Flood Deposits Research Articles

Perseverance rover reveals an ancient delta-lake system and flood deposits at Jezero crater, Mars.

Observations from orbital spacecraft have shown that Jezero crater on Mars contains a prominent fan-shaped body of sedimentary rock deposited at its western margin. The Perseverance rover landed in Jezero crater in February 2021. We analyze images taken by the rover in the 3 months after landing. The fan has outcrop faces, which were invisible from orbit, that record the hydrological evolution of Jezero crater. We interpret the presence of inclined strata in these outcrops as evidence of deltas that advanced into a lake. In contrast, the uppermost fan strata are composed of boulder conglomerates, which imply deposition by episodic high-energy floods. This sedimentary succession indicates a transition from sustained hydrologic activity in a persistent lake environment to highly energetic short-duration fluvial flows.

Roughness into the Channel Create the Flood Situation - A Case Study at Lower Reach of Shilabati River Basin, Paschim Medinipur, West Bengal

Roughness into the channel of streams and rivers determines several important hydraulic parameters must be properly represented in models for estimating water discharge and sediment transport. Hydraulic parameters mainly gradient, hydraulic radius, width, width-depth ratio, wetted perimeter and cross sectional area are considered for analysing the ability of channels to carry discharge but resisting forces are opposing component of this movement. This paper reviews to evaluate the different approaches used to identify the roughness and to understanding of how flow resistance is created by roughness in open channel flows. The Shilabati river basin embraces a portion of the eastern fringe of the Chotonagpur plateau. South west monsoon is the principal source of rainfall in this area. After the heavy storm, the low lying depression in the lower reach of this catchment attracts huge flood water and sediments from it upper catchment, sub-tributaries and larger catchments of neighbouring rivers mainly Damodar, Darakeswar, and Kangsabati. The upper courses are steeper (0.84) and rocky facilitating easy drainage, that gradually concentrates at lower reach as it lost its capacity due to sudden reduction of gradient (Gadghat, 0.08; Bandar, 0.02). In the Shilabati river the cross sectional area changes through time in response to fluctuations in discharge. Channel slopes near these gauging stations are surveyed, that shows continuously decreasing tendency towards lower catchment. Capacity of channel is measured by conveyance of flow. Roughness coefficient value at three gauging station (Banka 0.50, Gadghat near Ghatal 0.82 and at estuary, Banka,1) measuring by the Manning’s equation depicts that the resistance to flow increases steadily at downstream. Channel substrate mainly vegetation and netting also influences the boundary roughness and flow resistance. Friction from sediment load mainly grain roughness are responsible for generating resistance which steadily declines movement and create jamming of water which ultimately leads to flood and water storage situation.

Factors controlling iodine enrichment in a coastal plain aquifer in the North Jiangsu Yishusi Plain, China

Iodine is an essential micronutrient in the human diet and an appropriate human iodine intake level is important for population health. Excessive iodine intake is often associated with high iodine groundwater which serves as an important drinking water source in many regions. This study aims to identify the source and key hydrogeochemical processes for iodine accumulation and mobility in the groundwaters of the Northern Jiangsu Yishusi Plain. Combined hydrogeochemical and statistical analyses, specifically random forest modeling and factor analysis, were used to explore the mechanisms affecting the spatial distribution of iodine. The concentration of iodine in the investigated groundwaters was found to vary widely and to range between 4.8 and 4750 μg/L, with 48.9% of the total samples (674) exceeding the threshold value of 100 μg/L for toxic exposure, as defined by the Chinese high‑iodine standard guideline. High iodine concentrations are shown to mainly occur in the marine plain and the shallow aquifer associated with the floodplains of the Old Yellow River. The marine or lagoons-facies sediments were identified as the most plausible iodine source. In addition, mixing of groundwater with paleo-seawater might also have played a role in the coastal area. In contrast, the flood sediments of the Old Yellow River are shown to be an unlikely source. However, they serve as a cover layer that favored the development of reducing hydrogeochemical conditions that can trigger iodine mobilization via the reductive dissolution of iron oxides and the degradation of organic matter. Slow groundwater flow rates also appear to favor iodine release from sediments.

