Erosion rates across space and timescales from a multi-proxy study of rivers of eastern Taiwan

Fellin, Maria Giuditta; Chen, Chia-Yu; Willett, Sean D.; Christl, Marcus; Chen, Yue‐Gau

doi:10.1016/j.gloplacha.2017.07.012

Cited by 37 publications

(51 citation statements)

References 89 publications

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“…We note that the digital elevation model (DEM) resolution influences the absolute values of slope, especially in steep terrain (Mukherjee et al ., ). Nonetheless, assuming hillslope gradient and relief (Figures C and D) reflects relative differences in sediment supply to channels, we can expect that long‐term (centennial‐ to millennial‐timescale) sediment supply from hillslopes to channels has a strong spatial variation across the landscape, which is corroborated by cosmogenic nuclides (Fellin et al ., ). We also anticipate landslide susceptibility to closely follow this pattern of hillslope morphology.…”

Section: Resultsmentioning

confidence: 99%

Landslides control the spatial and temporal variation of channel width in southern Taiwan: Implications for landscape evolution and cascading hazards in steep, tectonically active landscapes

Yanites

Mitchell

Bregy

et al. 2018

Earth Surf Processes Landf

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Intense precipitation or seismic events can generate clustered mass movement processes across a landscape. These rare events have significant impacts on the landscape, however, the rarity of such events leads to uncertainty in how they impact the entire geomorphic system over a range of timescales. Taiwan is steep, tectonically active, and prone to landslide and debris flows, especially when exposed to heavy rainfall events. Typhoon Morakot made landfall in Taiwan in August of 2009, causing widespread landslides in southern Taiwan. The south to north trend in valley relief in southern Taiwan leads to spatial variability in landslide susceptibility providing an opportunity to infer the long‐term impact of such landslide events on channel morphology. We use pre‐ and post‐typhoon imagery to quantify the propagating impact of this event on channel width as the debris is routed through the landscape. The results show the importance of cascading hazards from landslides on landscape evolution based on patterns of channel width (both pre‐ and post‐typhoon) and hillslope gradients in 20 basins along strike in southern Taiwan. Prior to Typhoon Morakot, the river channels in the central part of the study area were about 3–10 times wider than the channels in the south. Following the typhoon, aggradation and widening was also a maximum in these central to northern basins where hillslope gradients and channel steepness is high, accentuating the pre‐typhoon pattern. The results further show that the narrowest channels are located where channel steepness is the lowest, an observation inconsistent with a detachment‐limited model for river evolution. We infer this pattern is indicative of a strong role of sediment supply, and associated landslide events, on long‐term channel evolution. These findings have implications across a range of spatial and temporal scales including understanding the cascade of hazards in steep landscapes and geomorphic interpretation of channel morphology. Copyright © 2018 John Wiley & Sons, Ltd.

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Section: Resultsmentioning

confidence: 99%

Landslides control the spatial and temporal variation of channel width in southern Taiwan: Implications for landscape evolution and cascading hazards in steep, tectonically active landscapes

Yanites

Mitchell

Bregy

et al. 2018

Earth Surf Processes Landf

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“…The northward trend is reduced, if we consider lower values of E b for basins CP (E6), TML (E5), CL (E4), DC (E3) and AL (W6) to exclude possible landslide erosion. In any case, the rates are relatively low compared to those of basins in central Taiwan (Derrieux et al, ; Fellin et al, ), likely reflecting the early‐collisional stage of the orogen in the southern part of the island.…”

Section: Discussionmentioning

confidence: 96%

The impact of storm‐triggered landslides on sediment dynamics and catchment‐wide denudation rates in the southern Central Range of Taiwan following the extreme rainfall event of Typhoon Morakot

Chen

Willett

West

et al. 2020

Earth Surf Processes Landf

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Extreme erosion events can produce large short‐term sediment fluxes. Such events complicate erosion rates estimated from cosmogenic nuclide concentrations in river sediment by providing sediment with a concentration different from the long‐term basin average. We present a detrital 10Be study in southern Taiwan, with multiple samples obtained in a time sequence bracketing the 2009 Typhoon Morakot, to assess the impact of landslide sediment on 10Be concentrations (N10Be) in river sediment. Sediment samples were collected from 13 major basins, two or three times over the last decade, to observe the temporal variation of N10Be. Landslide inventories with time intervals of 5–6 years were used to quantify sediment flux changes. A negative correlation between N10Be and landslide areal density indicates dilution of N10Be by landslide sediment. Denudation rates estimated from the diluted N10Be can be up to three times higher than the lowest rate derived from the same basins. Observed increases imply that, 3 years after the passage of Typhoon Morakot, fluvial channels still contain a considerable amount of sediment provided by hillslope landslides during the event. However, higher N10Be in 2016 samples indicate that the contribution from landslide sediment at the sampled grain size has decreased with time. The correlation between changes in N10Be and landslide area and volume is not strong, likely resulting from the stochastic and complex nature of sediment transport. To simultaneously evaluate the volume of landslide‐derived sediment and estimate the background denudation rate, associated with less impulsive sediment supply, we constructed a sediment‐mixing model with the time series of N10Be and landslide inventories. The spatial pattern of background erosion rate in southern Taiwan is consistent with the regional tectonic framework, indicating that the landscape is evolving mainly in response to the tectonic forcing, and this signal is modified, but not obscured by impulsive sediment supply. © 2019 John Wiley & Sons, Ltd.

