D_VA ST NASA 1(9)_hyd.pdf

Wallops Flight Facility (WFF) Causeway

Bridge Hydraulic Study

Phase III- Final Hydraulic and Scour Analysis Report

December 31, 2021

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Table of Contents

1. Introduction

2. Purpose

3. Methodology

3.1. Available Data

3.1.1. Federal Emergency Management Administration (FEMA)

3.1.2. National Oceanic and Atmospheric Administration (NOAA)

3.1.3. US Army Corps of Engineers (USACE)

3.1.4. Field Survey Data

3.1.5. Virginia LiDAR Dataset

3.1.6. Land Use and Land Cover Maps

4. Hydrologic Analysis

5. Hydraulic Analysis

5.1. Regional Model, Existing Conditions 2D TUFLOW Hydrodynamic Model

5.2. Local Model, Proposed Conditions 2D HEC-RAS 6.1 Hydrodynamic Model

6. Scour Calculations and Scour Countermeasure at Abutments

6.1. Stream Stability and Long-Term Scour

7. Phase III Conclusion

List of Appendices

Appendix A: StreamStat Hydrology

Appendix B: Sea Level Rise Calculations

Appendix C: 100-, and 500-year Combined Storm Surge Calculation

Appendix D: Proposed Bridge and Hydraulic Models

Appendix E: Scour Calculations and Scour Countermeasures at Abutment

List of Figures http://www.hwr-plc.com/

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Figure 1 : Location Map

Figure 2 : Wallops Flight Center Island Facility, Regional and Local 2D Hydrodynamic Model Domain ... 2

Figure 3 : FEMA’s Transects near the Project Location

Figure 4 : FEMA 100-year Flood Elevations, Flood Zone VE, Flood Elevation = 11.00’ (NAVD 88)

Figure 5 : NOAA Tidal Gage at Chincoteague Channel, South End, VA, (gauge No. 8630308)

Figure 6 : NOAA Tidal Gage Datums, Chincoteague Channel, South End, VA, (gauge No. 8630308)

Figure 7 : Harmonic Constituents for NOAA Gage 8630308, Chincoteague Channel, South end, VA

Figure 8 : NASA Wallops Center Project Locations relative to FEMA’s ADCIRC Model Domain

Figure 9 : Virginia LiDAR Inventory

Figure 10 : Terrain Data sources for the Regional Model

Figure 11: Mosaicked Terrain Surface for the Local Model

Figure 12: Land use Map (source: Accomack County GIS)

Figure 13: Watershed boundary delineated using USGS's StreamStat

Figure 14 Regional and Local Models’ domains

Figure 15 : 2D HEC-RAS Hydrodynamic Model (Local Model) Setup………………………………………………….. 17

Figure 16: Local Model, HEC-RAS 2D Model, 100-year Maximum Depth

Figure 17: Local Model, HEC-RAS 2D Model, 100-year Maximum Velocities

Figure 18: Existing Bridge (HWR field visit, 2/18/2021)

List of Tables

Table 1 : FEMA 10-, 50-, 100-, and 500-year Still Water Flood Elevations

Table 2 : Stability Indicators and Ratings for the Vertical and Horizontal Stability

Table 3: 100-yr Model Output Data at Approach and Bridge Sections and Computed Scour Depths

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1. Introduction

NASA Wallops Flight Facility (WFF) is located on Wallops Island in Accomack County, Virginia. Wallop

Center’s Island facilities are accessed via Causeway Road (State Route 803) which has a bridge crossing over Cat Creek (Figure 1). The existing bridge is approximately 1284 feet long and has 21 spans supported by 20 piers.

Figure 1 : Location Map

The proposed WFF project includes replacing the existing bridge over Cat Creek at almost the same alignment of the existing bridge. The available preliminary bridge design plans (also referred to as TS&L) from Federal Highway Administration (FHWA) shows that the proposed bridge will have 17 spans with varying lengths and supported by 16 piers for a total length of 1,830 feet. Furthermore, it shows that the proposed bridge’s vertical profile slope is at 1.75%. Cat Creek and the proposed bridge are located in an inner-coastal zone facility (Figure 2) where flood flows are influenced by daily tidal and storm surge cyclonic events such as Nor’easters and hurricanes.

Hassan Water Resources, PLC, (HWR) is pleased to perform and provide the PHASE III – Final Hydraulic and Scour Analysis Report showing the detailed hydrologic and high-resolution hydraulic analysis and

Local Model of the proposed bridge replacement project including sea level rise impact and complex

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(804) 543-8073 www.hwr-plc.com two-dimension (2D) hydrodynamic modeling and combined storm surge for the 100-year and 500-year coastal flood events which are equivalent to Category 1 and 3 Hurricanes, respectively.

Figure 2 : Wallops Flight Center Island Facility, Regional and Local 2D Hydrodynamic Model Domain

2. Purpose

The purpose of is study is to provide detailed Hydrologic and Hydraulic Analysis (HHA) of the project area using high-resolution hydrodynamic models to perform bridge scour analysis in accordance with

HEC-18 and HEC-25 (FHWA). In this phase (Phase III) of the study, HWR utilized HEC-RAS 6.1 software

(USACE) to develop a high-resolution hydraulic model utilizing field survey data and output data from

PHASE II regional hydrodynamic model. Furthermore, HWR utilized output data from the Local Model, post-construction conditions, to calculate scour at the proposed bridge substructure units.

3. Methodology

PHASE III - Final Hydraulic and Scour Analysis, is based on

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1. Applicable FHWA, FEMA, and USACE regulations, publications, and methodologies for bridges in coastal zones (such as HEC-25, FHWA),

2. High-resolution 2D hydrodynamic Local Model (Local Model), and

3. Output data from the Regional Hydrodynamic model (TUFLOW 2D) that was developed in PHASE

II.

