Year 2 Habitat Delineation Report 07/2023

OCEAN ISLE BEACH SHORELINE PROTECTION
PROJECT
YEAR 2 POST -CONSTRUCTION HABITAT
DELINEATION OF THE SHALLOTTE INLET
COMPLEX
PREPARED FOR
The Town of Ocean Isle Beach, North Carolina
Ocea n i sle
B E A C H
PREPARED BY
Coastal Protection Engineering of North Carolina, Inc.
COASTAL
PROTECTION
ENGINEERING
July 2023

YEAR 2 POST -CONSTRUCTION HABITAT DELINEATION OF THE
SHALLOTTE INLET COMPLEX
TABLE OF CONTENTS
1. Introduction................................................................................................................................1
2. Methodology
3. Results.........
2
3
4. Disscussion..................................................................................................................................9
LIST OF FIGURES
Figure 1. Map showing extents of beach fill placement for the Accretion Fillet and the CSRM
Project.....................................................................................................................................1
Figure 2. Shallotte Inlet Habitat Mapping Area......................................................................................... 2
Figure 3. Extent of habitats delineated during the Pre -Construction timeframe within the Shallotte
Inlet Habitat Mapping Area based on 2012 imagery............................................................................4
Figure 4. Extent of habitats delineated during the Year 1 Post -Construction timeframe within the
Shallotte Inlet Habitat Mapping Area based on 2022 imagery...........................................................5
Figure 5. Extent of habitats delineated during the Year 2 Post -Construction timeframe within the
Shallotte Inlet Habitat Mapping Area based on 2023 imagery...........................................................6
Figure 6. Intertidal flats observed within Shallotte Inlet on July 14, 2023.......................................................10
Figure 7. USACE Navigation maintenance material placed on the inlet shoreline, east of terminal
groin...........................................................................................................................................................12
LIST OF TABLESS
Table 2. Changes in extent of habitats within the Shallotte Inlet Habitat Mapping Area
between2022 and 2023.........................................................................................................................7
Table 2. Changes (in percentage) of the extent of habitats within the Shallotte Inlet Habitat
Mapping Area between 2022 and 2023..............................................................................................7
Figure 3. Changes in extent of habitats along the eastern portion of Ocean Isle Beach between
2022and2023.........................................................................................................................................8
Figure 4. Changes in extent of habitats along the western portion of Holden Beach between
2022 and 2023........................................................................................................................................9
Figure 5. Named storms passing within 100 miles of Ocean Isle Beach between 2012 and
2022........................................................................................................................................................11

1. INTRODUCTION
In order to mitigate chronic erosion experienced along the eastern portion of Ocean Isle Beach's
oceanfront shoreline so as to preserve the integrity of its infrastructure, provide protection to
existing development, and ensure the continued use of the oceanfront beach, the town implemented
its Shoreline Protection Project in the fall of 2021. The project involved the construction of a
1,050 ft. terminal groin structure and placement of fill on the east end of the island. The terminal
groin structure included the construction of a 750 ft. long rubble mound structure and a 300 ft.
long concrete capped sheet pile wall. The fill area required the placement of 272,936 cy of sand
to form a 3,214 ft. accretion fillet on the west side of the terminal groin. The Ocean Isle Beach
Shoreline Protection Project was completed between November 16 2021 and April 14 2022 with
final demobilization by April 30, 2022. Simultaneously, the US Army Corps of Engineers
(USACE) constructed their Coastal Storm Risk Management (CSRM) project for the town. This
project involved the placement of an additional 484,211 cy of sand from Goldsboro Street (Station
80+00) eastward toward the accretion fillet. Figure 1 shows the limits of the fill placement for the
accretion fillet, immediately west of the terminal groin structure, and the domain of the federal
CSRM project.
Figure 3. Map showing extents of beach fill placement for the Accretion Fillet and the CSRM Project.
Condition #20 of the town's CAMA Major Permit #107-16 states, "Unless specifically altered
herein, the permittee shall implement, at its expense, all mitigation and monitoring commitments
made in, or submitted with, the permit application, the Inlet Management Plan dated Received
DCM Wilmington 2/23/16, or the FEIS". Because the project had the potential to impact certain
biological resources and habitats found within the permit area, particularly within the Shallotte
Inlet complex, the FEIS (Final Environmental Impact Statement) included a commitment to
implement a habitat mapping effort. This effort includes the determination of the extent of biotic
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community types (habitats) within the 945-acre Shallotte Inlet Habitat Mapping Area domain
(Figure 2) prior to the construction of the project to serve as baseline conditions. Determining the
baseline conditions of these resources is a fundamental step in quantifying changes in response to
the implementation of the project. Accordingly, high -resolution aerial imagery was obtained in
2012 to assist with the delineation of habitat types within the Mapping Area with the results (acres
of habitat types) integrated into the FEIS.
