some relatively significant errors between measured and modeled data sets (ATM). It may have been better to provide model comparison data (currents and water surface elevations) using tidal harmonics instead of just RMS errors (ATM/CPE). Changes in tidal prism for the various alternatives would be beneficial and it is important to demonstrate it is passing the inlets correctly. This is a key element relative to inlet management and was not done (ATM/CRA). Although offshore current information is difficult to obtain, a comparison of the model to data comparison for offshore currents would be beneficial (ATM). The study did not consider any changes to overall exchange within the interior bay. This should be addressed even if negligible (ATM). April 2009 Page 7 of 17
Discussion should be added in terms of absolute velocities and their ability to move sand on the shoal (ATM). Additional discussion regarding tidal prism and change is mass balance would be beneficial (ATM). The effects of potential rapid shoreline changes must be analyzed over the transient effects on the flow within the inlet (CPE). The filtered water level data was given in absolute values which did not allow the reader to determine if the data was generally high or low (CPE). The report should include discussion of the values that were varied during calibration (CPE). The water level calibration was reasonable showing an error of 0.20-0.24 RMS. The current data calibration was not as good showing an error of.378 m/s RMS where peak velocities are ~1.3m/s (CPE/CRA). The report states the bathymetry was referenced to NAVD 88 which is close to Mean High Water in Sarasota County. Predicted tides were used as a boundary condition with no adjustment to a fixed datum such as NAVD88. Mean sea level or mean tide level may have been a better reference datum for the bathymetry (CPE). Data to show results of removing the low-frequency effects in the current data set as was done for the water levels is needed (CRA). Report states that there was good agreement for ADCIRC calculations and measurements for water levels and currents but no quantitative criteria for this assessment were provided (CRA). More discussion is needed to define the methodology for selecting the number and location of the 15 data stations used for the alternatives assessment (CRA). There are no evaluation stations in the work areas of some alternatives such as D2 (CRA). Wave Refraction Modeling (WABED) & Sediment Transport Modeling (M2D Beta): Wave refraction and sediment transport modeling were added to CTC s scope of work during the progress of developing the IMP. The US Army Corps of Engineers (USACE) authorized Sarasota County to utilize a beta or test version of their revised M2D sediment transport model for this effort. The County directed CTC to use the M2D model for evaluating the identified alternatives for Big Sarasota Pass. The USACE was to complete modeling efforts for New Pass which has not yet been completed as of the date of this report. While the USACE provided this model with the understanding it had been calibrated for use within the Big Sarasota Pass and New Pass system, CTC found many technical deficiencies. CTC spent a considerable amount of effort with the USACE resolving the major technical deficiencies to produce the provided results. The reviewers concluded that CTC s results made sense from a general analytical evaluation and were reasonable for use in screening the proposed alternatives. CRA stated that Predicted changes should represent an upper limit due to the most energetic of 20 year data being used. However, the technical deficiencies forced an inconsistent application of the effort for evaluating alternatives and precluded reviewers from fully supporting the results and April 2009 Page 8 of 17
they do not support reliance on the information as a decision making tool for the IMP. The reviewers also emphasize that sediment transport modeling is a difficult task and there is no existing tool which can currently provide results without a considerable margin of error. The reviewers do give credit to CTC s efforts recognizing the difficulty of their work and the current state of this science and technology The reviewers identify the following technical items as areas of deficiency or improvement: There was no qualitative or quantitative indication or discussion on the calibration for the water level, current, wave and morphology models (CPE/ATM/CRA). There is no technical basis for comparison of the modeled and observed morphodynamics. More emphasis should be given to the measured bathymetric and profile data which provide greater reliance (CPE). The M2D simulated currents should have been compared to the ADCIRC and measured data to show no significant alteration the flows and currents within the passes (CPE). There should be some discussion on stability between the ADCIRC and M2D models which were run with significantly different time steps of 1 sec and 90 sec respectively (CPE). Comparison of the modeled bathymetry and the measured bathymetry is needed (ATM). The model uses hindcast data which is a calculation of wave conditions within the region, and is standard practice. This data is a regional estimation of wind characteristics and does not account for local behavior. The model included important wave current interaction which is a significant physical process in the vicinity of these inlets (ATM). Wave-induced current due to wave breaking is not accounted for which no alternative approach exists to fully address this issue (CPE/ATM). Although water levels were measured, predicted tides were used for boundary conditions in M2D and WABED. There should be some discussion on why this is so (ATM). 