The determination of the internal structure of an effluent plume using MSS data

Multispectral scanner (MSS) data from a series of four flights over the Edinburgh sea outfall in the Firth of Forth have been analysed. The data reveal the existence of an integrated surface sewage plume resulting from discharge from a number of sub-surface vertical riser pipes connected to an outfall tunnel. After further processing, the structure of the plume is delineated and the existence of discrete sources of discharge within the plume is demonstrated. The capability to locate such sources with processed MSS data and thereby to monitor the performance of the outfall has significant commercial implications. Failure of the outfall system to discharge as designed (i.e. fully through all risers) can lead to marine growth and sedimentation within it and eventual long-term damage. The methods used ( principal components analysis, contrast stretching, etc) to process the MSS data to serve as monitoring tools are described.