The following further explains the methodologies used to perform PHASE III - Final Hydraulic and

Scour Analysis:

a) Utilize output data from the 2D Regional Hydrodynamic Model (Regional Model), which was completed in PHASE II, as Boundary Conditions (BC) in PHASE III – Final Hydraulic and Scour

Analysis. The Regional Model covers about 66 square miles including the project’s location. HWR used SMS and TUFLOW to develop and execute the Regional Model which produced the 100-, and 500-year stage hydrographs at the project location. The stage hydrographs are used as BC in the more detailed, high-resolution PHASE III Local Hydrodynamic Model (Local Model).

b) Integrate the detailed field survey and bathymetry data with available overbank data using

ArcGIS to create necessary 3D surface that is imported into HEC-RAS 6.1. The total area of the high-resolution 2D hydrodynamic model (Local Model) is 560 acres.

c) The Local Model utilizes a nested mesh with a 15 ft grid size at the existing and proposed bridges and roadways, and 75 ft at the overbanks further away from the project location.

d) HEC-RAS 6.1 was selected to develop and perform the detailed high-resolution Local Model due to its superior capabilities to integrate the bridge substructure units as solid obstructions in the

2D mesh when compared to TUFLOW.

e) Using the available flood stages from FEMA’s studies and flood maps including Zones EV and AE at the project location and include these data in the 100-, and 500-year storm surge hydrographs.

f) Utilize the USACE Sea Level Rise calculator to estimate an appropriate sea level rise at the proposed project location to integrate it in the 100-, and 500-year storm surge hydrographs.

g) Utilize available tidal data (from NOAA) to develop the combined storm surge hydrographs for the 100-, and 500-year (Category 1 and 3 Hurricanes, respectively) including anticipated sea level rise. The stage hydrograph is input in the Local Model as BC at the Atlantic Ocean side.

h) HWR obtained the 100-, and 500-year stage hydrographs from the Regional Model at the boundaries of the Local Model at six locations that represent the flood stages at the Left overbank (LOB), right overbank (ROB), and channel at approximately 1,000 feet north and south of the proposed bridge location. These six stage hydrographs were input in the Local Model (HEC-

RAS, Unsteady Flow Data) along with BC at Atlantic Ocean side.

i) 100-year post-construction conditions’ output data from the Local Model are used to calculate the 100-year scour depth at the proposed substructure units utilizing HEC-18, FHWA. All the elevations in this report are referenced to the NAVD88, US Feet vertical datum unless specified.

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3.1. Available Data

3.1.1. Federal Emergency Management Administration (FEMA)

FEMA performed a Flood Insurance Study (FIS) for Accomack County, Virginia available in FIS number

51001CV000B, dated May 18, 2015. The FIS shows still water flood elevations. AS shown in Figure 3, the project is located between transects 34 to 36. Transect No. 35 shows the maximum flood elevations for still water. Figure 4 shows a copy of the 10-, 50-, 100-, and 500-year flood elevations at transect 35 (FIS number 51001CV000B, Table 3, Transect Data, page 17).

FEMA’s published flood elevations are based on a detailed coastal analysis and mapping study, including two-dimension hydraulic model, for Accomack County (May 18, 2015). The detailed coastal study was conducted by USACE for FEMA (NFIP Coastal Storm Surge for Region III).

FEMA’s two-dimension hydraulic model and coastal analysis has mapped the Atlantic Coast around the Wallops Island (Project area) including Chincoteague Island and majority of Chesapeake Bay for the storm surge elevations, overland wave modeling, and wave runup. The storm surge hydraulic modeling was performed using the Advanced Circulation Model for Oceanic, Coastal and Estuarine

Waters (ADCIRC) which was dynamically coupled to the unstructured numerical wave model

Simulating Waves Nearshore (SWAN). HWR has obtained a copy of the bathymetric data which

FEMA and USACE used in the ADCIRC model and coastal analysis.

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Figure 3 : FEMA’s Transects near the Project Location (Source: FEMA, FIS number 51001CV000B, Table 3, Transect Data, page 26)

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Table 1 : FEMA 10-, 50-, 100-, and 500-year Still Water Flood Elevations

(Source: FEMA, FIS number 51001CV000B, Table 3, Transect Data, page 17)

Additionally, FEMA published Flood Insurance Rate Maps (FIRM) showing the 100, and 500-year flood elevations, Figure 4 at the project location.

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Figure 4 : FEMA 100-year Flood Elevations, Flood Zone VE, Flood Elevation = 11.00’ (NAVD 88)

(Source: FEMA Flood Insurance Rate Map (FIRM) No. 51001C0280G)

3.1.2. National Oceanic and Atmospheric Administration (NOAA)

NOAA maintains a tidal gauge (station ID is 8630308) in Chincoteague Channel, South End, VA which is not very far from the project location. Figure 5 shows the relative location of NOAA’s tidal gauge to the project location. Accordingly, data from the NOAA tidal gauge is used to develop the 100-year and 500-year combined storm surge hydrographs:

(https://tidesandcurrents.noaa.gov/datums.html?id=8630308).

Figure 5 : NOAA Tidal Gage at Chincoteague Channel, South End, VA, (gauge No. 8630308) https://tidesandcurrents.noaa.gov/datums.html?id=8630308

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Figure 6 and Figure 7 show the vertical datums for NOAA’s tidal gauge and harmonic constituents, respectively which are used in developing the combined storm surge hydrographs to convert the gauge data from station datum to NAVD88 vertical datum.

Figure 6 : NOAA Tidal Gage Datums, Chincoteague Channel, South End, VA, (gauge No. 8630308)

Figure 7 : Harmonic Constituents for NOAA Gage 8630308, Chincoteague Channel, South end, VA

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3.1.3. US Army Corps of Engineers (USACE)

In 2010, USACE developed a two-dimension ADCIRC hydraulic model to simulate wave action and runup data, which was used to produce flood elevations for FEMA flood studies. The domain of the

USACE’s model is expansive, it extends from Maryland shoreline south of Atlantic City to the

Virginia-North Carolina state line. HWR has obtained a copy of the ADCIRC model and utilized a portion of the bathymetric data that is applicable to this project (Figure 8).

Figure 8 : NASA Wallops Center Project Locations relative to FEMA’s ADCIRC Model Domain

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3.1.4. Field Survey Data

Field survey data was completed by others and provided to HWR on 12/15/2021. HWR used it to develop the 2D HEC-RAS Local Model and incorporated the post-construction conditions (TS&L plans provided by other on 12/10/2021) including the proposed bridge substructure units and roadway while removing the existing bridge.

3.1.5. Virginia LiDAR Dataset

To develop the 3D surface for the Local Model, HWR supplemented the field surveyed data and bathymetric with available overbank LiDAR obtained from the Virginia LiDAR Inventory website:

https://www.arcgis.com/apps/Viewer/index.html?appid=1e964be36b454a12a69a3ad0bc1473ce

The Virginia LiDAR Inventory Web Mapping Application provides access to LiDAR point cloud and individual project metadata collected in the Commonwealth of Virginia according to the USGS 3DEP specification. Data is obtained from NOAA, USGS, and VGIN data portals. HWR downloaded multiple tiles (Figure 9) to merge with the field survey data and developed a 3D surface necessary for the two dimension (2D) hydraulic models for this project in accordance with FHWA and USACE 2D hydrodynamic modeling guidelines.

