Presenters-0728
Abstract
Katie Turner, University of Colorado, Boulder
Modeling Downstream Impacts of Glacial Outburst Floods on Estuarine Morphodynamics and Water Transport
Since 2011, Juneau, Alaska, has experienced nearly annual glacial outburst floods (GLOFs, also known as jökulhlaups) from Suicide Basin, most recently the third-largest GLOF on record in August 2026, which occurred during our field campaign. The 2024 flood caused extensive damage, prompting the construction of temporary levees along the downstream river, which have reduced flood damage in 2025 and 2026. Although individual GLOFs are well documented, their cumulative effects on downstream estuarine morphology and water transport remain largely unknown, especially as levee confinement alters flood and sediment pathways. To address this gap, we are developing an integrated hydro-morphodynamic model that couples Delft3D Flexible Mesh (Delft3D-FM) and its D-Morphology module with the Lagrangian particle-tracking model dorado. Delft3D-FM simulates flow, sediment transport, and bed evolution, and the resulting velocity fields on evolving bathymetry drive dorado particles to quantify water transport through exposure time, a spatially resolved water transport timescale. In collaboration with the U.S. Geological Survey, U.S. Army Corps of Engineers, and University of Alaska Southeast, we present preliminary field and satellite observations from the Mendenhall-Juneau system following the August 2026 GLOF, including topobathymetric, hydrodynamic, and turbidity measurements collected across the estuary, and show how these data are being used to build and calibrate the hydro-morphodynamic model. We then outline planned simulations of repeated GLOFs, with morphology carried forward between events, to compare levee-confined and unconfined floods. By tracking changes in exposure time across pre- and post-flood bathymetry, these simulations will allow us to identify thresholds between recovery and reorganization and show how morphologic change alters estuarine circulation and exchange.
Tamara Aranguiz, University of Colorado, Boulder
Sediment effects on channel and drainage divide dynamics along strike-slip faults
Strike-slip faults offer a natural laboratory for investigating how rivers and hillslopes adjust to tectonic forcing. Lateral fault motion lengthens fault-crossing rivers until capture shortens them, driving a cycle of disequilibrium that propagates from channels to hillslopes and drainage divides. In this talk, I will show how landscape evolution modeling in Landlab, which I began developing during my PhD as a CSDMS visiting scholar in 2022, helps disentangle faulting and surface processes interactions. First, inspired by the hyperarid Atacama Fault System in Chile, I will present how landscapes with oscillating dry and humid periods respond to strike-slip faulting at variable slip rates. We found that hillslope-derived sediment during dry periods delays stream capture, increases the deflection of fault-crossing channels, and produces perturbed river profiles. I will then share ongoing work on drainage divides, inspired by the Wellington Fault in New Zealand, testing whether sediment alters divide migration. Adding weaker sediment over bedrock slightly changes relief but does not clearly control ridge mobility. Instead, simulating coarse-grained sediment produces long, fault-parallel rivers, as observed in nature, that prevent capture and keep divides stable. These results suggest that climate, sediment supply and slip rate shape how strike-slip disequilibrium is expressed in topography, and that grain size can control whether divides are mobile or stable. I will close sharing some of my postdoctoral work in Central Patagonia (~47°S), where Holocene ice loss above a low-viscosity slab window drives rapid glacial isostatic uplift. Using the Río Baker, my goal is to unravel how mantle properties, lithology and sediment supply influence river response and landscape evolution.Please acknowledge the original contributors when you are using this material. If there are any copyright issues, please let us know (CSDMSweb@colorado.edu) and we will respond as soon as possible.
Of interest for:
