Publication Abstract

Geostatistical modelling of surficial sediment composition in the North Sea and English Channel: using historical data to improve confidence in seabed habitat maps

Geostatistical modelling of surficial sediment composition in the North Sea and English Channel: using historical data to improve confidence in seabed habitat maps

D. Stephens*, R. Coggan* and M. Diesing*

This study aims to make the best use of historical data while addressing the need for a quantitative, repeatable procedure for the mapping of sediment composition over the UK areas of the North Sea and English Channel. The traditional approach has been qualitative, using expert interpretation to draw contours around point samples and so segment the sea bed into polygons representing different substrate types. The variability of sampling density of the observations and subsequent variability in confidence of the interpretation are usually not provided to the users of the resulting mapped layers, therefore they have no way of judging the confidence they should have in it; they just assume that ‘the map is correct’. An additional hurdle is that the output map often has a classification system applied (e.g. the Folk classification of sediment types) and this may not be fit for purpose for all end users; a classification scheme that has use to  a geologist may have little relevance to a biologist. Our objective was to use a database of historical samples obtained from the BGS (British Geological Survey) to model the spatial distribution of surficial sediment composition in a way that does not impose these constraints and permits the output of ‘bespoke’ maps, classified according to the needs of the end user. We achieved this using spatial prediction, specifically ‘Kriging with external drift’ (KED). Using a digital elevation model of the seabed as the ‘external drift’ significantly improves the outputs in comparison to ordinary Kriging (OK).

Reference:

D. Stephens*, R. Coggan* and M. Diesing* (2011) Geostatistical modelling of surficial sediment composition in the North Sea and English Channel: using historical data to improve confidence in seabed habitat maps. ICES CM 2011/G:11

D. Stephens*, R. Coggan* and M. Diesing*

ICES CM 2011/G:11