A preview of this full-text is provided by Springer Nature.
Content available from Journal of Coastal Conservation
This content is subject to copyright. Terms and conditions apply.
Vol.:(0123456789)
1 3
https://doi.org/10.1007/s11852-022-00906-y
Short‑term effect ofsea defense onshoreline andwave variability
inElmina 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 30m 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 550km of shoreline, various observations
(e.g., Armah and Amlalo 1998; Boateng 2006; Dadson etal.
2016;) report that there is about 280km 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 8m land annually in the cross-shore-
line direction (Wiafe etal. 2013; Anthony etal. 2019a, b)
on the eastern parts, that sometimes exceed 17m per annum
(Angnuureng etal. 2013; Jayson-Quashigah etal. 2021) at
more localized scales. On the western coast of Ghana, which
is mostly rocky, Boye and Fiadonu (2020) observed erosion
rates up to 1m/year. Presently, some sites have first-hand
information on the rates of shoreline change (e.g., Appean-
ing Addo etal. 2008; Wiafe etal. 2013; Jayson-Quashigah
etal. 2019; Angnuureng etal. 2020a; Brempong etal. 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
etal. 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 ofExcellence inCoastal Resilience
(ACECoR), School ofBiological Sciences, Centre
forCoastal Management, University ofCape Coast,
CapeCoast, Ghana
2 Department ofFisheries andAquatic Sciences, School
ofBiological Sciences, University ofCape Coast,
CapeCoast, Ghana
/ Published online: 8 November 2022
Journal of Coastal Conservation (2022) 26:57
Content courtesy of Springer Nature, terms of use apply. Rights reserved.