Figure 9 : Virginia LiDAR Inventory

In PHASE II, the 3D terrain data for the Regional Model covers approximately 66 square miles which extends beyond the proposed project limits. The purpose of the Regional Model’s extended 3D surface is to ensure accurate numerical simulation of the active hydrodynamic flow at the project location without influence or interaction with the hydrodynamic model https://www.arcgis.com/apps/Viewer/index.html?appid=1e964be36b454a12a69a3ad0bc1473ce

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Figure 10 : Terrain Data sources for the Regional Model

Upon reciept of the field surveyt data, HWR merged it with available LiDAR data within the project’s vicinity and developed the 3D terrain data for the Local Model which covers approximately 560 acres.

The terrain data used to in the Local Model is shown in Figure 11.

Figure 11: Mosaicked Terrain Surface for the Local Model

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3.1.6. Land Use and Land Cover Maps

The existing conditions land use data at the project and its vicinity was obtained from Accomack

County GIS data portal:

(https://accomack-county-virginia-open-data-portal-accomack.hub.arcgis.com/datasets/accomack-county-future-land-use).

Aerial imagery from ESRI Topographic Basemap "World Topographic Map” http://www.arcgis.com/home/item.html?id=10df2279f9684e4a9f6a7f08febac2a9 Map was used to validate the land use polygons and their attributes (Figure 12).

Figure 12: Land use Map (source: Accomack County GIS)

The land use data was used to estimate Manning’s roughness values for different land cover types which was used in the 2D HEC-RAS Local Model.

4. Hydrologic Analysis

The hydrodynamics at the project location is primarily a coastal storm surge per FEMA’s Flood Insurance

Study and flood maps. HWR performed the hydrologic calculations at the project location and the surrounding areas using USGS’s StreamStat web application for Cat Creek. The StreamStat results are available in Appendix A. Cat Creek watershed drainage area is approximately 16.8 sq. miles (Figure 13).

http://www.hwr-plc.com/ https://accomack-county-virginia-open-data-portal-accomack.hub.arcgis.com/datasets/accomack-county-future-land-use https://accomack-county-virginia-open-data-portal-accomack.hub.arcgis.com/datasets/accomack-county-future-land-use http://www.arcgis.com/home/item.html?id=10df2279f9684e4a9f6a7f08febac2a9

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Figure 13: Watershed boundary delineated using USGS's StreamStat.

Based on the StreamStat results, the peak flows resulting from overland runoff at the project location generated by a 100-year and 500-year storms are 1,970 cfs and 2,510 cfs, respectively.

Based FEMA’s Flood Insurance Study (FIS) flood Zone VE, the storm surge hydrographs should be used to calibrate the 2D hydrodynamic model. Accordingly, HWR utilized the Pooled Fund Study, Tidal

Hydraulic Modeling for Bridges (Development of Hydraulic Computer Models to Analyze Tidal and

Coastal Stream Hydraulic Conditions at Highway Structures), Ayers Associates, 2002, technical supervision provided by FHWA spreadsheet to calculate the combined 100-year and 500-yuear storm surge hydrographs (Appendix C).

HWR utilized the USACE Sea Level Rise Calculator, version 2019.21, to calculate the applicable sea level rise at the project location (Appendix B) to estimate the 100-year and 500-year combined storm surge hydrographs. The 100-year and 500-year combined storm surge hydrographs were used as the boundary conditions in the 2D hydrodynamic model (Regional Model, discussed in next section). The Regional

Model shows that the 100-year combined surge hydrograph peak flood discharge at the project location is 182,682 cfs.

Since the peak flood discharge from the combined storm surge hydrograph is greater than the overland runoff peak flood discharge, HWR will utilize output data resulting from the 100-year and 500-year combined storm surge (i.e., from the hydraulic model, not from overland hydrology) for all the scour analysis and countermeasure design.

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Anticipated sea level rise at the project location is calculated using the USACE calculator (Appendix B) for the year 2100. The sea level rise amount used in this study is the USACE intermediate = 1.8 ft.

Therefore, 1.8 ft is added to the 100-year (VE elevation = 11 ft) and 500-year (VE elev. = 13 ft).

Accordingly, the 100-year peak flood elevation at the Atlantic shoreline = 12.8 ft (NAVD88) and the 500-year peak flood elevation at the Atlantic shoreline = 14.8 ft.

5. Hydraulic Analysis

PHASE III hydraulic analysis is based on output data from PHASE II hydraulic analysis. PHASE III concentrates on the location of the proposed bridge and roadway approaches by developing a high-resolution hydraulic model (Local Model) to produce the finalized hydraulic analysis for this study. The following describes the development of PHASE III hydraulic analysis:

a) Utilize detailed field survey data (provided by others) to develop a 2D HEC-RAS hydrodynamic model that applies a high-resolution Local Model at the proposed bridge and roadway location to obtain detailed output data.

b) Utilize the output data (stage hydrographs) from PHASE II Regional Model as boundary conditions to the Local Model

c) Utilize the calculated 100-year Combined storm surge hydrograph as the boundary condition along the Atlantic Ocean portion of the Local Model.

HWR utilized HEC-RAS 6.1 Unsteady Flow Simulation to develop the high-resolution Local Model. HEC-

RAS 6.1 is capable of simulating a combined one/two-dimensional unsteady flow through a full network of open channels, floodplains, and alluvial fans. The unsteady flow component can be used to performed subcritical, supercritical, and mixed flow regime (subcritical, supercritical, hydraulic jumps, and drawdowns) calculations in the unsteady flow computations module. The hydraulic calculations for cross-sections, bridges, culverts, and other hydraulic structures that were developed for the steady flow component were incorporated into the unsteady flow module which is an improvement than TUFLOW model. Furthermore, HEC-RAS Mapper easily establishes a horizontal coordinate system; develops an

HEC-RAS terrain model; layout the geometric data model and extract terrain data; visualize results in the form of maps, plots, and tables. It also produces a three-dimensional plot of the terrain and many of the simulation results, in addition to inundation mapping and animations.

The most recent HEC-RAS 6.1 features an important capability to input waterway crossings like bridges.

It is how HEC-RAS 6.1 allows the blocked obstructions (such as piers) input in the simulation mesh. Unlike

TUFLOW, HEC-RAS 6.1 would allow input of a pier inside a grid cell (the grid cell does not have to be the same width as the pier) without distorting the cell’s geometry, which allows the remainder of the cell to remain active to flow(s) while blocking only the location of the pier within the cell.

