Abstract

It has been traditionally assumed, but never quantitatively demonstrated, that the topological properties of trellis channel networks are strongly influenced by the underlying geology. In this study, the topological properties of seven trellis networks underlain by a plunging syncline are analyzed and compared with those of 45 dendritic networks. The analysis of the trellis networks reveals (1) that tributaries flowing both downplunge and downdip are preferentially developed; (2) that there is an excess of obtuse over acute tributaries and chains, because the general alignment of the networks is such that most of the tributaries flowing downplunge are obtuse; (3) that cis links outnumber trans links as far downstream as diameter 7 links, owing to the preferential development of tributaries flowing downdip; (4) that, because the spacing of along-strike streams and ridges constrains the development of across-strike tributaries, there are strong spatial regularities in tributary size; and (5) that, for the same reason, the trellis networks contain a higher proportion of small tributaries and a lower proportion of large tributaries than do dendritic networks.

Thus, this study not only establishes that geological controls have a pronounced effect on the topological properties of trellis networks, but it shows how particular topological properties are affected by specific controls. As these controls vary from one area of trellis drainage to another, the topological properties of the channel networks might also be expected to vary. Consequently, no one set of topological properties can be considered typical of trellis networks.

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