IMO

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Note added at 18 mins (2014-08-18 17:53:07 GMT)
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The water channel is made deeper from the word głęboki, głębokość, etc.

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Note added at 4 hrs (2014-08-18 22:13:13 GMT)
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The context may even refer to overdeepening. For example,

Overdeepening is a characteristic of basins and valleys eroded by glaciers. An overdeepened valley profile is often eroded to depths which are hundreds of metres below the deepest continuous line (the thalweg) along a valley or watercourse. This phenomenon is observed under modern day glaciers, in salt-water fjords and fresh-water lakes remaining after glaciers melt, as well as in tunnel valleys which are partially or totally filled with sediment. When the channel produced by a glacier is filled with debris, the subsurface geomorphic structure is found to be erosionally cut into bedrock and subsequently filled by sediments. These overdeepened cuts into bedrock structures can reach a depth of several hundred metres below the valley floor
.
http://en.wikipedia.org/wiki/Overdeepening

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The overdeepening theory in river morphodynamics
http://www.researchgate.net/publication/242024461_The_overde...
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Downstream and upstream influence in river
meandering. Part 1. General theory and
application to overdeepening


http://journals.cambridge.org/download.php?file=/FLM/FLM438/...