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PHASE III hydraulic analysis for the project is based on two major hydrodynamic models:

a) In PHASE II, HWR developed a large scale 2D hydrodynamic model (Regional Model) that encompasses approximately 66 square miles centered at the project’s location. The Regional

Model was the preliminary hydraulic model using TUFLOW with moderate resolution (50’x50 grid mesh) and used the 100-year and 500-year combined storm surge hydrographs which were calibrated based on FEMA Zone VE plus sea level rise.

b) In PHASE III, HWR developed a high-resolution 2D hydrodynamic model (Local Model) utilizing the detailed field survey of the project site (provided by others) in addition to utilizing the output data from the Regional Model as boundary conditions for the Local Model. The Local Model is approximately 560 acres and utilizes a nested mesh with a 15 ft grid size at the existing and proposed bridges and roadways, and 75 ft at the overbanks further away from the project location.

5.1. Regional Model, Existing Conditions 2D TUFLOW Hydrodynamic Model

Since the project is located in a complex system of estuary, site conditions are predominantly coastal influenced which includes tides and combined storm surges (such as Nor’easters and hurricane events) from the Atlantic Ocean. The existing (and proposed) bridge crosses over Cat Creek which is tidally influenced through Tom’s cove which is located approximately 8 miles north of the Project location. Cat Creek continues due south to Kegotank Bay approximately 6 miles south of the project location where its confluences the Atlantic Ocean. In between Tom’s Cove and Kegotank Bay, there is a network of interconnected channels and swamp lands which experience flow reversal as the tides from the Atlantic Ocean ebbs and flows throughout the estuarian system.

To accurately simulate the complex hydrodynamic at the project site, HWR developed a 66 square mile, 2D hydrodynamic regional model using TUFLOW to properly simulate the time lag and hydraulic losses throughout the estuarian system. In order to calculate the bridge pier scour, the hydraulic model needs to be of high-resolution that is close to the pier size. Given the size of the estuary, a single high-resolution model will be computationally very large and inefficient. Thus, HWR developed the Regional Model with a local set up such that the entire estuarian system is properly modeled with a relatively coarser resolution model for PHASE II. In PHASES III and IV, a high-resolution model will be developed around the project area where its boundary conditions are obtained from the regional model (Figure 14).

The Regional Model is a 50ft X 50ft resolution 2D Cartesian grid based TUFLOW model. The existing conditions regional model is calibrated to the FEMA flood elevations plus sea level rise.

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Figure 14 Regional and Local Models’ domains

5.2. Local Model, Proposed Conditions 2D HEC-RAS 6.1 Hydrodynamic Model

HWR utilized the detailed field survey to develop a 560-acre high-resolution 2D hydrodynamic model using HEC-RAS 6.1 (USACE). The Local Model extends from the Atlantic Ocean on the east to

Radar Road on the west, which is approximately 2.3 miles long. The Local Model extends approximately 1,000 feet upstream and downstream from the existing bridge location. To perform a high-resolution modeling at the proposed bridge’s substructure units, for use in the scour calculations, HWR utilized a 15ft X 15ft Cartesian grid mesh at the bridge and roadway location and used 75 ft x 75ft grid mesh at the overbanks away from the project’s location. Furthermore, HWR utilized the output water surface elevations hydrographs (time series) from the Regional Model at the boundaries of the Local Model as the boundary conditions (Appendix D). HWR utilized

Manning’s Roughness Coefficient (n) are based on the NRCS table (Appendix D) obtained from this link:

https://www.wcc.nrcs.usda.gov/ftpref/wntsc/H&H/HecRAS/NEDC/lectures/docs/Manning%92s%2

0n-values%20for%20Kansas%20Dam%20Breach%20Analyses%20-%20Adopted%20071216.pdf.

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HWR utilized the latest TS&L proposed bridge design sheets (provided by others on 12/10/2021)

Finally, HWR used the high-resolution flow results (such as discharges, stages, and local velocities) which are obtained from the Local Model calculate scour depths at the proposed bridge’s abutments and piers.

Figure 15 : 2D HEC-RAS Hydrodynamic Model (Local Model) Setup

6. Scour Calculations and Scour Countermeasure at Abutments

HWR performed the scour analysis and calculations at the proposed bridge’s substructure units using the Hydraulic Toolbox, FHWA. HWR utilized the procedures included in HEC-18 and HEC-25, FHWA, to collect the output data from the Local Model and used it in the Hydraulic Toolbox (Appendix E).

Furthermore, HWR performed the necessary calculations for the scour countermeasure at the proposed abutments (Appendix D).

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6.1. Stream Stability and Long-Term Scour

The scour calculations and stream stability evaluations were performed using the procedures outlined in HEC-20 (Section 5.4.5, Tables 5.5 and 5.6), FHWA. Since the proposed bridge replacement will be located at the same horizontal alignment, data from the existing bridge inspection report are used in this evaluation as well.

Potential long-term scour includes general aggradation or degradation of the channel and/or the overbank areas causing an increase or decrease in the stream bed and/or overbank ground elevations. Field observations of the project site and bridge inspection report do not identify any evidence of obvious long-term aggradation, degradation, significant bank erosion, or bank mass waste or sloughing.

Table 2 shows the results of the stream stability indicators and ratings for the vertical and horizontal stability in accordance with HEC-20, Section 5.4.5 (FHWA). The overall stability indicator was estimated to be 30 which is less than 49. Thus, Cat Creek stream and overbank areas are stable and there is no long-term scour potential at the project site.

Table 2 : Stability Indicators and Ratings for the Vertical and Horizontal Stability

Stability Indicator Stability

Indicator No.

Rating Score

Reconnaissance and

Assessment

1- Watershed and floodplain activity

1 Excellent 1 Stable, forested, undisturbed watershed

2- Flow habit 2 Excellent 1 Perennial stream with no flashing flood history

3- Channel pattern

3 Excellent 2 Meandering with minor radius of curvature, primarily suspended load

4- Entrenchment / channel confinement (Vertical

Stability)

4 Excellent 2 Active floodplain; no signs of under cutting, and no levees

5- Bed material Fs (Vertical

Stability)

5 Poor 10 Very loose assortment with no packing. Large amount of bed material

< 4mm

6- Bar Development (Vertical

Stability)

6 Excellent 1 S < 0.02 and W/Y > 12

7- Obstructions, including bedrock outcrops and armor

7 Excellent 1 Not present

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Stability Indicator Stability

Indicator No.

