Sedimentation and sediment geochemistry in a tropical mangrove channel meander, Sungai Kerteh, Peninsular Malaysia

Abstract Tropical mangrove swamps are commonly characterized by dense networks of tidal channels that may show pronounced meandering and dendritic patterns. Channel meanders are sometimes accompanied by cut offs, and, like classical fluvial meanders, record changes in hydrology and sedimentation over time. Channel meandering can, thus, be an important process that contributes to spatial and temporal variability in the preserved record of the sedimentology and geochemistry of mangrove sediments. The aim of this study is to highlight changes in channel meander sedimentation in response to a meander cut-off in a tropical mangrove swamp. Two short sediment cores were sampled, respectively from a point bar (core KR1, 122 cm) at the junction with the neck cut-off and inside the cut-off (core KR2, 98 cm) in the Sungai Kerteh mangroves of Peninsular Malaysia. The profile comparison was based on sediment characteristics, total organic carbon (TOC) and selected elements (Fe, Na, Mg, Mn, Ba and Sr). Sedimentation rates at both sites were determined from 210Pb. A smaller standard deviation of mean grain size (MGS) was found at the point bar (4.37±0.51 ϕ) than in the cut-off (4.43 ±1.76 ϕ), indicating a difference in flow velocity between the two settings. A small difference in sedimentation rate between the upper (0.41 cm.yr-1) and bottom (0.50 cm.yr-1) parts of core KR1 suggests that water velocity at the point bar area has been rather uniform over the timescale of sedimentation. On the other hand, a higher sedimentation rate in the bottom (0.60 cm.yr-1), compared to the upper (0.39 cm.yr-1) part of core KR2 may reflect a reduction in sediment supply following cut-off. This change also resulted in increased accumulation of selected elements and TOC at the cut-off site from a depth of ~ 60 cm to the core-top segment probably associated with a slowing down of sediment settling. A higher TOC recorded in the cut-off (2.74±1.42%) compared to the point bar (1.14±0.46%) suggests a propensity for prolonged in-situ accumulation of organic matter in the abandoned meander bend. This study provides grain-size and sediment geochemical information that is consistent with patterns of long-term active and inactive sedimentation in the meander bends of mangrove channels.

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Sedimentation and sediment geochemistry in a tropical mangrove channel meander, Sungai Kerteh, Peninsular Malaysia

10.21203/rs.3.rs-27297/v2 ◽

2020 ◽

Author(s):

Hasrizal Bin Shaari ◽

Qatrunnada Mohd Nasir ◽

Che Abd Rahim Mohamed ◽

Abdul Hafidz Yusoff ◽

Wan Mohd Afiq Wan Mohd Khalid ◽

...

Keyword(s):

Grain Size ◽

Sedimentation Rate ◽

Sediment Cores ◽

Peninsular Malaysia ◽

Sediment Supply ◽

Sediment Geochemistry ◽

Spatial And Temporal Variability ◽

Tidal Channels ◽

Point Bar ◽

Meander Bends

Abstract Tropical mangrove swamps are commonly characterized by dense networks of tidal channels that may show pronounced meandering and dendritic patterns. Channel meanders are sometimes accompanied by cut offs, and, like classical fluvial meanders, record changes in hydrology and sedimentation over time. Channel meandering can, thus, be an important process that contributes to spatial and temporal variability in the preserved record of the sedimentology and geochemistry of mangrove sediments. The aim of this study is to highlight changes in channel meander sedimentation in response to a meander cut-off in a tropical mangrove swamp. Two short sediment cores were sampled, respectively from a point bar (core KR1, 122 cm) at the junction with the neck cut-off and inside the cut-off (core KR2, 98 cm) in the Sungai Kerteh mangroves of Peninsular Malaysia. The profile comparison was based on sediment characteristics, total organic carbon (TOC) and selected elements (Fe, Na, Mg, Mn, Ba and Sr). Sedimentation rates at both sites were determined from 210 Pb. A smaller standard deviation of mean grain size (MGS) was found at the point bar (4.37±0.51 ϕ) than in the cut-off (4.43 ±1.76 ϕ), indicating a difference in flow velocity between the two settings. A small difference in sedimentation rate between the upper (0.41 cm.yr -1 ) and bottom (0.50 cm.yr -1 ) parts of core KR1 suggests that water velocity at the point bar area has been rather uniform over the timescale of sedimentation. On the other hand, a higher sedimentation rate in the bottom (0.60 cm.yr -1 ), compared to the upper (0.39 cm.yr -1 ) part of core KR2 may reflect a reduction in sediment supply following cut-off. This change also resulted in increased accumulation of selected elements and TOC at the cut-off site from a depth of ~ 60 cm to the core-top segment probably associated with a slowing down of sediment settling. A higher TOC recorded in the cut-off (2.74±1.42%) compared to the point bar (1.14±0.46%) suggests a propensity for prolonged in-situ accumulation of organic matter in the abandoned meander bend. This study provides grain-size and sediment geochemical information that is consistent with patterns of long-term active and inactive sedimentation in the meander bends of mangrove channels.