1-yr morphologic changes were not realistic because they did not show any changes in the beaches/surf zone on Lido, south end of Longboat or north end of Siesta (CPE). The model should have been run for a 5 year period but was only run for 1. Monthly results and comparisons made it hard to gain an understanding of the long term results. Presentation of 6mo and 1 yr results with greater variety of output would have been more suitable (CPE). Problems with modeling were noted therefore the results should have been heavily qualified (CPE). WABED did not appear capable of handling multiple grain sizes and their relative friction factors and it was not clear how the consultant compensated for these deficiencies (CPE/CRA). Bottom friction in the wave model was not discussed (CPE). April 2009 Page 9 of 17
Artificially increased grain sizes were introduced into the model to provide realistic results (CRA). The model grid extent cut off significant portions of the interior bay and should have extended to areas of narrow constriction well away from the inlets. (CPE). Since the entire Sarasota Bay was not included in the simulations, tidal prisms and thus currents in the passes would be underestimated by the simulations and thus contribute to what is considered limited morphological change (CRA). There is potential for the collapse of the ebb shoal when considering some of the alternatives including channel realignment. Modeling indicates minimal transport in areas of the ebb shoal which would involve major changes in tidal prism for certain alternatives (CPE). Grid cell sizes are different for these models than ADCIRC (CRA). A comparison to the no-action alternative and observed inlet changed would be beneficial and provide some assurance of model calibration. The no-action alternative results not showing much change are odd since the most energetic year of wave data was used. Overall, shoaling and erosion is surprisingly minimal to modest given the most energetic year of data was used (CPE/CRA). M2D is in its beta version and relatively one of its first applications. Since it is 2D it has certain limitations, it cannot represent secondary flows known to occur in channel bends and may have trouble representing flows in Big Sarasota Pass where the alignment is not linear (CRA). Since morphological models are in their infancy the results should be viewed as indications rather than predictions of reality (CRA). Conclusions regarding some of the alternatives are drawn without apparent supporting information from modeling results (CPE). Concerns with reliability of morphological analysis, therefore a greater reliance should be placed on other data (CRA). Due to long term variability, 5yr morphology simulation would have been better than 1yr. The 5yr sets could have included a high energy year, low energy year and several average years. The wave data set (highest energy year) was atypical and should not have been used in formulating an IMP recommendation (CPE). Due to the inconsistency and difficulty experience during the modeling process we do not have confidence in the predicted morphological change rates (CRA). COASTAL ENGINEERING Based on predictive numerical modeling and analytical coastal engineering practice, the CTC team developed five alternative project conditions for each inlet in addition to the existing inlet conditions. With regard to these alternatives, the reviewers conducted the following tasks: Evaluated the specific alternative conditions presented Reviewed the feasibility of the alternative conclusions and recommendations Evaluated the potential hazards or unintended consequences inherent with each alternative condition for the study area and up/down drift reaches April 2009 Page 10 of 17
Provided input as to additional measures which could be taken to mitigate hazards or unintended consequences Reviewed the analytical results of the IMP study derived from modeling results and survey data Assessed the IMP study s consistency with standard coastal engineering practices; and Estimated the potential degree of error and uncertainty of the IMP study and alternatives Based on these tasks ATM and CRA conclude the recommended alternatives are reasonable and consistent with standard coastal engineering practices and there are no fatal or irreconcilable issues were noted within the review of all efforts to date (CRA). The estimated levels of uncertainty, inherent with the analysis taken, meet accepted standards and are directly related to the magnitude of each alternative effort. CPE offers guarded acceptance of the recommended alternatives basing their support on various conditions as noted below. The primary suggestions of additional measures which could be taken to mitigate hazards or unintended consequences were; to implement an active monitoring plan to baseline existing conditions; start with a small or test scale effort; monitor the effects of the work in comparison with baseline conditions; and continue with IMP implementation based on the outcome of monitoring results. It was also indicated that the regulatory process required for any specific project would thoroughly vet and incorporate any additional measures which could be taken to mitigate hazards or unintended consequences. The sediment budget was well received by ATM and CPE and both suggest it should be the basis for future evolution of the management plan (ATM). CRA considers the information useful but suggests the sediment budget and sand redistribution should be further reviewed by at least 2 firms and then vetted by a panel of experts. Specific items of comment from the reviewers are as follows: No alternative is free from risk and uncertainty and should be considered within the monitoring and adaptive management protocols that should be developed as part of the IMP (CRA). There are no alternatives or recommendations that match the overall sediment budget or stem from the sediment budget. Alternatives to optimize areas of gains/losses to maintain the shoreline in an efficient and effective manner should be provided (ATM). Need to address possible mitigation of localized hot spots (ATM). Need discussion regarding the merits of each New Pass alternative (ATM). 