Rating Score

Reconnaissance and

Assessment

8- Bank soil texture and coherence (Horizontal

Stability)

8 Excellent 3 Clay and Silty clay cohesive material

9- Average bank slope angle

(Horizontal Stability)

9 Excellent 1 Bank slope < 3:1, non-cohesive material

10- Vegetative or engineered bank protection (Horizontal

Stability)

10 Excellent 3 Wide band of vegetation over 90% density and cover

11- Bank cutting (Horizontal

Stability)

11 Excellent 2 Little and non-evident

12- Mass wasting or bank failure (Horizontal Stability)

12 Excellent 2 Little evidence of small bank wasting

13- Upstream distance to bridge from meander impact point (Horizontal Stability)

13 Excellent 1 More than 115 feet;

bridge is well aligned with river flow

Overall stability Score 30 < 49; Excellent

Vertical Stability Score (items

4 to 6, inclusive)

13 Minimal aggradation or degradation potential

Horizontal Stability Score

(items 8 to 13, inclusive)

12 Minimal potential for later migration

HWR utilized the procedures in HEC-18 to calculate the contraction scour and local scour at the project’s piers. Total pier scour = long term scour + contraction scour + local scour at pier.

Scour at the proposed abutments is calculated using the NCHRP Project 24-20 procedures in accordance with HEC-18, Sections 8.6 and 8.6.3 (FHWA). NCHRP Project 24-20 abutment scour equations include applicable contraction scour. Total scour at abutment = long term scour + scour at abutment.

Figure 16 and Figure 17 show the Local Model’s output data for the maximum 100-year flow depths and velocities, respectively. Figure 18 shows a picture of the existing bridge.

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Figure 16: Local Model, HEC-RAS 2D Model, 100-year Maximum Depth

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Figure 17: Local Model, HEC-RAS 2D Model, 100-year Maximum Velocities

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Figure 18: Existing Bridge (HWR field visit, 2/18/2021)

Table 3 summarizes the calculated scour depths for the 100-year storm surge at the proposed bridge using the Hydraulic Toolbox, FHWA. Appendix D includes

✓ Detailed 100-year output data from the HEC-RAS Local Model

✓ Hydraulic Toolbox scour calculation report

✓ Scour countermeasure calculations for abutment protection.

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Table 3: 100-yr Scour Depths, Hydraulic Toolbox 5.1, FHWA

Type of Scour

Live Bed or

Clear

Water

Location 100-Year Scour

Depth (ft)

Long Term N/A Cat Creek Stream Channel 0

Long Term N/A LOB (looking D/S) = West overbank

Long Term N/A ROB (looking D/S) = East overbank

Contraction Main Channel 1

Contraction LOB (looking D/S)

Contraction ROB (looking D/S)

Pressure flow potential No

Overbank Pier scour (local scour) Live Bed 15.76

Overbank Pier total scour Live Bed 16.76

Main Channel Pier scour (local scour) Live Bed 17.18

Main Channel Pier total scour Live Bed 18.18

Non-scourable (RQD > 50) Rock

Layer Elevation at Pier 0.00

Left Abutment total scour

(looking D/S), NCHRP Method Live Bed Left abutment (looking D/S) 9.46

Right Abutment total scour

(looking D/S), NCHRP Method Live Bed

Right abutment (looking

D/S) 10.2

7. Phase III Conclusion

The hydrodynamic model results show that the 100-year maximum water surface elevations at the proposed bridge location over Cat Creek are 11.85 ft (NAVD88), and total scour depths are included in

Table 3. Provide scour and erosion countermeasures at the proposed abutments and embankments by using CLASS II Rock Riprap (Nominal median particle diameter = 9 inches, and D100 = 1.5 foot) that extend from the toe of embankment up to elevation 12.00’ (NAVD 88). The riprap apron should be constructed in accordance with “Bridge Scour and Stream Instability Countermeasure, HEC-23, Volume

II, Design Guide 14 including Figure 14.8, FHWA”.

12/31/2021 An Equal Opportunity Company

(804) 543-8073 www.hwr-plc.com

Appendix A: StreamStat Hydrology

StreamStats Report

Basin Characteristics

Parameter Code Parameter Description Value Unit

DRNAREA Area that drains to a point on a stream 16.8 square miles

Peak-Flow Statistics Parameters [Coastal Plain 2011 5144]

Parameter Code Parameter Name Value Units Min Limit Max Limit

DRNAREA Drainage Area 16.8 square miles 0.06 7866

Peak-Flow Statistics Flow Report [Coastal Plain 2011 5144]

Region ID: VA Workspace ID: VA20210402201517611000 Clicked Point (Latitude, Longitude): 37.85181, -75.49028 Time: 2021-04-02 16:15:36 -0400

PIl: Prediction Interval-Lower, PIu: Prediction Interval-Upper, SEp: Standard Error of Prediction, SE: Standard Error (other -- see report)

Statistic Value Unit SEp

20-percent AEP flood 509 ft^3/s 44

10-percent AEP flood 748 ft^3/s 47

4-percent AEP flood 1150 ft^3/s 51

2-percent AEP flood 1530 ft^3/s 55

1-percent AEP flood 1970 ft^3/s 58

0.5-percent AEP flood 2510 ft^3/s 64

Peak-Flow Statistics Citations

Austin, S.H., Krstolic, J.L., and Wiegand, Ute,2011, Peak-flow characteristics of Virginia streams: U.S. Geological Survey Scientific Investigations Report 2011–5144, 106 p. + 3 tables and 2 appendixes on CD. (http://pubs.usgs.gov/sir/2011/5144/)

USGS Data Disclaimer: Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty.

USGS Software Disclaimer: This software has been approved for release by the U.S. Geological Survey (USGS). Although the software has been subjected to rigorous review, the USGS reserves the right to update the software as needed pursuant to further analysis and review. No warranty, expressed or implied, is made by the USGS or the U.S. Government as to the functionality of the software and related material nor shall the fact of release constitute any such warranty. Furthermore, the software is released on condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from its authorized or unauthorized use.

USGS Product Names Disclaimer: Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Application Version: 4.5.1

StreamStats Services Version: 1.2.22

NSS Services Version: 2.1.0 http://pubs.usgs.gov/sir/2011/5144/

(804) 543-8073 www.hwr-plc.com

Appendix B: Sea Level Rise Calculations

3/30/2021 Sea-Level Curve Calculator (Version 2019.21) https://cwbi-app.sec.usace.army.mil/rccslc/slcc_calc.html 1/5

Home

Latest News

Adaptation Policy/Plan

Responses to Climate Change Program

Climate Preparedness and Resilience

Public Tools Developed by

USACE

Interagency Activities

International Activities

Sea-Level Change Curve Calculator (Version 2019.21) This version employs the same computations as previous versions, yielding the same projections along with some additional functionality, the several additional gauges. Previous versions include 2017.55, 2015.46 and its manual (pdf, 1.4MB); 2014.88 and its manual (pdf, 4.5 MB); an calculator.

