DRAFT_Sandbridge_DDR_65percent-with-attachments.pdf

US ARMY CORPS

OF ENGINEERS®

NORFOLK DISTRICT

65% DESIGN DRAFT

DESIGN DOCUMENTATION REPORT (DDR)

SANDBRIDGE BEACH EROSION AND HURRICANE

PROTECTION BEACH NORUISHMENT PROJECT

OCTOBER 2025

DRAFT

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SANDBRIDGE BEACH EROSION AND HURRICANE PROTECTION BEACH

NORUISHMENT PROJECT

DESIGN DOCUMENTATION REPORT (DDR)

Table of Contents List of Tables List of Figures

1 GENERAL

A. PRIOR STUDIES AND REPORTS

2. PROJECT DESCRIPTION

A. AUTHORIZATION

B. BACKGROUND

3. PERTIENT DATA

A. BORROW AREA LOCATION

B. SURVEY DATUMS AND CONTROL

4. REFERENCES

5. ENGINEERING INVESTIGATION, DESIGN, AND CONSTRUCTION

A. COASTAL ENGINEERING INVESTIGATION

1. DATA AND DESIGN DISCUSSION

2. TIDES

3. TIDAL FREQUENCY

4. STORMS

a. Historical Storm Impacts to the Project Area

b. 1992 Feasibility Report Storm Selection

5. WAVE DATA

6. HISTORIC EROSION RATES AND NET LITTORAL DRIFT

a. Volume Changes

b. Linear Changes

c. Project Remaining

7. SEA LEVEL CHANGE

B. GEOTECHNICAL INVESTIGATION

C. SITE INVESTIGATION

1. UTILITIES

2. TOPOGRAPHIC AND HYDROGRAPHIC SURVEYS

D. DESIGN AND CONSTRUCTION

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1. BORROW AREA DREDGING

2. SITE ACCESS

3. BEACH LAYOUT

4. TRAFFIC CONTROL

a. Borrow Area Traffic

b. Protection and Maintenance of Traffic

5. MONITORING PLAN

6. APPENDICES

A. VIRGINIA BEACH 1984 TIDAL FREQUENCY

B. BEACH MONITORING REPORT FOR THE SANDBRIDGE BEACH EROSION CONTROL

PROJECT SANDBRIDGE, VIRGINIA NOVEMBER 2024

C. GEOTECHNICAL DESIGN

List of Tables

Table 5-1 - Saffir-Simpson Hurricane Scale Table 5- 2 - Summary of Sandbridge Volume Changes from the November 2024 Monitoring Report Table 5- 3 - A Summary of Linear Shoreline Changes from the November 2024 Monitoring Report Table 5- 4 - Estimated Remaining Design Life by Region, from the November 2024 Monitoring Report Table 5- 5 - Sea Level Changes by Tidal Epoch at Sewells Point

List of Figures Figure 2-1 - Project Location Figure 3-1 - Sandbridge Borrow Areas A & B Figure 3-2 - Tidal Diagram for Sandbridge Figure 5-1 - Datums for Chesapeake Bay Bridge Tunnel Tide Gauge Figure 5-2 - Duck, NC Tide Gauge Figure 5-3 - Sewells Point Tide Guage data during the 1933 Chesapeake-Potomac Hurricane .. 17 Figure 5-4 - Sewells Point Tide Guage data during the 1962 Ash Wednesday Storm Figure 5- 5 - A Comparison of the 1933 Hurricane and 1962 Ash Wednesday Storm Hydrographs Figure 5- 6 - SLAT Look-Back Analysis of the Sewells Point Tide Gauge Figure 5- 7 - Typical Cross Section for Non-Bulkhead Portion of the Project Figure 5- 8 - Typical Cross Section for Bulkhead portion of the Project

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1 GENERAL

A. PRIOR STUDIES AND REPORTS

Several reports and studies of varying scope and detail which concern the flooding, erosion, and related water resources problems of the study area have been previously accomplished by the Corps of Engineers, other Federal agencies, the Commonwealth of Virginia, and the

City of Virginia Beach. A brief description is presented in the following paragraphs. It should be noted that most of the reports have dealt with the evaluation of protection measures for the “resort strip” which is located approximately 5 miles to the north of

Sandbridge.

1. In 1952, the Corps of Engineers, in cooperation with the City of Virginia Beach, prepared a report on a beach erosion control study for Virginia Beach. The report, printed in House Document 186, 83rd Congress, 1st Session, concluded that artificial placement of sand on the beach between Rudee Inlet and 49th Street was justified. In this report, the

Chief of Engineers recommended authorizing Federal participation in an amount equal to the cost of protecting the Federally owned frontage, plus one-third of the first cost of measures for the restoration and protection of the other publicly owned portions of the shores of Virginia Beach. The plan of protection included (a) artificial placement of the ocean shore of approximately 1,100,000 cubic yards of suitable sand fill to widen the beach berm to a minimum width of approximately 100 feet at elevation 7 feet above the mean low water or elevation 5.4 National Geodetic Vertical Datum (NVGD) and (b) construction of a system of approximately 21 groin as deferred construction when experience indicated the need therefor.

2. In 1962, a brief review report on a beach erosion control study for Virginia Beach was made by the Corps of Engineers in cooperation with the Virginia Beach Erosion

Commission. Protection for the Sandbridge area was not considered as a part of this report. The review was made to determine the extent, if any, of Federal participation in the cost of periodic beach nourishment. The initial project was authorized prior to the passage of Public Law 826, 84th Congress, which provides a policy of Federal assistance

DRR – OCTOBER 2025 Page 4 for periodic nourishment. Federal participation was for a period of 25 years from the placement of an initial quantity of nourishment material equal to the deficiency of the design beach at that time. Federal participation in beach nourishment expired in February

1987.

