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1. [Preprint] Data-driven control reveals distributed flood adaptation priorities across large river networks

   https://doi.org/10.31223/X5675K  

   Oh, Jeil; Bartos, Matthew (February 2026, EarthArXiv)

   In the face of growing flood risks, decentralized adaptation measures like detention storage, enhanced infiltration, and floodplain reconnection have the potential to mitigate flood impacts at the river basin scale. However, optimal spatial allocation of flood control measures is complicated by the high dimensionality of hydrologic systems and the sensitivity of proposed strategies to climate uncertainty. To overcome these challenges, we propose a diagnostic framework that combines reduced-order data-driven modeling with optimal control to directly estimate reach-level attenuation targets without the need for iterative simulation and optimization. First, Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition with control (DMDc) are used to create a low-rank linear surrogate model of basin rainfall-runoff dynamics. A Linear Quadratic Regulator (LQR) is then applied to compute optimal reach-scale attenuation targets that mitigate flood impacts. Applied to a large river basin under a multi-model climate ensemble, the framework successfully determines distributed attenuation strategies that reduce bankfull discharge exceedances under varying adaptation budgets. Across scenarios, marginal increases to flow attenuation are found to yield diminishing returns to flood mitigation, while higher-emission scenarios retain substantially greater residual flood volume for the same effort level. Although attenuation allocation generally scales with mean flow, we identify tributary and transitional reaches where attenuation demand is disproportionate to local hydrologic size, showing that network-level flood dynamics produce spatial priorities that cannot be recovered from reach attributes alone. Taken together, the proposed framework provides a scalable approach for flood adaptation planning that is effective for basin- to continental-scale applications under climate uncertainty. 

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2. Forensic Hydraulic Analysis of Floodplain Connectivity Driven by Historical Beaver Dams in Colorado Headwater Streams

   https://doi.org/10.1002/rra.70165  

   Schultz, Kayla; Morrison, Ryan R; Rathburn, Sara; Mertz, Connor; Christensen, Nicholas (June 2026, River Research and Applications)

   ABSTRACT As ecosystem engineers, beavers (Castor canadensis) modify river corridor form through dam building. When beavers are removed from a river corridor, their unmaintained dams wash out, altering the stream's hydrologic regime. The assumption that beaver dams increase floodplain connectivity is frequently presumed but has not been directly quantified. To address this gap, we assessed changes in floodplain connectivity caused by the loss of beaver dams at three headwater streams in Colorado, USA. Using a forensic analysis of historical beaver activity, we developed two‐dimensional hydraulic models to compare metrics of floodplain connectivity under historical (beaver‐active) and present (no beaver activity) scenarios. At three simulated flood discharges, we quantified changes in the volume of water on the floodplain, the fraction of flow through the floodplain, the volumetric flux into the floodplain, and mean site and floodplain residence times. The loss of beaver dams decreased floodplain connectivity across all metrics (up to a 96.5% loss in connectivity) except mean floodplain residence time, which increased in the absence of dams. Sensitivity analysis results show that the flow state and condition of beaver dams can have reach‐scale impacts on floodplain connectivity. Notably, while we observed floodplain disconnection due to the loss of beaver dams at each site, the magnitude of change varied depending on both site‐specific characteristics and on the flood magnitude. We conclude that, in headwater streams, beaver dams play an important and quantifiable role in facilitating floodplain connectivity, and floodplain disconnection from the loss of dams has major implications for other ecological and geomorphic floodplain processes. These results are especially timely considering the increasing interest in beaver‐related restoration. 

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3. Flood Wave Attenuation as a Function of Floodplain Storage, Secondary Channel Conveyance, and Discharge

   https://doi.org/10.1029/2024WR038582  

   Tull, N; Passalacqua, P (May 2025, Water Resources Research)