EC 1165-2-212 (pdf, 845 KB) and its successor ER 1100-2-8162 (pdf, 317 KB) were developed with the assistance of coastal scientists from t Service and the US Geological Survey. Their participation on the USACE team allows rapid infusion of science into engineering guidance. ETL Procedures to Evaluate Sea Level Change: Impacts, Responses, and Adaptation.

EC 1165-2-212 (pdf, 845 KB) and its successor ER 1100-2-8162 (pdf, 317 KB) use the historic rate of sea-level change as the rate for the "US 1100-2-1 (pdf, 9.87 MB) , Procedures to Evaluate Sea Level Change: Impacts, Responses, and Adaptation.

The rate for the "USACE Intermediate Curve" is computed from the modified NRC Curve I considering both the most recent IPCC projections projections with the local rate of vertical land movement added.

The rate for the "USACE High Curve" is computed from the modified NRC Curve III considering both the most recent IPCC projections and mo with the local rate of vertical land movement added.

The three scenarios proposed by the NRC result in global eustatic sea-level rise values, by the year 2100, of 0.5 meters, 1.0 meters, and 1.5 m equation to include the historic GMSL change rate of 1.7 mm/year and the start date of 1992 (which corresponds to the midpoint of the current Epoch of 1983-2001), instead of 1986 (the start date used by the NRC), results in updated values for the coefficients (b) being equal to 2.71E- I, 7.00E-5 for modified NRC Curve II, and 1.13E-4 for modified NRC Curve III.

The three local relative sea level change scenarios updated from EC 1165-2-212 (pdf, 845 KB) (and and its successor ER 1100-2-8162), Equa Figure to the right of the table. ETL 1100-2-1 (pdf, 9.87 MB) , Procedures to Evaluate Sea Level Change: Impacts, Responses, and Adaptation

EC 1165-2-212, Equation 2: E(t) = 0.0017t + bt2

This on-line Sea Level Change Calculator has several added features which are detailed in the User's Manual. The superseded calculator is a plot both the USACE and NOAA curves in feet or meters relative to either NAVD88 or LMSL.

Alternate Projections:

The West Coast National Research Council 2012 West Coast projections are available when a west coast gauge is selected.

The New York State Department of Environmental Conservation Proposed Regulation 6 NYCRR Part 490 projections for New York City an when the NOAA gauge, "The Battery" or "Montauk Point" is selected.

The New York City Panel on Climate Change 2013/2015 projections are available for The Battery (8518750) for New York City.

The Maryland Climate Change Commission 2013 Projections are available when selecting a gauge in Maryland.

The University of Maryland Center for Environmental Science 2018 Projections are available when selecting a gauge in Maryland.

The CARSWG REGIONAL SEA LEVEL SCENARIOS FOR COASTAL RISK MANAGEMENT Report 2016 The US Global Change Research Program 2017 (NOAA et al. 2017)

This calculator also develops the SLC curves between the user entered dates using equation #3 in ER 1100-2-8162.

USACE Sea Level Change Curve Calculator (2017.55) Project Name: NASA Wallops Flight Center

Select Gauge: Kiptopeke, VA

Scenarios Source:

USACE 2013

Output Units: Feet Meters Output Datum: LMSL NAVD88 Critical Elevation #1 (ft) :

7.3 NAVD88 - Description:

Critical Elevation #2 (ft) :

11 NAVD88 - Description: FEMA Zone VE

SLC Rate:? NOAA 2006 Rates or enter rate (ft/yr) Display Data

FEMA BFE (ft): ? Information 7.3 (NAVD88) Search for BFE here Project Start Year: 2021

Interval Year: 5

Project End Year: 2100

User's Index (ft): ? 11 Description: 100-yr FEMA ZONE VE

Datum Shift from NAVD88 to MSL: 0.48 feet EWL Type: Highs Lows EWL Source: NOAA Website NOAA (GEV) USACE (Percentile) 100 yr difference (m) =

Click on project area. The nearest gauge/grid point will be use the selected Scenario Sou

*** note - there may be factors other than proximity to con Compliant

Non-Compliant Inactive

FEMA 100-yr Still Water Elev

Sea-Level Change Curve Calculator

Gauge: 8632200, Kiptopeke

Compliant 2006 Rate: 3.48mm/yr From: 1951 To:

Le https://www.usace.army.mil/corpsclimate/ https://www.usace.army.mil/corpsclimate/News_2017.aspx https://www.usace.army.mil/corpsclimate/climate_policies.aspx https://www.usace.army.mil/corpsclimate/Responses_to_Climate_Change.aspx https://www.usace.army.mil/corpsclimate/Climate_Preparedness_and_Resilience.aspx https://www.usace.army.mil/corpsclimate/Public_Tools_Dev_by_USACE.aspx https://www.usace.army.mil/corpsclimate/CCAWWG.aspx https://www.usace.army.mil/corpsclimate/International_Activities.aspx https://cwbi-app.sec.usace.army.mil/rccslc/slcc_calc_2017_55.html https://cwbi-app.sec.usace.army.mil/rccslc/ccaceslcurves_2015_46.html https://cwbi-app.sec.usace.army.mil/rccslc/docs/Sea_Level_Change_Curve_Calculator_User_Manual_2015_46_FINAL.pdf https://cwbi-app.sec.usace.army.mil/rccslc/ccaceslcurves_2014_88.html https://cwbi-app.sec.usace.army.mil/docs/SLC_Calculator_Manual_2014_88.pdf https://cwbi-app.sec.usace.army.mil/rccslc/docs/EC_1165-2-212%20-Final_10_Nov_2011.pdf http://www.publications.usace.army.mil/Portals/76/Publications/EngineerRegulations/ER_1100-2-8162.pdf http://www.publications.usace.army.mil/Portals/76/Publications/EngineerTechnicalLetters/ETL_1100-2-1.pdf https://cwbi-app.sec.usace.army.mil/rccslc/docs/EC_1165-2-212%20-Final_10_Nov_2011.pdf http://www.publications.usace.army.mil/Portals/76/Publications/EngineerRegulations/ER_1100-2-8162.pdf http://www.publications.usace.army.mil/Portals/76/Publications/EngineerTechnicalLetters/ETL_1100-2-1.pdf https://cwbi-app.sec.usace.army.mil/rccslc/docs/EC_1165-2-212%20-Final_10_Nov_2011.pdf http://www.publications.usace.army.mil/Portals/76/Publications/EngineerRegulations/ER_1100-2-8162.pdf http://www.publications.usace.army.mil/Portals/76/Publications/EngineerTechnicalLetters/ETL_1100-2-1.pdf https://cwbi-app.sec.usace.army.mil/rccslc/docs/SLC_Calculator_Manual_2014_88.pdf http://cpo.noaa.gov/sites/cpo/Reports/2012/NOAA_SLR_r3.pdf https://www.nap.edu/catalog/13389/sea-level-rise-for-the-coasts-of-california-oregon-and-washington http://www.dec.ny.gov/regulations/103877.html http://onlinelibrary.wiley.com/doi/10.1111/nyas.12593/pdf http://www.umces.edu/sites/default/files/pdfs/SeaLevelRiseProjections.pdf https://www.umces.edu/sites/default/files/Sea-Level%20Rise%20Projections%20for%20Maryland%202018_0.pdf https://www.hsdl.org/?abstract&did=792698 https://tidesandcurrents.noaa.gov/publications/techrpt83_Global_and_Regional_SLR_Scenarios_for_the_US_final.pdf http://www.publications.usace.army.mil/Portals/76/Publications/EngineerRegulations/ER_1100-2-8162.pdf http://www.fema.gov/national-flood-insurance-program/base-flood-elevation https://msc.fema.gov/portal http://tidesandcurrents.noaa.gov/est/est_station.shtml?stnid=8632200 http://leafletjs.com/ https://cwbi-app.sec.usace.army.mil/rccslc/slcc_calc.html 2/5