3. A brief hurricane survey report on Virginia Beach, Virginia was prepared in 1965 in compliance with Public Law 71, 84th Congress, 1st Session. Protection for the Sandbridge area was not considered as a part of this report. The report on the hurricane problem, printed in House Document 268, 89th Congress, 1st Session, recommended that no Federal expenditure be made and that the report be distributed to local interests for use in establishing flood plain regulatory measures and evacuation procedures.

4. A study of Rudee Inlet was initiated in connection with an investigation of Virginia

Beach Streams authorized by the Committee of Public Works in the House of

Representatives on June 21, 1965. In view of the close relationship of Rudee Inlet to the beach erosion and hurricane protection project, the Chief of Engineers approved the inclusion of Rudee Inlet as part of the Phase I study authorized for Virginia Beach.

However, a separate report was prepared on the inlet since any plan selected for Rudee

Inlet would require that the proposed project bypass if there were no inlet or no Federal navigation project at Rudee Inlet.

5. A feasibility report for beach erosion and hurricane protection was completed in 1970 and published in House Document 92-365, 92nd Congress, 2nd Session. It encompassed the entire shoreline of Virginia Beach from the North Carolina line to Little Creek Inlet in

Chesapeake Bay. The feasibility report recommended that the existing project for beach erosion control in the City of Virginia Beach, Virginia be modified to provide for the construction of a Federal project for beach erosion control and hurricane protection between Rudee Inlet and 89th Street, a distance of about 6 miles. The report determined that a plan considered for hurricane protection, consisting of 24,300 ft of sand dune and berms designed to protect against a tidal flood stage equal to that produced by the 420-year design storm, was not economically justified for the Sandbridge area.

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6. As a result of the above recommendation, a Phase I report on Virginia Beach was prepared in partial response to Section 1(a) of the 1974 Water Resource Development

Act. In this report, the Chief of Engineers recommended the construction of a new seawall from Rudee Inlet to 57th Street, the raising and/or widening of the existing sand dune from 57th Street to 89th Street and the maintenance of a beach berm with a minimum width of 100 feet between 49th Street and 89th Street. Based on a lack of economic justification, it was determined that no Federal interest existed in protection for the

Sandbridge area. It was a result of this authority, acting through the Sandbridge

Restoration Association (SBRA), hired a consultant to review the conclusions reach in the Phase I Sandbridge effort. The consultant indicated that feasible plans of improvement existed based on a number of cost and benefit considerations. The Board of

Engineers for Rivers and Harbors considered the Norfolk District and North Atlantic

Division negative findings for Sandbridge as well as the SBRA report and issued its own findings in a December 1986 report. The report concluded that a beach erosion plan only exhibited the most likely engineering feasibility although the report concluded that none of the plans were economically feasible. Subsequent to the Board of Engineers for Rivers and Harbors, report, the Office of the Chief of Engineers conducted a national survey of dredging costs and determined that revised lower unit sand costs might indicate that an economically justified plan exists. Using this information, a Supplemental

Preauthorization report was prepared which indicated that a berm only plan was economically justified. Subsequent efforts were directed toward the completion of a

Feasibility report to accompany a final Office of the Chief of Engineers report.

7. Rudee Inlet became a Federal navigation project in December 1983. A Local

Cooperation Agreement was signed in April 1986 with the local sponsor, the City of

Virginia Beach. The authorized plan of improvement consists of a 10-foot-deep entrance channel from the Atlantic Ocean through the inlet; a 7-foot-deep inner channel, safety area, and turning basin; and an 18-foot-deep sand trap. Annual maintenance dredging requirements are estimated at 220,000 cubic yards in the entrance channel and sand trap, all of which will be used for beach nourishment of the resort strip. The maintenance

DRR – OCTOBER 2025 Page 6 schedule for the interior areas is based on a 10-year-cycle, and averages approximately

3,000 cubic yards.

8. In 1985, the Virginia General Assembly permitted the installation of approximately

640 feet of timber bulkhead for eight oceanfront properties. This stretch of Sandbridge was the most extensive to be hardened to that date. Previously, the maximum number of continuously bulkheaded lots was four. Over the years, single-lot bulkheads were installed mostly along the southern section of the of the community where chronic erosion problems existed. In 1986, two lots adjacent to the eight were hardened, creating a continuous 800-foot timber bulkhead. Hurricane Charlie in 1986, along with several northeasters from 1986 – 1988 caused excessive erosion of the berm and dune. This led to the Sandbridge Bulkhead Impact Study issued by the Virginia Institute of Marine

Science (VIMS) in 1990. The main recommendation of this study was for the establishment of a beach nourishment program.

9. In December 1987, the District completed a reevaluation report under authority of

Sections 933 and 934 of the Water Resources Development Act of 1986 (Public Law 99-

662) for the reach of beach between Rudee Inlet and 49th Street. Under the Section 933 authority, a total of 1.2 million cubic yards of sand was placed on Virginia Beach from the Cape Henry Channel. The project was completed in October 1989. The reevaluation report concluded that, under Section 934 authority, Federal participation is warranted in the cost of nourishing the beach between Rudee Inlet and 49th Street with artificial placement of suitable sand fill to provide and maintain a berm having a width of approximately 100 feet at elevation 5.4 feet National Geodetic Vertical Datum of 1929

(NGVD) for an additional 10-year period. This project in effect extends the beach nourishment project authorized by the River and Harbor Act of 1962 which expired in

February 1987. Funds for extending the project, however, were not budgeted until such time as the effectiveness if the Section 933 sand supplied to the beach from the Cape

Henry Channel has been diminished to a level where further nourishment is needed. The

Section 934 authority applied only to existing Federal projects and therefore not applicable to Sandbridge.