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“…The normalized channel steepness index ( k sn ) is calculated using a concavity index of 0.5 and a critical threshold drainage area ( A cr ) of 1 km 2 following Fellin et al (). The basin‐averaged k sn is then calculated as mean k sn of all individual reaches (1‐km segments).…”

Section: Methodsmentioning

confidence: 99%

“…Samples with asterisk (*) are from tributaries, and ZS13-7 from the Chenyoulan River and ZS13-10 from the Qingshui River. b The normalized channel steepness index (k sn ) is calculated using a concavity index of 0.5 and a critical threshold drainage area (A cr ) of 1 km 2 following Fellin et al (2017). The basin-averaged k sn is then calculated as mean k sn of all individual reaches (1-km segments).…”

Section: Calculation Of Denudation Rates Using 10 Be (Meteoric)/ 9 Bementioning

confidence: 99%

Denudation Rate Changes Along a Fast‐Eroding Mountainous River With Slate Headwaters in Taiwan From ¹⁰Be (Meteoric)/⁹Be Ratios

et al. 2020

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The novel 10Be (meteoric)/9Be system, where 10Be is delivered by precipitation and stable 9Be is released by weathering, provides denudation rates over weathering‐erosion timescales. The new tool is applicable to quartz‐poor lithologies, for example, mafic rock and claystone, which are not readily accessible by the commonly used in situ‐produced 10Be in quartz. We provide a first application of this proxy to a tectonically active mountainous river, the Zhuoshui River in Taiwan. Taiwan Rivers supply a disproportionately high suspended and dissolved flux to the oceans and are often underlain by fine‐grained shale/slate. 10Be (meteoric)/9Be‐derived denudation rates (Dmet) from the Zhuoshui Catchment are highest in the slate‐dominated headwaters (4–8 mm/year), and much lower (1–2 mm/year) along the midlower reaches with mixed lithologies. At the basin‐wide scale, we find a poor correlation between Dmet and basin‐averaged channel steepness despite a small climatic gradient. Because large lithological heterogeneities exist in this basin, we invoke a lithological effect to explain this poor correlation. Relying on a revised stream power incision model that incorporates rock erodibility, the resulting lithology‐ and runoff‐adjusted ksn (kLrsn) can be reconciled with denudation rates with the highest erodibility predicted to prevail in the Miocene slate of low metamorphic grade and high fracture density. This model suggests that the lithological heterogeneity can alter the coupling between surface denudation and channel morphology. On a broader perspective, the successful application of the 10Be (meteoric)/9Be proxy shows its applicability as a tracer for erosion and sediment transport processes in fast‐eroding mountain belts underlain by slate lithologies.

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Erosion rates across space and timescales from a multi-proxy study of rivers of eastern Taiwan

Cited by 37 publications

References 89 publications

Landslides control the spatial and temporal variation of channel width in southern Taiwan: Implications for landscape evolution and cascading hazards in steep, tectonically active landscapes

Landslides control the spatial and temporal variation of channel width in southern Taiwan: Implications for landscape evolution and cascading hazards in steep, tectonically active landscapes

The impact of storm‐triggered landslides on sediment dynamics and catchment‐wide denudation rates in the southern Central Range of Taiwan following the extreme rainfall event of Typhoon Morakot

Denudation Rate Changes Along a Fast‐Eroding Mountainous River With Slate Headwaters in Taiwan From ¹⁰Be (Meteoric)/⁹Be Ratios

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Erosion rates across space and timescales from a multi-proxy study of rivers of eastern Taiwan

Cited by 37 publications

References 89 publications

Landslides control the spatial and temporal variation of channel width in southern Taiwan: Implications for landscape evolution and cascading hazards in steep, tectonically active landscapes

Landslides control the spatial and temporal variation of channel width in southern Taiwan: Implications for landscape evolution and cascading hazards in steep, tectonically active landscapes

The impact of storm‐triggered landslides on sediment dynamics and catchment‐wide denudation rates in the southern Central Range of Taiwan following the extreme rainfall event of Typhoon Morakot

Denudation Rate Changes Along a Fast‐Eroding Mountainous River With Slate Headwaters in Taiwan From 10Be (Meteoric)/9Be Ratios

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Denudation Rate Changes Along a Fast‐Eroding Mountainous River With Slate Headwaters in Taiwan From ¹⁰Be (Meteoric)/⁹Be Ratios