In order to assess the extent of change to these habitats following the construction of the project,
post -construction habitat delineation efforts will be performed on an annual basis for three (3)
years. The first post -construction delineation was performed soon after the construction of the
Shoreline Protection Project in 2022. This report fulfills the requirement for the second post -
construction habitat delineation event.
Figure 2. Shallotte Inlet Habitat Mapping Area.
2. METHODOLOGY
Ortho-rectified color digital imagery of the 945-acre Shallotte Inlet Habitat Mapping Area was
acquired for the 2012 pre -construction assessment and subsequent post -construction assessments
in accordance with NOAA's Coastal Services Center 2001 Guidance for Benthic Habitat Mapping
— An Aerial Photographic Approach (Finkbeiner et al., 2001) and through coordination with
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NMFS Habitat Conservation Division. The 2012 imagery was acquired on February 13, 2012 from
a fixed wing manned aircraft and obtained by the State of North Carolina and accessed for use via
NC OneMap. The Year 1 and Year 2 post -construction imagery was obtained on June 6, 2022
and May 14, 2023, respectively via drone (eBee X outfitted with a Trimble RTK R10 GPS system
and a SODA 3D RGB camera).
For the pre -construction 2012 imagery, visual interpretations of biotic community types were
digitally mapped using ArcView 9.3 software over high -resolution georeferenced digital
multispectral aerial photographs as part of the initial pre -construction assessment of biotic
communities. The methods employed for interpretation of aerial photography included visual
analysis of color variations in the photographs to delineate habitats. Following the development of
the preliminary biotic community mapping within the Shallotte Inlet Habitat Mapping Area via
visual interpretation, field investigations were conducted to groundtruth the initial delineations.
Sites selected for groundtruthing were determined by identifying areas that were difficult to
classify from the aerial photography. These locations were visited, and the biotic community type
(as identified through aerial photographic interpretation) was then verified. Based on the results of
the field investigations, the preliminary habitat map was revised as necessary, and acreages were
determined for ten (10) distinct habitat types within the survey area including: Dry Beach, Wet
Beach, Dune, Early Successional Upland Vegetation, Scrub Vegetation, Upland Forest, Intertidal
Flats, Salt Marsh, Subtidal, and Residential.
For the 2022 and 2023 post -construction efforts, the digital data was photogrammetrically
processed using Pix4D Mapper Pro and ESRI's Are Pro version 2.8 to create a georeferenced
orthomosaic. In compliance with State and Federal agency requests, digital image acquisition was
scheduled, to the greatest extent possible, to coincide with good weather conditions and an ebb
tide that may provide for increased accuracy of habitat interpretation. Resolution of all sets of
imagery was sufficient (<0.6 in [2 ft]) to accurately delineate the ten (10) distinct habitat types
within the survey area. —For a more accurate portrayal of residential habitat coverage in areas
covered by tree canopy, open source NCDOT road and parcel data was obtained. This was useful
for delineating roads and finding houses that were difficult to find through the canopy, specifically
in the region surrounding Saucepan Creek. Topology of habitat features was retained by leveraging
map topology enabled cartographic production tools available in Arc Pro. Ground truthing efforts
were conducted on October 7, 2022 and July 14, 2023 to verify the habitat types delineated for the
Year 1 and Year 2 post -construction delineation efforts, respectively.
3. RESULTS
Figures 3, 4, and 5 depict the locations of the various habitats delineated within the Shallotte Inlet
Habitat Mapping Area based on the 2012 (Pre -Construction), 2022 (Year 1-Post Construction),
and 2023 (Year 2-Post Construction) delineations, respectively. The acres of each habitat type
delineated from each year are depicted in Table 1 along with the change in acreages for each habitat
type between the time periods. Table 2 depicts the percent change of each habitat type between
the Pre -Construction condition and the Year 2 Post -Construction condition as well as the percent
change of each habitat type between Year 1 and Year 2 Post -Construction conditions.
