Mean ebb tide

MTLW Mean tide low water (mean ebb tide)... 

The depth over the ebb shoal is of interest for navigation channel design and as a basic bulk parameter characterizing ebb shoals. Floyd examined the maximum depth of the channel he at the entrances to tidal rivers and the maximum depth of the ebb shoal hs (which is referred to as the saddle of the entrance bar). The terminology saddle denotes the lowest point on the ebb shoal or entrance bar. Floyd compiled data from several rivers each in Australia, the USA, and New Zealand, and two river entrances from other countries, and found the following simple relation, with depth referenced to mean tide level (approximately the same as msl) ... 

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