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10. In March 1992, USACE Norfolk District completed the Final Feasibility Report and

Environmental Assessment of the Sandbridge Beach Erosion Control and Hurricane

Protection study. This report was a technical evaluation of economic, engineering, and environmental issues. The recommended National Economic Development (NED) plan is a berm 50 feet wide at elevation 6 feet NGVD, using a construction and periodic maintenance source 3 miles offshore. Construction and periodic maintenance will be accomplished by hopper dredge/hopper barge with suitable pumpout facilities and/or by ocean-capable cutterhead dredges with booster pumps as necessary. Estimated initial construction requirements were 972,00 cubic yards (inclusive of 2 years advance nourishment), while 500,000 cubic yards of material will be placed on the beach every 2 years follow project construction.

11. In 1996, Norfolk District completed a Limited Reevaluation Report (LRR) on the

Sandbridge Beach Erosion Control and Hurricane Protection project. The purpose of the

LRR was to provide current project economics for the NED plan authorized in PL 102-

580 (WRDA 1992). This included updated structure inventories and prices to for project benefits and costs.

12. In December 1997, VIMS released a study on the possible wave alternations along

Sandbridge beach due to dredged of the borrow area. No significant change to the shoreline was noted in the breaking waves or in the longshore sediment transport rates.

13. The project economic data and calculations were updated again in 2002, with another

LRR. Like the 1996 LRR, this LRR updated costs and benefits to the 1992 NED. This

LRR used storm frequency analyses from the 1994 Virginia Beach General Reevaluation

Report. The depth-damage analysis was based on the same procedures used in preparation of the authorization document and was compared with 1994 FEMA/FIA velocity and non-velocity depth-damage table.

2. PROJECT DESCRIPTION

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A. AUTHORIZATION

This project is authorized under Section 501 of the Water Resources Development Act 1986

(PL 99-662). Sections 103 and 101c of WRDA 1986, PL 99-662, as amended, 933 USC

2213, USC 2211 specify the cost sharing requirements applicable Section 101(22) of the

Water Resources Development Act of 1992 (PL 102-580), as modified by Section 338 of the

Water Resources Development Act of 2000 (PL 106-541).

B. BACKGROUND

The project area (Figure 2-1) is located within the Sandbridge community of Virginia

Beach in the southeastern region of Virginia known as Hampton Roads. The city is about 94 miles southeast of Richmond, VA, and 155 miles south-southeast of Washington, D.C.

Virginia Beach is the both the largest city in the Hampton Roads region and within the

Commonwealth of Virginia, with a population of 459,470 from the 2020 census. Virginia

Beach is 497 square miles, which is split nearly equally between land (249 square miles) and water (248 square miles). Sandbridge is a coastal community along the southeastern portion of Virginia Beach. It is situated between the Atlantic Ocean and the Back Bay of

Currituck Sound, boarded to the north by the US Navy’s Dam Neck base and to the south by the Back Bay National Wildlife Refuge and False Cape State Park. It is approximately 5 miles south of Virginia Beach’s “resort beach” and, while mostly a residential community, includes summer beach rentals as part of Virginia Beach’s tourism industry.

The proposed action would involve beach nourishment at the Sandbridge oceanfront, an area approximately 5 miles long and 125 feet wide. The specific beach area covered extends from the U.S. Naval Fleet Anti-Air Warfare Training Center at Dam Neck to the north to

Back Bay National Wildlife Refuge to the south (Figure 1). The project dimensions include a 50-foot wide berm at an elevation of 6 feet North American Vertical Datum (NGVD) with a foreshore slope of approximately 1:20 (one vertical value to 20 horizontal) for a distance of approximately 5 miles (Figure 2).

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Figure 2-1 - Project Location

3. PERTIENT DATA

A. BORROW AREA LOCATION

The designated borrow area is Sandbridge Shoal, located approximately 3 nautical miles from the shoreline, outside of Virginia’s territorial sea (Figure 3-1). There are two selected borrow areas within Sandbridge Shoal, Area B to the north and Area A to the south; depths range from 30 to 65 feet. The area between the two borrow areas is off limits due to the presence of a buried Navy submarine communications cable. The Bureau of Ocean Energy

Management (BOEM) manages the borrow areas as they are Outer Continental Shelf sand resources, governed under the Outer Continental Shelf Lands Act.

Beach quality sand would most likely be removed by trailing suction hopper dredge. The hopper dredge is equipped with dragheads and a hopper which collects sand. When the hopper is full, material is transported to a pump out buoy located offshore. The material would then be pumped through a discharge pipeline, which runs along the ocean floor, and up onto the beach where bulldozers and graders will distribute the material. Approximately

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1.5 to 2.0 million cubic yards (cy) of beach quality sand would be placed on the beach depending upon weather conditions, availability of funding, and behavior of subsequently placed material at the project site. The cycle may occur less often, but probably no less than once every 5 years.

Figure 3-1 - Sandbridge Borrow Areas A & B

B. SURVEY DATUMS AND CONTROL

Horizontal data is tied to the State Plane Coordinate System using North American Datum of

1983 (NAD83. Horizontal data shall be tied to the State Plane Coordinate System using

North American Datum of 1983 (NAD83, Virginia South, 4502). Distances are in feet by horizontal measurement. Coordinates are Virginia South Zone. Vertical data is tied to the

North American Vertical Datum of 1988. Elevations are in feet. Figure 3-2 is an image of the Datum Diagram for the project. DRAFT

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Figure 3-2 - Tidal Diagram for Sandbridge