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Sedimentation and sediment geochemistry in a tropical mangrove channel meander, Sungai Kerteh, Peninsular Malaysia

Progress in Earth and Planetary Science ◽

10.1186/s40645-020-00362-y ◽

2020 ◽

Vol 7 (1) ◽

Author(s):

Hasrizal Shaari ◽

Qatrunnada Mohd Nasir ◽

Hui-Juan Pan ◽

Che Abd Rahim Mohamed ◽

Abdul Hafidz Yusoff ◽

...

Keyword(s):

Grain Size ◽

Sediment Cores ◽

Peninsular Malaysia ◽

Sediment Geochemistry ◽

Spatial And Temporal Variability ◽

Tidal Channels ◽

Point Bar ◽

Mean Grain Size ◽

Meander Bends ◽

Meander Evolution

Abstract Tropical mangrove swamps are commonly characterized by dense networks of tidal channels that may show pronounced meandering and dendritic patterns. Channel meanders are sometimes accompanied by cut-offs, and, like classical fluvial meanders, record changes in hydrology and sedimentation over time. Channel meandering can, thus, be an important process that contributes to spatial and temporal variability in the preserved record of the sedimentology and geochemistry of mangrove sediments. The aim of this study is to highlight changes in channel meander sedimentation in response to a meander cut-off in a tropical mangrove swamp. Two short sediment cores were sampled, respectively from a point bar (core KR1, 122 cm) at the junction with the neck cut-off and inside the cut-off (core KR2, 98 cm) in the Sungai Kerteh mangroves of Peninsular Malaysia. The profile comparison was based on sediment characteristics, total organic carbon (TOC), and selected elements (Fe, Na, Mg, Mn, Ba, and Sr). A smaller standard deviation of mean grain size (MGS) was found at the point bar (4.37 ± 0.51 ϕ) than in the cut-off (4.43 ± 1.76 ϕ), indicating a difference in flow velocity between the two settings. In turn, these changes in grain size influence channel meander evolution via associated changes in TOC and heavy metals. In order to clarify these relationships, we used principal components analysis and factor analysis. An increased accumulation of selected elements and TOC at the cut-off site from a depth of ~ 60 cm to the core-top segment was probably associated with a slowing down of sediment settling. A higher TOC recorded in the cut-off (2.74 ± 1.42%) compared to the point bar (1.14 ± 0.46%) suggests a propensity for prolonged in situ accumulation of organic matter in the abandoned meander bend. This study provides grain size and sediment geochemical information that is consistent with patterns of active and inactive sedimentation in the meander bends of mangrove channels.

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Sedimentation and sediment geochemistry in a tropical mangrove channel meander, Sungai Kerteh, Peninsular Malaysia

10.21203/rs.3.rs-27297/v3 ◽

2020 ◽

Author(s):

Hasrizal Bin Shaari ◽

Qatrunnada Mohd Nasir ◽

Hui-Juan Pan ◽

Che Abd Rahim Mohamed ◽

Abdul Hafidz Yusoff ◽

...

Keyword(s):

