Summary of key issues:
|Description||Characterisation of the link between hydrodynamics and estuary morphology in terms of simple empirical formulae to describe both the estuary equilibrium (or quasi-equilibrium) and its subsequent evolution following disturbance to the system|
|Temporal applicability||Typically applied over long-term time periods (10-100 years)|
|Spatial applicability||Generally applied along the length of the estuary.|
|Links with other tools||
|Data sources||Bathymetry: maps and charts, aerial photography, topographic and bathymetric surveys, remote sensing imagery
Discharge/Tidal prism: As bathymetry and/or the results of flow modelling
Littoral drift: Wave models and/or observed wave data and littoral drift models
Suspended sediment concentration: field measurements at several places within the estuary
Sediment type: analysed grab samples, water samples, Admiralty Chart sediment information
|Necessary software tools / skills||Regime theory covers a range of skills depending on the complexity of the application. At its simplest level the skills required are similar to those of HTA, i.e.:
|Limitations||Estuary/Inlet Entrance Regime Theory
|Example applications||Lune Estuary, Mersey estuary|
Regime theory describes an approach to channel theory that assumes some form of equilibrium relationship between certain morphological parameters, such as width, or depth and hydraulic parameters such as hydraulic slope, discharge, or flow velocity. A summary of the range of relationships available has been drawn together by Spearman (Spearman, 1995). Where sufficient historic data are available, these relationships can be used to explore temporal aspects of the estuary development (ABP Research, 1999; ABPmer, 2003). Increasingly, however they are being used in conjunction with hydrodynamic models to create a form of hybrid model that can iterate to the equilibrium state (see Hybrid methods).
Regime relationships can be used to consider the implications of a change. If an area is to be reclaimed or dredged, then some of the gross properties of the estuary will be altered. Regime relationships can be used to determine whether the changes are likely to move the system towards or away from the particular equilibrium condition and whether or not the change is likely to be significant.
Regime Theory involves the characterisation of the link between hydrodynamics and estuary morphology in terms of a simple empirical formula(e) which can be used to describe both the estuary equilibrium (or quasi-equilibrium) and its subsequent evolution following disturbance to the system. The theory is applied in two distinct forms – application to estuary and tidal inlet entrances and application throughout estuary systems. Regime methods using flow models enable more detailed flow input to the regime algorithm and can be used as a hybrid model. Either way the flow model will require validation of tidal currents and water levels.