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While there were only negligible changes (<10%) to the extent of salt marsh, subtidal, dune, and
upland forest between the Pre -Construction and Year 2 Post -Construction assessments, there were
significant changes in acreages (>10%) for six (6) of the delineated habitat types. Of these,
intertidal flats, dry beach, early successional upland vegetation, and scrub/shrub vegetation
habitats all decreased in extent over this period while residential, and wet beach habitat types
increased (Table 2). Between the Year 1 Post Construction (2022) and Yea 2 Post -Construction
(2023) assessments, the majority of the habitat types demonstrated negligible changes (>10%
change). Intertidal flats, dry beach, early successional upland vegetation, and scrub/shrub
vegetation, however, demonstrated changes in extent greater than 10%. Specifically, intertidal
flats increased by 128.1 % and the dry beach increased by 75.1 % while the extent of early
successional upland vegetation and scrub/shrub vegetation decreased by 41.8% and 18.5%,
respectively, over the one-year period (Table 2).
N
s
a
zl
Rofmn�c: 0 500 1.000 2000.Feel
Figure 3. Extent of habitats delineated during the Pre -Construction timeframe within the Shallotte Inlet
Habitat Mapping Area based on 2012 imagery.
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Hal tiat 2022 Acreage
Spatial Reference: L
MAD 1983 StatePlane North Carolina FIPS 320C (US Feet)
Coastal Protection Englneering,UN CW, NCDOT
Figure 4. Extent of habitats delineated during the Year 1 Post -Construction timeframe within the Shallotte
Inlet Habitat Mapping Area based on 2022 imagery.
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Figure S. Extent of habitats delineated during the Year 2 Post -Construction timeframe within the Shallotte
Inlet Habitat Mapping Area based on 2023 imagery.
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Table 1. Changes in extent of habitats within the Shallotte Inlet Habitat Mapping Area between 2022 and 2023.
Red cells indicate a reduction in acreage between imagery dates and green cells indicate an increase in acreage
between imagery dates.
2012 Pre-
2022
2023
Change in
Change in
Yr. 1 Post-
Yr. 2 Post-
Habitat
Con.
Acreage
Acreage
(Acres)
Con.
Con.
(2012- 2023)
(2022- 2023)
Acres
Acres
Intertidal Flats
15.57
2.49
5.68
Dry beach
43.35
17.18
30.08
-13.27
179
Early Successional
Upland Vegetation
12.86
9.69
5.71
-7.15
-3.98
Salt Marsh
151.45
155.23
157.49
6.04
2.26
Residential
92.11
94.52
101.71
9.60
7.19
Subtidal
495.03
509.66
499.72
4.69
-9.94
Scrub/Shrub
22.66
24.27
19.79
-2.37
-4.48
Vegetation
Dune
41.68
45.63
43.36
1.68
-2.27
Upland Forest
41.28
45.29
42.33
1.05
-2.96
Wet Beach
29.36
41.39
39.48
10.12
Total (Acres)
945.35
945.35
945.35
N/A
N/A
Table 2. Changes (in percentage) of the extent of habitats within the Shallotte Inlet Habitat Mapping Area
between 2022 and 2023. Red cells indicate a reduction in percentage between imagery dates and green cells
indicate an increase in percentage between imagery dates.
2022
2023
2012 Pre-
% Change
% Change
Habitat
Con.
Yr. 1 Post-
Yr. 2 Post-
in Acreage
in Acreage
Con.
Con.
(Acres)
(2012- 2023)
(2022- 2023)
Acres
Acres
Intertidal Flats
15.57
2.49
5.68
-63.5%11W
128.1% MR
Dry beach
43.35
17.18
30.08
-30.6%
75.1%
Early Successional
Upland Vegetation
12.86
9.69
5.71
-55.6%
Salt Marsh
151.45
155.23
157.49
4.0%
1.5%
Residential
92.11
94.52
101.71
10.4%
7.6%
Subtidal
495.03
509.66
499.72
0.9%
-2.0%
Scrub/Shrub
22.66
24.27
19.79
-
-18.5%
Vegetation
Dune
41.68
45.63
43.36
4.0%
-5.0%
Upland Forest
41.28
45.29
42.33
2.5%
-6.5%
Wet Beach
29.36
41.39
39.48
34.5%
Total (Acres)
945.35
945.35
945.35
N/A
N/A
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Changes in the extent of each habitat type between the Year 1 Post -Construction (2022) and Year
2 Post -Construction (2023) assessments were also determined for the discrete areas along the
eastern portion of Ocean Isle Beach and the western end of Holden Beach; both are portions within
the larger Shallotte Inlet Habitat Mapping Area. As shown in Table 3, of the 164.2 acre -area along
the eastern portion of Ocean Isle Beach, there was a substantial increase (>10%) of intertidal flats
and dry beach habitat between the first two post -construction assessments. During the same
timeframe there was a >10% reduction in the extent of early successional upland vegetation and
scrub/shrub vegetation.
