Morphodynamic modelling of a wave-driven river mouth sandspit in data-scarce coastal environments: an example at the Volta River Mouth, Ghana, West Africa

• Modelling sandspits formed at a river mouth with limited measured data. • Incorporated satellite-derived/global bathymetries and a data schematisation approach. • Results were validated using satellite-derived quantities and previous findings. • Seasonality of significant wave heights influence river mouth sandspit morphology. The morphodynamic behaviour of river mouth sandspits, sustained by wave-driven longshore sediment transport, is governed by complex interactions between prevailing hydrodynamics and anthropogenic forcing. At many coastal environments, the lack of field-measured datasets, more often than not, hampers long-term morphodynamic investigations on river mouth sandspits, thus making them data-scarce locations. This study investigates the wave-dominated and micro-tidal Volta River mouth in Ghana using process-based Delft3D model simulations. The simulations of the river mouth’s unrestricted (natural) updrift spit state were undertaken using hydrodynamic data schematisation approaches and satellite-derived and global bathymetries. Model results showed that, among varying wave conditions, relatively higher wave heights (∼1.8–1.9 m) facilitate a narrow-width spit growth at a faster rate. Conversely, an elongating spit with a slower growth rate and a larger width was observed under relatively moderate wave heights (∼1.2–1.3 m). The results indicate that the growth rate of an unrestricted spit decreases with increasing width. These findings are important for understanding how unrestricted spit’s formation and morphodynamic evolution affect river mouths. Most importantly, the results can be related to morphodynamic feedback during spit breaching events, formation of intruded spits, narrowing or closure of river mouths, and inland flooding of surrounding estuarine and coastal communities.