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1. Permafrost extent sets drainage density in the Arctic

   https://doi.org/10.1073/pnas.2307072120  

   Del_Vecchio, Joanmarie; Palucis, Marisa C; Meyer, Colin R (February 2024, Proceedings of the National Academy of Sciences)

   Amplified warming of high latitudes and rapid thaw of frozen ground threaten permafrost carbon stocks. The presence of permafrost modulates water infiltration and flow, as well as sediment transport, on soil-mantled slopes, influencing the balance of advective fluvial processes to diffusive processes on hillslopes in ways that are different from temperate settings. These processes that shape permafrost landscapes also impact the carbon stored on soil-mantled hillslopes via temperature, saturation, and slope stability such that carbon stocks and landscape morphometry should be closely linked. We studied $>$69,000 headwater basins between 25° and 90 °N to determine whether the thermal state of the soil sets the balance between hillslope (diffusive) and fluvial (advective) erosion processes, as evidenced by the density of the channel networks (i.e., drainage density) and the proportion of convex to concave topography (hillslopes and river valleys, respectively). Watersheds within permafrost regions have lower drainage densities than regions without permafrost, regardless of watershed glacial history, mean annual precipitation, and relief. We find evidence that advective fluvial processes are inhibited in permafrost landscapes compared to their temperate counterparts. Frozen soils likely inhibit channel development, and we predict that climate warming will lower incision thresholds to promote growth of the channel network in permafrost landscapes. By demonstrating how the balance of advective versus diffusive processes might shift with future warming, we gain insight into the mechanisms that shift these landscapes from sequestering to exporting carbon. 

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2. Drainage network signatures of landscape reorganization in post‐glacial landscapes

   Kwang, Jeffrey S; Wickert, Andrew D; Larsen, Isaac J (December 2023, American Geophysical Union)

   Earth's drainage networks encode clues that can be used to decipher geologic and geomorphic history. Dendritic drainage patterns, the most common, typically form on approximately homogeneous bedrock. Variations in rock properties or lithologic structure can disrupt dendritic patterns and form, e.g., trellis or rectangular networks. Although textbooks include such lithological–drainage links, the mechanisms driving drainage reorganization via lithologic variability remain poorly understood. To cast light on this mystery, we study drainage patterns in post-glacial landscapes of the Upper Mississippi River Valley (UMRV). Pleistocene glaciers deposited till across parts of this region, burying a landscape of fluvially dissected sedimentary rock whose buried valley network differs from modern-day drainage patterns. As the current river network erodes and exhumes the bedrock, it comes to a geomorphic "decision point": Does it reorganize to recreate the paleodrainage network, or does it maintain its new drainage pattern? To understand this decision-making, we conducted idealized landscape evolution modeling experiments. Modeled landscapes that reintegrated more of the paleodrainage network exhibited higher tortuosity, measured by dividing the real flowpath length by shortest path-length to the outlet, and obtuse tributary-junction angles. We apply this metric to two adjacent landscape types in the UMRV: (1) never glaciated (Driftless Area, DA) and (2) formerly till-mantled (Driftless-style Area, DSA), and measure the basin-averaged tortuosity for sub-basins draining streams of order 1 through 7. Across the UMRV, tortuosity increases as the maximum stream order of the sub-basin increases. For each order, tortuosity is statistically higher in areas that had been previously buried and re-exhumed (DSA) than the DA, indicating that the rivers in the DSA have reintegrated the paleodrainage network since deglaciation. For the 1st and 2nd order sub-basins, the mean basin-averaged tortuosity in the DSA is ~1-2% higher than the DA (p-value < 0.01) and ~10-14% higher (p-value < 0.01) in the 6th and 7th order sub-basins. Our analysis suggests that a drainage-based metric, tortuosity, can identify landscapes where lithological heterogeneity or structure plays a dominant role in drainage organization. 

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3. Impacts of geographic variability and geologic history on the distribution of post-settlement alluvium (PSA) across the upper Midwest, USA

   https://doi.org/10.1016/j.catena.2025.108939  

   Anders, Alison M; Rhoads, Bruce L (June 2025, CATENA)

   NA (Ed.)