Grain Size ◽

Sediment Cores ◽

Peninsular Malaysia ◽

Sediment Geochemistry ◽

Spatial And Temporal Variability ◽

Tidal Channels ◽

Point Bar ◽

Mean Grain Size ◽

Meander Bends ◽

Meander Evolution

Abstract Tropical mangrove swamps are commonly characterized by dense networks of tidal channels that may show pronounced meandering and dendritic patterns. Channel meanders are sometimes accompanied by cut offs, and, like classical fluvial meanders, record changes in hydrology and sedimentation over time. Channel meandering can, thus, be an important process that contributes to spatial and temporal variability in the preserved record of the sedimentology and geochemistry of mangrove sediments. The aim of this study is to highlight changes in channel meander sedimentation in response to a meander cut-off in a tropical mangrove swamp. Two short sediment cores were sampled, respectively from a point bar (core KR1, 122 cm) at the junction with the neck cut-off and inside the cut-off (core KR2, 98 cm) in the Sungai Kerteh mangroves of Peninsular Malaysia. The profile comparison was based on sediment characteristics, total organic carbon (TOC) and selected elements (Fe, Na, Mg, Mn, Ba and Sr). A smaller standard deviation of mean grain size (MGS) was found at the point bar (4.37±0.51 ϕ) than in the cut-off (4.43 ±1.76 ϕ), indicating a difference in flow velocity between the two settings. In turn, these changes in grain size influence channel meander evolution via associated changes in TOC and heavy metals. In order to clarify these relationships, we used principal components analysis and factor analysis. An increased accumulation of selected elements and TOC at the cut-off site from a depth of ~ 60 cm to the core-top segment was probably associated with a slowing down of sediment settling. A higher TOC recorded in the cut-off (2.74±1.42%) compared to the point bar (1.14±0.46%) suggests a propensity for prolonged in-situ accumulation of organic matter in the abandoned meander bend. This study provides grain-size and sediment geochemical information that is consistent with patterns of active and inactive sedimentation in the meander bends of mangrove channels.

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Characteristics of Point-Bar Development under the Influence of a Dam: Case Study on the Dráva River at Sigetec, Croatia

Journal of Environmental Geography ◽

10.1515/jengeo-2015-0003 ◽

2015 ◽

Vol 8 (1-2) ◽

pp. 23-30 ◽

Cited By ~ 6

Author(s):

Tímea Kiss ◽

Márton Balogh

Keyword(s):

Grain Size ◽

Power Plants ◽

Human Impacts ◽

Bank Erosion ◽

Sediment Supply ◽

Grain Size Analysis ◽

Size Analysis ◽

Point Bar ◽

Sediment Size ◽

Drava River

Abstract Before the extensive engineering works the Dráva River had braided pattern. However in the 19-20th centuries river regulation works became widespread, thus meanders were cut off, side-channels were blocked and hydroelectric power plants were completed. These human impacts significantly changed the hydro-morphology of the river. The aim of the present research is to analyse meander development and the formation of a point-bar from the point of view of indirect human impact. Series of maps and ortho-photos representing the period of 1870-2011 were used to quantify the longterm meander development, rate of bank erosion and point-bar aggradation. Besides, at-a-site erosion measurements and grain-size analysis were also carried out. As the result of reservoir constructions during the last 145 years floods almost totally disappeared, as their return period increased to 5-15 years and their duration decreased to 1-2 days. The channel pattern had changed from braided to sinuous and to meandering, thus the rate of bank erosion increased from 3.7 m/y to 32 m/y. On the upstream part of the point-bar the maximum grain size is 49.7-83.4 mm and the mean particle size is 7.6 mm, whilst on the downstream part the maximum grain size was only 39.7-39.9 mm and mean sediment size decreased to 6.1 mm. Due to the coarse sediment supply and the decreasing stream energy the point-bars develop quickly upstream and laterally too.

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Middle Holocene environmental reconstruction and climatic inferences through multi-proxy records from Seymareh lake sediments (Zagros Mts., Iran)

10.5194/egusphere-egu21-12511 ◽

2021 ◽

Author(s):

Michele Delchiaro ◽

Giulia Iacobucci ◽

Francesco Troiani ◽

Marta Della Seta ◽

Paolo Ballato ◽

...

Keyword(s):

