Floods from natural rock-material dams

O’Connor, Jim E.; Beebee, Robin A.

doi:10.1017/cbo9780511635632.008

Cited by 53 publications

(57 citation statements)

References 143 publications

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“…3). Assuming failure of a 130-m-tall dam, peak discharge is approximately 8.4 × 10 5 m 3 ∕s through the 610-m-wide and 101-m-deep channel, comparable to other outburst floods from lakes of this depth and volume (34). This discharge approximates the water transport capacity of the channel at this location for steady and uniform flow.…”

Section: Resultsmentioning

confidence: 76%

“…The dam catchment area was approximately 5;500 km 2 , which accounts for 58% of the modern Eel River watershed, and enclosed the bulk of the highly erodible Central Belt Mélange rock in the catchment (25,32). In comparison to most landslide dams that occur in steep mountainous topography with high gradient rivers (33,34), the Eel River and adjacent hillslopes have relatively low gradients (0.003 and 0.3-0.35, respectively), such that the paleolake was vast, extending approximately 55-km upstream (Fig 1 and Fig. S4).…”

Section: Resultsmentioning

confidence: 99%

“…Although evidence indicating how the dam failed is currently lacking, large landslide dams frequently fail catastrophically via mass failure, overtopping, or piping (33,34), and they are particularly vulnerable in tectonically active areas such as the Eel River catchment. We estimate the maximum potential outburst-flood discharge from the paleolake assuming complete catastrophic failure of the dam and critical flow through the breach; a reasonable approach given the relatively large lake volume (34).…”

Section: Resultsmentioning

confidence: 99%

“…We estimate the maximum potential outburst-flood discharge from the paleolake assuming complete catastrophic failure of the dam and critical flow through the breach; a reasonable approach given the relatively large lake volume (34). Gradual erosion of the dam or infilling of the lake with sediment could have produced a lesser discharge.…”

Section: Resultsmentioning

confidence: 99%

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Landslide-dammed paleolake perturbs marine sedimentation and drives genetic change in anadromous fish

Mackey

Roering

Lamb

2011

Proc. Natl. Acad. Sci. U.S.A.

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Large bedrock landslides have been shown to modulate rates and processes of river activity by forming dams, forcing upstream aggradation of water and sediment, and generating catastrophic outburst floods. Less apparent is the effect of large landslide dams on river ecosystems and marine sedimentation. Combining analyses of 1-m resolution topographic data (acquired via airborne laser mapping) and field investigation, we present evidence for a large, landslide-dammed paleolake along the Eel River, CA. The landslide mass initiated from a high-relief, resistant outcrop which failed catastrophically, blocking the Eel River with an approximately 130-m-tall dam. Support for the resulting 55-km-long, 1.3-km 3 lake includes subtle shorelines cut into bounding terrain, deltas, and lacustrine sediments radiocarbon dated to 22.5 ka. The landslide provides an explanation for the recent genetic divergence of local anadromous (ocean-run) steelhead trout (Oncorhynchus mykiss) by blocking their migration route and causing gene flow between summer run and winter run reproductive ecotypes. Further, the dam arrested the prodigious flux of sediment down the Eel River; this cessation is recorded in marine sedimentary deposits as a 10-fold reduction in deposition rates of Eel-derived sediment and constitutes a rare example of a terrestrial event transmitted through the dispersal system and recorded offshore.erosion | Franciscan mélange | genetic introgression R ivers are a crucial link between terrestrial and marine environments, facilitating the transfer of water, sediment, carbon, and solutes to the oceans (1-3), while providing a bidirectional corridor for the movement of animals and nutrients (4). Although fluvial processes that facilitate these functions are usually envisioned as continuous, large river-blocking landslides can have punctuated and persistent effects on the form, sediment-transport capacity, and habitability of river networks. Landslide debris and associated reservoir sedimentation can reside in the channel for >10 4 years (5-8), and the effects of large landslides on the landscape and river habitat can persist long after the landslide mass is removed (9-11). Less apparent is the long-term legacy of landslides on ecosystem dynamics and offshore sediment dispersal because it can be difficult to relate these secondary effects, which can have a broad geographic scope, to specific paleolandslide events.Owing to high rates of erosion (1, 2, 12-14), endangered redwood forests, 20th century floods (13, 15), vast land-use effects (1), minimal engineered damming (13), and a proximal marine depocenter (16-18), the Eel River, CA (Fig. 1) is one of the most intensively studied fluvial-marine systems in the world. Characterized by weak, highly sheared accretionary mélange rock prone to slope instability (12,14), active tectonics associated with the Mendocino triple junction (19,20), and high seasonal peak discharges (15, 21), the Eel River boasts the highest sediment yield of any nonglacial river in the contiguous United States...

