Dynamical controls on estuarine bathymetry: Assessment against UK database

New theories for estuarine bathymetry provide formulations for: (1) depth at the mouth, D versus river flow, Q; (2) tidal intrusion length L versus D and Z (tidal amplitude) and (3) a zone of morphological existence, delineated on a framework of Z versus D. Here, these theories are assessed against a database for 80 UK estuaries. Overall there is good agreement between theory and observations for the sizes and shapes of estuaries classified as either ‘Coastal Plain’ or ‘Bar Built’. Likewise, most estuaries are shown to lie within the theoretical ‘zone of bathymetric existence’. These encouraging agreements enable the theories to be used to: (1) enhance our understanding of existing morphologies, (2) identify anomalous estuaries and (3) make future predictions regarding likely impacts from global climate change and related management scenarios. Subsequent examination of regional historical patterns of morphological evolution, introducing detailed local knowledge, should help to explain these anomalies and refine the new theories. By 2100, we anticipate changes in UK estuaries due to (‘precautionary’) projected 25% changes in river flow of: Order (0.5–5 km) in lengths and Order (50–250 m) in breadths. Corresponding changes due to a projected sea level rise of 50 cm are increases in both lengths of Order (1–2.5 km) and breadths of Order (70–100 m). In both cases, the bigger changes will occur in larger estuaries.