0.01 Plot EWL/BFE/Tides:

None Select Curve: USACE High

NASA Wallops Flight Center 8632200, Kiptopeke, VA

NOAA's 2006 Published Rate: 0.01142 feet/yr User Index of 11.00 feet added to predicted values for 100-yr FEMA ZONE VE

Print Curves NASA Wallops Flight Center

8632200, Kiptopeke, VA NOAA's 2006 Published Rate: 0.01142 feet/yr

User Index of 11.00 feet added to predicted values for 100-yr FEMA ZONE VE All values are expressed in feet relative to NAVD88

Print Table

Print Intersections Table

Version of Data : 05/17/2017

ID: 8632200

Reference Datum: NAVD88 Name: Kiptopeke, VA HAT: 1.97 (ft) MHHW: 1.04 (ft)

Estimated Relative Sea Level Change Projections - Gauge: 8632200, Kiptopeke, VA

2030 2040 2050 2060 2070 2080 2090 210

Year

R

SL

C in fe et

(N

AV

D

2021 10.85 10.93 11.16 2025 10.90 10.99 11.30 2030 10.95 11.08 11.49 2035 11.01 11.18 11.70 2040 11.07 11.27 11.92 2045 11.13 11.38 12.17 2050 11.18 11.48 12.43 2055 11.24 11.59 12.71 2060 11.30 11.71 13.01 2065 11.35 11.83 13.33 2070 11.41 11.95 13.67 2075 11.47 12.08 14.02 2080 11.53 12.21 14.40 2085 11.58 12.35 14.79 2090 11.64 12.49 15.20 2095 11.70 12.64 15.63 2100 11.75 12.79 16.08

Year USACE Low

USACE

Int

USACE

High

USACE High N/A 2025 N/A USACE Int N/A 2042 N/A USACE Low N/A 2062 N/A

Curve Intersections

FEMA 100-yr Still Water Elev (yr)

FEMA Zone VE (yr)

BFE

(yr) https://cwbi-app.sec.usace.army.mil/rccslc/slcc_calc.html 3/5

MHW: 0.81 (ft) MSL: -0.48 (ft) MLW: -1.79 (ft) MLLW: -1.90 (ft) NAVD88: 0.00 (ft) EWL Type: NOAA GEV (NAVD88) EWLs adjusted to 2021 using the historic rate.

*100 Yr: 5.46 (ft) 50 Yr: 5.07 (ft) 20 Yr: 4.58 (ft) 10 Yr: 4.23 (ft) 5 Yr: 3.89 (ft) 2 Yr: 3.41 (ft) Yearly: 2.72 (ft) Monthly: NaN (ft) From: 1951 To: 2007 Years of Record: 56

* Caution: period of record is less than return period *

Print Gauge Datums & EWL

* Caution: period of record is less than return period * Print Gauge Datum Chart

Estimated Relative Sea Level Change from 2021 To 2100NASA Wallops Flight Center

8632200, Kiptopeke, VA NOAA's 2006 Published Rate: 0.01142 feet/yr

User Index of 11.00 feet added to predicted values for 100-yr FEMA ZONE VE All values are expressed in feet

Print Curves Estimated Relative Sea Level Change from 2021 To 2100NASA Wallops Flight Center 8632200, Kiptopeke, VA

NOAA's 2006 Published Rate: 0.01142 feet/yr User Index of 11.00 feet added to predicted values for 100-yr FEMA ZONE VE

All values are expressed in feet

Tidal Datums and Extreme Water Levels, Gauge: 8632200, Kiptopeke, VA

-2

Datums/EWL relative to NAVD88 (ft)

H ei gh t a bo ve

N

AV

D

(f t)

Estimated Relative Sea Level Change Projections From 2021 To 2100 - Gauge: 8632200, Kiptopeke, VA

2030 2040 2050 2060 2070 2080 2090 210

Year

R

SL

C in fe et https://cwbi-app.sec.usace.army.mil/rccslc/slcc_calc.html 4/5

Print Table

NOAA's Diagram of Annual Exceedance Probabilities

NOAA's Annual Exceedance Probabilities Diagram

Extreme Water Levels for Period of Record

Station's Home Page Station's Datums Page

Station's Average Seasonal Cycle Station's Interannual Variation

Revised 18 July 2017

Accessibility Contact Us

FOIA

Information Quality Act

Link Disclaimer No Fear Act Privacy and Security Public Inquiries

SHARP

iSALUTE Site Map USA.gov

2021 0.00 0.00 0.00 2025 0.05 0.07 0.14 2030 0.10 0.16 0.33 2035 0.16 0.25 0.53 2040 0.22 0.35 0.76 2045 0.27 0.45 1.00 2050 0.33 0.56 1.27 2055 0.39 0.67 1.55 2060 0.45 0.78 1.85 2065 0.50 0.90 2.17 2070 0.56 1.03 2.50 2075 0.62 1.15 2.86 2080 0.67 1.29 3.23 2085 0.73 1.43 3.63 2090 0.79 1.57 4.04 2095 0.85 1.71 4.47 2100 0.90 1.86 4.91

