bridge hydraulics report - SR A1A North Causeway Bridge

BRIDGE HYDRAULICS REPORT FOR THE

SR-A1A NORTH BRIDGE OVER THE INTRACOASTAL WATERWAY PROJECT DEVELOPMENT AND ENVIRONMENT (PD&E) STUDY

IN ST. LUCIE COUNTY

FOR FLORIDA DEPARTMENT OF TRANSPORTATION DISTRICT 4

FINANCIAL PROJECT ID: 429936-2-22-01

PREPARED FOR:

KIMLEY-HORN AND ASSOCIATES, INC. 1920 WEKIVA WAY, SUITE 200 WEST PALM BEACH, FL. 33411

PREPARED BY:

INTERA INCORPORATED CERTIFICATE OF AUTHORIZATION NUMBER 00009062

2114 NW 40th TERRACE, SUITE A-1 GAINESVILLE, FL 32605

OCTOBER 2016

Bridge Hydraulics Report SR-A1A North Bridge over the Intracoastal Waterway

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Project Index and Engineer’s Certification

I. Project Information SR-A1A over the Intracoastal Waterway Bridge Replacement St. Lucie County, Florida

II. Governing Standards and Specifications a) AASHTO Guide Specifications for Bridges Vulnerable to Coastal Storms

(2008) b) FDOT Bridge Hydraulics Handbook (2012) c) FDOT Drainage Manual (January 2016) d) FDOT Plans Preparation Manual (January 2016)

III. Computer Programs used for Calculations and Analysis a) ADCIRC version 48 b) SWAN Cycle III version 40.20 c) Microsoft Office Excel 2013

The official record of this report is the electronic file digitally signed and sealed under 61G15-23.004, F.A.C. I, Mark Gosselin, Ph.D., P.E., hereby state that this report, as listed in the following Table of Contents, is, to the best of my knowledge and belief, true and correct and represents the described work in accordance with current established engineering practices. I hereby certify that I am a Licensed Professional Engineer in the State of Florida practicing with INTERA Incorporated, and that I have supervised the preparation of and approve the evaluations, findings, opinions and conclusions hereby reported.

This document has been digitally signed and sealed by Mark Gosselin, Ph.D., P.E. on XX/XX/XX using a Digital Signature. Printed copies of this document are not considered signed and sealed and the signature must be verified on any electronic copies.

INTERA Incorporated 2114 NW 40th Terrace, Suite A-1

Gainesville, FL 32605 Phone (352) 332-2323

Certificate of Authorization No. 9062 Mark Gosselin, Ph.D., P.E.

Florida P.E. #54594


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TABLE OF CONTENTS

TABLE OF CONTENTS ..................................................................................................... i LIST OF FIGURES ............................................................................................................ ii LIST OF TABLES ............................................................................................................. iii EXECUTIVE SUMMARY ............................................................................................... iv 1 INTRODUCTION ....................................................................................................1 2 STUDY AREA .........................................................................................................2

2.1 Tidal Benchmarks ............................................................................................... 3 2.2 Sediment Characteristics ..................................................................................... 4 2.3 Field Investigation .............................................................................................. 5 2.4 FEMA Flood Map ............................................................................................... 5 2.5 Proposed Bridge Geometry ................................................................................. 6 2.6 Hurricane History.............................................................................................. 15 2.7 Sea Level Rise................................................................................................... 17

3 HYDRAULIC MODELING ..................................................................................18 3.1 Model Development.......................................................................................... 19 3.2 Model Simulations ............................................................................................ 23

3.2.1 Limited Model Calibration ......................................................................... 23 3.2.2 Boundary Conditions .................................................................................. 26 3.2.3 Storm Surge Simulations ............................................................................ 28

4 SCOUR CALCULATION .....................................................................................33 4.1 Long-Term Channel Conditions ....................................................................... 33

4.1.1 Channel Migration ...................................................................................... 34 4.1.2 Aggradation/Degradation ............................................................................ 40

4.2 Contraction Scour ............................................................................................. 42 4.3 Local Scour ....................................................................................................... 45

5 OTHER DESIGN CONSIDERATIONS ................................................................49 5.1 Wave Climate.................................................................................................... 49 5.2 Abutment Protection ......................................................................................... 53 5.3 Clearances ......................................................................................................... 54

6 REFERENCES .......................................................................................................55 APPENDIX A – Geotechnical Report Excerpts ............................................................. A-1 APPENDIX B – Site Visit Photographs ..........................................................................B-1 APPENDIX C – Scour Calculations ................................................................................C-1 APPENDIX D – Abutment Protection Calculations ...................................................... D-1 APPENDIX E – Bridge Hydraulics Recommendation Sheet Information ...................... E-1


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LIST OF FIGURES Figure 2.1 Bridge Location Map (Source: Google Earth) ............................................ 2 Figure 2.2 Proposed Bridge Location of the SR A1A North Bridge over the

Intracoastal Waterway (Source: Google Earth) .......................................... 3 Figure 2.3 NOAA Tidal Benchmark #8722219 Location Map (Source:

http://www.co-ops.nos.noaa.gov) ............................................................... 4 Figure 2.4 FEMA Flood Map 12111C0177J (Source: http://msc.fema.gov) ............... 6 Figure 2.5 Elevation Profile (1 of 7) ............................................................................ 7 Figure 2.6 Elevation Profile (2 of 7) ............................................................................ 8 Figure 2.7 Elevation Profile (3 of 7) ............................................................................ 9 Figure 2.8 Elevation Profile (4 of 7) .......................................................................... 10 Figure 2.9 Elevation Profile (5 of 7) .......................................................................... 11 Figure 2.10 Elevation Profile (6 of 7) .......................................................................... 12 Figure 2.11 Elevation Profile (7 of 7) .......................................................................... 13 Figure 2.12 Substructure Detail.................................................................................... 14 Figure 2.13 Historical Hurricane Paths Passing within 50 nmi of the Project

Location (1851 – Present) (Source: https://coast.noaa.gov/hurricanes/) ........................................................... 15

Figure 3.1 Hydraulic Model Mesh ............................................................................. 21 Figure 3.2 Hydraulic Model Mesh at the Project Site ................................................ 22 Figure 3.3 Calibration at Wabasso Tide Gage ........................................................... 25 Figure 3.4 Calibration at Jensen Beach ..................................................................... 25 Figure 3.5 Hydraulic Model Boundary Conditions .................................................... 27 Figure 3.6 Contours of Velocity Magnitude and Velocity Vectors at the Time

of Maximum Velocity during the 100-Year Storm Surge ........................ 29 Figure 3.7 Water Surface Elevation Time Series at the SR A1A North Bridge ........ 30 Figure 3.8 Velocity Magnitude Time Series at the SR A1A North Bridge ................ 31 Figure 3.9 Flow Rate Time Series at the SR A1A North Bridge ............................... 32 Figure 4.1 Historic Aerial Photograph of the Proposed SR A1A Bridge

Location (FDOT 1969) ............................................................................. 36 Figure 4.2 Historic Aerial Photograph of the Proposed SR A1A Bridge

Location (FDOT 1980) ............................................................................. 37 Figure 4.3 Historic Aerial Photograph of the Proposed SR A1A Bridge

Location (Google Earth 1994) .................................................................. 38 Figure 4.4 Historic Aerial Photograph of the Proposed SR A1A Bridge

Location (Google Earth 2006) .................................................................. 39 Figure 4.5 Historic Aerial Photograph of the Proposed SR A1A Bridge

Location (Google Earth 2016) .................................................................. 40 Figure 4.6 Measured Bed Elevations South Profile (Phase 2 Scour Evaluation)....... 42 Figure 4.7 Case 1C: Abutments Set Back from Channel (Source: HEC-18) ............. 44 Figure 5.1 ASCE 7-10 3-second Peak Gust Wind Speed (Source:

http://windspeed.atcouncil.org)................................................................. 50 Figure 5.2 Significant Wave Height Contour Plot during the 100-year Return

Period Hurricane Event ............................................................................. 52 Figure 5.3 Wave Height Profiles during the 100-year Return Period Hurricane

Event ......................................................................................................... 53


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LIST OF TABLES Table ES-1 Hydraulic Design Data ............................................................................... iv Table ES-2 Design and Check Event Scour Elevations ................................................. v Table 2.1 Tidal Benchmark Information for NOAA Station No. 8722219 ................ 3 Table 2.2 Historical Hurricanes Passing within 50 nmi of Project Location

(1851 – Present) ........................................................................................ 16 Table 3.1 Error Summary for Water Level Calibration ............................................ 26 Table 3.2 Storm Surge Hydraulic Model Results ..................................................... 28 Table 4.1 Contraction Scour Calculations for the Design and Check Events........... 45 Table 4.2 100-year Return Period Total Scour Estimates for the SR A1A

North Bridge ............................................................................................. 47 Table 4.3 500-year Return Period Total Scour Estimates for the SR A1A

North Bridge ............................................................................................. 48 Table 5.1 Summary of 100-year Wave Climate ....................................................... 51 Table 5.2 Summary of Riprap Protection ................................................................. 54


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EXECUTIVE SUMMARY

The Florida Department of Transportation District 4 has contracted with Kimley-Horn

and Associates, Inc. to develop the Project Development and Environment (PD&E) Study

for the replacement of the existing bascule SR-A1A North Bridge (Bridge No. 940045)

over the Intracoastal Waterway (ICWW) with a new high level bridge. In support of this

project, Kimley-Horn subcontracted INTERA Incorporated to develop this Bridge

Hydraulics Report which documents the design hydraulic parameters, calculates scour,

and provides hydraulic recommendations.

This Bridge Hydraulic Report (BHR) developed the design hydraulic parameters

associated with hurricane-generated storm surge design flood events. A two-dimensional

ADCIRC model of the Intracoastal Waterway through the Indian River Lagoon,

describing both the waterway and nearby Fort Pierce Inlet and extending north and south

along the Indian River Lagoon, yielded the input flow conditions for the scour

calculations and the design of the abutment protection. The hydraulic analysis included

modeling the 50-year, 100-year, and the 500-year return period storm surge events. Table

ES-1 summarizes the design hydraulic conditions associated with each return period.

Examination of the historical behavior of the shoreline in the vicinity of the proposed SR

A1A North Bridge indicated no significant meandering or lateral bank migration.

Predicted scour elevations were calculated at each pier for the 100-year and 500-year

return period runoff events. Table ES-2, below, summarizes the design and check event

scour elevations at each bridge pier.