Table 3. Changes in extent of habitats along the eastern portion of Ocean Isle Beach between 2022 and 2023.
Red cells indicate a reduction in acreage between imagery dates and green cells indicate an increase in acreage
between imagery dates.
2022
2023
Change in
% Change
Habitat
Acreage
Acreage
Acreage
Between 2022
(OIB)
(OIB)
Between 2022
and 2023
and 2023
Intertidal Flats
0.8
1.5
0.7
78.6%
Dry beach
11.0
14.7
3.7
34.1 %
Early Successional Upland
Vegetation
2.5
1.0
-1.6
-61.7%
Salt Marsh
2.1
.2
-36.0%
Residential
7.1
7.7
0.7
9.6%
Subtidal
113.9
117.3
3.4
3.0%
Scrub/Shrub Vegetation
3.1
1.4
-1.7
-55.0%
Dune
4.7
4.9
0.2
3.8%
Upland Forest
0
0
0
0%
Wet Beach
JL 17.9
13.6
-4.2
-23.6%
Total (Acres)
164.2
164.2
N/A
N/A
Of the 305.8-acre area along the western end of Holden Beach, there was a substantial (>10%)
increase of intertidal flats and dry beach habitat between the Year 1 Post -Construction (2022) and
Year 2 Post -Construction (2023) delineation events. No habitats within this area and timeframe
were reduced by more than 10% between these two assessments (Table 4).
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Table 4. Changes in extent of habitats along the western portion of Holden Beach between 2022 and 2023. Red
cells indicate a reduction in acreage between imagery dates and green cells indicate an increase in acreage
between imagery dates.
Change in
2022
2023
% Change
AcreageBetween
Habitat
Acreage
Acreage
2022
Between 2022
(OI B)
(OI B)
and 2023
and 2023
Intertidal Flats
0.17
0.20
0.03
r 17.6%
Dry beach
6.1
14.7
8.6
140.1 %
Early Successional Upland
5.1
4.7
-0.4
-6.9%
Vegetation
Salt Marsh
95.8
97.4
1.6
1.7%
Residential
16.3
16.7
0.4
2.1 %
Subtidal
98.7
91.6
-7.1%
Scrub/Shrub Vegetation
16.9
15.8
-1.1
-6.6%
Dune
40.8
38.3
-2.5
-6.0%
Upland Forest
5.6
6.0
0.4
6.6%
Wet Beach
20.4
20.4
0.0
0.1%
Total (Acres)
305.8
305.8
N/A
N/A
4. DISSCUSSION
This habitat monitoring study was implemented to document changes that have occurred to the
biotic communities following the construction of the Town's 2022 Shoreline Protection Project.
The project was completed between mid -November 2021 and mid -April 2022. The spatial extent
of ten (10) different habitat types delineated from aerial imagery obtained in May 2023 serves as
the Year 2 Post -Construction assessment. Between the Year 1 and Year 2 Post -Construction
assessments, there was a considerable increase in the percent of dry beach (+75.1 %) and intertidal
flats (+128.1%) and a decrease of early successional upland vegetation (41.1%), and scrub/shrub
vegetation (18.5%) within the entire study area. As depicted in Figure 5 and 6, several intertidal
flats had appeared in the inlet in 2023 accounting for the large increase in this habitat type.
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Figure 6. Intertidal flats observed within Shallotte Inlet on July 14, 2023.
The increase of dry beach between the Year I and Year 2 Post -Construction assessments was
apparent along the area immediately east of the terminal groin on Ocean Isle Beach where much
of this area was previously classified as wet beach. In fact, as depicted in Table 3, the dry beach
habitat increased by 3.7 acres (34.1 %) on Ocean Isle Beach between the two assessments. On
Holden Beach, the amount of dry beach along the inlet shoreline and westernmost oceanfront
shoreline increased from 6.1 acres to 14.7 acres (+140.1%) during this same time frame.
