coastal erosion of Long Bay

2. Outline
Introduction
● Importance
● Location
● The Issue
Current Solutions
● Beach Nourishment
● Hydraulic Structures
Recommendations and Conclusion

3. Introduction

4. Importance of Coastal Health
● Beaches, dunes and bluffs are natural buffers between land and sea
● A healthy shoreline provides several key features to the coastal area
○ Land protection from storm surges
○ Reduction of erosion
○ Filter for land runoff
○ Habitats for many coastal flora and fauna species
○ A beautiful and lively landscape
Beach Dune Bluff

5. Area of Interest: South
Carolina’s Long Bay
Coast
Charleston
https://locatesc.com/Search/PropertyDetails?propertyI
D=5a202ee5-0cdb-e911-b5e9-000d3a12f430

6. The Issue
● Beach renourishment and revitalization
costs the US $150 million annually
● Nourishment practices often disrupt
bottom cover due to dredging
● Erosion in nearly every other
circumstance is controlled by
preventative measures rather than
restorative measures
● Most permanent structures that are
implemented for erosion prevention wind
up having a negative effect

7. Human Interaction
Climate Change
Erosion by Wind/Water
● Overfishing
● Nutrient and sediment input
● Pollution
● Introduction of exotic species
● Habitat destruction through
dredging
● Resource exploitation
● Rise in seawater levels
● Habitat reduction
● Introduction of exotic species
(species finding new habitats
within desired temp. range)
● Loss of surface soil, carbon
and soil biota
● Sedimentation of streams and
watercourses
Unhealthy Coastline

8. Impact of Humans
overfishing
Human Interaction
Dredging
Introduction of
Invasive Species
Modification of
Coastal Habitats
Modification of Coastal habitats
● Construction on coastlines can
disrupt local species
Soil and Nutrient runoff
● Pollution runoff changes the
nutrient levels in the water
Dredging
● Additional soil can suffocate
seagrasses and change the
shoreline
Introducing Invasive Species
● Reduce biodiversity and kill-off
vulnerable species
Overfishing
● Removes species at a rate faster
than they can replenish
Human Interaction
● Inexperienced divers can disrupt
coastal habitats
https://www.epa.sa.gov.au/soe_2013/main/coast-3-what-are-the-pressures.html

9. Current Solutions

10. Groins
● Shoreline structure perpendicular to the
beach
● Traps longshore flow of sand
● Maintains sand at desired site but transfers
erosion down the beach
● Perpetuating cycle
Updraft
Downdraft

11. Case Study: Groins
● Gopalpur Port on the East Coast of India
● 530 meter Southern groin implemented in
2008
● 370 meter Northern groin
● Beach profile, shoreline change, and
sedimentology were monitored every month
for a year
● Erosion observed north of the northern groin
and south of the southern groin

12. Beach Nourishment (Beach Fill)
● Deposit sand on beach to widen
accessible area
● No permanent structures
● Costly, temporary solution
● May increase erosion rates
● Disrupts benthic life in turbid
waters
● Increases coastal shelf which
endangers swimmers

13. Case Study: Beach Nourishment
● Wrightsville, North Carolina
● 3 million cubic feet of sand pumped onto
14,000 ft of beach
● Was restored in 1966 and again in 1970
● By 1976, the beach had become very steep
and was manually flattened
● However, by 1977, the beach had become
steep again
● 8 total restorations performed since.

14. Jetties
● Man-made structures built on either side
of coastal inlet
● Allow channel to stay open for
navigation
● Longer than groins creating larger
updraft and smaller downdraft of
sediment
● Can become clogged with sand and must
be dredged

15. Case Study: Jetties
● Most famous jetty found at
the Great Salt Lake in Utah
● 1,500 ft long and 15 ft wide
● Created by sculptor Robert
Smithson in 1970
● Would still function if paired
with another

16. Recommendations and
Conclusion

17. UAV and LiDAR
● Light Detection And Ranging (LiDAR)
is a way to collect 3 dimensional data
through the use of UAVs or satellites
● LiDAR remote sensing uses light pulses
and timing to determine distance from
an object
● Can provide an accurate and detailed
map of ground elevation as well as
vegetation cover

18. MIKE21 and MIKE3
MIKE21 models coastal and marine processes two-dimensionally
MIKE3 models coastal and marine processes three-dimensionally
These models work in tandem to simulate:
○ Coastal soil erosion
○ Overland flooding
○ Tidal patterns and predictions
○ Major storm events
They also process momentum, continuity, temp,
Salinity, and density equations

19. Equations Used in MIKE Software
The equilibrium tidal potential 𝜂T
Tidal potential is the potential force that
stretches a body (water) towards or away from
another body’s center of mass (moon) due to a
gravitational gradient. This is used in the MIKE
software when calculating the effect of the tide
on the sediment and erosion potential and is
expressed in tidal force per unit mass.

20. Suspended Sediment
Vs - suspended sediment volume
eB - suspension efficiency
ef - suspension efficiency
DB - dissipation rate due to breaking
Df - average dissipation rate
s - specific gravity
wf - fall velocity
Ps - sediment suspension probability
Suspended sediment is a defining factor in coastal erosion
and can be modeled by the following:
Vs is a measurement of suspended sediment volume per
unit area. MIKE software uses this calculation in
sediment transport simulations.

21. Recommendations for
Long Beach
● Using more advanced mapping
such as UAV and LiDAR
● Using more models
● Using more advanced models
● Pay attention to the specific
needs of the coastline in question

22. Conclusion
● Prevent > restore
● Using improved modeling and mapping
software can assist in finding the right
solution for specific circumstances
● Unexplored options, such as vegetative
management, could be a path to pursue

23. Thank You!