Table ES-1 Hydraulic Design Data

Flood Data Design

(50-Year) Flood

Base (100-year)

Flood

Greatest (500-year)

Flood Stage Elevation (ft-NAVD88) +6.0 +8.2 +12.7

Discharge (cfs) 103,100 104,200 98,800 Maximum Velocity (ft/s) 4.4 4.4 4.7

Exceedance Probability (%) 2 1 0.2 Frequency (year) 50 100 500


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Table ES-2 Design and Check Event Scour Elevations

Pier

100-year Total Scour Elevation

(ft-NAVD)

500-year Total Scour Elevation

(ft-NAVD) Pier 2 6.3 1.1 Pier 3 2.0 -5.6 Pier 4 0.4 -7.4 Pier 5 -0.4 -8.1 Pier 6 0.9 -7.1 Pier 7 -0.1 -8.4 Pier 8 1.0 -7.1 Pier 9 -4.0 -12.4 Pier 10 -21.9 -23.4 Pier 11 -22.5 -27.4 Pier 12 -25.7 -30.2 Pier 13 -26.2 -31.0 Pier 14 -26.2 -31.4 Pier 15 -28.0 -33.3 Pier 16 -28.0 -33.5 Pier 17 -30.3 -35.7 Pier 18 -33.5 -39.1 Pier 19 -28.9 -36.0 Pier 20 -29.9 -36.4 Pier 21 -26.6 -32.4 Pier 22 -20.2 -20.5 Pier 23 -7.6 -14.5 Pier 24 -11.6 -14.2 Pier 25 -0.8 -8.1 Pier 26 -0.2 -7.5 Pier 27 -0.6 -10.0

Abutment protection comprises a double layer of Coastal Rubble Riprap Protection with

a median weight of 290 lbs and a minimum specific gravity of 2.20. This material should

overlay the standard FDOT bedding stone and an appropriately sized geotextile filter

fabric.


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1 INTRODUCTION

The Florida Department of Transportation District 4 has contracted with Kimley-Horn

and Associates, Inc. to develop the Project Development and Environment (PD&E) Study

for the replacement of the existing bascule SR-A1A North Bridge (Bridge No. 940045)

over the Intracoastal Waterway (ICWW) with a new high level bridge. In support of this

project, Kimley-Horn subcontracted INTERA Incorporated to develop this Bridge

Hydraulics Report which documents the design hydraulic parameters, calculates scour,

and provides hydraulic recommendations.

This Bridge Hydraulic Report (BHR) combines the latest FHWA and FDOT technical

guidelines with hydraulic modeling and coastal engineering methodologies required by

the nature of the study area. For the complex coastal hydrodynamics of the study area, the

guidelines recommend a sophisticated methodology consistent with prevailing

conditions. For the coastal hydrodynamic system within this study area, a two-

dimensional hydrodynamic model describing the Indian River Lagoon provided

predictions of flow conditions at the bridge during extreme (50-, 100-, and 500-year

return period) events.

Following this introduction and a brief description of the study area (Chapter 2), this

report addresses the tasks performed to calculate the bridge hydraulics and scour at the

site associated with the 50-, 100-, and 500-year return period events. Chapter 3 describes

the setup and application of the hydrodynamic models. Chapter 3 also documents the

results of model simulations and the parameters necessary for calculating scour. Chapter

4 describes the results of the scour analysis based on the hydrodynamic parameters

presented in Chapter 3 and the pier and sediment parameters. Finally, Chapter 5 presents

other design considerations necessary for the project including wave modeling, and

abutment protection design.


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2 STUDY AREA

Calculation of a bridge’s hydraulic characteristics and associated scour requires detailed

knowledge of the study area and bridge substructure characteristics. The proposed bridge

will replace the existing SR-A1A North Bridge over the ICWW (Bridge No. 940045) in

St. Lucie County, FL (Figure 2.1 and Figure 2.2). The proposed bridge is located just

north of Ft. Pierce Inlet approximately 2.3 waterway miles from the Atlantic Ocean.

Given the proposed bridge’s location, the structure will experience high flows from storm

surge propagation through the inlet. Flow characteristics and scour calculations at the

bridge require knowledge of the tidal characteristics, sediment characteristics, bridge

substructure, and hurricane history.

Figure 2.1 Bridge Location Map (Source: Google Earth)

Bridge Location

8


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Figure 2.2 Proposed Bridge Location of the SR A1A North Bridge over the Intracoastal Waterway (Source: Google Earth)

2.1 Tidal Benchmarks Table 2.1 presents tidal datums on the Indian River Lagoon for the National Oceanic and

Atmospheric Administration (NOAA) Tidal Benchmark Number 8722219 (Figure 2.3)

located near the proposed bridge location at the SR-A1A South Bridge. These values

represent the 1983 – 2001 tidal epoch and were referenced to NOAA’s Trident Pier, Port

Canaveral control tide station.

Table 2.1 Tidal Benchmark Information for NOAA Station No. 8722219

Tidal Datum Type Elevation (ft-NAVD88)

Mean Higher High Water (MHHW) -0.14 Mean High Water (MHW) -0.29

Mean Sea Level (MSL) -0.97 Mean Tide Level (MTL) -1.00 Mean Low Water (MLW) -1.72

Mean Lower Low Water (MLLW) -1.85

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Figure 2.3 NOAA Tidal Benchmark #8722219 Location Map (Source: http://www.co-ops.nos.noaa.gov)

2.2 Sediment Characteristics Classification of the soil type is necessary to ensure appropriate application of the FDOT

scour methodology. The FDOT scour manual provides the procedure for scour analysis

for non-cohesive soils. Scour in non-cohesive sediments is dependent on many factors,

one of which is the median sediment diameter (D50). Unfortunately, no geotechnical

information regarding grain size gradation was obtained in support of this project.

Borings obtained during the parallel seismic testing performed on the existing bridge by

Applied Foundation Testing in 2015 (Appendix A) indicate that the near surface

sediments are gray sand and shell. Given the proximity of the project to the inlet, the

http://www.co-ops.nos.noaa.gov/


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sediment size was assumed as typical Florida beach sand with a median diameter of 0.2

mm. This value is based on experience with projects throughout the Districts with bridges

spanning tidal waterways near inlets.

2.3 Field Investigation INTERA personnel performed a field investigation of the project location during the

evaluation of the existing bridge under the Bridges with Unknown Foundations Scour

Evaluation program in February 2012. The investigation was conducted to assess the

conditions of the existing bridge and floodplain surrounding the existing alignment. The

areas on the south sides of the bridge along both approaches are well vegetated. The area

along the north side is occupied by a boat launch/parking area on the east approach and a

marina on the west approach. The east abutment protection comprises a seawall with sand

cement slope protection between the seawall and the abutment. The west abutment

protection comprises a seawall with rubble riprap toe protection and a fabric-formed

grout-filled mattress between the seawall and the abutment. Notably, the south side of the

protection contains a section that is completely grouted. Photographs from the field visit

are contained in Appendix B.

2.4 FEMA Flood Map The project location is depicted in FEMA Flood Map No. 12111C0177J (Figure 2.4). The

majority of the project corridor occupied by the proposed structure lies within Zone VE

(Elevation 8). Areas identified as Zone “VE” are “Areas subject to inundation by the 1-

percent-annual-chance flood event with additional hazards due to storm-induced velocity

wave action.” There are no regulatory floodways within the limits of this project.


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Figure 2.4 FEMA Flood Map 12111C0177J (Source: http://msc.fema.gov)

2.5 Proposed Bridge Geometry The proposed plan for the bridge involves constructing a new high level bridge to replace

the bascule bridge. Figure 2.5 through Figure 2.11 display the proposed bridge profile.

Figure 2.12 presents the substructure detail. As the figures illustrate, the replacement

bridge comprises fourteen 156’-9” spans on the west approach, three 182-ft spans over

the navigation section, and nine 156’-9” spans on the east approach. The total bridge

length is 4,308 ft. The bridge starts at begin bridge station 135+07.66 and ends at station

178+15.66. The proposed low chord of the bridge is + 12.95 ft-NAVD88 at the east end

bridge station. The bridge provides 86 ft of clearance at the navigation span. The

superstructure of the bridge is supported by 26 intermediate piers consisting of complex

piers. The piers each comprise an 8’x30’ pier column, a 30’x45’ pile cap, and a 4x6 pile

group consisting of 30” square concrete piles. The piles in the pile group are spaced 7.5 ft

apart in each direction.

Project Location


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Figure 2.5 Elevation Profile (1 of 7)


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Figure 2.12 Substructure Detail


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2.6 Hurricane History The project location has been significantly influenced by hurricanes. Investigation of

NOAA’s HURDAT database reveals that from 1851 to 2015, 39 hurricanes have passed

within 50 nmi of the project location. Figure 2.13 shows the paths of these hurricanes.

The figure shows that more hurricanes traverse perpendicular to the coast (exiting and

entering) than pass by the project parallel to the coast. Table 2.2 lists the storms passing

within 50 nmi by year. Notably, the list does not include the most recent hurricane,

Hurricane Matthew (2016).