   Accelerated floodplain sedimentation related to agricultural development of uplands has produced postsettlement alluvium (PSA) along rivers throughout the upper Midwest, U.S.A. Landscape characteristics, surficial sediments, and soils in the region vary geographically in relation to differences in geologic history, yet the extent to which this geographic variability influences PSA accumulation remains unexplored. This study uses existing data to assess how non-dimensional PSA thickness varies with landscape characteristics, surficial sediments, soils and climate. Geographic variability is associated with three subregions: 1) areas glaciated during the Late Wisconsin Episode (LWE), 2) areas glaciated during Pre-Illinois and Illinois Episodes (PI&IE), and 3) the Paleozoic Plateau (PP), an area where evidence of Quaternary glaciation is highly localized and does not influence geomorphic characteristics of the landscape. These subregions differ significantly in average geomorphic characteristics, including mean watershed slope (WS), mean local relief (LR), fraction of non-contributing area (NCA), pre-settlement drainage density (DD), and mean normalized river steepness (KSN). Native vegetation type also differs systematically between the subregions, creating significant differences in the frequency of alfisols (Alfi) and molisols (Mol). Thickness of last glacial loess (Loess) also varies across the region, although not systematically between the subregions identified. Non-dimensional PSA thickness differs significantly among the subregions, increasing systematically with landscape age, reflecting faster upland erosion rates and stronger connectivity of uplands to river corridors in older landscapes relative to more recently glaciated landscapes. Nondimensional PSA thickness is significantly positively correlated with LR, KSN, WS, Loess, Alfi, and Mol and significantly negatively correlated with NCA. Non-visibly distinct PSA is present in some LWE watersheds characterized by significantly lower KSN and WS relative to other LWE watersheds in which PSA is visibly distinct. PSA thickness and visibility reflect catchment-wide landscape characteristics and watershed-scale river steepness, which emphasize the importance of geographic setting, geological history, and landscape geomorphic characteristics for understanding historical river sediment dynamics. Spatial variability in PSA thickness also serves as an indicator of river system sensitivity to land-use change, providing insight into the relative impact of humans on rivers within different geographic settings. 

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4. Drainage network reorganization in landscapes buried by glacial deposits

   Kwang, Jeffrey S; Wickert, Andrew D; Larsen, Isaac J (December 2022, American Geophysical Union)

   For landscapes to achieve a topographic steady state, they require steady tectonic uplift and climate, and a bedrock that is uniformly erodible in the vertical direction. Basic landscape evolution models predict that incising drainage networks will eventually reach a static geometric equilibrium – that is, the map-view channel pattern will remain constant. In contrast, natural rivers typically incise through heterogeneous bedrock, which can force reorganization of the drainage structure. To investigate how lithological variability can force landscape reorganization, we draw inspiration from formerly glaciated portions of the upper Mississippi Valley. In this region, depth-to-bedrock maps reveal buried dendritic river networks dissecting paleozoic sedimentary rock. During the Pleistocene, ice advance buried the bedrock topography with glacial till, resurfacing the landscape and resetting the landscape evolution clock. As newly formed drainage networks develop and incise into the till-covered surface, they exhume the buried bedrock topography. This then leads to a geomorphic "decision point": Will the rivers follow the course of the bedrock paleodrainage network? Or will they maintain their new pattern? Using a numerical landscape evolution model, we find that two parameters determine this decision: (1) the contrast between the rock erodibility of the glacial till (more erodible) and of the buried sedimentary rock (less erodible) and (2) the orientation of the surface drainage network with respect to the buried network. We find that as the erodibility contrast increases, the drainage pattern is more likely to reorganize to follow the buried bedrock valleys. Additionally, as the alignment of the two networks increases, the surface drainage network also tends to restructure itself to follow the paleodrainage network. However, when there is less contrast and/or alignment, the surface drainage pattern becomes superimposed on the bedrock topography, with streams cutting across buried bedrock ridges. Our results agree with field studies demonstrating that variability in erodibility exerts a first-order control on landscape evolution and morphology. Our findings can provide insight into how lithologic variation affects surface processes, drives drainage reorganization, and creates geopatterns. 

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5. Reconstructing Eocene Antarctic river drainage from provenance analysis of Amundsen Sea embayment sediments

   https://doi.org/10.1126/sciadv.aea2373  

   Marschalek, James W; van_de_Flierdt, Tina; Siddoway, Christine S; Thomson, Stuart N; Paxman, Guy_J G; Jamieson, Stewart_S R; Conrad, Ethan; Licht, Kathy J; Hemming, Sidney R; Bentley, Michael J; et al (December 2025, Science Advances)

   Sedimentary records can illuminate relationships between the climate, topography, and glaciation of West Antarctica by revealing its Cenozoic topographic and paleoenvironmental history. Eocene fluvial drainage patterns have previously been inferred using geochemical provenance data from an ~44– to 34–million year deltaic sandstone recovered from the Amundsen Sea Embayment. One interpretation holds that a low-relief, low-lying West Antarctic landscape supported a >1500-kilometer transcontinental river system. Alternatively, higher-relief topography in central West Antarctica formed a drainage divide between the Ross and Amundsen seas. Here, zircon U-Pb data from Amundsen Sea Embayment sediments are examined alongside known regional bedrock provenance signatures. These analyses suggest that all observed provenance indicators in the Eocene sandstone derive from West Antarctic rocks. This implies that a local river system flowed off a West Antarctic drainage divide, helping constrain the mid-Late Eocene evolution of West Antarctic topography with implications for the history of rifting and the characteristics of sediments infilling interior basins. 

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