Connectivity patterns in contrasting types of tableland sandstone relief revealed by Topographic Wetness Index

• Published in: The Science of the total environment Vol. 656; pp. 1046 - 1062
• Main Authors: Jancewicz, Kacper, Migoń, Piotr, Kasprzak, Marek
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.03.2019
• Subjects: bedrock; drainage; Geomorphic connectivity; hills; Hydrological connectivity; karsts; landscapes; runoff; sandstone; Sandstone geomorphology; sediments; streams; Sudetes; Topographic Wetness Index; topography; Hydrological connectivity; Sudetes; Sandstone geomorphology; Topographic Wetness Index; Geomorphic connectivity
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2018.11.467

Recognition of structural connectivity is particularly challenging in terrains lacking a hierarchical fluvial system, but typified by strong bedrock control, extreme ruggedness of relief, the presence of sinks (closed depressions) as in karst, or considerably modified by anthropogenic interventions. In this paper, the issue of connectivity mapping in such a very rugged terrain – a sedimentary tableland underlain by sandstones, mudstones and marls – is addressed. Three specific geomorphic contexts were selected for detailed study. These are steep escarpments, canyon-riddled cuesta backslopes, and residual tabular hills (mesas), with relative relief of 100–300 m. This work is primarily based on geomorphometric approach, with the Topographic Wetness Index used as a tool to recognize pathways of water and possible sediment transfer across the sandstone tableland. In addition, maps of distribution of closed depressions were generated. High resolution (1 m) digital terrain models provided input topographical data. The results of desk research were verified by the results of field work aimed at recognition of visible signatures of geomorphological connectivity in the physical landscape. Specific connectivity patterns were identified for each setting, with two common features being strong structural control due to regular joint pattern and the presence of numerous sinks, resulting in widespread surface disconnectivity. Furthermore, differences between structural and functional connectivity emerge. The latter occurs very rarely, during rather infrequent extreme precipitation events, and there are only a few evident, permanent sediment transfer pathways in the areas subject to analysis. The presence of well-jointed and porous sandstones accounts for drainage diversion underground and restricted surface runoff from the tableland and hence, for an underdeveloped network of perennial streams and clearly identifiable valley morphology. [Display omitted] •TWI reveals contrasting structural connectivity patterns in rugged sandstone terrain.•High degree of structural (joint) control on connectivity•Drainage diversion underground and hydrological sinks typify the area.•Field work proved necessary to offer proper interpretation of TWI maps.