Spatial variability in nearshore hydrodynamic regimes, morphodynamic zonation, and sediment transport along the southwestern Nigerian barrier–lagoon coastal system

Emmanuel Ike; Abdulkarim Rabiu; Idris Isa; Mohammed Auwal Yusuf

Authors

Emmanuel Ike
[email protected]

Department of Physics, Faculty of Physical Sciences, Modibbo Adama University, Yola, Nigeria
Abdulkarim Rabiu
Department of Marine Geology/Geophysics, Nigerian Institute for Oceanography and Marine Research, Lagos, Nigeria
Idris Isa
Department of Physics, School of Secondary Education and Science Program, Federal College of Education, Yola, Nigeria
Mohammed Auwal Yusuf
Department of Physics, Faculty of Science, Yobe State University, Damaturu, Nigeria

Keywords:

Nearshore hydrodynamics, Morphodynamic zonation, Barrier–lagoon coast, Coastal evolution

Abstract

This study examines spatial variability in nearshore hydrodynamics and its implications for sediment transport and coastal evolution along the southwestern Nigerian barrier--lagoon coast. Field measurements (Seme, Yovoyan, Lekki, Okun-Ajah, and Orimedu) reveal pronounced alongshore heterogeneity in wave characteristics, breaker type distribution, and longshore currents. Plunging breakers dominate Seme (60 -- 90%) and Orimedu (70 -- 90%), indicating reflective to intermediate conditions, while Lekki is characterized by spilling breakers (80 -- 90%), consistent with a dissipative morphodynamic state. Okun-Ajah exhibits the highest wave energy (1.3 -- 1.5 m) and steep incidence angles (30 -- 45^o), marking it as the most dynamically active and erosion-prone sector. Breaker interval (0.16 -- 0.80 s) and wave inclination (10 -- 45^o) show strong spatial variability, reflecting differences in nearshore wave transformation processes. Longshore current velocities (0.17 -- 0.66 ms^-1) increase with wave obliquity, confirming wave direction as a key control on alongshore sediment transport. Statistical analyses reveal non-normal distributions and significant zonal differences in wave height, inclination, and breaker interval, with Okun-Ajah emerging with a high-energy anomaly. Strong co-variation between wave height and inclination (r=0.94) coupled with weak correlations with current velocity indicates that sediment transport is governed by interacting hydrodynamic and morphological controls rather than single forcing variables. Three hydrodynamic regimes are identified: dissipative (Lekki), reflective--intermediate (Seme--Yovoyan--Orimedu), and high-energy oblique-attack (Okun-Ajah), defining a morphodynamic gradient driven by spatial variations in wave energy flux and breaker angle. These findings offer a transferable framework for erosion risk assessment and shoreline management in wave-dominated barrier--lagoon environments.

Dimensions

REFERENCES

[1] S. W. H. Hoagland, C. R. Jeffries, J. L. Irish, R. Weiss, K. Mandli, S. Vitousek, C. M. J. Johnson & M. A. Cialone, ``Advances in morphodynamic modeling of coastal barriers: A review'', Journal of Waterway, Port, Coastal, and Ocean Engineering 149 (2023) 03123001. https://doi.org/10.1061/JWPED5.WWENG-1825.

[2] W. Duffy, D. F. Belknap & J. T. Kelley, ``Morphology and stratigraphy of small barrier-lagoon systems in Maine'', Marine Geology 88 (1989) 243. https://doi.org/10.1016/0025-3227(89)90100-X.

[3] T. M. Beck & P. Wang, ``Morphodynamics of barrier-inlet systems in the context of regional sediment management, with case studies from west-central Florida, USA'', Ocean & Coastal Management 177 (2019) 31. https://doi.org/10.1016/j.ocecoaman.2019.04.022.

[4] D. J. Sherman & P. A. Garès, ``The geomorphology of coastal environments'', Geomorphology 48 (2002) 1. https://doi.org/10.1016/S0169-555X(02)00172-1.