1.1 million CY proposed to be mined from the New Pass shoal should be considered as an alternative. The sediment budget could be the basis for this evaluation (ATM). The Big Sarasota Pass alternatives are more thoroughly vetted than the New Pass alternatives which are based primarily on modeling results (ATM). In lieu of modeling results a sediment budget analysis could be used to support recommended alternatives (CPE). April 2009 Page 11 of 17
The recommendation against Alternative C seems premature because it would reduce erosion on the shoreline south of the inlet, possibly reduce erosion on south Lido Key and cause the southern ebb shoal to collapse on the beach and possible development of beach ridges an the northwest areas of Siesta Key (CPE). The recommendations do not address environmental issues (CPE). The volumes considered for excavation are modest and small relative to the overall shoal volumes. Alternative channel alignments represent the highest risk and certainty in the modeling is not sufficient to alleviate these concerns (CRA). Some of the potential unintended consequences could be possible lowering of the Big Sarasota Pass ebb shoal; changes in the pocket beaches along north Siesta Key; and alternations in the western beaches of Siesta Key north of Point of Rocks. If not properly addressed the first and last of these are most likely (CRA). A long term policy of adaptive management is recommended (CRA). Robust long term monitoring is recommended for attaining the stated study goals (CRA). A smaller amount than the recommended 836,000 CY of material in Alternative D3 should be removed in any initial dredging (CRA). The high rate of shoaling for Alternative C is somewhat counter intuitive since the new channel would be more hydraulically efficient and tend to limit shoaling. The high rate of shoaling may be due to the high energy wave data set which included several extreme storm events (CPE). A shoreline response would be expected when dredging close to the southern end of Lido Key but the model shows no changes (CPE). Based on comments above, Big Sarasota Pass Alternative C conclusions are not valid (CPE). REVIEW OF CTC s DRAFT FINAL IMP REPORT In association with the evaluation of the three subject areas listed above, the reviewers provided their comments on CTC s draft final report titled Comprehensive Inlet Management Program, Big Pass and New Pass Management Alternatives dated April 2008. Based on the IMP body of work, this report is intended to provide Sarasota County with a management plan which addresses all three objectives of the effort including a) controlling erosion on adjacent beaches; b) providing a sand management strategy, and c) facilitating safe navigation. The reviewer s evaluation of CTC s draft final report identified its sufficiency to serve as a framework for development of a comprehensive inlet management plan for both passes but it insufficiently utilized the project data to appropriately address all three objectives and provide a practical management plan. A specific weakness of the report is that it overemphasizes modeling which should be superseded by the goals (a, b and c) outlined above. Using the reviewer s comments and suggested revisions noted below, CTC intends to revise their draft report and provide the County with a final management plan inclusive of content which sufficiently addresses all objectives of the planning effort. April 2009 Page 12 of 17
There should be enough sand accumulating in the Big Sarasota Pass ebb shoal and inlet marginal shoal on Lido Key to nourish the adjacent beaches (CRA). There is insufficient discussion provided to fully address the first goal (a). Areas of hot spot erosion should be identified and discussed. Implementation of structural solutions should be evaluated or addressed, even if not a viable option (ATM). The report does not specifically address the second goal (b) by making recommendations that match the overall sediment budget or stem from the sediment budget, matching with net gains/losses. There are no strategies or options to optimize areas of gains/losses to maintain the shoreline in an efficient and effective manner. The report needs to address possible mitigation of localized hot spots (ATM). Report does not provide an overall analysis of the navigation needs/strategy (goal c) in the area with emphasis on Big Sarasota Pass vs. New Pass, travel times, benefits/costs of maintaining one inlet over the other as a navigable channel. Evaluation needed for existing/future usage patterns, vessel types/drafts. Navigation safety issues should be identified for each passage any accidents how did they occur associated with inlet conditions/channel orientation/other vessels/etc (ATM) Report overemphasizes modeling which should be superseded