Year USACE Low

USACE

Int

USACE

High http://tidesandcurrents.noaa.gov/est/stickdiagram.shtml?stnid=8632200 http://tidesandcurrents.noaa.gov/est/est_station.shtml?stnid=8632200 http://tidesandcurrents.noaa.gov/stationhome.html?id=8632200 http://tidesandcurrents.noaa.gov/datums.html?units=1&epoch=0&id=8632200 http://tidesandcurrents.noaa.gov/sltrends/seasonal.htm?stnid=8632200 http://tidesandcurrents.noaa.gov/sltrends/residual.htm?stnid=8632200 http://www.facebook.com/USACEHQ http://twitter.com/USACEHQ http://www.youtube.com/CORPSCONNECTION http://www.flickr.com/photos/usacehq http://www.usace.army.mil/Accessibility.aspx http://www.usace.army.mil/Contact.aspx http://www.usace.army.mil/FOIA.aspx http://www.usace.army.mil/InformationQualityAct.aspx http://www.usace.army.mil/LinkDisclaimer.aspx http://prhome.defense.gov/nofear http://www.usace.army.mil/PrivacyandSecurity.aspx mailto:hq-publicaffairs@usace.army.mil http://www.usace.army.mil/Portals/2/docs/EEO/SHARP_Poster_2013.pdf https://www.inscom.army.mil/isalute/ http://www.usace.army.mil/SiteMap.aspx http://www.usa.gov/ http://www.army.mil/ https://cwbi-app.sec.usace.army.mil/rccslc/slcc_calc.html 5/5

(804) 543-8073 www.hwr-plc.com

Appendix C: 100-, and 500-year Combined Storm Surge Calculation

Wallops Flight Facility (WFF) Causeway Bridge Replacement Coastal Two-Dimension Hydrodynamic Numerical Model

Coastal Hydrodynamic Caluctaions

Combined Storm Surge, 100-year and 500-year

3/20/2021

3/20/2021

Wallops Flight Facility (WFF) Causeway Bridge Replacement

Coastal Two-Dimension Hydrodynamic Numerical Model Applicable NOAA Station ID: 8630308, CHINCOTEAGUE CHANNEL, SOUTH END VA

Sine Daily

COMPUTE DAILY TIDE HYDROGRAPH USING SINE FUNCTION

Pooled Fund Study, Tidal Hydraulic Modeling for Bridges (Development of Hydraulic Computer Models to Analyze Tidal and

Coastal Stream Hydraulic Conditions at Highway Structures), Ayers Associates, 2002, technical supervision provided by FHWA}.

Edit time specifications and daily tide parameters as appropriate. Stage is recomputed automatically.

Use auto fill of columns A and B to extend time, if necessary.

NOAA Station ID: 8630308, CHINCOTEAGUE CHANNEL, SOUTH END VA

TIME SPECIFICATIONS

Time Shift 2.500 hr (allows tidal phase shift)

The input value is used to approximate the NOAA station's observed tidal data.

Time Increment 0.500 hr https://tidesandcurrents.noaa.gov/datums.html?id=8630308

DAILY TIDE PARAMETERS

Tidal Range 2.160 ft (elevation difference between high tide and low tide)

The input value is based on NOAA's Southern Chincoteague

Island station = Mean Range of Tide

Cycle Length 12.421 hr (time for completion of one tidal cycle)

The input value is based on NOAA's station data. Cycle length

= angular speed of the M2 constituent (from the Harmonic

Consitituants) = 360 / M2 constituent speed

Datum Shift 1.310 ft (added to station datum value)

The input value is based on NOAA's station datum data , attached below.

https://tidesandcurrents.noaa.gov/datums.html?id=8630308

TIME STAGE (shifted) hr ft Accordingly, all elevations are referenced to the NAVD88

0.000 2.340

0.500 2.388

1.000 2.369

1.500 2.281

2.000 2.132

2.500 1.931

3.000 1.690

3.500 1.425

4.000 1.152

4.500 0.890

5.000 0.654

5.500 0.461

6.000 0.321

6.500 0.244

7.000 0.235

7.500 0.294

8.000 0.418

8.500 0.599

9.000 0.825

9.500 1.082

10.000 1.353

10.500 1.622

11.000 1.871

11.500 2.084

12.000 2.248

12.500 2.352

13.000 2.390

13.500 2.359

14.000 2.262

14.500 2.104

15.000 1.895

15.500 1.649

16.000 1.382

16.500 1.110

17.000 0.851

17.500 0.621

18.000 0.435

18.500 0.304

19.000 0.238

19.500 0.240

20.000 0.310

20.500 0.443

21.000 0.632

21.500 0.864

0.0

1.0

2.0

3.0

0 3 6 9 12 15 18 21 24

S ta g e ft

Time, hr

Daily Tide Hydrograph

22.000 1.124

22.500 1.396

23.000 1.663

23.500 1.907

24.000 2.113

24.500 2.268

25.000 2.362

25.500 2.390

26.000 2.348

26.500 2.240

27.000 2.074

27.500 1.858

28.000 1.608

28.500 1.339

29.000 1.068

29.500 0.812

30.000 0.588

30.500 0.410

31.000 0.289

31.500 0.233

32.000 0.246

32.500 0.327

33.000 0.470

33.500 0.666

34.000 0.903

34.500 1.167

35.000 1.439

35.500 1.703

36.000 1.943

36.500 2.141

37.000 2.287

37.500 2.371

38.000 2.388

38.500 2.335

39.000 2.218

39.500 2.043

40.000 1.821

40.500 1.566

41.000 1.296

41.500 1.026

42.000 0.774

42.500 0.556

43.000 0.387

43.500 0.276

44.000 0.231

44.500 0.254

45.000 0.345

45.500 0.497

46.000 0.701

46.500 0.944

47.000 1.210

47.500 1.482

48.000 1.743

48.500 1.977

49.000 2.168

49.500 2.305

50.000 2.378

50.500 2.384

51.000 2.321

51.500 2.194

52.000 2.010

52.500 1.782

53.000 1.524

53.500 1.252

54.000 0.984

54.500 0.737

55.000 0.526

NOAA Tidal Data for 2018

NOAA/NOS/CO-OPS

Disclaimer: These data are based upon the latest information available as of the date of your request, and may differ from the published tide tables.

Annual Tide…