Sedimentation Rate ◽

Water Discharge ◽

Sediment Supply ◽

Grain Size Analysis ◽

Size Analysis ◽

The Holocene ◽

Middle Holocene ◽

Lake System ◽

Proxy Records ◽

The Impact

The Seymareh landslide is the largest rock slope failure (44&#8201;Gm3) ever recorded on the exposed Earth surface. It detached &#8764;10&#8201;ka BP from the northeastern flank of the Kabir-Kuh anticline (Zagros Mts., Iran) originating the natural dam responsible for the formation of a three-lake system (Seymareh, Jaidar, and Balmak lakes, with an area of 259, 46, and 5 km2, respectively). The lake system persisted for &#8764;3000 yr during the Holocene before its emptying phase due to overflow. A sedimentation rate of 21&#8201;mm&#8201;yr&#8722;1 was estimated for the Seymareh lacustrine deposits, which increased during the early stage of lake emptying because of enhanced sediment yield from the lake tributaries.&#160;To reconstruct the climatic and environmental impact on the lake infilling, we reviewed the geomorphology of the basins and combined the results with multi-proxy records from a 30 m thick lacustrine sequence in Seymareh Lake. Major analyses comprise grain size analysis, carbon and oxygen stable isotopes of carbonate-bearing sediments, and X-ray diffraction analysis of clay minerals.Lake overflowing is largely accepted as the main response to variations in water discharge and sediment supply since the alternation from dry to wet phases enhances sediment mobilization along hillslopes decreasing the accommodation space in the downstream sedimentary basins. In this regard, during the early-middle Holocene, the Seymareh area, as well as the entire Middle East, was affected by short-term climate changes at the millennial-scale, as testified by both paleoecological and archaeological evidence. Indeed, several records from Iranian lakes (i.e., Mirabad, Zeribar, Urmia) well documented the temperature and the moisture conditions of the western Zagros Mountains during the Holocene. During the early Holocene, the precipitation remained low up to 6 ka BP, reaching the driest condition around 8-8.2 ka BP. The impact of this abrupt climate change is evident across West Asia, where the first large villages with domesticated cereals and sheeps disappeared, converting to small hamlets and starting habitat-tracking. As regards the Seymareh area, a more irregular distribution of rainfalls and their increasing seasonality may support rhexistasy conditions, during which the scarce vegetation cover enhances both the hillslope erosion and sedimentation rate in the basins, most likely contributing to the overflow of Seymareh Lake.&#160;

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Modeling shelter abundance for juvenile Atlantic salmon in a residual flow reach of a hydro power plant using SSIIM 2

10.5194/egusphere-egu21-13319 ◽

2021 ◽

Author(s):

Spyros Pritsis ◽

Nils Ruther ◽

Kordula Schwarzwälder ◽

Anastasios Stamou

Keyword(s):

Grain Size ◽

Atlantic Salmon ◽

Size Distribution ◽

Grain Size Distribution ◽

Sediment Supply ◽

Substrate Composition ◽

Juvenile Atlantic Salmon ◽

River Reach ◽

Bed Changes ◽

Shelter Availability

Nowadays, the aquatic biodiversity is highly under pressure due to anthropogenic changes of the rivers such hydraulic structures changing the diversity of flow and aquatic fauna as well as sediment continuity. This can have severe consequences on the fish population in the river reach. Fish are strongly depending on a certain substrate composition throughout all their life stages. Juveniles for example are depending on a certain availability of shelter in the substrate in order to survive this stage.Therefore, we investigate the effects of changes in the sediment composition at a hydropower plant in Switzerland on the availability of potential shelter for juvenile fish. By utilizing the observed correlation between parameters describing the fine tail of a riverbed&#8217;s grain size distribution and shelter abundance for juvenile Atlantic salmon, we predict the available shelter in a river reach by using a 3D hydrodynamic numerical model directly coupled to a morphodynamic model. The initial substrate composition was assumed to be spatially uniform, its parameters based on a grain size distribution curve derived from collected sediment samples.This model can now be used for habitat improvement scenario modeling. Based on the assumption that a specific mixture of sediment coming from upstream travelling through the river reach will positively influence the potential shelter availability, different scenarios can be investigated. The baseline for comparison was the simulation of the bed changes without any sediment supply from upstream. The baseline discharge was set to 100 m3 /s and was applied for 24 hours. The resulting bed changes create a map of the potential shelter availability of this grain size mixture. Then, two scenarios with sediment inflow from the upstream boundary were simulated. One coarse and one fine mixture of sediment were chosen as inputs, with the goal of investigating their impact on shelter abundance. The former designed to have a positive effect while the latter expected to reduce interstitial voids in the substrate and have a negative effect on available shelter.The investigation is conducted as part of the EU Horizon 2020 funded project FIThydro (funded under 727830)

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The Toba Volcanic Event and Interstadial/Stadial Climates at the Marine Isotopic Stage 5 to 4 Transition in the Northern Indian Ocean

Quaternary Research ◽

10.1006/qres.2001.2291 ◽

2002 ◽

Vol 57 (1) ◽

pp. 22-31 ◽

Cited By ~ 61

Author(s):

Hartmut Schulz ◽

Kay-Christian Emeis ◽

Helmut Erlenkeuser ◽

Ulrich von Rad ◽

Christian Rolf

Keyword(s):