Glacial outburst flood in the marginal zone of the Wartanian Glaciation: An example from Adamów, central Poland

In this study, a glacial lake-outburst flood was documented in the immediate foreland of the maximum phase of the Wartanian (Warthian, Late Saalian, MIS 6) Glaciation at Adamów in south central Poland. The structural and textural analyses of the sediments, as well as palaeohydraulic analysis, were carried out in the proximal part of the outwash plain where a fragment of the floodwater drainage system comprising buried erosional channels have been documented. Their fill reached a thickness of up to 11 m and was composed of poorly sorted, massive gravels with boulders, as well as horizontally, sub-horizontally, low-angle, and cross-stratified gravels. The coarse sediments were found to be inversely and normally graded. These sediments constituted the records of two subsequent flooding episodes. In the channel fill, the lenticular accumulations of gravel were identified and interpreted as buried large gravel dunes, while exhibiting a thickness of up to 2.5 m. Traces of sediment diapirism at the contact of channel fill and underlying sediments were also documented. Deformation was observed to originate from liquefaction caused by the rapid depositional loading of flood deposits. The example used in this study exhibited that the impact of glacial lake-outburst floods in shaping the marginal zones and foreland of ice sheets in the North European Plain was higher than that considered earlier. This example also showed a different case of glacial outburst flood in the foreland of the Middle Pleistocene ice sheets of Europe than that already known, which includes the discharge of sub- or englacial meltwater reservoirs emanated from a large proglacial ice-dammed lake.

Palaeoflood hydrology of the fluvial continental records of western India: A synthesis

Palaeoflood hydrology has emerged as an important tool to infer quantitative and qualitative aspects of ungauged floods based on their physical evidence. Palaeoflood studies in India have largely been undertaken in the rivers of Peninsular India, western India, Ganga plains and the Himalayas to determine the magnitude and age of extreme floods and their connection to variations in the monsoon intensity. Usually, the alluvial domains are unfavourable for the occurrence and preservation of flood deposits and related discharge estimation. However, the alluvial rivers of western India owing to their semi–confined banks comprising late Pleistocene sediments provide an opportunity for investigating both, the high magnitude flood events as well as average flow conditions. In this synthesis we concisely review the recent palaeohydrological studies in western India in terms of flood magnitude, occurrence of extreme events and its relation to the southwest monsoon variability over various time scales. Based on palaeo–fluvial reconstructions, the sedimentation pattern during late Pleistocene appears to be related to changes in channel gradient and the water surface width rather than to discharge variability. On the other hand, the aggradation in channels during early Holocene was largely controlled by the huge sediment influx and the incision that followed was in response to the increase in the discharge and competence of the river flow. The slackwater records from the bedrock channels have revealed that the large magnitude flood events occurred during wet climate phases during the last two millennia. A clustering of high magnitude events at climatic transitions and arid periods during mid–late Holocene has been surmised. Further the flood associated deposits delimited within Quaternary fluvial landforms and channel morphology are vital as these allow quantification of past flood discharges, velocities and stage levels and thus improve the future flood predictions.

Fluvial sedimentation and its reservoir potential at foreland basin margins: A case study of the Puig-reig anticline (South-eastern Pyrenees)

Fluvial fans represent one of the dominant sedimentary systems at the active margins of non-marine foreland basins. The Puig-reig anticline at the north-eastern margin of the Ebro Foreland Basin (SE Pyrenees, Spain) exposes continuous outcrops of Late Eocene-Early Oligocene fluvial deposits, from proximal to medial fluvial fan environments. The proximal deposits are found in the north limb of the anticline, especially in the northwest zone. These deposits are characterised by conglomerates with minor interbedded sandstones, with thick and wide sheet-like geometries with unscoured or variably scoured basal surfaces. These are interpreted to be the deposits of unconfined flash floods and wide-shallow channel streams. The medial deposits, covering the rest of the anticline, consist of interbedded conglomerates, sandstones and claystones. These are interpreted to have been deposited from braided to meandering channel streams and overbank areas. Distal deposits are found towards the south, beyond the anticline, and are characterised by sandstone and clay deposits of terminal lobes and lacustrine deltas. This study assesses the impact of the primary depositional characteristics, diagenesis and deformation of the most heterolithic portion of the system, with implications for increasing our understanding of folded fluvial reservoirs. Diagenetic processes, mainly mechanical compaction and calcite cementation, resulted in overall low intergranular porosity, with limited relatively high porosity developed in sandstone lithofacies in the medial deposits. Deformation associated with thrusting and fold growth resulted in the formation of abundant fractures, with relatively high fracture intensities observed in sandstone lithofacies in the anticline crest. This study shows that post-depositional processes can both improve and diminish the reservoir potential of basin proximal fluvial deposits, through the development of fracture networks and by compaction-cementation. The comparison of the Puig-reig anticline with other similar settings worldwide indicates that foreland basin margin locations may be potential areas for effective reservoirs, even in the case of low intergranular porosity.