The reduction in acreage of early successional upland vegetation and scrub/shrub vegetation
occurred in various locations throughout the study area including along the northern shore of the
intracoastal waterway behind Ocean Isle Beach where some of the former vegetated habitat has
been converted to residential development. In addition, overwash just east of the terminal groin
appears to have converted some of the previously existing vegetative habitat to dry beach and
dunes. Furthermore, a portion of the early successional vegetation transitioned previously found
within the confines of the upland dredge disposal area along the AIWW on the north side of Holden
Beach has matured and been converted over time to either scrub vegetation or upland forest habitat.
The observed changes to the extent of habitats from within the Shallotte Inlet Habitat Mapping
Area over time can be a result of many factors. These factors may include the effects from the
Shoreline Protection Project, nearby dredge and fill operations, storm events, coastal development,
the natural dynamics of the Shallotte Inlet ocean bar channel, and other factors. It is difficult to
discern the root cause of the changes to the extent of habitats within the study area considering the
wide variety of potential factors that could influence the area. By nature, the Shallotte Inlet
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complex is dynamic as it is situated within a high-energy environment and is subject to changes
associated with naturally occurring phenomena including tropical storms, hurricanes, and
nor'easters. Between 2012 and 2022, nine (9) named storms passed within 100 miles of Ocean
Isle Beach (Table 5). These storms, bringing strong winds and heavy seas, can alter the landscape
within the study area as a result of storm surge overwashing the dunes and shoreline erosion.
Hurricane Ian passed in proximity to the study area on September 30, 2022 causing high waves
and coastal erosion within the study area.
Table 5. Named storms Passing within 100 miles of Ocean Isle Beach between 2012 and 2022.
Name of Storm
Year
Distance (miles) from
Ocean Isle Beach
Tropical Storm Beryl
2012
30
Hurricane Arthur
2014
65
Tropical Storm Ana
2015
21
Hurricane Matthew
2016
42
Hurricane Florence
2018
8
Hurricane Dorian
2019
46
Tropical Storm Eta
2020
86
Tropical Storm Isaias
2020
0
Hurricane Ian
2022
60
The position and orientation of Shallotte Inlet's ocean bar channel can be influenced by storms
and, in turn, can influence periods of erosion and accretion along the inlet shorelines of Holden
Beach and Ocean Isle Beach. As the ocean bar channel meanders to the east (toward Holden
Beach), the ebb tide shoal builds in the nearshore waters off the island affording protection from
wave attack on along the western portion of Holden Beach while exposing the eastern portion of
Ocean Isle Beach to higher amounts of wave energy. This can lead to accretion along Holden
Beach's inlet shoreline and westernmost oceanfront shoreline and induce erosion along the inlet
shoreline and easternmost oceanfront shoreline on Ocean Isle Beach. When the ocean bar channel
migrates eastward toward Ocean Isle Beach, the opposite effects would be anticipated. A
bathymetric survey performed in June 2022 indicated that the ocean bar channel was oriented in
the center of the inlet and nearly perpendicular to the oceanfront shorelines and therefore, when in
this orientation, neither island's inlet nor oceanfront shorelines would be strongly impacted by
ocean bar channel -induced forces.
Along with the construction of the Shoreline Protection Project and CSRM project, which entailed
the placement of 757,000 cy of material west of the terminal groin and were completed in April of
2022, the USACE deposited material dredged during the maintenance of the Atlantic Intracoastal
Waterway (AIWW) at the on the east end of Ocean Isle Beach within the study area in February
2023. A total of—75,000 cubic yards of material was placed over a 1,500-ft segment of Ocean Isle
Beach's oceanfront shoreline just to the east of the terminal groin as a result of that project (Figure
7). The placement of material in this location may have contributed to the increase of dry beach
habitat along the oceanfront shoreline on Ocean Isle Beach observed during the Year 2 Post -
Construction assessment.
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Figure 7. USACE Navigation maintenance material placed on the inlet shoreline, east of terminal groin (Photo
taken 2/22/23).
Each of the various factors mentioned above, including the construction of the Town's Shoreline
Protection Project, has the ability to shape the geographic extent of the various habitats within the
highly dynamic study area. It is not possible, however, to determine if the construction of the
Shoreline Protection Project has specifically or fundamentally altered any of the habitat types
within the study area. It is anticipated that the study area will continue to equilibrate to the new
hydrodynamic conditions resulting from storms, the orientation of the ocean bar channel, the
placement of the fill material, the construction of the terminal groin, and the periodic dredging of
the Shallotte Inlet borrow area.
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