   Abstract The elevation of natural river levees can vary considerably along the length of a river, and low‐lying features such as secondary floodplain channels allow for hydrologic exchange between a river and its floodplain over a range of discharges. This hydrologic, “river‐floodplain connectivity” plays a role in attenuating flood waves and transporting fluvial material to floodplain ecosystems. However, flood wave attenuation and transport are also limited by the available storage provided by floodplains. In this study, we explore the combined controls of river‐floodplain connectivity and floodplain width on flood wave attenuation and transport, and how those controls change as flood magnitude increases. We develop idealized river‐floodplain models based on the geometry of the lower Trinity River in Texas, USA, varying floodplain width, peak discharge, and degree of river‐floodplain connectivity, which we prescribe by varying the width of a secondary channel connecting the river to the floodplain. We show that attenuation transitions from connectivity‐limited to storage‐limited as discharge increases. Secondary channel conveyance allows for floodplain inundation at lower discharges, but also fills the floodplain faster and, for larger floods, can cause higher flood peaks downstream. Greater secondary channel conveyance and wider floodplains increase fluxes to the floodplain, but secondary conveyance allows the floodplain to drain faster while wider floodplains have longer average residence times. This study presents a framework for understanding how secondary channel conveyance and floodplain width combine to modulate lateral flow exchange, residence times, and flood wave attenuation, and can guide successful management of river systems and future restoration efforts. 

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4. The floodplain wood budget: Linking wood dynamics and ecogeomorphic processes

   https://doi.org/10.1002/esp.70244  

   Lininger, Katherine B; Welsh, Josie; Ruiz‐Villanueva, Virginia (January 2026, Earth Surface Processes and Landforms)

   Abstract Und erstanding floodplain wood transport, deposition and storage is necessary to fully close wood budgets in river corridors (the channel, floodplain and hyporheic zone). However, most work on wood in river corridors has focussed on in‐channel wood. Here, we review current understanding of wood dynamics in floodplains using a floodplain wood budget to highlight the processes that change floodplain wood storage. We discuss autochthonous and hillslope recruitment to the floodplain, floodplain wood decay and burial/exhumation, controls on lateral wood fluxes between the floodplain and the channel, and fluvial wood transport within the floodplain itself. We compile wood load data for floodplains and channels in locations in which data on floodplain wood loads exist, finding that floodplains are an important storage location for wood within the river corridor across diverse environments. We briefly review the impacts of floodplain wood on physical and ecological processes and then summarise important knowledge gaps that limit understanding of floodplain wood dynamics. We emphasise that future research should address methods to determine wood piece source location and track wood within the river corridor; mechanistically explore coupled flow‐sediment‐vegetation‐wood processes across spatial and temporal scales; extend observations of floodplain wood loads and storage characteristics and explore multiple size classes of organic matter; and work to inform management decisions related to floodplain wood. Because it may be less likely to be transported downstream and interact with infrastructure, floodplain wood may be less hazardous than in‐channel wood but can still provide ecological benefits and enhance physical complexity. Improving our understanding of wood dynamics on floodplains is thus important for supporting river management. 

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5. Empirical Evidence of Dynamic Hydrogeomorphic Feature Inundation in a Lowland Floodplain

   https://doi.org/10.1002/hyp.70043  

   Cain, Molly R; Hixson, Jase L; Jones, C Nathan; Rhoads, Bruce L; Ward, Adam S (January 2025, Hydrological Processes)

   NA (Ed.)

   ABSTRACT Floodplains along low‐gradient, meandering river systems contain diverse hydrogeomorphic features, ranging from isolated depressions to hydrologically‐connected channels. These ephemerally‐flooded features inundate prior to river water overtopping all banks, enhancing river‐floodplain connectivity during moderately high flow stages. Predicting when and where ecological functions occur in floodplains requires understanding the dynamic hydrologic processes of hydrogeomorphic features, including inundation and exchange. In this study, we examined storm event‐scale inundation and exchange dynamics along a lowland, meandering river system in central Illinois (USA). We monitored surface water presence/absence, surface water level, and groundwater level across floodplain hydrogeomorphic feature types (i.e., isolated depression, backwater channel, and flow‐through channel). Using these data, we evaluated inundation onset and recession characteristics, drivers of groundwater‐surface water interactions, and direction of hydrologic exchange with the river channel. Surface water presence/absence patterns suggested inundation onset timescales were primarily controlled by microtopography and recession timescales were correlated with floodplain elevation. Employing a novel hysteresis approach for characterising groundwater‐surface water interactions, we observed distinct patterns indicating differences in water sources across hydrogeomorphic units and event characteristics. Finally, differences in hydraulic head along floodplain channels revealed that channels with multiple inlets/outlets (i.e., flow‐through channels) conveyed down‐valley flow and channels with single inlets primarily functioned as sinks of river‐derived water to the floodplain with short source periods. These results highlight the heterogeneity of hydrologic processes that occur along lowland, meandering river‐floodplains, and more specifically, point to the important role hydrogeomorphic features play in controlling dynamic connectivity within the river corridor. 

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