[5] O. A. Dada, R. Almar & P. Morand, ``Coastal vulnerability assessment of the West African coast to flooding and erosion'', Scientific Reports 14 (2024) 890. https://doi.org/10.1038/s41598-023-48612-5.

[6] J. Thomas, J. George, D. Van Proosdij & E. Murphy, ``Wave dynamics and potential longshore sediment transport at Shippagan, Gulf of St Lawrence: Insight into seasonal variability and extreme weather events'', Frontiers in Marine Science 12 (2025) 1579807. https://doi.org/10.3389/fmars.2025.1579807.

[7] B. Castelle & G. Masselink, ``Morphodynamics of wave-dominated beaches'', Cambridge Prisms: Coastal Futures 1 (2023) e1. https://doi.org/10.1017/cft.2022.2.

[8] K. D. Splinter, I. L. Turner, M. A. Davidson, P. Barnard, B. Castelle & J. Oltman-Shay, ``A generalized equilibrium model for predicting daily to interannual shoreline response'', Journal of Geophysical Research: Earth Surface 119 (2014) 1936. https://doi.org/10.1002/2014JF003106.

[9] R. Ibaceta, K. D. Splinter, M. D. Harley & I. L. Turner, ``Enhanced coastal shoreline modeling using an ensemble Kalman filter to include nonstationarity in future wave climates'', Geophysical Research Letters 47 (2020) e2020GL090724. https://doi.org/10.1029/2020GL090724.

[10] A. D. Ashton & A. B. Murray, ``High-angle wave instability and emergent shoreline shapes: 2. Wave climate analysis and comparisons to nature'', Journal of Geophysical Research: Earth Surface 111 (2006) F04012. https://doi.org/10.1029/2005JF000423.

[11] Y. Kim, R. S. Mieras, D. Anderson & T. Gallien, ``A numerical study of sheet flow driven by skewed-asymmetric shoaling waves using SedWaveFoam'', Journal of Marine Science and Engineering 9 (2021) 936. https://doi.org/10.3390/jmse9090936.

[12] A. Luijendijk, G. Hagenaars, R. Ranasinghe, F. Baart, G. Donchyts & S. Aarninkhof, ``The state of the world's beaches'', Scientific Reports 8 (2018) 6641. https://doi.org/10.1038/s41598-018-24630-6.

[13] Y. Wu, E. Zhao, X. Li & S. Zhang, ``Application of wave-current coupled sediment transport models with variable grain properties for coastal morphodynamics: A case study of the Changhua River, Hainan'', Ocean Science 21 (2025) 473. https://doi.org/10.5194/os-21-473-2025.

[14] M. P. de Ridder, J. Kramer, J. P. den Bieman & I. Wenneker, ``Validation and practical application of nonlinear wave decomposition methods for irregular waves'', Coastal Engineering 183 (2023) 104311. https://doi.org/10.1016/j.coastaleng.2023.104311.

[15] H. Hanson, M. Larson & N. C. Kraus, ``Calculation of beach change under interacting cross-shore and longshore processes'', Coastal Engineering 57 (2010) 610. https://doi.org/10.1016/j.coastaleng.2010.02.002.

[16] B. G. Ruessink, D. J. R. Walstra & H. N. Southgate, ``Calibration and verification of a parametric wave model on barred beaches'', Coastal Engineering 48 (2003) 139. https://doi.org/10.1016/S0378-3839(03)00023-1.

[17] O. Adekola & G. Mitchell, ``The Niger Delta wetlands: Threats to ecosystem services, their importance to dependent communities and possible management measures'', International Journal of Biodiversity Science, Ecosystem Services & Management 7 (2011) 50. https://doi.org/10.1080/21513732.2011.603138.

[18] R. Almar, E. Kestenare, J. Reyns, J. Jouanno, E. J. Anthony, R. Laibi, M. Hemer, Y. Du Penhoat & R. Ranasinghe, ``Response of the Bight of Benin (Gulf of Guinea, West Africa) coastline to anthropogenic and natural forcing, Part 1: Wave climate variability and impacts on the longshore sediment transport'', Continental Shelf Research 110 (2015) 48. https://doi.org/10.1016/j.csr.2015.09.020.

