Channel Response and Reservoir Delta Evolution From Source to Sink Following an Extreme Flood

Eidmann, Johanna; Rathburn, Sara L.; White, Daniel C.; Huson, K.

doi:10.1029/2020jf006013

Cited by 3 publications

(1 citation statement)

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“…Floods in mountainous catchments often coincide with rainfall-induced landslides on steep valley walls that may deliver substantial volumes of sediment into ooded channels (e.g., Rathburn et al, 2017, Abanco et al, 2021 and downstream receiving waters (Eidmann et al, 2022). Landslides may interact with and in uence channel processes in several ways.…”

Section: Introductionmentioning

confidence: 99%

Landslide-channel feedbacks amplify channel widening during floods

Bennett,

Panici,

Rengers

et al. 2024

Preprint

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Channel widening is a major hazard during floods, particularly in confined mountainous catchments where roads and buildings compete for space with river channels. Flood-induced channel widening is also an important process in eroding and shaping the landscape. However, channel widening during floods is not well understood and not always explained by hydraulic variables alone, with implications for flood risk management. Floods in mountainous regions often coincide with landslides triggered by heavy rainfall on steep valley sides. Whilst the long-term impact of increased sediment supply on channel widening is well established, landslide-channel interactions at the event timescale are not well known or documented. Here we demonstrate with an example from the Great Colorado Flood in 2013, a 1000-yr precipitation event that induced a 200-yr flood, and 100-yrs of erosion, how landslide-channel feedbacks can substantially amplify channel widening and flood risk. We use a combination of field analysis and multiphase flow modeling to document landslide-channel interaction during the flood event in which sediment delivered by landslides temporarily dammed the channel before failing and bulking the flow with sediment resulting in large channel widening. We propose that such landslide-flood interactions will become increasingly important to account for in flood hazard assessment as flooding and landsliding increase with extreme rainfall under climate change.

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Section: Introductionmentioning

confidence: 99%

Landslide-channel feedbacks amplify channel widening during floods

Bennett,

Panici,

Rengers

et al. 2024

Preprint

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Post‐fire sediment attenuation in beaver ponds, Rocky Mountains, CO and WY, USA

Dunn,

Rathburn,

Wohl

2024

Earth Surf Processes Landf

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We evaluated the post‐fire sediment dynamics in beaver ponds to examine these ponds' contributions to sediment storage following disturbance. Beaver dams and beaver mimicry structures impound water and sediment, a function that is of growing interest in wildfire‐prone landscapes. Wildfires typically lead to high sediment loading into rivers in the years following fire, constituting a disturbance to aquatic ecosystems and a challenge to water resource managers. Previous work establishes that beaver dams trap substantial volumes of sediment, but sedimentation appears spatially and temporally heterogeneous and it remains unclear the extent to which short‐term pulses of sediment are attenuated by these structures. We examine the conditions under which beaver dams and beaver mimicry structures store post‐fire sediment by quantifying the sediment volume of 40 ponds, about half of which were burned in large wildfires in the Colorado and Wyoming Rocky Mountains in 2020. The median relative volume of burned ponds is 85%, which is greater than the median for unburned ponds (58%), meaning that burned ponds store higher relative volumes of sediment when pond size is accounted for. Furthermore, sediment accumulated at a median rate of 3.0 cm/year over the entire history of the pond. Post‐fire sedimentation rates, with a median of 20.4 cm/year, were an order of magnitude higher than pre‐fire rates with a median of 1.8 cm/year. In addition, vegetation and geomorphic characteristics correlated with sediment storage in ponds. Sediment surveys confirmed that ponds with greater surface areas contain higher volumes of sediment. Additionally, older ponds and ponds abandoned by beavers stored higher volumes of sediment compared to recently constructed ponds, ponds actively maintained by beaver, and beaver mimicry structures. These findings demonstrate that beaver ponds and mimicry structures may function as sediment sinks capable of attenuating post‐fire sediment. The biogeomorphic context, defined across multiple scales from the pond to the catchment, provides additional explanation for the wide range of sediment storage observed and remains an important consideration for beaver‐based restoration, catchment sediment management, and resilience evaluation.

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