Figure 2.13 Historical Hurricane Paths Passing within 50 nmi of the Project Location (1851 – Present) (Source: https://coast.noaa.gov/hurricanes/)

https://coast.noaa.gov/hurricanes/


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Table 2.2 Historical Hurricanes Passing within 50 nmi of Project Location (1851 – Present)

Storm Name Date NOT NAMED 1857 Oct 05, 1857 to Oct 12, 1857 UNNAMED 1865 Oct 14, 1865 to Oct 25, 1865 UNNAMED 1865 Oct 18, 1865 to Oct 25, 1865 UNNAMED 1870 Oct 17, 1870 to Oct 22, 1870 UNNAMED 1870 Oct 19, 1870 to Oct 22, 1870 UNNAMED 1871 Aug 12, 1871 to Aug 23, 1871 UNNAMED 1871 Aug 14, 1871 to Aug 23, 1871 UNNAMED 1871 Aug 17, 1871 to Aug 30, 1871 UNNAMED 1873 Sep 25, 1873 to Oct 10, 1873 UNNAMED 1873 Sep 26, 1873 to Oct 10, 1873 UNNAMED 1876 Oct 10, 1876 to Oct 25, 1876 UNNAMED 1876 Oct 12, 1876 to Oct 23, 1876 UNNAMED 1878 Oct 13, 1878 to Oct 25, 1878 UNNAMED 1878 Oct 18, 1878 to Oct 25, 1878 UNNAMED 1880 Aug 17, 1880 to Sep 02, 1880 UNNAMED 1880 Aug 24, 1880 to Sep 01, 1880

NOT NAMED 1881 Aug 16, 1881 to Aug 22, 1881 UNNAMED 1885 Aug 21, 1885 to Aug 28, 1885 UNNAMED 1893 Aug 15, 1893 to Sep 02, 1893 UNNAMED 1893 Sep 25, 1893 to Oct 15, 1893 UNNAMED 1915 Jul 31, 1915 to Aug 05, 1915 UNNAMED 1926 Jul 22, 1926 to Aug 02, 1926 UNNAMED 1928 Aug 03, 1928 to Aug 13, 1928 UNNAMED 1928 Sep 06, 1928 to Sep 21, 1928 UNNAMED 1933 Jul 24, 1933 to Aug 05, 1933 UNNAMED 1933 Aug 31, 1933 to Sep 07, 1933 UNNAMED 1939 Aug 07, 1939 to Aug 19, 1939 UNNAMED 1948 Sep 18, 1948 to Sep 26, 1948 UNNAMED 1949 Aug 23, 1949 to Sep 01, 1949

KING 1950 Oct 13, 1950 to Oct 20, 1950 HAZEL 1953 Oct 07, 1953 to Oct 16, 1953 CLEO 1964 Aug 20, 1964 to Sep 05, 1964

ISBELL 1964 Oct 08, 1964 to Oct 17, 1964


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Storm Name Date DAVID 1979 Aug 25, 1979 to Sep 08, 1979 ERIN 1995 Jul 31, 1995 to Aug 06, 1995

IRENE 1999 Oct 12, 1999 to Oct 19, 1999 FRANCES 2004 Aug 25, 2004 to Sep 10, 2004 JEANNE 2004 Sep 13, 2004 to Sep 29, 2004 WILMA 2005 Oct 15, 2005 to Oct 26, 2005

2.7 Sea Level Rise According to the 2016 FDOT Drainage Manual: “the design of coastal projects (including

new construction, reconstruction and projects rebuilding drainage systems) must include

a sea level rise analysis to assess impacts to design.” The manual provides sea level rise

data based on historical tidal records gathered by the National Water Level Observation

Network (NWLON) and managed by the NOAA. The station closest to the project

location is the Miami Beach, FL station (8723170). The manual reports that the station

experiences a rise of 2.39 mm/year. Employing a start date from the middle of the

previous tidal epoch (1992), an expected construction date of 2020, and a 75-year life, the

project is expected to experience 0.81 ft of sea level rise by 2095. Notably, the elevations

presented herein do not include this adjustment.


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3 HYDRAULIC MODELING

According to FHWA and FDOT guidelines, computation of scour requires knowledge of

specific hydraulic parameters. Determining these parameters requires a detailed hydraulic

analysis of the study area. Due to the complex nature of storm surge propagation through

Fort Pierce Inlet upstream to the bridge locations, a time-dependent, two-dimensional

hydrodynamic numerical model is required for simulation of hurricane events. Given the

complexity of modeling surge propagation, the Advanced Circulation Model for Ocean,

Coastal, and Estuarine Waters (ADCIRC) is best suited for the modeling efforts.

ADCIRC is a numerical model developed specifically for generating long duration

hydrodynamic circulation along shelves, coasts, and within estuaries. The intent of the

model is to produce numerical simulations for very large computational domains in a

unified and systematic manner. The collaboration of many researchers have led to the

development of the ADCIRC model including investigators at the University of Notre

Dame (J.J. Westerink), the University of North Carolina at Chapel Hill (R.A. Luettich),

the University of Texas at Austin (M.F. Wheeler and C. Dawson), the University of

Oklahoma (R. Kolar), the State of Texas (Jurji), and the Waterways Experiment Station

(N. Scheffner) (adcirc.org).

Both the U.S. Army and Navy have extensively applied ADCIRC for a wide range of

tidal and hurricane storm surge predictions in regions including the western North

Atlantic, Gulf of Mexico and Caribbean Sea, the Eastern Pacific Ocean, the North Sea,

the Mediterranean Sea, the Persian Gulf, and the South China Sea. ADCIRC employs

computational models of flow and transport in continental margin waters to predict free

surface elevation and currents for a wide range of applications including evaluating

coastal inundation, defining navigable depths and currents in near shore regions, to

assessing pollutant and/or sediment movement on the continental shelf.

ADCIRC is a robust computer program for solving the equations of motion for a moving

fluid on a rotating earth. The equation formulation includes applying the traditional

hydrostatic pressure and Boussinesq approximations and discretizing the equations in

space via the finite element (FE) method and in time via the finite difference (FD)


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method. The ADCIRC program includes both a two-dimensional depth integrated (2DDI)

mode and a three-dimensional (3D) mode. For both, the model solves for elevation via

the depth-integrated continuity equation in Generalized Wave-Continuity Equation

(GWCE) form. The model solves for velocity via either the 2DDI or 3D momentum

equations. These equations retain all the nonlinear terms. ADCIRC includes solution

capabilities in either a Cartesian or a spherical coordinate system.

The GWCE is solved via either a consistent or a lumped mass matrix and an implicit or

explicit time stepping scheme. If a lumped, fully explicit formulation is specified, no

matrix solver is necessary. In all other cases, the GWCE is solved using the Jacobi

preconditioned iterative solver from the ITPACKV 2D package. The 2DDI momentum

equations are lumped and therefore require no matrix solver.

Possible boundary conditions for the model include specified elevation (harmonic tidal

constituents or time series); specified boundary normal flow (harmonic tidal constituents

or time series); zero boundary normal flow; slip or no slip conditions for velocity;

external barrier overflow out of the domain; internal barrier overflow between sections of

the domain; surface stress (wind and/or wave radiation stress); atmospheric pressure; or

outward radiation of waves (Sommerfield condition). ADCIRC can be forced with:

elevation boundary conditions; normal flow boundary conditions; surface stress (wind)

boundary conditions; tidal potential; or an earth load/self attraction tide.

3.1 Model Development The model inputs include a bathymetric mesh and storm hydrographs at the Atlantic

Ocean boundary. The offshore hydrographs where obtained from the Florida Department

of Environmental Protection (FDEP) as recommended by Sheppard and Miller (2003).

The bathymetric mesh configuration was generated using aerial photographs and USGS

Quadrangle maps. The mesh contains bathymetry interpolated from NOAA datasets for

both the nearshore (coastal relief data set) and open ocean (ETOPO2 data set) regions.

Recent survey data obtained by Sea Diversified, Inc. in support of this project provided

information on bathymetry in and around the project site. A 2007 LiDAR survey

provided information on the topography surrounding the bridge site. The model mesh


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extends 40 miles offshore, includes the Sebastian, Fort Pierce, and St. Lucie Inlets, and

includes the Indian River Lagoon in its entirety from Cape Canaveral to Stuart, FL.

Figure 3.1 and Figure 3.2 present the mesh configuration along with contours of depth

from NAVD88. Figure 3.1 displays the entire model mesh while Figure 3.2 illustrates the

resolution necessary to define features in and around the bridge. The mesh includes

77,174 triangular elements with 39,670 nodes located at the corners of the elements. All

simulations included specified Manning’s n bottom friction (n = 0.025 for water elements

and 0.1 for residential upland topography, determined through calibration) and globally

specified lateral eddy viscosity (ESL = 7.0 m2/s). The time step for the simulations

equaled 1 second.


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Figure 3.1 Hydraulic Model Mesh


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Figure 3.2 Hydraulic Model Mesh at the Project Site


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3.2 Model Simulations

3.2.1 Limited Model Calibration A calibrated model ensures an accurate depiction of the hydraulic characteristics in the area

of interest. Calibration resulted from iterative adjustments to the model parameters and

mesh extents until differences between measured and ADCIRC calculated flow properties

became acceptable. Error calculations quantify these results. For this study, error

estimation included mean error, root-mean square (rms) error, and percent error.

The following equation provides an estimate of the mean error, E, the average of the

deviation of the calculated from the measured values (water surface elevation):

NE

N

iimc∑

=

−= 1

)( χχ

where χc is the calculated value, χm is the measured value, and N is the total number of data

points. A positive value for the mean error would indicate that the model overestimates the

event, while a negative value would indicate the model underestimates the event.

The root-mean square error, Erms, given by the following equation, indicates the absolute

error of the comparison. The variables remain the same as indicated above.

( )N

E

N

iimc

rms

∑ −= =1

2χχ

The final error estimator, Epct, is the percent error. This variable gives an indication of the

degree to which the calculated values misrepresent the measured values. Percent error,

defined in terms of rms error, is given as

RE

E rmspct =

where R is a representative range of the variable χ. The R-value for the percent error

water level calculations equals the average of the measured water level ranges; i.e., the

average difference between high and low values over the period of the record. For this

effort, the R-value for the percent error water level calculations equals the total measured


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range of the tidal signal. This range, rather than the average of the measured tidal ranges

(i.e., the average difference between consecutive high and low values over the period of

the measurement) is more representative of the tidal signals in the Indian River Lagoon

given that they are significantly affected by meteorological forcing.

The University of Florida Coastal and Oceanographic Engineering Laboratory,

under contract to Kimley-Horn and Associates, Inc., provided the measured data for both

the water level and flow rate calibration. The synoptic water surface elevation data,

discussed in Chapter 3.0, spans an 8-week period from March 23, 2002 to June 6, 2002.

For the calibration and spring tide simulation, the measurements obtained during a one-

month period from April 1, 2002 to April 30, 2002 provided the data for both calibration

and specification of the boundary condition. Two tide gages provide data for water

surface elevation calibration: Wabasso and Jensen Beach.

Iterative adjustments of the element friction — Manning’s n value — produced an

average rms error of 0.24 ft and an average percent error of 12.4% for the water level

calibration of the inshore gages. Figure 3.3 and Figure 3.4 compare the predicted model

water level to the measured water level at the different gage locations. The figures show

that the tidal signal at the Wabasso gage was greatly affected by meteorological events.

From the figure, the model performed adequately replicating the correct range of

oscillations; however, it does not capture the low frequency oscillations associated with

meteorological effects at this gage. This is expected given that calibration simulations did

not include meteorological forcing. At the Jensen Beach gage, however, the model

performed much better at replicating the gage measurements. Table 3.1 presents error

calculations for the water level calibration. The rms errors are both less than 0.3 ft. As

such, the model is considered calibrated for water surface elevation.