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Section: Resultsmentioning

confidence: 76%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Landslide-dammed paleolake perturbs marine sedimentation and drives genetic change in anadromous fish

Mackey

Roering

Lamb

2011

Proc. Natl. Acad. Sci. U.S.A.

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“…After 25 hours, the impoundment lake overtopped the landslide deposit in a topographically low trough establishing a new river-channel location. Because of the relatively shallow slope of the new river channel through the landslide deposit, the rate of erosion was moderate without the rapid dam breaching and outburst flood sometimes associated with landslide-dammed impoundments (Costa and Schuster, 1988;Korup, 2002;O'Connor and Beebee, 2009).…”

Section: Introductionmentioning

confidence: 99%

Preliminary assessment of aggradation potential in the North Fork Stillaguamish River downstream of the State Route 530 landslide near Oso, Washington

Magirl¹,

Keith²,

Anderson³

et al. 2015

Scientific Investigations Report

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For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment-visit http://www.usgs.gov or call 1-888-ASK-USGS.For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod/.Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. ). The landslide killed 43 people. After overtopping and establishing a new channel through the landslide, the river incised into the landslide deposit over the course of 10 weeks draining the impoundment lake and mobilizing an estimated 280,000±56,000 m 3 of predominantly sand-sized and finer sediment. During the first 4 weeks after the landslide, this eroded sediment caused downstream riverbed aggradation of 1-2 m within 1 km of the landslide and 0.4 m aggradation at Whitman Road Bridge, 3.5 km downstream. Winter high flows in 2014-15 were anticipated to mobilize an additional 220,000±44,000 m 3 of sediment, potentially causing additional aggradation and exacerbating flood risk downstream of the landslide. Analysis of unit stream power and bed-material transport capacity along 35 km of the river corridor indicated that most fine-grained sediment will transport out of the North Fork Stillaguamish River, although some localized additional aggradation was possible. This new aggradation was not likely to exceed 0.1 m except in reaches within a few kilometers downstream of the landslide, where additional aggradation of up to 0.5 m is possible. Alternative river response scenarios, including continued mass wasting from the landslide scarp, major channel migration or avulsion, or the formation of large downstream wood jams, although unlikely, could result in reaches of significant local aggradation or channel change.

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Controls on the breach geometry and flood hydrograph during overtopping of noncohesive earthen dams

Walder

Iverson

Godt

et al. 2015

Water Resources Research

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Overtopping failure of noncohesive earthen dams was investigated in 13 large-scale experiments with dams built of compacted, damp, fine-grained sand. Breaching was initiated by cutting a notch across the dam crest and allowing water escaping from a finite upstream reservoir to form its own channel. The channel developed a stepped profile, and upstream migration of the steps, which coalesced into a headcut, led to the establishment of hydraulic control (critical flow) at the channel head, or breach crest, an arcuate erosional feature that functions hydraulically as a weir. Novel photogrammetric methods, along with underwater videography, revealed that the retreating headcut maintained a slope near the angle of friction of the sand, while the cross section at the breach crest maintained a geometrically similar shape through time. That cross-sectional shape was nearly unaffected by slope failures, contrary to the assumption in many models of dam breaching. Flood hydrographs were quite reproducible-for sets of dams ranging in height from 0.55 m to 0.98 mwhen the time datum was chosen as the time that the migrating headcut intersected the breach crest. Peak discharge increased almost linearly as a function of initial dam height. Early-time variability between flood hydrographs for nominally identical dams is probably a reflection of subtle experiment-to-experiment differences in groundwater hydrology and the interaction between surface water and groundwater.

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Floods from natural rock-material dams

Cited by 53 publications

References 143 publications

Landslide-dammed paleolake perturbs marine sedimentation and drives genetic change in anadromous fish

Landslide-dammed paleolake perturbs marine sedimentation and drives genetic change in anadromous fish

Preliminary assessment of aggradation potential in the North Fork Stillaguamish River downstream of the State Route 530 landslide near Oso, Washington

Controls on the breach geometry and flood hydrograph during overtopping of noncohesive earthen dams

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