Oil spills in estuaries are less studied and less understood than their oceanic counterparts. Despite the significant risk oil spills present to estuaries, its dynamics in estuarine environments present a gap in academic literature. To address this gap, this study undertakes a numerical analysis of the influence of environmental factors on oil spill transport in tide-dominated estuaries.
This study develops and analyses a range of numerical simulations for the Humber Estuary, using TELEMAC3D (a coupled hydrodynamic and oil spill model). For modelling studies such as this, there are multiple combinations of variables that can be considered, however, this study focuses on the influence of seasonal fluvial discharge variations, projected climatic conditions (sea level rise and projected river flow) and varying lateral points of release on oil spill transport in tide-dominated estuaries. Consequently, the influence of other variables (e.g. sediment transport and morphology, flooding and storm events) on oil slick transport is not considered in this study.
The key findings were:
there is a statistically significant (P<0.05) difference in the influence of hydrodynamic conditions on oil slick impacted area, length and distance travelled;
the influence of seasonal discharge on oil slick spreading is dependent on the time of release within a tidal cycle;
the influence of sea level rise and projected changes in river flow on oil slick transport dynamics is relatively insignificant;
water current magnitude is the key determinant of the differences in dynamics between oil slicks released along the estuary length; and
the differences in the dynamics of oil slick released along the estuary width is strongly determined by differences in lateral current speed and direction.
It is the first time that these dynamics have been illustrated and advanced. The implications of these findings for operational oil spill response are the need to:
take cognisance of time of oil release within a tidal period;
understand how the interaction of river discharge and tidal range influences oil slick dynamics, as this will aid responders in assessing the likely oil trajectories;
be aware of axial and lateral variations in current magnitude and direction in the estuary and how it affects oil slicks from a release location;
take cognisance of the interaction between oil slick and estuary bank and how it influences oil slicks overall travel distance; and
understand the interaction between oil release location, the geometry of the estuary and current magnitude and direction to effectively deal with oil slicks in a tide-dominated estuary.
Considering the complexity of estuaries, findings from this study may be unique to tide-dominated estuaries.