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Figure 3.3 Calibration at Wabasso Tide Gage

Figure 3.4 Calibration at Jensen Beach

-1.60

-1.40

-1.20

-1.00

-0.80

-0.60

-0.40

-0.20

0.00

0.20

0.40

3/30

/02

4/4/

02

4/9/

02

4/14

/02

4/19

/02

4/24

/02

4/29

/02

5/4/

02

Date

Wat

er S

urfa

ce E

leva

tion

(ft-N

AVD

88)

MeasuredModeled

-2.50

-2.00

-1.50

-1.00

-0.50

0.00

0.50

1.00

3/30

/02

4/4/

02

4/9/

02

4/14

/02

4/19

/02

4/24

/02

4/29

/02

5/4/

02

Date

Wat

er S

urfa

ce E

leva

tion

(ft-N

AVD

88)

MeasuredModeled


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Table 3.1 Error Summary for Water Level Calibration

Water Level Station Mean Error (ft)

RMS Error (ft)

Percent Error

Representative Range (ft)

Wabasso -0.10 0.20 14.7% 1.39

Jensen Beach -0.15 0.28 11.0% 2.50

3.2.2 Boundary Conditions Once calibrated, the model simulated storm surge propagation to develop the design

conditions at the bridge site. Three surge hydrographs — the 50-, 100-, and 500-year —

were applied at the offshore model boundary to produce three sets of hydraulic conditions

at the bridge. The hydrographs, presented in Figure 3.5, were developed by Dean and

Chiu (1988) and recommended for use in FDOT projects by Sheppard and Miller (2003).


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Figure 3.5 Hydraulic Model Boundary Conditions

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

0 5 10 15 20 25 30 35 40

Wat

er S

urfa

ce E

leva

tion

(ft-N

AVD)

Simulation Time (hrs)

50-year

100-year

500-year


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3.2.3 Storm Surge Simulations The model simulated the storm surge propagation and overland flooding associated with

the 50-, 100-, and 500-year events. Table 3.2 presents a summary of the modeling results.

From the table, the design (50-year) high water reaches +6.0 ft-NAVD88. Base flood

elevations reach +8.2 ft-NAVD88 which compares well with the reported base flood

elevation contained in the FEMA Flood Map that notes the bridge as residing within

Zone VE (Elevation 8). Notably, the maximum flow rate drops during the 500-year event.

This is associated with the overtopping of the east approach roadway during this event.

Figure 3.6 presents contours of the flow velocity magnitude overlaid with vectors of flow

direction at the time of maximum velocity for the 100-year return period storm surge

simulation. Flow generally aligns with the channel except near the east causeway

shoreline where the flow accelerates as it makes the turn from the channel leading from

the inlet. Figure 3.7 through Figure 3.9 contain time series plots of water surface

elevation, velocity magnitude, and flow rate for the 50-, 100-, and 500-year storm surge

events at the bridge location. Water surface elevations attenuate as they pass through the

inlet with a reduction of one to three feet depending on return period as compared with

the offshore values. The effect of causeway overtopping during the 500-year event is

evident in Figure 3.8 and Figure 3.9. In both figures the magnitude of the flow velocity

and flow for the 500-year event drops significantly as the surge overtops the causeway

diverting flow from the bridge opening.

Table 3.2 Storm Surge Hydraulic Model Results

Flood Data Design

(50-Year) Flood

Base (100-year)

Flood

Greatest (500-year)

Flood Stage Elevation (ft-NAVD88) +6.0 +8.2 +12.7

Discharge (cfs) 103,100 104,200 98,800 Maximum Velocity (ft/s) 4.4 4.4 4.7

Exceedance Probability (%) 2 1 0.2 Frequency (year) 50 100 500


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Figure 3.6 Contours of Velocity Magnitude and Velocity Vectors at the Time of Maximum Velocity during the 100-Year

Storm Surge


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Figure 3.7 Water Surface Elevation Time Series at the SR A1A North Bridge

-2.0

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

0 10 20 30 40 50

Wat

er S

urfa

ce E

leva

tion

(ft-N

AVD)


50-year

100-year

500-year


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Figure 3.8 Velocity Magnitude Time Series at the SR A1A North Bridge

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 10 20 30 40 50

Velo

city

(fps

)


50-year

100-year

500-year


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Figure 3.9 Flow Rate Time Series at the SR A1A North Bridge

-60,000.0

-40,000.0

-20,000.0

0.0

20,000.0

40,000.0

60,000.0

80,000.0

100,000.0

120,000.0

0 10 20 30 40 50

Flow

Rat

e (c

fs)


50-year

100-year

500-year


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4 SCOUR CALCULATION

Total scour consists of three components: (1) long-term channel conditions

(aggradation/degradation and meandering), (2) contraction scour, and (3) local scour.

Unlike long-term scour, the contributions of local and contraction scour are derived from

the results of the hydraulic analysis presented in Section 3. Their corresponding scour

computations apply empirical equations developed by FDOT in conjunction with the

University of Florida (Sheppard & Renna, 2005). The formulation of the complex pier

scour calculation methodology follows techniques described in the Hydraulic

Engineering Circular No. 18 (HEC-18) (Arneson, et. al., 2012). These equations require

inputs such as main channel flow, local velocities (magnitude and direction), and depth of

flow. The runoff model simulations presented in Section 3 provide the values for these

parameters. This section presents discussions of the scour components and the results of

these scour calculations for the proposed SR A1A North Bridge over the Intracoastal

Waterway.

Scour depth computations require values for the depth-averaged critical velocity of the

waterway necessary to begin sediment motion on the bed. Calculating these values

requires a representative median sediment size (D50 = 0.2 mm, Section 2.2). The next

three sections will cover long-term scour, contraction scour, and local pier scour.

4.1 Long-Term Channel Conditions Most of the bridges in the National Bridge Inventory (NBI) that cross alluvial streams

continually adjust their beds and banks (Lagasse, Schall, Johnson, Richardson,

Richardson, & Chang, 1991). Channel stability at the bridge crossing depends on the

stream system. Changes upstream and downstream affect stability at the bridge crossing.

Natural and man-made disturbances may result in changes in sediment load and flow

dynamics resulting in adverse changes in the stream channel at the bridge crossing. These

changes may include channel bank migration, aggradation, or degradation of the channel

bed. During channel migration, one bank tends to erode laterally while the opposite bank


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tends to accrete. During aggradation or degradation of a channel, the channel bed and

thalweg tend to accrete or erode.

Channel stability, as characterized by channel migration and aggradation/degradation of

the channel bed, is an important consideration in evaluating the potential scour at a bridge

for two reasons. First, because aggradation and degradation influence the channel’s

hydraulic properties, any hydraulic modeling must consider their effects when

determining design scour conditions. Second, bank migration, thalweg shifting, and

degradation may cause foundation undermining regardless of whether the bridge

experiences the design storm event. This section presents an analysis of channel

migration and aggradation/degradation of the channel bed at the bridge opening. This

analysis forecasts channel stability based on historic observations near the bridge. The

analysis incorporates a review of available historic aerials in the vicinity of the bridge.

These help to evaluate channel migration and thalweg position within the channel banks

and aggradation or degradation of the bed.

4.1.1 Channel Migration Lateral channel migration is an important factor to consider when deciding on a bridge’s

location. Rivers and streams are dynamic entities that can continually shift banklines and

move both laterally and downstream. Bridges, on the other hand, are static entities that

fix the river/stream at a specific location. This juxtaposition of a bridge’s immobility and

a river’s instability can lead to erosion of the approach embankment, changes in the

contraction or local scour due to changes in flow direction, or increases in abutment

scour. Factors affecting lateral channel migration include stream geomorphology, bridge

crossing location, flood characteristics, characteristics of the bed and bank material, and

wash load (Richardson & Davis, 2001).

Identification of lateral channel migration occurs through examination of historic aerial

photographs, historic shoreline locations, historic bathymetries, bridge inspection reports,

and current condition of the upstream and downstream banks. Figure 4.1 through Figure

4.5 display aerial photographs from 1969 to 2016 at the proposed replacement bridge

location. From the figures, the east causeway has shown little change in terms of

shoreline location. In fact, the shorelines indicate significant establishment of mangrove


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vegetation along the approach roadway. On the west, the most significant change

involves the marina construction between the 1980 and 1994 photographs. The shoreline

to the north of the west end of the bridge is well vegetated and has not changed in

location. This indicates low potential for migration of the channel within the time scales

associated with the lifetime of the bridge. As such, future channel migration is considered

not to contribute to long term scour.


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Figure 4.1 Historic Aerial Photograph of the Proposed SR A1A Bridge Location (FDOT 1969)


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Figure 4.2 Historic Aerial Photograph of the Proposed SR A1A Bridge Location (FDOT 1980)


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Figure 4.3 Historic Aerial Photograph of the Proposed SR A1A Bridge Location (Google Earth 1994)


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4.1.2 Aggradation/Degradation Aggradation and degradation are long-term streambed elevation changes due to natural or

man-induced causes. Aggradation entails the deposition of material eroded from the

channel or watershed upstream of the bridge. Degradation entails the lowering or

scouring of the streambed due to a deficit in sediment supply from upstream. There are

no mechanisms within the ICWW that will contribute to long term degradation.

Examples of these mechanisms which would intercept sediment before reaching the

project location include dams and reservoirs, cutoffs of meander bends, changes in the


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downstream channel base level (downstream stage controlled by tidal fluctuation at the

inlet), gravel mining from the streambed (not applicable), and diversion of water into or

out of the stream. None of these apply for the ICWW.

Examination of degradation is best performed through comparison long term

measurements at the bridge crossing. The 2015 Bridge Inspection Report for the existing

bridge did not include surveyed profiles. However, historic profiles are available from the

Phase 1 Scour Evaluation Report from 1980 to 1995. Figure 4.6 presents measured

profiles along the south face of the existing bridge. From the plot, the profiles indicate

general aggradation over the 15-year period. For comparison, a recent study of the Peter

P. Cobb Bridge (SR A1A South Bridge), located approximately one mile to the south of

the existing bridge, indicated that historic profiles generally fluctuate on the order of 2-3

ft. For conservatism, long term scour is incorporated into the bridge design on the order

of the fluctuation found at the Peter P. Cobb Bridge. As such, long term scour is set equal

to 3 ft for the piers located in the ICWW.