4. REFERENCES

1. EM 1110-2-1100, Coastal Engineering Manual

2. EP 1100-2-1, Procedures to Evaluate Sea Level Change: Impacts, Responses, and

Adaption

3. EM 1110-2-1619, Risk-Based Analysis for Flood Damage Reduction Studies

4. ER 1110-1-1300, Cost Engineering Policy and General Requirements

5. ER 1110-2-1150, Engineering and Design for Civil Work Projects

6. ER 1110-2-1200, Plans and Specifications for Civil Works

7. ER 1110-1-8155, Specifications

8. ER 1110-2-1302, Civil Works Cost Engineering

9. ER 1110-2-8162, Incorporating Sea Level Change in Civil Works Programs

10. ER 1165-2-131, Local Cooperation Agreements for New Start Construction Projects

11. EP 11-1-4, Value Engineering: A Profitable Partnership

12. EM 1110-1-1005, Control and Topographic Surveying

13. EM 1110-1-1804, Geotechnical Investigations

14. EM 1110-1-2909, Geospatial Data and Systems

15. EM 1110-2-1003, Hydrographic Surveying

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16. Shore Protection Manual

5. ENGINEERING INVESTIGATION, DESIGN, AND CONSTRUCTION

A. COASTAL ENGINEERING INVESTIGATION

1. DATA AND DESIGN DISCUSSION

The beach templates for the 2027 renourishment are based on the 1992 Feasibility

Report. This DDR will discuss both the data used in the 1992 report and current environmental conditions. When the project is re-evaluated, all these conditions, particularly the storm suite, water levels, waves, erosion rates, and sea level change rates need to be updated with current data.

2. TIDES

As noted in the 1992 report, Virginia Beach’s Atlantic Ocean coast experiences a semi-diurnal tide. The mean tide range at the time of the report was 3.4 ft, with a spring tide of

4.1 ft.

Sandbridge is nearly splits the distance between two current tide gauges. To the north, and approximately 25 miles (40 km), is the Chesapeake Bay Bridge Tunnel (CBBT)

Chesapeake Channel (8638901) tide gauge. Figure 5-1 shows the tide datum relative to

MLLW. The mean tide (MN) is 2.66 ft, with a great diurnal tide (GT) is 3.02 ft.

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Figure 5-1 - Datums for Chesapeake Bay Bridge Tunnel Tide Gauge

About 35 miles (56 km) to the south, is the Duck, NC tide gauge (8651370), and the tidal datum is shown in figure 5-2. The mean tide is 3.22 ft with a great diurnal tide of 3.69 ft.

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Figure 5-2 - Duck, NC Tide Gauge

Finally, the current plans used the tide datum previously shown in figure 3-2. MLLW was determined using a tidal zoning plan furnished by the National Ocean Service (NOS).

3. TIDAL FREQUENCY

The 1992 Feasibility Report used the tidal frequency relationship determined in the 1984

Virginia Beach, Virginia, Beach Erosion Control and Hurricane Protection, Phase I GDM.

The close proximately of the projects allowed the Sandbridge team to assume similar tidal conditions between the two sites, given they are approximately five miles apart and along the open coast to the Atlantic Ocean. However, Virginia Beach only had intermittent tidal data between 1959 and 1971. The Virginia Beach project had to establish a tidal frequency relationship between Norfolk Harbor and the Virginia Beach

Resort Beach. The Norfolk Harbor tide gauge (known as the Sewells Point, VA tide

DRR – OCTOBER 2025 Page 15 gauge, 8638610), has a complete tide record starting in 1928. Appendix A is the tidal frequency used in both the Virginia Beach and Sandbridge studies, comparing the exceedance frequency (in percent) to the water elevation in NGVD.

4. STORMS

a. Historical Storm Impacts to the Project Area

Three general types of major storms affect Eastern Virginia in the form of tropical storms, hurricanes, and northeasters.

The term “tropical storm” is applied to a localized intense cyclonic circulation, low pressure wind system. They form over tropical oceans and with high winds above 39 miles per hour (mph) to 73 mph, and include heavy rainfall, large waves, and tidal surges.

The term “hurricane” is applied to an intense cyclonic storm originating in the tropical and subtropical latitudes of the Atlantic Ocean north of the equator. These storms normally gain intensity as they move over water in the southern latitudes. Alternatively, they tend to decay or decrease in intensity as they pass over land or move into the northern latitudes where conditions prevent sustaining energy for the storm. A hurricane is characterized by low barometric pressure, high winds (over 74 mph), heavy rainfall, large waves, and tidal surges.

Intensity of hurricanes are classified and rated based on the Saffir-Simpson Hurricane

Scale. A 1-5 rating system is used where Category 5 being the most intense and Category

1 being the least intense. See table 5-1 below for the categories:

Table 5-1 - Saffir-Simpson Hurricane Scale

CATEGORY WIND (MPH) DAMAGE POTENTIAL

5 > 157 Very Catastrophic

4 130 – 156 Catastrophic

3 111 – 129 Devastating

2 96 - 110 Extreme

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1 74 - 95 Dangerous

“Northeaster” (also Nor’easter) is the term given to storms that occur during the fall, winter, and spring months along the Atlantic Coast. A northeaster is characterized by high winds circulating around an essentially stationary low-pressure system, producing high tides, large waves, and heavy rainfall along the coast. Like all cyclonic wind systems in the northern hemisphere, the wind direction is always rotating inward and counterclockwise about the low-pressure area. Typically, winds originate from the northeast quadrant relative to this area; hence the term "northeaster." Nor’easters sometimes develop into complex storms with more than one influencing pressure cell.

The location of high-pressure centers and low-pressure centers with respect to each other may greatly intensify the wind speeds that would be expected from a single storm cell.

Strong winds reaching almost hurricane strength may occur over many thousands of square miles. Nor’easters may form with little or no advance warning and have been known to persist for as long as a week to ten days. However, the average duration of these storms lasts about two or three days.

b. 1992 Feasibility Report Storm Selection

The 1992 Feasibility Study used storm data developed for the 1984 Virginia Beach study.

