This discussion deals with buried channels as a factor in reservoir feasibility and is introduced by a broad classification of buried channels. Firstly, buried channels are by definition abandoned erosional features and, along the channels, one can expect to find coarsely granular bed-load stream deposits or, in the case of glacially eroded channels, similar deposits arising from sub-glacial drainage or a pre-glacial river. Because buried channels are seldom without this feature they nearly always pose a leakage problem beneath the dam or from the reservoir perimeter, if they are so placed. Naturally the leakage problem depends upon connection of the permeable channel fill with the reservoir. If the valley is covered by an extensive impermeable deposit fully spanning the rock channel, the buried channel may not after all be a problem, but very careful investigation of the impermeable layer is essential. Channels in the current bedrock surface filled with Pleistocene/Recent deposits are usually related in some way to present topography and a thorough knowledge of the local drainage conditions and geology makes it possible at least to suspect their presence, if not to have a close idea as to where they are, and of the order of their depth. There is another category, less frequently encountered, of ‘fossil buried channels’ where a bedrock surface related to another geological Era is involved, and an unconformity has been brought close to the present surface by crustal movements and erosion. These are illustrated in England and Wales by Triassic wadis which are more

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