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Figure 4.6 Measured Bed Elevations South Profile (Phase 2 Scour Evaluation)

4.2 Contraction Scour An abrupt decrease in cross-sectional area at a bridge crossing causes an increase in

velocity that results in contraction scour (a lowering of the channel bottom over the entire

width of the cross section). Changes in cross-sectional area can result from either natural

channel constriction or encroachment of a bridge structure by both the abutments and the

piles. HEC-18 presents several equations for contraction scour given various

encroachment conditions (cases). The Case 1A (Figure 4.7) description in HEC-18

(abutments project into the main channel, where the causeway is a surrogate for the

abutments) describes the particular conditions applicable to the SR A1A North Bridge. In

this case, the river channel width becomes narrower either due to the bridge abutments

projecting into the channel or the bridge being located at a narrowing reach of the river.

Computing contraction scour for the bridge requires determining whether the scour is

live-bed or clear water. Across the cross section, the velocities exceed the critical velocity

-60

-50

-40

-30

-20

-10

0

0 500 1000 1500 2000 2500

Dist

ance

from

Top

of R

ail (

ft)

Bridge Station (ft)

1995

1980


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for the sediment during both the 100- and 500-year return period flood events. Thus, the

contraction scour within the main channel is considered live bed.

Contraction scour computations follow the Modified Laursen Live Bed Contraction

Scour Equation located in HEC-18 (Section 6.3):

𝑦𝑦2𝑦𝑦1

= �𝑄𝑄2𝑄𝑄1�67�

�𝑊𝑊1

𝑊𝑊2�𝑘𝑘1

where y1 is the average depth of the upstream cross section, Q1 and Q2 are the flow rates

through the upstream and downstream cross sections, and W1 and W2 are the bottom

widths of the upstream and downstream cross sections. k1 is a constant dependent on the

amount of suspended material.

Inputs for the calculations come directly from the storm surge modeling for the 100- and

500-year events. The inputs and results for the 100- and 500-year contraction scour

computations for the proposed bridge crossing are listed in Table 4.1 From the table, the

contraction at the bridge yielded an expected scour depth of 2.6 ft for the 100-year event

and 2.8 ft for the 500-year event.


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Figure 4.7 Case 1C: Abutments Set Back from Channel (Source: HEC-18)


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Table 4.1 Contraction Scour Calculations for the Design and Check Events

Parameter

100-year Design Event

500-year Check Event

Constant k1 0.59 0.59 Flow rate at contracted section (cfs) Q2 104,180 98,827 Flow rate at upstream section (cfs) Q1 104,465 93,626 Bottom width at contracted section (ft) W2 1,667 1,667 Bottom width at upstream section (ft) W1 2,347 2,347 Depth in upstream section (ft) y1 15.2 12.1 Equilibrium depth in contracted section (ft) y2 18.6 16.3 Depth at Bridge before Scour (ft) y0 16.0 13.6 Scour depth (ft) ys 2.56 2.80 Recommended Scour depth (ft) 2.6 2.8

4.3 Local Scour Local scour refers to bed erosion around obstacles in the path of flow such as bridge piers

and abutments. Local scour results from increased shear and normal stresses applied to

the bed near the structure due to the presence of the structure. Local pier scour depends

on structure geometry, current velocity, angle of attack (the angle between the flow

direction and the major axis of the pier/pile group), flow depth, and soil characteristics.

Local scour may occur at bridge piers and abutments but this report addresses local pier

scour since the abutments will have scour protection.

The State of Florida methodology for calculating local pier scour was applied to this

bridge. The Florida DOT guidelines (Sheppard and Renna, 2005) for calculating local

pier scour require application of the scour equations developed by the FDOT and based

on the latest research from the University of Florida for the analysis of complex pier

geometries. This methodology combines the individual scour depths produced by the

column, pile cap, and pile group. The local scour is then added to the general and

contraction to produce the design scour depths. The FDOT equations predict the scour

hole depth based on sediment characteristics, flow parameters, and bent geometry. The

flow parameters include depth, velocity, and angle of attack. The bent geometry includes

the dimensions of the pier column, pile cap, and pile group.


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Application of the FDOT methodology to calculate the scour for the SR A1A North

Bridge yielded pier scour depths for the design (100-year) event and the check event

(500-year). Inputs for this calculation included the median sediment diameter (from

Section 2.2), the design contraction scour (Section 4.2), the maximum flow properties

during the design event (Section 3.2.3), and the proposed bridge pier configurations

(Section 2.5). Appendix C presents scour calculation input and output tables and Table

4.2 and Table 4.3 list calculated contraction scour, local pier scour, and total scour depths

for the 100-year design event and the 500-year check event. From the table, the largest

scour for both the design and check events occurs at the piers near the east causeway

shoreline where the velocity and angles of attack are the greatest.


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Table 4.2 100-year Return Period Total Scour Estimates for the SR A1A North Bridge

Bent Number

Assumed Initial Bed Elevation

(ft-NAVD)

Bed Degradation

(ft)

Contraction Scour

(ft)

Local Scour

(ft)

Total Scour

(ft)

Total Scour Elevation

(ft-NAVD)

Pier 2 +8.9 0.0 0.0 0.0 0.0 +8.9 Pier 3 +5.6 0.0 2.6 1.0 3.6 +2.0 Pier 4 +4.0 0.0 2.6 1.0 3.6 +0.4 Pier 5 +3.2 0.0 2.6 1.0 3.6 -0.4 Pier 6 +4.5 0.0 2.6 1.0 3.6 0.9 Pier 7 +3.5 0.0 2.6 1.0 3.6 -0.1 Pier 8 +4.6 0.0 2.6 1.0 3.6 +1.0 Pier 9 +5.5 0.0 2.6 6.9 9.5 -4.0 Pier 10 -6.1 3.0 2.6 10.2 15.8 -21.9 Pier 11 -6.9 3.0 2.6 9.9 15.5 -22.5 Pier 12 -8.5 3.0 2.6 11.6 17.2 -25.7 Pier 13 -8.2 3.0 2.6 12.4 18.0 -26.2 Pier 14 -7.5 3.0 2.6 13.1 18.7 -26.2 Pier 15 -8.7 3.0 2.6 13.7 19.3 -28.0 Pier 16 -8.7 3.0 2.6 13.7 19.3 -28.0 Pier 17 -11.0 3.0 2.6 13.7 19.3 -30.3 Pier 18 -13.9 3.0 2.6 14.0 19.6 -33.5 Pier 19 -8.7 3.0 2.6 14.6 20.2 -28.9 Pier 20 -8.3 3.0 2.6 16.0 21.6 -29.9 Pier 21 -3.9 3.0 2.6 17.1 22.7 -26.6 Pier 22 +5.1 0.0 2.6 22.7 25.3 -20.2 Pier 23 +4.9 0.0 2.6 9.9 12.5 -7.6 Pier 24 +3.4 0.0 2.6 12.4 15.0 -11.6 Pier 25 +2.8 0.0 2.6 1.0 3.6 -0.8 Pier 26 +3.4 0.0 2.6 1.0 3.6 -0.2 Pier 27 +3.0 0.0 2.6 1.0 3.6 -0.6


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Table 4.3 500-year Return Period Total Scour Estimates for the SR A1A North Bridge

Bent Number

Assumed Initial Bed Elevation

(ft-NAVD)

Bed Degradation

(ft)

Contraction Scour

(ft)

Local Scour

(ft)

Total Scour

(ft)

Total Scour Elevation

(ft-NAVD)

Pier 2 +8.9 0.0 2.8 5.0 7.8 +1.1 Pier 3 +5.6 0.0 2.8 8.4 11.2 -5.6 Pier 4 +4.0 0.0 2.8 8.6 11.4 -7.4 Pier 5 +3.2 0.0 2.8 8.5 11.3 -8.1 Pier 6 +4.5 0.0 2.8 8.8 11.6 -7.1 Pier 7 +3.5 0.0 2.8 9.1 11.9 -8.4 Pier 8 +4.6 0.0 2.8 8.9 11.7 -7.1 Pier 9 +5.5 0.0 2.8 15.1 17.9 -12.4 Pier 10 -6.1 3.0 2.8 11.5 17.3 -23.4 Pier 11 -6.9 3.0 2.8 14.6 20.4 -27.4 Pier 12 -8.5 3.0 2.8 16.0 21.8 -30.2 Pier 13 -8.2 3.0 2.8 17.1 22.9 -31.0 Pier 14 -7.5 3.0 2.8 18.1 23.9 -31.4 Pier 15 -8.7 3.0 2.8 18.8 24.6 -33.3 Pier 16 -8.7 3.0 2.8 19.0 24.8 -33.5 Pier 17 -11.0 3.0 2.8 18.9 24.7 -35.7 Pier 18 -13.9 3.0 2.8 19.5 25.3 -39.1 Pier 19 -8.7 3.0 2.8 21.5 27.3 -36.0 Pier 20 -8.3 3.0 2.8 22.3 28.1 -36.4 Pier 21 -3.9 3.0 2.8 22.7 28.5 -32.4 Pier 22 +5.1 0.0 2.8 22.8 25.6 -20.5 Pier 23 +4.9 0.0 2.8 16.6 19.4 -14.5 Pier 24 +3.4 0.0 2.8 14.7 17.5 -14.2 Pier 25 +2.8 0.0 2.8 8.1 10.9 -8.1 Pier 26 +3.4 0.0 2.8 8.1 10.9 -7.5 Pier 27 +3.0 0.0 2.8 10.2 13.0 -10.0


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5 OTHER DESIGN CONSIDERATIONS

In addition to calculation of the bridge hydraulics and associated scour, this Bridge

Hydraulics Report also addresses other design considerations for the SR A1A North

Bridge. These include wave climate, abutment protection design, and clearances. This

chapter presents these design considerations.

5.1 Wave Climate Proper design of coastal bridges includes an examination of the wave climate associated

with hurricane events. As such, the design wave heights must be determined for both the

abutment protection scheme and to compute wave loading on all bridge deck spans

located within the wave crest envelope (if applicable).

Determination of the design wave properties at the bridge site requires knowledge of the

wind properties at the bridge site. The Applied Technology Council

(http://windspeed.atcouncil.org) provides a tool for determining wind speeds via ASCE

7-10. From the website (Figure 5.1), the 100-year return interval 3-second peak gust wind

speed equals 131 mph. Converting this value to a 10-min average results in a wind speed

of 93.3 mph. This value was employed as a wind boundary condition in the wave

modeling.