Arabian Sea ◽

Water Productivity ◽

Ice Core ◽

Sediment Cores ◽

Sediment Accumulation ◽

Sediment Supply ◽

Volcanic Event ◽

Additional Support ◽

Marine Isotope Stage 5 ◽

A Minor

AbstractThe Toba volcanic event, one of the largest eruptions during the Quaternary, is documented in marine sediment cores from the northeastern Arabian Sea. On the crest of the Murray Ridge and along the western Indian continental margin, we detected distinct concentration spikes and ash layers of rhyolithic volcanic shards near the marine isotope stage 5–4 boundary with the chemical composition of the “Youngest Toba Tuff.” Time series of the Uk′37-alkenone index, planktic foraminiferal species, magnetic susceptibility, and sediment accumulation rates from this interval show that the Toba event occurred between two warm periods lasting a few millennia. Using Toba as an instantaneous stratigraphic marker for correlation between the marine- and ice-core chronostratigraphies, these two Arabian Sea climatic events correspond to Greenland interstadials 20 and 19, respectively. Our data sets thus depict substantial interstadial/stadial fluctuations in sea-surface temperature and surface-water productivity. We show that variable terrigenous (eolian) sediment supply played a crucial role in transferring and preserving the productivity signal in the sediment record. Within the provided stratigraphic resolution of several decades to centennials, none of these proxies shows a particular impact of the Toba eruption. However, our results are additional support that Toba, despite its exceptional magnitude, had only a minor impact on the evolution of low-latitude monsoonal climate on centennial to millennial time scales.

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MARINE SEDIMENT CHARACTERISTICS AT KARIMUN JAVA SEA BASED ON STRATIGRAPHIC PROFILE ANALYSIS, TOTAL SUSPENDED SOLID (TSS) AND GRAIN-SIZE ANALYSIS (GRANULOMETRY)

Jurnal Ilmu dan Teknologi Kelautan Tropis ◽

10.29244/jitkt.v3i1.7832 ◽

2011 ◽

Vol 3 (1) ◽

Cited By ~ 1

Author(s):

Suryantini Suryantini ◽

Aris Ismanto ◽

Indarta Kuncoro Aji ◽

Dwi Fajar Saputri ◽

Helfinalis Helfinalis

Keyword(s):

Grain Size ◽

Sea Water ◽

Total Suspended Solid ◽

Suspended Solid ◽

Sediment Supply ◽

Grain Size Analysis ◽

Size Analysis ◽

Research Activities ◽

Sea Bed ◽

Java Sea

A sedimentology survey was conducted during “Pelayaran Kebangsaan” research activities with a marine vessel of "Baruna Jaya VIII" in Karimun Java Sea. The objectives of the research were to determine the characteristics of marine water and its sediment, which are important control for coral reef growth in the study area. The survey acquired samples of Total Suspended Sediment (TSS) and gravity coring. Several analyses were then carried out on those samples; TSS analysis to determine the amount of suspended sediments in sea water that reflect the water quality for marine ecology, stratigraphic profile and sediment thickness pattern analyses to determine the sources of sediment, and grain-size analysis based on granulometry to determine deposition energy and grain-size distribution in the area. Those analyses were both conducted on-board Baruna Jaya VIII research vessel and P2O LIPI laboratory in Jakarta. The results showed that in Java Sea nearby Karimun Java Islands, the sediment supply came from the surrounding islands. Two sedimentary units were found in this area. The first units has thickness of tens centimeter from sea bed surface. It is characterized by grayish green color, grain size variation from clay to coarse sand, soft or low density and abundance with shells. The second unit is located beneath the first one, indicated by sharp contact. It is characterized by brownish color, higher density resembling the density of rock, less compacted and can be broken easily by hand, with occasionally thin carbon lenses or remnant of decomposed vegetation, and less shell or fossil At sea surface, TSS distribution shows value between 0.018 and 0.034 gr/l, with average of 0.025 gr/l, whereas at near bottom sea, it ranges between 0.024 and 0.030 gr/l, with average value of 0.027 gr/l. The granulometry shows that more than 50% of sediment is characterized by the abundance of grain size greater than 3 phi. It suggest that sea water around Karimun Java Islands was clear and the current was relatively calm. These conditions were relatively stable for a long time span. Those sea characteristics were important for successful growth of coral reefs and its complementary marine biotas. However, further studies and researches based on chemical and physical characteristics of sea water, and plankton and microbiology variation and abundances are necessary to confirm those presuppositions.Keywords: total suspended solid, gravity coring, stratigraphic profile, granulometry, Karimun Java Sea

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Late Quaternary sedimentation on the southwestern Scotian Slope, eastern Canada: relationship to glaciationGeological Survey of Canada Contribution 20070176.