Hurricane tracks from 1886 – 1966 that passed within 250 miles of Virginia Beach were analyzed. This is a total of 50 hurricanes over the 81-year timeframe. There are two storms highlighted throughout the report, as they produced the highest water levels during the study. The first is the 1933 Chesapeake-Potomac hurricane, which passed directly over Norfolk, VA on 23 August 1933. The region reported windspeeds between

70 – 80 mph, and the Sewells Point tide gauge recorded a 5 ft storm surge, which is the record for Norfolk, VA (figure 5-3). DRAFT

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Figure 5-3 - Sewells Point Tide Guage data during the 1933 Chesapeake-Potomac Hurricane

The second storm a nor’easter that occurred between 5 – 9 March 1962, known as the

“Ash Wednesday Storm of 1962.” This storm produced winds between 65 – 80 mph and elevated water levels over several tidal cycles, the largest being a 4.5 ft storm surge

(figure 5-4)

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Figure 5-4 - Sewells Point Tide Guage data during the 1962 Ash Wednesday Storm

A comparison of the hydrographs from the 1984 Virginia Beach report is below (figure 5-

5).

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Figure 5- 5 - A Comparison of the 1933 Hurricane and 1962 Ash Wednesday Storm

Hydrographs

Section 3 of the 1984 study goes through the process of calculating the Standard Project

Hurricane (SPH) and the design hurricane. The SPH for Virginia Beach is a hurricane with a maximum windspeed of 110 mph and a corresponding storm surge of 12.21 ft

(NGVD). This is a strong category 2 hurricane. However, as the report notes, the formulation process presented in the main report concluded that protection against a

12.21 ft storm surge was not practical. The Virginia Beach study instead calculated a 50-year storm (2% frequency of occurrence) as the study’s design storm. This storm has maximum sustained winds of 99 mph (a weak category 2 hurricane) with a storm surge of

10.0 ft.

5. WAVE DATA

The primary source of data and calculations for the 1984 study came from the Coastal

Engineering Research Center’s (CERC) Technical Report 77-1 (the Shore Protection

Manual) and the Atlantic Coast Hindcast, Shallow-Water, Significant Wave Information

(WIS Phase III). Paragraphs 11 – 15 of Section 3 in the 1984 provide details on the

DRR – OCTOBER 2025 Page 20 general wave and swell climate for Virginia Beach. Generally, waves are out of the northeast in the fall and winter, while they are predominately out of the south in the spring and summer.

The determination of wave heights and runup calculations were based on the solitary wave theory methodology as detailed in the 1984 Shore Protection Manual (SPM), Volume I, Chapter 2, Section II – 7. Wave runup calculations were performed on the eroded profile in accordance with the methods in the 1984 SPM.

6. HISTORIC EROSION RATES AND NET LITTORAL DRIFT

As noted in the 1992 Feasibility Study, Sandbridge is just north of a divergent nodal point. The general net littoral transport from Sandbridge to Cape Henry is in a north direction. Additionally, the 1984 Virginia Beach Study mentions that the waves approach the shore from a due east make an angle of 12° with the shoreline, which tends to create a slight northward transport.

The 1985 Sandbridge Phase I General Design Memorandum analyzed the Sandbridge shoreline from 1937 – 1984. The average annual erosion rate was between 5 and 6 ft. The annual erosion for the future without project condition on the study used 6 ft.

As part of the Operations and Maintenance (O&M) of the project, the City of Virginia

Beach conducts annual surveys of the beach profile. The City completed the most recent survey in November 2024. The 65% design submittal beach volumes are based on this survey. The final design will be based on the 2025 data when it is available. The monitoring report is attached to this DDR. The monitoring report calculates both volumetric and linear changes to the beach. A summary of the current erosion rates is below:

a. Volume Changes

The annual monitoring report (appendix B) compares calculated volumes at Mean Low

Water (MLW, -2.2 ft NAVD88), - 8 ft NAVD88, and -16 ft NAVD88, in order to capture changes on the dune and berm, nearshore, and deeper portions of the profile.

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Additionally, the report compares the one-year rate (“recent period”), as well as the current conditions compared to the beach profile following the most recent renourishment completed July 2020 (“long-term period”). The project is broken into reaches, noted as

Regions A – E. Table 5-2 below is taken from the 2024 monitoring report.

Table 5- 2 - Summary of Sandbridge Volume Changes from the November 2024 Monitoring Report

The monitoring report notes that between fall 2023 and fall 2024, Sandbridge experienced average volume gains above MLW and the -8 ft NAVD 88 contours, with mixed gains and loss above the -16 ft NAVD 88 contour. This may be from impacts to the

DRR – OCTOBER 2025 Page 22 project site from late-season tropical storms and hurricanes in 2023. Compared to the volumes of the previous renourishment, the MLW contour experienced calculated erosion rates of -1.6 cubic yards (cy.)/ft./yr. The -8 ft NAVD 88 contour experienced -2.9 cy./ft./yr., and the -16 ft NAVD 88 contour is calculated to have a volumetric erosion rate of -5.2 cy./ft./yr. Since the 2020 construction, the report estimates that the losses for the

MLW, -8 ft NAVD 88 contour, and the -16 ft NAVD 88 contour are 261,00 cy. (25% of the placed volume), 315,000 cy. (18% of the placed volume), and 374,900 cy. (22% of the placed volume), respectively.

b. Linear Changes

The monitoring report compares the shoreline defined by three areas on the beach. The first is the berm, defined at +5.2 NAVD88. Next is Mean High Water (MHW), at +1.3

NAVD88. The last area is the foreshore, which is calculated as the average of the berm

(+5.2 ft NAVD88), +3.0 ft NAVD88, MHW (+1.3 ft NAVD88) and -1.5 NAVD88.