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Figure 5.1 ASCE 7-10 3-second Peak Gust Wind Speed (Source:

http://windspeed.atcouncil.org)

In support of this study, the wave climate in the vicinity of the SR A1A North Bridge was

assessed through the development of a numerical wave model. For this project, the

Simulated Waves Nearshore (SWAN) Model was employed for generation of waves in

the area of interest. SWAN is a two-dimensional, third-generation wave model that

computes random, short-crested wind-generated waves in coastal regions and inland

waters and was developed by the Delft University of Technology of the Netherlands.

The SWAN model mesh employed the same mesh detailed in the Section 3.1. The 100-

year 10-minute wind of 93.3 mph was applied across the entire SWAN model mesh with

its direction rotated in 10-degree increments for a total of 360-degrees of rotation. The

http://windspeed.atcouncil.org/


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SWAN model run was completed with the initial water surface elevation set to the

maximum 100-year water surface elevation at the bridge during the storm surge event.

This step was taken in order to obtain a conservative estimate of the wave conditions at

the bridge.

The maximum wave heights at the bridge occur when the wind blows along the axis of

the Indian River Lagoon from the north. The largest significant wave height across the

bridge is 5.7 ft within the ICWW corresponding to a maximum wave height of 10 ft. The

peak period associated with the largest waves is 4.7 seconds. Figure 5.2 illustrates a

contour plot of significant wave height in feet for the project location. The contours

represent the maxima over all wind directions. Figure 5.3 presents profiles of significant

and maximum wave height as well as the wave crest elevation along the bridge corridor.

The figure displays how the wave heights are greatest at the deep sections within the

ICWW and depth limited on the causeways. Following the AASHTO code (AASHTO

2008), the maximum wave height was calculated as 80% greater than the significant

wave height. Table 5.1 summarizes the wave climate associated with 100-year design

conditions.

Table 5.1 Summary of 100-year Wave Climate

Water Surface Elevation

(ft, NAVD)

Significant Wave Height

(ft)

Wave Period

(seconds)

Maximum Wave

Height (ft)

Wave Crest Elevation

(ft-NAVD) +8.2 5.7 4.7 10.3 +15.4


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Figure 5.2 Significant Wave Height Contour Plot during the 100-year Return

Period Hurricane Event


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Figure 5.3 Wave Height Profiles during the 100-year Return Period Hurricane Event

5.2 Abutment Protection For abutment protection under design currents, HEC-23 (Lagasse et al., 2009)

recommends that the engineer determine the stone size from the Ishbash equation. For

abutment protection under design wave conditions, the van der Meer methodology would

determine the required riprap median stone diameter.

The modified Isbash equation provides the methodology for sizing armor stone under

design currents. The equation yields a median stone diameter of 0.61 ft (7 in.).

Application of the van der Meer (USACE, 2011) method for sizing a riprap yielded a

median stone weight of 836 lbs (1.8 ft median diameter) for the conditions experienced

on the east causeway during the design event. Given the larger diameter produced by this

equation, the wave climate determined the abutment protection size requirements.

Appendix D summarizes these calculations.

0

2

4

6

8

10

12

14

16

18

-600 -400 -200 0 200 400 600 800 1000 1200

Wav

e He

ight

s (ft

), W

ave

Cres

t Ele

vatio

n (ft

-NAV

D)

Distance from West Causeway Shoreline (ft)

SignificantWave Height

Maximum WaveHeight

Wave CrestElevation


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Given these results, this study recommends a double layer of FDOT Coastal Rubble

Riprap protection with a median weight of 836 lbs for the abutment protection (Table

5.2). The riprap shall extend from the MSE wall at least 10 ft from the abutment. The

riprap must have a thickness of at least twice the median stone diameter (3.6 ft) and

should rest on top of a 1-ft thick layer of bedding stone overlaying a geotextile filter

fabric. The protection should longitudinally extend the length of the MSE wall on both

sides of each bridge.

Table 5.2 Summary of Riprap Protection

Material Type Weight

Maximum Pounds

Weight 50% Pounds

Weight Minimum Pounds

Minimum Blanket Thickness in Feet

Limestone 3,343 836 334 3.6 Ensure that at least 97% of the material by weight is smaller than Weight Maximum pounds. Ensure that at least 50% of the material by weight is greater than Weight 50% pounds. Ensure that at least 85% of the material by weight is greater than Weight Minimum pounds.

5.3 Clearances The proposed low chord elevation of +12.95 ft-NAVD88 provides 6.95 ft above the

design (50-year) high water elevation. This exceeds the 2-ft requirement for debris

clearance. The bridge provides 86 ft of clearance above the mean high water. This

exceeds the required minimums for both navigation (6 ft) and for construction over

extremely aggressive waterways (12 ft, for chlorides). The clearance that the bridge

provides above the maximum wave crest elevation ranges from 2 ft to 70 ft over the

length of the bridge. This exceeds the 1-ft recommendation. Hydraulic recommendations

are detailed in Appendix E.


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55

6 REFERENCES

Arneson, L.A., L.W. Zevenbergen, P.F. Lagasse, and P.E. Clopper. (2012). Evaluating Scour at Bridges Fifth Edition, Hydraulic Engineering Circular No. 18. U.S. Department of Transportation, Federal Highways. Washington: U.S. Department of Transportation.

Dean, R. G., Chiu, T. Y., and Wang, S. Y. (1988). Combined Total Storm Tide Frequency Analysis for St. Lucie County, Florida. Division of Beaches and Shores Department of Natural Resources. Beaches and Shores Resource Center, Institute of Science and Public Affairs. Tallahassee, Florida.

Florida Department of Transportation (2016). Drainage Manual. Office of Design, Drainage Section, Tallahassee, FL.

Florida Department of Transportation (2016). Standard Specifications for Road and Bridge Construction. Office of Program Management, Tallahassee, FL.

Federal Highway Administration. (1997). Bridge Scour and Stream Instability Countermeasures. Hydraulics Engineering Circular No. 23. Washington, DC.: U.S. Departement of Transport.

Lagasse, E. F., Schall, J. D., Johnson, F., Richardson, E. V., Richardson, J. R., & Chang, F. (1991). Stream Stability at Highway Structures. Hydraulic Engineering Circular No. 20. Washington DC: US Department of Transportation.

Sheppard, D. M., & Renna, R. (2005). Florida Bridge Scour Manual. Florida Department of Transportation. Tallahassee: FDOT.

U.S. Army Corps of Engineers. (2002). Coastal Engineering Manual. Engineer Manual 1110-2-1100, U.S. Army Corps of Engineers, Washington, D.C. (in 6 volumes)

U.S. Army Corps of Engineers. (1995). Design of Coastal Revetments, Sea Walls, and Bulkheads EM 1110-2-1614. Corps of Engineers, Waterways Experiment Station. Vicksburg: Waterways Experiment Station.

U.S. Army Corps of Engineers. (1984). Shore Protection Manual, Vol. I and II. Vicksburg, Mississippi, USA: Waterway Experiment Station, Corps of Engineers.


FPID: 429936-2-22-01

A-1

APPENDIX A – GEOTECHNICAL REPORT EXCERPTS

From: Report of Parallel Seismic Testing

Ft. Pierce North Causeway (FDOT Bridge No 940045)

AFT Project No.: 215103

By Applied Foundation Testing


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A-2


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A-3


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A-4


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B-1

APPENDIX B – SITE VISIT PHOTOGRAPHS


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B-2

Photograph 1 Bridge Number


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B-3

Photograph 2 East Approach


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B-4

Photograph 3 Bridge Viewed from East Approach


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B-5

Photograph 4 Northeast Abutment


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B-6

Photograph 5 Northeast Bank


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B-7

Photograph 6 Northeast Waterway


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B-8

Photograph 7 Northwest Bank


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B-9

Photograph 8 North Waterway


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B-10

Photograph 9 Southeast Waterway


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B-11

Photograph 10 South Waterway


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B-12

Photograph 11 Southwest Waterway


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B-13

Photograph 12 North Bridge Face


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B-14

Photograph 13 East Abutment


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B-15

Photograph 14 Northeast Bank


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B-16

Photograph 15 East Abutment


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B-17

Photograph 16 Southeast Abutment Seawall


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B-18

Photograph 17 Southeast Abutment


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B-19

Photograph 18 Undermining, Southeast Abutment Seawall


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B-20

Photograph 19 Erosion Near the End of the Southeast Abutment Seawall


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B-21

Photograph 20 South Bridge Face


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B-22

Photograph 21 Northwest Abutment


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B-23

Photograph 22 North Bridge Face


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B-24

Photograph 23 Toe Protection, Northwest Abutment


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B-25

Photograph 24Alternate View, Northwest Abutment Toe Protection


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B-26

Photograph 25 West Abutment


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B-27

Photograph 26 Toe Protection, West Abutment


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B-28

Photograph 27 Pooling of Water on Southwest Abutment


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B-29

Photograph 28 Alternate View, Pooling of Water on Southwest Abutment


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B-30

Photograph 29 South Bridge Face


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B-31

Photograph 30 South Waterway


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B-32

Photograph 31 Alternate View, South Waterway


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B-33

Photograph 32 Seawall, South Bank of West Approach


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C-1

APPENDIX C – SCOUR CALCULATIONS


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C-2

100- and 500-year Local Scour Calculation Inputs

Pier description D50(mm)

Angle of

Attack Depth

(ft) V

(ft/s) bcol (ft)

Lcol (ft)

Hcol (ft)

f1 (ft) f2 Kscolumn

Bpc (ft)

lpc (ft)

T (ft)

Hpc (ft) Kspc

Hpg (ft) n m

n- spacing

m-spacing

bi (ft)

Pier_2-100 0.2 3.1 0.5 0.3 8.0 30.0 -2.30 7.5 11.0 1 30.0 45.0 8.0 -10.3 1 -10.3 4 6 7.5 7.5 2.5

Pier_3-100 0.2 3.1 0.5 0.3 8.0 30.0 0.92 7.5 11.0 1 30.0 45.0 8.0 -7.1 1 -7.1 4 6 7.5 7.5 2.5

Pier_4-100 0.2 3.1 0.6 0.3 8.0 30.0 2.59 7.5 11.0 1 30.0 45.0 8.0 -5.4 1 -5.4 4 6 7.5 7.5 2.5

Pier_5-100 0.2 3.1 1.3 0.3 8.0 30.0 3.33 7.5 11.0 1 30.0 45.0 8.0 -4.7 1 -4.7 4 6 7.5 7.5 2.5

