The classification of intertidal mudflats

Twenty attributes of 18 mudflats from North-west Europe have been analysed statistically to establish a classification scheme. Correlation analysis, multidimensional scaling and cluster analysis have revealed five effective levels of mudflat classification. The first level is obtained using tidal range as the discriminator. This is followed by sub-divisions defined by exposure to waves and by mudflat slope. Slope is separated into steep slope >0.04, and low slope <0.04, with a further possible category of very steep slope (∼0.16). Further analysis of meso and macrotidal mudflats (tidal ranges 2–6 m) revealed additional sub-division according to dry density; low density <600 k gm−3, medium density 600–1000 kg m−3, and high density >1000 kg m−3. Analysis of biological data showed significant differences for the upper mudflats, where sediment type and grain size are the best physical descriptors of the biological attributes, but none for the middle and lower flats. The results agree well with a previously published typology, which can be used to extend this statistical classification to account for such features as bedforms. However, this requires comparison with a greater range of data.