Table 5- 3 - A Summary of Linear Shoreline Changes from the November 2024 Monitoring

Comparing the location of the berm, MHW, and overall foreshore from fall 2023 to fall

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2024, the berm experienced -6.0 ft/yr erosion (which is the erosion rate used in the 1992

Feasibility Study), while the MHW and foreshore were calculated to have erosion rates of

8.2 ft./yr. and 5.6 ft./yr. (the positive values indicating accretion/seaward movement) respectively. Since the 2020 construction, the average rates of erosion for the berm, MHW, and foreshore are -12.1 ft./yr., -15.5 ft./yr., and -14.2 ft./yr., with the northern end of the project site experiencing the highest rates of erosion.

c. Project Remaining

Table 5-4 compares the remaining project life by both volume (the first two rows) and linear change (the bottom two rows). The monitoring report goes into further detail, and while the project averages look very good, the southern end of the project (Region A) is the section in most critical need for renourishment.

Table 5- 4 - Estimated Remaining Design Life by Region, from the November 2024 Monitoring

7. SEA LEVEL CHANGE

Norfolk District estimated sea level change in the 1992 Feasibility Study by looking at the sea level variation at the Sewells Point gauge. The study looked at the three previous tidal epochs, noting the sea level referenced to NGVD. Table 5-5 below is the data from the Hydraulics and Hydrology Appendix of the study (Table C-2 in the study).

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Table 5- 5 - Sea Level Changes by Tidal Epoch at Sewells Point

Epoch (years) NGVD (feet) Change (feet)

1924 – 1942 4.87

1941 – 1959 5.15 +0.28

1960 – 1978 5.39 +0.24

The calculated rate of sea level change from Sewells Point was 0.0137 ft/yr in the 1992 study.

Comparing the 1992 study conditions to current conditions, the USACE Sea Level

Analysis Tool (SLAT) analyzed the mean sea level trends for the Sewells Point tide gauge in accordance with USACE Engineer Regulation (ER) 1100-2-8162 “Incorporating

Sea Level Change in Civil Works Programs” and Engineering Pamphlet (EP) 1100-2-1, “Procedures to Evaluate Sea Level Change: Impacts, Responses, and Adaptation.” The

SLAT calculated the total record Sea Level Change (SLC) rate at 4.84 mm/yr (0.16 ft/yr) between August 1927 – September 2025, and the 40-year SLC record at 6.61 mm/yr

(0.22 ft/yr), between October 1985 – September 2025. Figure 5-6 shows a plot of the

Look-Back Analysis which contains the monthly Mean Sea Level (MSL) and 5-year

MSL moving average. While it is not an exact comparison to the levels in table 5-5, as that table is in ft, NGVD and the plot is in ft, NAVD88, it is notable that the rate of SLC is an order of magnitude higher now that it was when the beach was designed.

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Figure 5- 6 - SLAT Look-Back Analysis of the Sewells Point Tide Gauge

B. GEOTECHNICAL INVESTIGATION

The geotechnical investigation, including the SAW OpenGround 2018 logs and grain size data, and the 2018 Schnabel investigation of Sandbridge Shoal Borrow Sites Area A & B, is attached at the end of this DDR, in appendix C.

C. SITE INVESTIGATION

1. UTILITIES

As of the 2019 renourishment, there were not public utilities in the federal project along the beach. The no dredging area between Sandbridge Shoal Borrow Sites A & B are marked on the plans.

DRR – OCTOBER 2025 Page 26

2. TOPOGRAPHIC AND HYDROGRAPHIC SURVEYS

Topographic and hydrographic surveys shall be completed before and after construction to determine the correct volume of material placed on the shoreline and that the construction template is met.

D. DESIGN AND CONSTRUCTION

1. BORROW AREA DREDGING

All sand material supplied from the Sandbridge Shoal Borrow Area A shall be in accordance with the project specifications.

2. SITE ACCESS

The contractor shall reference the project plans and specifications for location of site access.

3. BEACH LAYOUT

The 1992 Feasibility Study produced the design beach template currently used for this project. It features a protective beach berm with an average width of 35 – 90 feet at an elevation of +7.0 ft ± 0.5 ft NAVD88 along the entire 5-mile shoreline where an adequate berm does not presently exist. This renourishment will place sand at +7.5 ft NAVD 88 height and 90-foot berm width from the toe of the dune or bulk. Figures 5-7 and 5-8 show typical cross sections along the project as denotated by station number. From station 0 + 00 to 38 + 00, the only structures behind the dune are a public parking lot and a road. However, north of station 38+00, there are numerous bulkheads along the private properties adjacent to the federal project. Many of these were built in the mid-late 1980s and are noted in the 1992 Feasibility Study. DRAFT

DRR – OCTOBER 2025 Page 27

Figure 5- 7 - Typical Cross Section for Non-Bulkhead Portion of the Project

Figure 5- 8 - Typical Cross Section for Bulkhead portion of the Project

DRR – OCTOBER 2025 Page 28

Beach fill layout shall be done in accordance with the project construction specifications and plans.

4. TRAFFIC CONTROL

a. Borrow Area Traffic

The vessel traffic in the borrow areas may consist of a wide variety of types and sizes of vessels. Hampton Roads is also the home base for shallow and medium draft commercial seafood vessels, barges, tugs, pleasure crafts, and various other crafts. The Contractor shall follow pre-construction notifications in the specifications to alert the U.S. Coast

Guard to dredging operations in the borrow area.

b. Protection and Maintenance of Traffic

During construction, the Contractor shall provide access and temporary relocated roads as may be necessary to maintain vehicular traffic and protect the public. Measures for the protection and diversion of traffic, including the provision of watchmen and flagmen erection of barricades, placing of lights around and in front of equipment and the work, and the erection and maintenance of adequate warning, danger, and direction signs, shall be in accordance with the laws and regulations governing the respective activity.

Securely place barricades clearly visible with adequate illumination to provide sufficient visual warning of the hazard during both day and night. In the event of a conflict between laws and jurisdictions governing the work, the most stringent shall prevail. The

Contractor's traffic on roads selected for hauling material to and from the site shall interfere as little as possible with public vehicular and pedestrian traffic.

Traffic control plans including measures to reduce erosion of temporary roadbeds b construction traffic, especially during wet weather. Plan shall include measures to minimize the amount of mud transported onto paved public roads by vehicles or runoff.