Pier_6-100 0.2 16.1 0.1 0.3 8.0 30.0 2.05 7.5 11.0 1 30.0 45.0 8.0 -5.9 1 -5.9 4 6 7.5 7.5 2.5

Pier_7-100 0.2 3.1 1.1 0.3 8.0 30.0 3.08 7.5 11.0 1 30.0 45.0 8.0 -4.9 1 -4.9 4 6 7.5 7.5 2.5

Pier_8-100 0.2 5.8 0.5 0.3 8.0 30.0 2.05 7.5 11.0 1 30.0 45.0 8.0 -5.9 1 -5.9 4 6 7.5 7.5 2.5

Pier_9-100 0.2 24.2 0.5 1.2 8.0 30.0 2.05 7.5 11.0 1 30.0 45.0 8.0 -5.9 1 -5.9 4 6 7.5 7.5 2.5

Pier_10-100 0.2 6.3 10.6 2.9 8.0 30.0 15.66 7.5 11.0 1 30.0 45.0 8.0 7.7 1 7.7 4 6 7.5 7.5 2.5

Pier_11-100 0.2 5.4 11.5 2.9 8.0 30.0 16.50 7.5 11.0 1 30.0 45.0 8.0 8.5 1 8.5 4 6 7.5 7.5 2.5

Pier_12-100 0.2 11.8 13.0 3.1 8.0 30.0 18.02 7.5 11.0 1 30.0 45.0 8.0 10.0 1 10.0 4 6 7.5 7.5 2.5

Pier_13-100 0.2 13.8 12.8 3.4 8.0 30.0 17.75 7.5 11.0 1 30.0 45.0 8.0 9.8 1 9.8 4 6 7.5 7.5 2.5

Pier_14-100 0.2 15.3 12.1 3.7 8.0 30.0 17.09 7.5 11.0 1 30.0 45.0 8.0 9.1 1 9.1 4 6 7.5 7.5 2.5

Pier_15-100 0.2 16.0 13.3 4.0 8.0 30.0 18.29 7.5 11.0 1 30.0 45.0 8.0 10.3 1 10.3 4 6 7.5 7.5 2.5

Pier_16-100 0.2 14.8 13.2 4.2 8.0 30.0 18.26 7.5 11.0 1 30.0 45.0 8.0 10.3 1 10.3 4 6 7.5 7.5 2.5

Pier_17-100 0.2 13.5 15.5 4.3 8.0 30.0 20.60 7.5 11.0 1 30.0 45.0 8.0 12.6 1 12.6 4 6 7.5 7.5 2.5

Pier_18-100 0.2 14.9 18.4 4.3 8.0 30.0 23.45 7.5 11.0 1 30.0 45.0 8.0 15.5 1 15.5 4 6 7.5 7.5 2.5

Pier_19-100 0.2 19.4 13.1 4.2 8.0 30.0 18.26 7.5 11.0 1 30.0 45.0 8.0 10.3 1 10.3 4 6 7.5 7.5 2.5

Pier_20-100 0.2 24.7 12.7 4.3 8.0 30.0 17.82 7.5 11.0 1 30.0 45.0 8.0 9.8 1 9.8 4 6 7.5 7.5 2.5

Pier_21-100 0.2 32.0 8.2 4.6 8.0 30.0 13.43 7.5 11.0 1 30.0 45.0 8.0 5.4 1 5.4 4 6 7.5 7.5 2.5

Pier_22-100 0.2 42.0 1.0 5.5 8.0 30.0 1.66 7.5 11.0 1 30.0 45.0 8.0 -6.3 1 -6.3 4 6 7.5 7.5 2.5

Pier_23-100 0.2 28.5 1.0 1.4 8.0 30.0 1.66 7.5 11.0 1 30.0 45.0 8.0 -6.3 1 -6.3 4 6 7.5 7.5 2.5

Pier_24-100 0.2 40.9 4.8 0.9 8.0 30.0 3.21 7.5 11.0 1 30.0 45.0 8.0 -4.8 1 -4.8 4 6 7.5 7.5 2.5

Pier_25-100 0.2 23.6 5.4 0.4 8.0 30.0 3.76 7.5 11.0 1 30.0 45.0 8.0 -4.2 1 -4.2 4 6 7.5 7.5 2.5


FPID: 429936-2-22-01

C-3


Angle of

Attack Depth

(ft) V

(ft/s) bcol (ft)

Lcol (ft)

Hcol (ft)

f1 (ft) f2 Kscolumn

Bpc (ft)

lpc (ft)

T (ft)

Hpc (ft) Kspc

Hpg (ft) n m

n- spacing

m-spacing

bi (ft)

Pier_26-100 0.2 26.1 4.7 0.4 8.0 30.0 3.18 7.5 11.0 1 30.0 45.0 8.0 -4.8 1 -4.8 4 6 7.5 7.5 2.5

Pier_27-100 0.2 21.9 5.1 0.4 8.0 30.0 3.58 7.5 11.0 1 30.0 45.0 8.0 -4.4 1 -4.4 4 6 7.5 7.5 2.5

Pier_2-500 0.2 4.3 3.1 0.7 8.0 30.0 -2.06 7.5 11.0 1 30.0 45.0 8.0 -10.1 1 -10.1 4 6 7.5 7.5 2.5

Pier_3-500 0.2 4.3 3.1 0.7 8.0 30.0 1.16 7.5 11.0 1 30.0 45.0 8.0 -6.8 1 -6.8 4 6 7.5 7.5 2.5

Pier_4-500 0.2 4.3 3.1 0.7 8.0 30.0 2.83 7.5 11.0 1 30.0 45.0 8.0 -5.2 1 -5.2 4 6 7.5 7.5 2.5

Pier_5-500 0.2 4.3 3.1 0.7 8.0 30.0 3.57 7.5 11.0 1 30.0 45.0 8.0 -4.4 1 -4.4 4 6 7.5 7.5 2.5

Pier_6-500 0.2 11.8 3.1 0.7 8.0 30.0 2.29 7.5 11.0 1 30.0 45.0 8.0 -5.7 1 -5.7 4 6 7.5 7.5 2.5

Pier_7-500 0.2 4.3 4.1 0.7 8.0 30.0 3.32 7.5 11.0 1 30.0 45.0 8.0 -4.7 1 -4.7 4 6 7.5 7.5 2.5

Pier_8-500 0.2 6.6 3.6 0.7 8.0 30.0 2.29 7.5 11.0 1 30.0 45.0 8.0 -5.7 1 -5.7 4 6 7.5 7.5 2.5

Pier_9-500 0.2 12.4 3.6 2.1 8.0 30.0 2.29 7.5 11.0 1 30.0 45.0 8.0 -5.7 1 -5.7 4 6 7.5 7.5 2.5

Pier_10-500 0.2 1.2 13.7 4.3 8.0 30.0 15.10 7.5 11.0 1 30.0 45.0 8.0 7.1 1 7.1 4 6 7.5 7.5 2.5

Pier_11-500 0.2 10.3 14.5 4.6 8.0 30.0 15.94 7.5 11.0 1 30.0 45.0 8.0 7.9 1 7.9 4 6 7.5 7.5 2.5

Pier_12-500 0.2 15.4 16.1 4.9 8.0 30.0 17.46 7.5 11.0 1 30.0 45.0 8.0 9.5 1 9.5 4 6 7.5 7.5 2.5

Pier_13-500 0.2 17.5 15.8 5.3 8.0 30.0 17.19 7.5 11.0 1 30.0 45.0 8.0 9.2 1 9.2 4 6 7.5 7.5 2.5

Pier_14-500 0.2 18.9 15.1 5.7 8.0 30.0 16.53 7.5 11.0 1 30.0 45.0 8.0 8.5 1 8.5 4 6 7.5 7.5 2.5

Pier_15-500 0.2 19.7 16.3 6.1 8.0 30.0 17.73 7.5 11.0 1 30.0 45.0 8.0 9.7 1 9.7 4 6 7.5 7.5 2.5

Pier_16-500 0.2 18.8 16.2 6.4 8.0 30.0 17.70 7.5 11.0 1 30.0 45.0 8.0 9.7 1 9.7 4 6 7.5 7.5 2.5

Pier_17-500 0.2 18.3 18.5 6.6 8.0 30.0 20.04 7.5 11.0 1 30.0 45.0 8.0 12.0 1 12.0 4 6 7.5 7.5 2.5

Pier_18-500 0.2 20.6 21.3 6.7 8.0 30.0 22.89 7.5 11.0 1 30.0 45.0 8.0 14.9 1 14.9 4 6 7.5 7.5 2.5

Pier_19-500 0.2 26.2 16.0 6.8 8.0 30.0 17.70 7.5 11.0 1 30.0 45.0 8.0 9.7 1 9.7 4 6 7.5 7.5 2.5

Pier_20-500 0.2 33.1 15.5 7.0 8.0 30.0 17.26 7.5 11.0 1 30.0 45.0 8.0 9.3 1 9.3 4 6 7.5 7.5 2.5

Pier_21-500 0.2 42.1 11.0 7.0 8.0 30.0 12.87 7.5 11.0 1 30.0 45.0 8.0 4.9 1 4.9 4 6 7.5 7.5 2.5

Pier_22-500 0.2 35.3 1.0 6.6 8.0 30.0 1.90 7.5 11.0 1 30.0 45.0 8.0 -6.1 1 -6.1 4 6 7.5 7.5 2.5

Pier_23-500 0.2 33.2 2.5 2.2 8.0 30.0 1.90 7.5 11.0 1 30.0 45.0 8.0 -6.1 1 -6.1 4 6 7.5 7.5 2.5


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C-4


Angle of

Attack Depth

(ft) V

(ft/s) bcol (ft)

Lcol (ft)

Hcol (ft)

f1 (ft) f2 Kscolumn

Bpc (ft)

lpc (ft)

T (ft)

Hpc (ft) Kspc

Hpg (ft) n m

n- spacing

m-spacing

bi (ft)

Pier_24-500 0.2 39.7 4.4 1.6 8.0 30.0 3.45 7.5 11.0 1 30.0 45.0 8.0 -4.6 1 -4.6 4 6 7.5 7.5 2.5

Pier_25-500 0.2 31.8 4.9 0.6 8.0 30.0 4.00 7.5 11.0 1 30.0 45.0 8.0 -4.0 1 -4.0 4 6 7.5 7.5 2.5

Pier_26-500 0.2 36.4 4.3 0.6 8.0 30.0 3.42 7.5 11.0 1 30.0 45.0 8.0 -4.6 1 -4.6 4 6 7.5 7.5 2.5