by the goals outlined above (ATM). Intro should address the historical context of the report and the need of the study including: discussion of maintaining Big Sarasota Pass vs. New Pass and navigation interests of the area; relevance and variability of grain size and its importance to use on various beaches; potential for backpassing sand to Lido in relation to the overall sediment budget; erosion effects of migrating channel on the south shore of Big Pass (CPE). The report suffers from not addressing the historical context of the report and the need of the study (CPE). The report does not adequately update the Inlet Management Plan for either Big Sarasota Pass or New Pass (CPE). No inlet management plan for New Pass is presented (CPE) Section 5.5 recommends an alternative not morphologically modeled but engineering judgment suggests the recommendation is prudent (CPE). Greater effort should be made to quantify the natural variability of the morphology of the Big Sarasota Pass ebb shoal through digitization of all aerial photography (CRA). Quantify the effect of all past Lido Key nourishment on the growth of the Big Sarasota Pass ebb shoal. This quantity would represent a justifiable amount of sand to be removed and recycled to Lido Key (CRA). The effects of a closed Midnight Pass regarding tidal prism and growth of the Big Sarasota Pass ebb shoal should be examined (CRA). Aerials should be digitized and analyzed for statistical trend when moving forward for any plans to develop a specific project (CRA). Any reduction in sand volume greater than that which has been artificially added is expected to contribute to a decrease in the (ebb shoal s) protection beyond natural conditions (CRA). April 2009 Page 13 of 17
Natural bypassing to Siesta Key would be adversely impacted if a volume of material is dredged which is greater than that artificially introduced to the system (CRA). The key is to establish the volume of sand residing in the shoal as a result of nourishing Lido Key and not to remove more than that amount. Initially, do not remove more than a portion of that amount (CRA). More discussion is needed to address possibilities of what is the most desirable state of the Big Sarasota Pass shoal Is it possible to dredge sand to improve beaches north and south of Big Sarasota Pass without creating an undesirable condition increasing the risk of erosion and storm surge?...could any alternatives improve the condition of the BP shoal? (CRA) Alternatives or modifications to the shoal and inlets should be small in scope and well monitored and analyzed for effects which are discernable. This adaptive approach should be a mandatory component of any engineering that modifies the configuration of the sand (CRA). CTC should determine how much sand can be removed from the Big Sarasota Pass shoal with out reducing the degree of wave sheltering it provides to subaerial beaches and waterfront development. There has been some progress but the results to date are not definitive (CRA). Removal of an amount less than 700,000 CY from the Big Sarasota Pass shoal system appears adequate. An initial removal of 100,000 200,000 CY is suggested (CRA). Information assembled is adequate and acceptable as a blueprint for a planning document. But in its present form the IMP is not specifically detailed to proceed with a specific large scale dredging program unless a high level of uncertainty and risk of loss is willing to be accepted (CRA). Implement a monitoring program as soon as possible to begin a systematic collection of baseline data to compare results of any alternation to the sediment budget (CRA). What are the specific factors used in determining the alternative dredge pathways? They appear subjective rather than quantitative based on data and modeling results (CRA). The recommended BP shoal dredging alternative would improve navigation. No sections of the report discuss existing or future navigation requirements, safety concerns or potential benefits (CPE). The need to address the differences in existing data and coordination with other consultant s previous work was not addressed (CRA). There are weak connections between the numerical modeling, data collected and analyzed and discussion of the alternatives (CRA). The rational, justification and design of the field data collection and archived information is difficult to follow (CRA). The report should stress the uncertainties and noise inherent on the inshore and inlet systems under investigation (CRA). While environmental considerations will be fully vetted within the regulatory process, there should be some discussion of the biological baseline and some cursory April 2009 Page 14 of 17
consideration of the environmental constraints to be included with the management and alternatives which support the IMP (ATM). No baseline data is provided to assess the goal of inlet usage and safety. Data such as usage patterns, travel times between major routes, usage by vessel class, berth sizes, locations and number of reported accidents would provide a basis for the assessment of this goal (ATM). Significant wind events measured during collection were not represented within the model simulations and may be a major contributor to discrepancies in comparisons of measured to modeled data (ATM). Water quality was not provided and may be needed for alternatives which reflect a significant alteration of tidal prism (ATM). The following are the reviewer s specific suggested revisions to the draft final report. (P = Page; T = Table; F = Figure; P#/#.#.