The contractor shall reference the project specifications for any other direction on the traffic control, in particular Section 01 50 00, paragraph 3.3 (Traffic Provisions).

DRR – OCTOBER 2025 Page 29

5. MONITORING PLAN

A comprehensive monitoring program in accordance with USACE guidance (CEM Part

V, Chapter 4) is planned for the Sandbridge Beach Erosion Control and Hurricane

Protection Project to assess and ensure project functionality throughout its design lifetime. This monitoring supports the design efforts for periodic re-nourishment. The cost for the annual monitoring is the responsibility of the local sponsor at the time of the monitoring. The monitoring costs will be credited to the local sponsor when a periodic nourishment is conduct making them ultimately cost shared in accordance with the cost sharing of the initial project construction. Beach profile surveys will allow assessment of anticipated beachfill performance and determination of re-nourishment volume and timing requirements. An annual monitoring report will be prepared that presents the data collected and the corresponding analysis of project performance, including recommendations on re-nourishment requirements.

6. APPENDICES

A. VIRGINIA BEACH 1984 TIDAL FREQUENCY

B. BEACH MONITORING REPORT FOR THE SANDBRIDGE BEACH EROSION CONTROL

PROJECT SANDBRIDGE, VIRGINIA NOVEMBER 2024

C. GEOTECHNICAL DESIGN

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EXCEEDENCE FREQUENCY IN-PERCENT

Beach Monitoring Report for the Sandbridge Beach Erosion Control Project

Sandbridge, Virginia November 2024

Prepared by:

And

W a terwa y

Prepared for:

City of Virginia Beach, Virginia: Department of Public Works

February 2025

Waterway Surveys & Engineering, Ltd.

Virginia Beach, Virginia

Coastal Protection Engineering of North Carolina, Inc.

Wilmington, NC i

COASTAL PROTECTION ENGINEERING OF NORTH CAROLINA, INC.

for the Beach Erosion Control Project

EXECUTIVE SUMMARY

The most recent beach restoration at Sandbridge in Virginia Beach, Virginia was constructed between the months of April and July 2020 as part of an ongoing beach erosion control project.

The southern limit of the restoration is located at Little Island Park and extends north approximately 5.3 miles to the boundary of the Fleet Combat Training Center at Dam Neck. The 2020 restoration marks the 5th time Sandbridge has been nourished for beach erosion control.

The project is federally authorized for a berm width of 50 ft. at an elevation of +5.2 ft. NAVD88 and a slope of 1:20 (V:H) to the existing beach profile. During the 2020 event, approximately 1.7 million cubic yards of sand were dredged from an offshore borrow area and placed on the beach in front of the design template as advanced fill. Five primary regions are defined from south to north as Regions A, B, C, D and E. Region A begins at Little Island Park at the project’s southern limit and extends to the fishing pier (Station 0+00 to Station 30+00). Region B begins near the fishing pier and extends to Molly Cooper Road (Station 35+00 to Station 85+00). Region C includes Molly Cooper Road to Rock Lane (Station 90+00 to Station 145+00). Region D is inclusive of shoreline between Rock Lane and Sandbridge Road (Station 150+00 to Station 225+00). Region E covers the northern project limits from Sandbridge Road to the Fleet Combat Training Center at Dam Neck (Station 230+00 to Station 275+00).

Survey data collected during the November 2024 monitoring survey was used to quantify shoreline and volumetric changes over the 4.3-year (52-month) post-nourishment period (July 2020 to November 2024) and changes that have occurred during the most recent 12-month period (October/November 2023 to November 2024). These two time periods will be referred to as “long-term” and “recent” in the report. The project area was impacted by several storms during the recent monitoring period, most notably four storms that occurred in December 2023, January 2024 (Winter Storm Finn), March 2024, and September 2024 (Tropical Cyclone 8). Therefore, it should be noted that shoreline and volumetric changes measured during the recent period were influenced by the impacts from these storm events. A summary of the recent and long-term shoreline and volumetric changes within the fill placement area and the estimated design life remaining based on the MHW shoreline changes is included in Table ES-1.

ii

Table ES-1 Summary of Recent and Long-Term Shoreline and Volumetric Changes within the Sandbridge Fill Placement Area Comparison Parameter Quantity

Recent Period October/November 2023 vs. November

Average Shoreline Change at MHW (+1.3 ft. NAVD88) 8.2 ft.

Volume Change Above MLW (-2.2 ft. NAVD88) 62,000 cy

Volume Change Above -8 ft. NAVD88 -34,400 cy

Volume Change Above -16 ft. NAVD88 -254,000 cy

Long-Term Period July 2020 vs.

November 2024

Average Shoreline Change Rate at MHW (+1.3 ft. NAVD88) -15.5 ft./yr.

Cum. Volume Change Rate Above MLW ( -2.2 ft. NAVD88) -46,100 cy/yr.

Cum. Volume Change Rate Above -8 ft. NAVD88 -80,700 cy/yr.

Cum. Volume Change Rate Above -16 ft. NAVD88 -145,100 cy/yr.

Template vs.

November 2024

Average Remaining Design Life Based on MHW Changes 10.1 years

Critical Remaining Design Life Based on MHW Changes (Region A) 3.7 years

Recent Volume Changes

Volume changes calculated during the recent monitoring period showed that the project beach experienced minimal changes along the upper portion of the project beach profiles with slight gains above MLW (2.3 cy/ft.) and slight losses above -8 ft. NAVD88 (-1.3 cy/ft.). Larger losses were experienced on the deeper portion of the profiles above -16 ft. NAVD88 (-9.2 cy/ft.). An evaluation of the project area shows that all regions experienced volume gains above the MLW contour, whereas above the -8 ft. NAVD88 contour Regions A, B, and C experienced losses while Regions D and E experienced volume gains. Analysis of the changes above the -16 ft. NAVD88 contour showed that all regions experienced losses over the recent period, as shown in Table ES-2. The volume changes during the recent period are likely influenced by recovery from storms that impacted the area in the months prior to the November 2024 survey.