Pier_27-500 0.2 30.4 4.8 0.7 8.0 30.0 3.82 7.5 11.0 1 30.0 45.0 8.0 -4.2 1 -4.2 4 6 7.5 7.5 2.5


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100- and 500-year Local Scour Calculation Outputs

Pier name Uc

(ft/s) Ulb-peak

(ft/s) D* col

(ft) D* pc

(ft) D*pg (ft) D*cp (ft)

Yse (ft)

Pier_2-100 0.823029 4.115143 0 0 0 0 0 Pier_3-100 0.823029 4.115143 0 0 0 0 1.0* Pier_4-100 0.841986 4.209932 0 0 0 0 1.0* Pier_5-100 0.922383 4.611914 0 0 0 0 1.0* Pier_6-100 0 0 0 0 0 0 1.0* Pier_7-100 0.905012 4.525062 0 0 0 0 1.0* Pier_8-100 0.823029 4.115143 0 0 0 0 1.0* Pier_9-100 0.823029 4.115143 0 42.44936 13.01326 55.46263 6.895937 Pier_10-100 1.140584 11.0795 0 1.286524 11.23759 12.52412 10.15094 Pier_11-100 1.149058 11.54027 0 1.195279 10.7638 11.95908 9.940415 Pier_12-100 1.161806 12.26984 0 0.988572 13.46274 14.45132 11.62672 Pier_13-100 1.160194 12.17509 0 1.017155 14.10528 15.12243 12.36065 Pier_14-100 1.154346 11.83749 0 1.115026 14.64483 15.75986 13.06075 Pier_15-100 1.164178 12.4106 0 0.966338 14.9343 15.90064 13.66004 Pier_16-100 1.163393 12.36386 0 0.924126 14.49471 15.41883 13.65565 Pier_17-100 1.180095 13.39778 0 0.722991 14.27534 14.99833 13.65382 Pier_18-100 1.197929 14.59742 0 0.565077 14.85404 15.41912 14.02959 Pier_19-100 1.162603 12.31694 0 0.904702 16.25653 17.16123 14.64789 Pier_20-100 1.159378 12.12743 0 1.03411 18.34498 19.37909 15.98929 Pier_21-100 1.11389 9.744824 0 2.056908 19.27464 21.33154 17.13507 Pier_22-100 0.895006 4.475032 0 32.93136 17.23266 50.16401 22.71766 Pier_23-100 0.895102 4.475511 0 43.604 16.95997 60.56397 9.912087 Pier_24-100 1.058207 7.455688 1.016365 36.5462 16.93321 54.49578 12.36703 Pier_25-100 1.070454 7.907951 0 0 0 0 1.0*


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Pier name Uc

(ft/s) Ulb-peak

(ft/s) D* col

(ft) D* pc


Yse (ft)

Pier_26-100 1.056018 7.377615 0 0 0 0 1.0* Pier_27-100 1.064511 7.685147 0 0 0 0 1.0*

Pier_2-500 1.012745 5.99167 10.22487 3.770313 0 13.99518 4.964028 Pier_3-500 1.012745 5.99167 1.556256 35.39786 8.532709 45.48682 8.408597 Pier_4-500 1.012745 5.99167 0.0753 38.61241 9.501677 48.18938 8.619323 Pier_5-500 1.012745 5.99167 0 36.85546 9.723545 46.57901 8.494671 Pier_6-500 1.012745 5.99167 0.430342 38.45975 11.68353 50.57362 8.799206 Pier_7-500 1.041817 6.890631 0.223568 36.06222 9.764263 46.05005 9.075772 Pier_8-500 1.028294 6.456815 0.654694 37.22929 9.980484 47.86447 8.933387 Pier_9-500 1.028294 6.456815 0.741466 30.12161 13.00379 43.86687 15.10185 Pier_10-500 1.167259 12.59585 0 3.298149 8.494859 11.79301 11.52006 Pier_11-500 1.17316 12.95839 0 2.959558 13.02968 15.98923 14.62025 Pier_12-500 1.184044 13.65463 0 2.511297 14.8432 17.35449 15.9568 Pier_13-500 1.182088 13.52682 0 2.614545 15.55158 18.16612 17.05055 Pier_14-500 1.177376 13.22378 0 2.841171 15.99838 18.83956 18.08724 Pier_15-500 1.185328 13.73918 0 2.509865 16.38075 18.89062 18.76548 Pier_16-500 1.184688 13.69697 0 2.460072 16.06383 18.5239 18.96879 Pier_17-500 1.198492 14.63703 0 1.970459 16.06788 18.03834 18.89674 Pier_18-500 1.213147 15.70568 0 1.548839 17.08733 18.63617 19.45698 Pier_19-500 1.183396 13.61216 0 2.497408 18.72149 21.2189 21.53113 Pier_20-500 1.180095 13.39778 0 2.689923 19.13661 21.82653 22.31477 Pier_21-500 1.144436 11.28661 0 4.934746 17.3435 22.27825 22.69249 Pier_22-500 0.895006 4.475032 0 31.61401 18.95337 50.56738 22.82917 Pier_23-500 0.990378 5.380679 0.550114 35.45701 18.3719 54.37902 16.6014 Pier_24-500 1.04916 7.138277 0.51118 33.59995 17.86959 51.98072 14.70482


FPID: 429936-2-22-01

C-7

Pier name Uc

(ft/s) Ulb-peak

(ft/s) D* col

(ft) D* pc


Yse (ft)

Pier_25-500 1.060351 7.532951 0.359406 40.39682 17.23268 57.9889 8.07107 Pier_26-500 1.046769 7.056695 0.451606 43.50377 17.07873 61.03411 8.089318 Pier_27-500 1.058207 7.455688 0.411738 36.76732 17.67035 54.8494 10.17854

*Scour depth of 1.0 ft assumed for conservatism.


FPID: 429936-2-22-01

D-1

APPENDIX D – Abutment Protection Calculations

Armor Stone Calculation Using van der Meer (1988) Non-Overtopped Slopes (procedure developed by Ferrante [1999]) Input cot α 2.0 Hs 1.10 m Tp 4.70 s P 0.5 ρs 2200 kg/m3 ρw 1025 kg/m3 N 7500 g 9.81 m/s2 Tp/Tm 1.25 Sd 2 Intermediate Tm 3.76 s Lo 22 m a 0.031 Hsc 0.4 m ∆ 1.15 Kpl 12.23 Ksu 0.19 Output

Hs is greater than Hsc

Therefore, plunging wave Plunging M50 379 kg 836 lbs

0.4 tons (U.S)

D50 0.6 m 1.8 ft


FPID: 429936-2-22-01

D-2

HEC-23 (Lagasse et al., 2009) Input

avg. channel flow depth 4.0 ft contracted section velocity V 4.70 ft/s

contracted section depth y 4.0 ft Unit weight of stone wa 137.28 lbs/ft3 Unit weight of water ww 64 lbs/ft3

abutment type vertical wall

Intermediate Froude No. [V/(gy)0.5] 0.41

K 1.02 spec gravity 2.15

∆ = ρs/ρ-

1 1.15 yK/∆ 3.56 Output D50 0.61 ft

7.3 in

W50 31.3 lbs


FPID: 429936-2-22-01

E-1

APPENDIX E – BRIDGE HYDRAULICS RECOMMENDATION SHEET INFORMATION


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E-2

HYDRAULIC DESIGN DATA Note:

1. The stage elevation of the design flood overtops the bridge, and subsequently, the area of the opening during the design flood only includes the area beneath the bridge.

The hydraulic data is shown for informational purposes only to indicate the flood discharges and water surface elevations which may be anticipated in any given year. This data was generated using highly variable factors determined by a study of the watershed. Many judgments and assumptions are required to establish these factors. The resultant hydraulic data is sensitive to changes, particularly antecedent conditions, urbanization, channelization, and land use. Users of this data are cautioned against the assumption of precision which cannot be obtained.

Terms: Design Flood: Utilized to assure a desired level of hydraulic performance. Base Flood: Has a 1% chance of being exceeded in any given year (100 year frequency) Overtopping Flood: Causes flow over the highway, over a watershed divide, or thru emergency relief structures. Greatest Flood: The most severe that can be predicted where overtopping is not practicable.

Water Surface Elevations: N.H.W. (Non-Tidal) NA M.H.W. (Tidal) -0.29 ft-NAVD Control (Non-Tidal NA M.L.W. (Tidal) -1.72 ft-NAVD

Flood Data: Max Event of Record Design Flood Base Flood □ Overtopping or ■ Greatest Flood Stage Elev. NAVD88(ft) +6.0 +8.2 +12.7 Discharge (cfs) 103,100 104,200 98,800 Average Velocity (ft/s) 4.4 4.4 4.7 Exceedance Prob. (%) 2 1 0.2 Frequency (yr) 50 100 500 Scour Predictions for proposed structure described above:

Pier Information Total Scour Elevation Numbers Size and Type Long Term Scour Elev. Worst Case < 100 yr. Worst Case < 500 yr.

Freq. (yr) 100 Freq. (yr) 500 Piers 2-9* 30” sq. conc. pile -4.0 -4.0 -12.0 Piers 10-21 30” sq. conc. pile -33.5 -33.5 -39.1

Piers 22 30” sq. conc. pile -20.2 -20.2 -20.5

Piers 21-27 30” sq. conc. pile -11.6 -11.6 -14.5


FPID: 429936-2-22-01

E-3

HYDRAULIC RECOMMENDATIONS

1. Begin Bridge Station 135+07.66 End Bridge Station 178+15.66 Skew Angle 0°

2. Clearance Provided: Nav: Horiz. 152 ft Vert. 86 ft Above El. -0.29 ft Drift: Horiz. 148 ft Vert. 6.95 ft Above El. +6.0 ft 3. Minimum Clearance: Nav: Horiz. 10 ft Vert. 6 ft Above El. -0.29 ft Drift: Horiz. Vert. 2 ft Above El. +6.0 ft 4. Abutments: Begin Bridge End Bridge

Rubble Grade: Coastal Rubble Riprap Coastal Rubble Riprap Slope: Varies Varies

Buried or Non-Buried Horiz. Toe: Buried Buried Toe Horiz. Distance: 10 ft 10 ft

Limit of Protection Length of MSE Wall Length of MSE Wall

5. Deck Drainage:

Remarks: See Bridge Hydraulics Report for scour elevations by pier number.

Date post:	26-Apr-2023
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bridge hydraulics report - SR A1A North Causeway Bridge

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