The Estuary Environment Classification (Hume et al. 2007; 2003) provides a framework for classifying New Zealand’s estuaries. This controlling factors classification is based on broad scale physical components of the landscape or ‘controlling factors’ such as climate, oceanic and riverine conditions, and catchment characteristics that cause or ‘control’ differences and similarities in the physical and biological characteristics of estuaries. The classification differentiates estuaries at 3 levels of detail. Level 1 differentiates global scale variation based on differences in climatic and oceanic processes, which are discriminated by the factors: latitude, oceanic basins and large landmasses. Level 2 differentiates estuaries into 8 categories (or estuary types ) on the basis of variation in estuary hydrodynamic processes, whic