A scoping review of the vulnerability of Nigeria's coastland
to sea-level rise and the contribution of land subsidence
F. Ikuemonisan, V. Ozebo
Department of Physics, University of Lagos, Nigeria
P. Minderhoud
Gamma Remote Sensing, Gumligen, Switzerland
P. Teatini
Dept. of Civil, Environmental and Architectural Engineering, University of Padova, Padova, Italy
M. Woillez
Agence Française de Développement, France
ABSTRACT
Nigeria's low-lying coastal
region, with its various economic
activities, is vulnerable to global
sea-level rise triggered by
climate change. In some areas,
this threat can be amplified by
land subsidence, which can
severely hamper coastal
resilience. Several studies have
investigated the vulnerability of
Nigeria to global sea-level rise,
but only few studies have
investigated the role of
increasing subsidence rates in
some low-lying coastal cities,
and none has provided a
comprehensive review of the
combined effects of these two
phenomena. We propose here a
synthesis of available literature
on land subsidence and relative
sea-level rise along the Nigerian
coasts and identify current
knowledge gaps. In addition, this
study provides an in-depth
analysis of land subsidence in
the Port Harcourt area, using
recently acquired Sentinel-1
satellite data. The findings
indicate that land subsidence
occurs in four coastal area:
Lagos, Port Harcourt, Uyo, and
Warri. However, the absence of
active GNSS stations to calibrate
and validate InSAR
measurements poses the results
quite uncertain. Another
significant knowledge gap is the
lack of records of groundwater
withdrawals and piezometric
evolution in recent decades. This
information is necessary for
reliable quantification of the link
between groundwater
extractions and land subsidence.
Integrating measurements of
recent sea-level changes with
vertical land motion and
piezometric data would be
necessary to improve
knowledge on land subsidence
in Nigeria and provide relative
sea-level rise projections. It is
necessary to separate
processes occurring on a global
scale, such as sea-level rise,
which are not directly under the
control of the Nigerian
authorities, from processes
occurring locally, such as
anthropogenic land subsidence,
which could be mitigated. This
study is a first step towards the
development of effective
mitigation and adaptation
strategies against relative sea-
level rise in Nigeria.