Long Term Volume Changes

The results of the long-term analysis show the overall trend remains erosional along the project area above the MLW, -8 ft. NAVD88, and -16 ft. NAVD88 contours with average annual erosion rates of -1.6 cy/ft./yr., -2.9 cy/ft./yr., and -5.2 cy/ft./yr., respectively. The analysis shows that Regions A, C, and E generally have the highest erosion rates since construction, while Regions B and D have eroded at slightly lower rates, as shown in Table ES-2. The volumetric analysis estimates that the average long-term trend has resulted in a total volume loss of approximately 349,900 CY above -8 ft. NAVD88, which is equivalent to 20% of the volume of sand deposited during the 2020 maintenance event. The volume losses above MLW and -16 ft. NAVD88 were approximately 199,700 CY and 628,900 CY, which equate to 19% and 37%, respectively, of the volume of sand deposited during the 2020 nourishment event.

iii

Recent Linear Changes

The recent shoreline changes showed that the project area had a seaward advance at the MHW and foreshore positions at annualized rates of +8.2 ft./yr. and +5.6 ft./yr., respectively; however, the berm position showed an average landward retreat of -6.0 ft./yr. The analysis showed that shoreline advances were measured in all the regions at the MHW contour and foreshore positions, apart from Region B where shoreline recession was measured at the foreshore position. The annualized recession rate was the highest in Region A (-19.5 ft./yr.) at the berm contour. The annualized rates were all positive in Region E, the northernmost region, above all contours.

Long Term Linear Changes

Linear shoreline changes being tracked by the monitoring program (berm, MHW, and foreshore) have experienced recession since the 2020 maintenance event; however, the long-term trend shows that the recession rates have decreased at the contours analyzed when compared with the previous long-term rates based on the October/November 2023 survey. The MHW position has receded at the highest overall annual average rate of -15.5 ft./yr. followed by the foreshore position at a rate of -14.2 ft./yr. The average rate of change at the berm contour was the lowest at -12.1 ft./yr. All of the contours and regions experienced a reduction in the long-term erosion rate since Oct./Nov. 2023. Region E had the highest rate of recession for the MHW contour and foreshore position, while Region A had the highest rate of recession at the berm contour as shown in Table ES-2. The long-term rates at the berm, MHW, and foreshore positions were the lowest in Region B.

Remaining Life of Project

The analysis of the linear and volumetric changes used to estimate the remaining design life showed that the MHW and foreshore positions across the entire project remain seaward of the design template by average widths of 155.9 ft. (69% remaining) and 164.1 ft. (73% remaining), respectively. Approximately 90% and 91% of the volume remained above both MLW (82.3 cy/ft.)

and -8 ft. NAVD88 (93.8 cy/ft.) relative to the design template.

An overview of the project area shows that Regions C and E support the widest sections of the project at the MHW contour and the foreshore position seaward of the design template. Regions C and E also have the most volume remaining above the MLW and -8 ft. NAVD88 contours of the volume deposited in those regions in 2020. The southern 3,000 ft. of the project (Region A) has the narrowest width relative to the design template with average widths at the MHW contour and foreshore of 55.6 ft. (44%) and 61.0 ft. (49%), respectively. Region A was also the most eroded region with 36.2 cy/ft. or 72% of the fill deposited in 2020 remaining above MLW and 43.3 cy/ft.

or 70% remaining above -8 ft. NAVD88 as of November 2024.

The analysis calculated the average design life estimates for the entire project ranged from 10.1 to 11.6 years based on the MHW and foreshore changes and 32.6 to 50.1 years based on the volume changes above -8 ft. NAVD88 and above MLW, respectively (Table ES-2). The longest iv design life remaining was estimated for Region E when considering the shoreline analysis and Region D when considering the volume analysis, while the shortest remaining design life, ranging from 3.7 to 15.3 years, was estimated for Region A (southernmost region) for both analyses.

Based on the results of the analysis, the minimum remaining life of the design template in each region is dictated by changes at the MHW contour. As of November 2024, the estimates based on the changes at the MHW contour indicate that Region A has a remaining design life of 3.7 years (or roughly to July 2028). Estimated remaining design life for all regions based on both linear and volume changes are summarized in Table ES-2.

Critical Areas

As mentioned above, the shoreline and volumetric changes indicate that Region A (Stations 0+00 to 30+00) remains the most vulnerable region within the project area. Region A has the least volume and shoreline width remaining seaward of the design template. As of November 2024, the southernmost profile (Station 0+00) was the only location where some portion of the profile has eroded into the design template. As a result, approximately 600 CY of fill would be required to restore the design template. The long-term volume change rate above the -8 ft. NAVD88 contour suggests the area has a remaining life of 12.5 years (May 2037) or 3.7 years (July 2028) based on the MHW linear analysis. Given the overall results of the November 2024 monitoring, Region A appears to be the most vulnerable area where a portion of the beach within the region has eroded landward of the design template.

v

Table ES-2 Summary Statistics for the Sandbridge Longshore Regions

Post-Nourishment (July 2020) to November 2024.

Parameters Project Average

Region A (0+00 - 30+00)

Region B (35+00 - 85+00)

Region C (90+00 - 145+00)

Region D (150+00 - 225+00)

Region E (230+00 - 275+00)

Volume Change Above MLW (-2.2 ft. NAVD88) Recent Volume Change

Oct./Nov. 2023 to November 2024 (cy/ft.)

2.3 1.8 0.1 1.7 3.3 4.0

Total Volume Change July 2020 to November

2024 (cy/ft.)

-7.1 -10.3 -7.0 -8.7 -3.4 -9.1

Long-Term Change…