Using Physiography as a Lens to Understand Stream Network Expansion and Contraction Across Spatiotemporal Scales

Delaney M. Peterson , C. Nathan Jones, Kaci Zarek, Michelle Wolford, Chelsea Smith, Charles Thomas Bond , Stephen Plont, Maggi Kraft, Shannon Speir, Sam Zipper , Sarah E Godsey, Jonathan Benstead, Arial Shogren, Kevin Kuehn, Carla Atkinson

Non-perennial streams (i.e., streams that cease flowing regularly across time or space) comprise 60% of the global river network and play an important role in the physical, chemical, and biological functions of downstream waters. However, predicting the dynamic spatiotemporal patterns of network expansion and contraction remains a key challenge across regulatory, practitioner, and research communities, especially given that most investigations focus on high-relief watersheds. To address this challenge, here we employed physiography as a lens to investigate the impacts of geology, soil characteristics, topography, and vegetation on spatial and temporal patterns of stream network expansion and contraction. We instrumented three low-relief headwater networks spanning the Coastal Plain, Piedmont, and Appalachian Plateaus physiographic provinces in the southeastern United States. In each network, we utilized ≥ 20 water presence/absence sensors across two water-years (2023 and 2024) to investigate seasonal and interannual variability in network extent. Network expansion and contraction was driven by a combination of physiographic variables, and existing topography-based methods of predicting network expansion and contraction performed poorly. Our results also emphasize the role that sensor placement plays in understanding network-scale patterns, as deploying sensors in areas of greatest hydrologic variability better captured the full range of network expansion and contraction. This study demonstrates that low-relief stream networks do not conform to existing topography-based perceptual models of network expansion and contraction, and that consideration of other factors such as soils and vegetation are required to explain network expansion and contraction in these ubiquitous landscapes.