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The geometry of many beaches could influence wave intensity and shoreline changes. To determine the response of embayed beaches to varied wave forcing is more challenging because of diverse flow patterns within the bays. This is even more complex when coastal defenses are constructed within the bay which affects the long-shore and cross-shore currents, maybe changing the direction of flow in line with the orientation of an installed structure. Beach surveys with Unmanned Aerial Vehicle flights and video camera systems were conducted from January, 2019 to April, 2021 to assess changes in beach morphology at the Elmina beach. The goal was to further evaluate the shoreline changes prior to April 2020 of the sea defense construction and the period of post-defense construction (May 2020 to April 2021). Our results reveal that the sandy part of the beach has become shorter while erosion has intensified during and after the construction of the sea defense. Waves have decreased heights and periods during the post-defense period although they remain important for high shoreline erosion. The beach became steeper as well as showing significant loss of sand as a consequence of the revetment sea defense construction activity. The sandy portion of the remaining beach will be rapidly eroded if the revetment defense is not extended to the rest of the beach.
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Vol.:(0123456789)
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https://doi.org/10.1007/s11852-022-00906-y
Short‑term effect ofsea defense onshoreline andwave variability
inElmina Bay, Ghana
D.B.Angnuureng1,2· G.Amankona1 · E.K.Brempong1,2· E.Attipoe1
Received: 17 March 2022 / Revised: 19 October 2022 / Accepted: 20 October 2022
© The Author(s), under exclusive licence to Springer Nature B.V. 2022
Abstract
The geometry of many beaches could influence wave intensity and shoreline changes. To determine the response of embayed
beaches to varied wave forcing is more challenging because of diverse flow patterns within the bays. This is even more
complex when coastal defenses are constructed within the bay which affects the long-shore and cross-shore currents, maybe
changing the direction of flow in line with the orientation of an installed structure. Beach surveys with Unmanned Aerial
Vehicle flights and video camera systems were conducted from January, 2019 to April, 2021 to assess changes in beach mor-
phology at the Elmina beach. The goal was to further evaluate the shoreline changes prior to April 2020 of the sea defense
construction and the period of post-defense construction (May 2020 to April 2021). Our results reveal that the sandy part of
the beach has become shorter while erosion has intensified during and after the construction of the sea defense. Waves have
decreased heights and periods during the post-defense period although they remain important for high shoreline erosion.
The beach became steeper as well as showing significant loss of sand as a consequence of the revetment sea defense con-
struction activity. The sandy portion of the remaining beach will be rapidly eroded if the revetment defense is not extended
to the rest of the beach.
Keywords Beach elevation· Bay beaches· Elmina beach· Jetties· Revetments
Introduction
The coastal zone of Ghana is defined as a low-lying area
below the 30m contour covering 6.5% of the 238,535 km2
land area (Armah and Amlalo 1998). It is one of the low-
lying areas in the region that makes it susceptible to con-
tinuous erosion. The shoreline along the coast of Ghana,
like the rest of the world, has changed rapidly over the years
in response to changes in the natural environment. With
approximately 550km of shoreline, various observations
(e.g., Armah and Amlalo 1998; Boateng 2006; Dadson etal.
2016;) report that there is about 280km of sandy beaches
along the entire coastline while the rest of the coastline con-
sists of steep, partly cliffed rocky shores. It is estimated that
the ocean claims 2 to 8m land annually in the cross-shore-
line direction (Wiafe etal. 2013; Anthony etal. 2019a, b)
on the eastern parts, that sometimes exceed 17m per annum
(Angnuureng etal. 2013; Jayson-Quashigah etal. 2021) at
more localized scales. On the western coast of Ghana, which
is mostly rocky, Boye and Fiadonu (2020) observed erosion
rates up to 1m/year. Presently, some sites have first-hand
information on the rates of shoreline change (e.g., Appean-
ing Addo etal. 2008; Wiafe etal. 2013; Jayson-Quashigah
etal. 2019; Angnuureng etal. 2020a; Brempong etal. 2021),
but the whole shoreline position keeps changing through
time because of erosion or recovery.
Natural phenomena such as wave, sediment supply, sea-
level rise, and human actions such as sand mining, and infra-
structure development (houses, bridges, dams, and roads,
etc.), are promoters of erosion that trigger disproportionate
conditions to escalate the rate of shoreline changes (Anim
etal. 2013) along the entire coastline. The need for more
coastal defense structures arises directly from the increasing
coastal erosion that affects many coasts. A review (Alves
* G. Amankona
amankonahgodfred10@gmail.com
1 Africa Centre ofExcellence inCoastal Resilience
(ACECoR), School ofBiological Sciences, Centre
forCoastal Management, University ofCape Coast,
CapeCoast, Ghana
2 Department ofFisheries andAquatic Sciences, School
ofBiological Sciences, University ofCape Coast,
CapeCoast, Ghana
/ Published online: 8 November 2022
Journal of Coastal Conservation (2022) 26:57
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... This coast provides a home for many highly specialised fauna and flora [17]. The coastal environment of Ghana is characterised by the presence of sand and rocks [18,19]. On the east, where the coast is predominantly sandy and low-lying, the beach is highly vulnerable to episodic erosion and coastal flooding from wave ...
... Currently the entire beach is fenced with a revetment and a mini port is being built. Previous studies have noted that this beach was eroding around 3.4 m/yr between 1895 and 2002 [32], and later accreting around 4 m/yr between 2019 and 2022 [19]. This present study found that (Table 3, Figure 3a). ...
... Generally, coastal protections would function but their maintenance and extended effect on adjacent beaches has always been challenging [8,19]. ...
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