[19] E. J. Anthony, R. Almar & T. Aagaard, ``Recent shoreline changes in the Volta River delta, West Africa: The roles of natural processes and human impacts'', African Journal of Aquatic Science 41 (2016) 81. https://doi.org/10.2989/16085914.2015.1115751.

[20] R. B. Adesina, Z. He, H. O. Oladejo, O. A. Dada & H. J. Ajibade, ``High-resolution wave modeling of the southwestern Nigerian coastal shelf: Implications on geomorphic contrasts between barrier-lagoon and mud coasts'', Marine Geology 470 (2024) 107253. https://doi.org/10.1016/j.margeo.2024.107253.

[21] A. J. Osanyintuyi, Y. Wang & N. A. H. Mokhtar, ``Nearly five decades of changing shoreline mobility along the densely developed Lagos barrier-lagoon coast of Nigeria: A remote sensing approach'', Journal of African Earth Sciences 194 (2022) 104628. https://doi.org/10.1016/j.jafrearsci.2022.104628.

[22] M. I. Vousdoukas, R. Ranasinghe, L. Mentaschi, T. A. Plomaritis, P. Athanasiou, A. Luijendijk & L. Feyen, ``Sandy coastlines under threat of erosion'', Nature Climate Change 10 (2020) 260. https://doi.org/10.1038/s41558-020-0697-0.

[23] R. L. Folk & W. C. Ward, ``Brazos River bar [Texas]: A study in the significance of grain size parameters'', Journal of Sedimentary Research 27 (1957) 3. https://doi.org/10.1306/74d70646-2b21-11d7-8648000102c1865d.

[24] M. Wiggins, T. Scott, G. Masselink, R. J. McCarroll & P. Russell, ``Predicting beach rotation using multiple atmospheric indices'', Marine Geology 426 (2020) 106207. https://doi.org/10.1016/j.margeo.2020.106207.

[25] F. Zăinescu, J. E. A. Storms, A. Vespremeanu-Stroe, H. van der Vegt, M. Schuster & E. J. Anthony, ``Wave-influenced delta morphodynamics, long-term sediment bypass and trapping controlled by relative magnitudes of riverine and wave-driven sediment transport'', Geophysical Research Letters 51 (2024) e2024GL111069. https://doi.org/10.1029/2024GL111069.

[26] O. Adeaga, R. Folorunsho, B. A. K. Foli & O. Akinbaloye, ``Assessment of shoreline change along the coast of Lagos, Nigeria'', Remote Sensing in Earth Systems Sciences 4 (2021) 186. https://doi.org/10.1007/s41976-021-00059-w.

[27] O. B. Olatinsu, O. A. Adegbulugbe & A. A. Ige-Adeyeye, ``Multi-technique subsoil characterisation in the coastal environment of Lekki Peninsula, Lagos, southwest Nigeria'', NRIAG Journal of Astronomy and Geophysics 14 (2025) 51. https://doi.org/10.1080/20909977.2025.2449791.

[28] K. Vos, K. D. Splinter, M. D. Harley, J. A. Simmons & I. L. Turner, ``CoastSat: A Google Earth Engine-enabled Python toolkit to extract shorelines from publicly available satellite imagery'', Environmental Modelling & Software 122 (2019) 104528. https://doi.org/10.1016/j.envsoft.2019.104528.

[29] N. G. Obaje, Geology and Mineral Resources of Nigeria, Springer, Berlin, Germany, 2009. https://doi.org/10.1007/978-3-540-92685-6.

[30] M. A. Olade, ``Evolution of Nigeria's Benue Trough (aulacogen): A tectonic model'', Geological Magazine 112 (1975) 575. https://doi.org/10.1017/S001675680003898X.

