Mapping the Unresolved Tidal Resource in Estuaries

Estuarine geometry often amplifies the tidal range. Tidal amplitude can be amplified in an estuary due to three processes: shoaling and funnelling of tidal energy flux, and, when estuary length-scales are close to the tidal period, tidal-wave resonance. The amplification of the tidal energy resource (via increased tidal amplitude and associated currents) is juxtaposed to areas of high electricity demand (industry ports and residential areas), and yet the tidal resource of many estuaries is unknown due to computational difficulties. For example, a bespoke high-resolution hydrodynamic models of every estuarine system globally is not possible; instead, a simple set of rules to focus resource mapping efforts may be suitable approach. Indeed, given that significant changes to estuarine tidal dynamics can occur within the life-time of some tidal energy developments (due to the balance between the tide and river-flow climatology, sea level rise and sedimentation). We aim to develop a simple approach resolve the global estuarine tidal energy resource and how this may change within the coming century. A simple 1-D analytical model is presented, which can account for the major physical processes of estuarine tidal amplification. We find changes to estuarine tidal dynamics within the lifetime of a development should be considered, both for resource mapping and annual yield assessment, but also within the baseline scenario in assessing the environmental impact of a development (i.e. should changes to the estuary be based on present day or 2100 tidal dynamics?).