# = Page and section #) P3- Provide more discussion on the pre-sampling data collection plan or design. P3- Justification is needed of the spatial field of sampling based on the natural variability of the topography being profiled. P3- Explain why the LIDAR was not fully usable for the study. P4/2.3- Discussion on the mean/median grain size with regard to its potential use on a beach is needed or additional discussion on why bimodality negates this consideration and some alternative criteria are needed. P4/2.2.3- A reference for the statement that the carbonite sediment is typically in the form of aragonite or calcite is needed. P5- Clarify the inconsistent depths and locations which are used for determining the volume of potential borrow material on the Big Sarasota Pass ebb shoal. P6- Add discussion on criteria for suitable sand for beach nourishment. P6- The discussion on calculating an underestimated volume of sand in Big Sarasota Pass ebb shoal is an important element and needs more explanation. P6/2.3.3- Report units vary and should be consistent in English units. P6/2.3.3- Clarify why calculations were limited to -6.5ft when portions of the ebb shoal are emergent at low tide. P9- Addition information is needed for calibration of the models. What is hydraulically coupled and why is it important? Add discussion of this in the report. P9/T1- Convert all units to English to match text and other tables. P9/2.4.2- Clarify the 2 nd sentence of data collection and methodology P10- Clarify if there is concern regarding deployment of the current meters. P10- Add discussion regarding the duration as well as the characteristics of storms. P13- Variabilities are on the order of +-25% to as high as 50%. Incorporate a discussion on variability. P17/F11- The table does not define a time period or label the 2 lines on the plot. P18- There are too many qualifying adverbs, no explanation of interesting cyclic changes. The sediment budget seems disjointed and the processes seem weakly linked with the transport rates. Revisions should be made to clarify and qualify. April 2009 Page 15 of 17
P18,19/3.3.1,3.3.2- The report should include a table of quantified changes. The absence of this is an omission and affects the completeness and validity of the report. P22/F12- Volumes in F12 are not consistent with those presented in T2. P24/T4- Specify a time period. If it is 87-06 the values would not be consistent with the sediment budget in F15. Section 4- Add discussion on what s the basis for the established grid spacing Section 4- Add discussion on how to sweep together the different modeling results. Section 4- Is there a scale problem when linking all of the various model results? Section 4- Need an estimate of the error terms and uncertainties in each step of the data section assembled for modeling and when designing and running the models. Section 4- Clarify if the WIS wave data has a significant noise problem? P29,30,31- The alternatives evaluation should consider grain size. Their variation has the potential to affect performance and costs. P31/4.2- Evaluation of inlet modification w/adcirc is directed primarily at flow and not impacts to shoals or shorelines. Therefore, the results have limited application and relevance to the questions being posed. Suggest revisions to include consideration of the shoals and shorelines. P31,34/T7,8- Maximum and minimum predicted increases are not indicated nor are the relative magnitude of predicted changes. P32- Need explanation of what plugs are. P35/2 nd Para- Compare the results of M2D and ADCIRC data to verify the flow portion of the M2D model. P36/2 nd Para- P38,39/F19,20- Figures are in metric units while majority of others are in English. Convert to English. P44/3.2- Revise this section to adequately describe the cost of the considered alternatives. P44- Identify when the USACE data will become available. It appears the discussions of alternatives and predicted outcomes are highly dependent on this info. P44- The environmental discussion should be in a separate section outlining the impacts to the ecology of the beach and inlets systems. Filter feeders at the base of the food chain should be included. P45- The alternative economics seem based on subjective analyses rather and objective. The beach quality sand would have a value in excess of $6/CY. P46- The summary seems to bypass the bulk of quantitative data and analyses. P46/2 nd Para- The Big Sarasota Pass Alternative B recommendation seems improper since it was not morphologically modeled. P48/3 rd Para- Lido Key backpassing should be considered. P48/3 rd Para- The concept of contact point or contact zone is not well established and should be referenced. P48- Issue of compatibility is raised and the sand transport process is subjective. There are a lot of weak adverbs in the explanation of predicted outcomes. Revise to be more definitive. P49- States it s not obvious what physical and biological implications may associated with these changes then the text goes on to specify moderate, negligible, might be, and highly probable terms to qualify the changes. This needs clarification. April 2009 Page 16 of 17
P49/T9- Is it possible to account for volumes as small as those shown for they seem to be within the noise level for these analyses. P49/T10- The table title is Recommended Alternatives while Alternative C is labeled as Not Recommended. Revise table to be consistent. P51/T11- The title is Recommended Borrow Area Mining Alternative Priorities while Alternative D2 is labeled as Not Recommended. Revise table to be consistent. April 2009 Page 17 of 17