[31] J. Benkhelil, ``The origin and evolution of the Cretaceous Benue Trough (Nigeria)'', Journal of African Earth Sciences (and the Middle East) 8 (1989) 251. https://doi.org/10.1016/S0899-5362(89)80028-4.

[32] M. I. Titocan, M. P. Ibitola, B. R. Faleye & A. S. Oc, ``Spatial assessment of the textural characteristics and sorting of beach deposits on the barrier lagoon coastal complex, Lagos Nigeria'', Journal of Geology & Geophysics 7 (2018) 1. https://doi.org/10.4172/2381-8719.1000334.

[33] A. P. Aizebeokhai & K. D. Oyeyemi, ``Application of geoelectrical resistivity imaging and VLF-EM for subsurface characterization in a sedimentary terrain, southwestern Nigeria'', Arabian Journal of Geosciences 8 (2015) 4083. https://doi.org/10.1007/s12517-014-1482-z.

[34] K. O. Emery, ``A simple method of measuring beach profiles'', Limnology and Oceanography 6 (1961) 90. https://doi.org/10.4319/lo.1961.6.1.0090.

[35] D. N. Joanes & C. A. Gill, ``Comparing measures of sample skewness and kurtosis'', Journal of the Royal Statistical Society: Series D (The Statistician) 47 (1998) 183. https://doi.org/10.1111/1467-9884.00122.

[36] W. H. Kruskal & W. A. Wallis, ``Use of ranks in one-criterion variance analysis'', Journal of the American Statistical Association 47 (1952) 583. https://doi.org/10.1080/01621459.1952.10483441.

[37] P. Schober, C. Boer & L. A. Schwarte, ``Correlation coefficients: Appropriate use and interpretation'', Anesthesia & Analgesia 126 (2018) 1763. https://doi.org/10.1213/ANE.0000000000002864.

[38] J. A. Battjes, ``Surf similarity'', Coastal Engineering Proceedings 1 (1974) 26. https://doi.org/10.9753/icce.v14.26.

[39] E. B. Thornton & R. T. Guza, ``Transformation of wave height distribution'', Journal of Geophysical Research: Oceans 88 (1983) 5925. https://doi.org/10.1029/JC088iC10p05925.

[40] S. D. António, J. van der Werf, E. Horstman, I. Cáceres, J. Alsina, J. van der Zanden & S. Hulscher, ``Influence of beach slope on morphological changes and sediment transport under irregular waves'', Journal of Marine Science and Engineering 11 (2023) 2244. https://doi.org/10.3390/jmse11122244.

[41] M. A. Hemer, X. L. Wang, R. Weisse & V. R. Swail, ``Advancing wind-waves climate science: The COWCLIP Project'', Bulletin of the American Meteorological Society 93 (2012) 791. https://doi.org/10.1175/BAMS-D-11-00184.1.

[42] J. A. Goff, B. J. Kraft, L. A. Mayer, S. G. Schock, C. K. Sommerfield, H. C. Olson, S. P. S. Gulick & S. Nordfjord, ``Seabed characterization on the New Jersey middle and outer shelf: Correlatability and spatial variability of seafloor sediment properties'', Marine Geology 209 (2004) 147. https://doi.org/10.1016/j.margeo.2004.05.030.

[43] C. A. M. King, Applied Coastal Geomorphology, Springer, Dordrecht, Netherlands, 1972. https://doi.org/10.1007/978-1-349-15424-1.

[44] Intergovernmental Panel on Climate Change, Climate Change 2021: The Physical Science Basis. Working Group I Contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom, 2023. https://www.ipcc.ch/report/ar6/wg1/

[45] L. H. Holthuijsen, Waves in Oceanic and Coastal Waters, Cambridge University Press, Cambridge, United Kingdom, 2007. https://www.researchgate.net/publication/253127661_Waves_in_Oceanic_and_Coastal_Waters

[46] D. M. Kennedy, W. J. Stephenson & L. A. Naylor, Coastal Cliffs: Morphology and Management, Springer, Cham, Switzerland, 2016. https://doi.org/10.1007/978-3-319-29084-3.