Canadian Journal of Earth Sciences ◽

10.1139/e07-075 ◽

2008 ◽

Vol 45 (3) ◽

pp. 267-285 ◽

Cited By ~ 8

Author(s):

Thian Hundert ◽

David J.W. Piper

Keyword(s):

Late Quaternary ◽

Sediment Cores ◽

Sediment Supply ◽

Scotian Shelf ◽

Eastern Canada ◽

Glacial Retreat ◽

Air Gun ◽

Continental Slopes ◽

History Of ◽

Seismic Reflection Profiles

The sedimentary record on continental slopes has the potential to preserve a record of glacial retreat on the adjacent continental shelf. The glacial history of the southwestern part of the Scotian Shelf is poorly known. Air-gun and high-resolution sparker profiles and numerous sediment cores up to 10 m long have been used to determine the character of sedimentation on the southwestern Scotian Slope since the last glacial maximum (LGM). Seismic-reflection profiles show that glacial till was deposited at shallow depths on the upper continental slope, and correlation to dated piston cores farther downslope show that this till dates from the LGM. Slope sedimentation at this time was dominated by local ice and deposited as plume fallout and turbidites. Progressively increasing importance of red-brown sediment derived from glacial supply to Laurentian Channel indicates retreat of ice from the shelf edge and diminishing supply of proglacial sediment from the calving embayment in the mid-Scotian Shelf. With the termination of distal proglacial sediment supply, the sedimentation rate diminished rapidly and hemipelagic sedimentation prevailed through the Holocene.

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Effects of episodic sediment supply on experimental step-pool channel morphology, bedload transport and channel stability

10.5194/egusphere-egu21-10160 ◽

2021 ◽

Author(s):

Jiamei Wang ◽

Marwan A. Hassan ◽

Matteo Saletti ◽

Xingyu Chen ◽

Xudong Fu ◽

...

Keyword(s):

Grain Size ◽

Morphological Changes ◽

Mass Movement ◽

Channel Morphology ◽

Bedload Transport ◽

Sediment Supply ◽

Primary Control ◽

Channel Stability ◽

Flume Experiments ◽

Small Magnitude

Steep step-pool streams are often coupled to adjacent hillslope, directly receiving episodic sediment supply from mass movement processes such as landslides and debris flows. The response of step-pool channels to the variations in sediment supply remains largely unexplored. We conducted flume experiments with a poorly sorted grain-size distribution in an 8%-steep, 5-m long flume with variable width at the University of British Columbia, to study the effects of episodic sediment supply on channel evolution. After a conditioning phase with no feed, the channel was subjected to sediment pulses of different magnitude and frequency under constant flow discharge. High-resolution data of hydraulics, bedload transport, bed surface grain size, and channel morphology were collected every 10-20 minutes and an additional time at the end of each pulse.In response to sediment pulses, we recorded an increase in bedload transport rates, channel aggradation, bed surface fining, and continuous step formation and collapse. In between pulses, bedload rates dropped by several orders of magnitude, net erosion occurred, the bed surface gradually coarsened, and steps became more stable. The small-magnitude high-frequency pulses caused smaller but more frequent spikes in bedload transport, bed surface evolution, and thus step stability. Instead, the large-magnitude low-frequency pulses cause larger changes but provided a longer time for the channel to recover. This suggests that in step-pool channels pulse magnitude is a key control on channel rearrangement, while pulse frequency controls how fast and strong the recovery is.The frequency and stability of steps varied as a function of local channel width, showing that channel geometry is a primary control on step formation and stability even under episodic sediment supply conditions. Instead, the effect of sediment pulses is less important because the total number and average survival time of steps were similar among runs with different pulses. The critical Shields stress decreased following sediment pulses, then increased immediately after, and fluctuated until the next pulse. The variations in sediment supply caused cycles in bedload transport rate, surface and bedload texture, thus controlling the variability in the threshold for motion.Our results indicate that episodic sediment supply is a primary control on the evolution of step-pool channels, with sediment feed magnitude affecting mostly morphological changes, and sediment feed frequency controlling channel stability.

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