Late Holocene Relative Sea-Level Change and the Implications for the Groundwater Resource, Humber Estuary, UK

This thesis presents new late Holocene relative sea-level reconstructions in the Humber Estuary, and examines the relationship between sea-level change and the salinisation of the groundwater resource.

Relative sea-level reconstructions were produced using lithological and biostratigraphical analyses from two sites. Single and multi-proxy transfer functions were developed using diatom and foraminifera training sets from three sites in the Humber Estuary, with the multi-proxy transfer function providing the best performance. However, the application of the transfer functions was limited by the availability of modern analogues and generally poor preservation of microfossils.

Eight new sea-level index points were produced, providing constraints of relative sea-level change between 4022-1470 cal years BP. The reconstructions were consistent with existing data, offering new constraints for the previously identified expansion and contraction of estuarine conditions during the late Holocene. In the outer estuary, two sea-level index points provided a record for an expansion between 3395-3227 cal years BP not previously constrained by sea-level index points. In the inner estuary, the sea-level index points indicated an expansion of estuarine conditions at 4022 cal years BP. Two of the points now provide the youngest constraints for the inner estuary.

Multiple sea level and groundwater abstraction scenarios for time periods in the past and future were undertaken using a numerical model. These determined the contribution of sea level and abstraction to changes in the groundwater and saline intrusion; sea-level rise increased saline waters within the aquifer, and abstraction induced additional saline intrusion. Future sea-level rise will also result in an increase in aquifer salinity. A lack of data and consensus over the current conditions of the aquifer and groundwater was identified, with significant further research across multiple disciplines required for sustainable management and use of the groundwater resource.