A new approach for measuring surface hydrological connectivity

Wolstenholme, Joshua M.; Smith, Mark W.; Baird, Andy J.; Sim, Thomas G.

Abstract

The development of surface hydrological connectivity is a key determinant of flood magnitude in drylands. Thresholds in runoff response may be reached when isolated runoff-generating areas connect with each other to form continuous links to river channels, enabling these areas to contribute to flood hydrographs. Such threshold behaviour explains observed nonlinearities and scale dependencies of dryland rainfall–runoff relationships and complicates attempts at flood prediction. However, field methods for measuring the propensity of a surface to transmit water downslope are lacking, and conventional techniques of infiltration measurement are often inap- propriate for use on non-agricultural drylands. Here, we argue for a recon- ceptualization of the dryland surface runoff process, suggesting that the downslope transfer of water should be considered alongside surface infiltration; that is, there is a need for the “aggregated” measurement of infiltration and overland flow hydraulics. Surface application of a set volume of water at a standardized rate generates runoff that travels downslope; the distance it travels downslope is determined by infiltration along the flow, integration of flow paths, and flow resistance. We demonstrate the potential of such a combined measurement system coupled with structure-from- motion photogrammetry to identify surface controls on runoff generation and trans- fer on dryland hillslopes, with vegetation, slope, surface stone cover, and surface roughness all having a significant effect. The measurement system has been used on slopes up to 37 compared with the flat surface typically required for infiltration methods. On average, the field workflow takes ~10–15 min, considerably quicker than rainfall simulation. A wider variety of surfaces can be sampled with relative ease, as the method is not restricted to stone and vegetation-free land. We argue that this aggregated measurement represents surface connectivity and dryland runoff response better than standard hydrological approaches and can be applied on a much greater variety of dryland surfaces.

Citation

Wolstenholme, J. M., Smith, M. W., Baird, A. J., & Sim, T. G. (2019). A new approach for measuring surface hydrological connectivity. Hydrological Processes, 15. https://doi.org/10.1002/hyp.13602

• Journal Article Type: Article
• Acceptance Date: Sep 20, 2019
• Online Publication Date: Oct 29, 2019
• Publication Date: Oct 29, 2019
• Deposit Date: Nov 5, 2019
• Publicly Available Date: Oct 30, 2020
• Journal: Hydrological Processes
• Print ISSN: 0885-6087
• Electronic ISSN: 1099-1085
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Pages: 15
• DOI: https://doi.org/10.1002/hyp.13602
• Keywords: Connectivity; Drylands; Infiltration; Flow pathways; Flow resistance; Roughness; Structure from Motion; Surface runoff
• Public URL: https://hull-repository.worktribe.com/output/3088137
• Publisher URL: https://onlinelibrary.wiley.com/doi/full/10.1002/hyp.13602
• Related Public URLs: http://eprints.whiterose.ac.uk/151510/
• Additional Information: Received: 2019-04-12; Accepted: 2019-09-20; Published: 2019-10-29