Key factors influencing metal concentrations in sediments along Western European Rivers: A long-term monitoring study (1945–2020)

Since 1945, a large amount of heterogeneous data has been acquired to survey river sediment quality, especially concerning regulatory metals such as Cd, Cr, Cu, Hg, Ni, Pb, and Zn. Large-scale syntheses are critical to assess the effectiveness of public regulations and the resiliency of the river systems. Accordingly, this data synthesis proposes a first attempt to decipher spatio-temporal trends of metal contamination along seven major continental rivers in Western Europe (France, Belgium, Germany, and the Netherlands). A large dataset (>12,000 samples) from various sediment matrices (bed and flood deposits – BFD, suspended particulate matter – SPM, dated sediment cores – DSC) was set up based on monitoring and scientific research from the 1950s to the 2010s. This work investigates the impact of analytical protocols (matrix sampling, fractionation, extraction), location and time factors (related to geology and anthropogenic activities) on metal concentration trends. Statistical analyses highlight crossed-interactions in space and time, as well as between sediment matrices (metal concentrations in SPM ≃ DSC > BFD) and extraction procedures (also related to river lithology). Major spatio-temporal trends are found along several rivers such as (i) an increase of metal concentrations downstream of the main urban industrial areas (e.g. Paris-Rouen corridor on the Seine River, Bonn-Duisburg corridor on the Rhine River), (ii) a long-term influence of former mining areas located in crystalline zones, releasing heavily contaminated sediments for decades (Upper Loire River, Middle Meuse section), (iii) a decrease of metal concentrations since the 1970s (except for Cr and Ni, rather low and stable over time). The improvement of sediment quality in the most recent years in Europe reflects a decisive role of environment policies, such as more efficient wastewater treatments, local applications of the Water Framework Directive and urban industrial changes in the river valleys.

Flood deposits characterization in Citarum Riverbank Area in Bandung Regency, West Java, Indonesia

Citarum River, the longest river in West Java, is one of the most strategic rivers yet one of the most polluted rivers causing a series of floods throughout history. Understanding shallow flood deposits characteristics may infer the past flooding episode and predict future flood deposits distribution. This research aims to analyze grain size and elemental distributions of flood deposits found in the Citarum Riverbank Area at several districts in Bandung Regency, West Java. Shallow coring resulted in soil samples showing that the samples were dominated by clay and silt. Element analysis revealed that Si and Al are the major elements followed by high concentrations of Fe-oxide in all soil samples. Based on these findings, it is presumed that there were two major episodes of past-floods that occurred in the research area.

Reconstruction of an extreme flood hydrograph and morphodynamics of a meander bend in a high‐peak discharge variability river (Powder River, USA)

AbstractUnderstanding of morphodynamic processes associated with large‐scale floods has recently improved following significant advances of modern technologies. Nevertheless, a clear link between flood discharge and in‐channel sedimentation processes remains to be resolved. The hydrological and geomorphological data available for the meandering Powder River (Montana, USA) since 1977 makes it a perfect laboratory to investigate connections between flood discharge and point‐bar sedimentation processes. This study focuses on a point‐bar that accreted laterally ca 70 m during a 50‐year recurrence flood, which lasted about 14 days in May 1978. In September 2018, a trench ca 2 m deep and 70 m long was excavated through the axial point‐bar deposits, and the 1978 flood deposits were delineated based on georeferenced pre‐flood and post‐flood cross‐section surveys. Sedimentological data show that point‐bar deposits accumulated at the early and late flood stages, when the flow was confined to the channel, and have similarities with classical facies models in terms of palaeocurrent patterns and vertical grain‐size trend. However, during high‐stage flood conditions, when the flow overtopped the bar, cross‐cutting of the bar and armouring were typical processes. Integration of sedimentological and palaeo‐hydrological data highlight that the relation between channel cross‐sectional area and flood discharge play a key role in preserving bar deposits. The integrated approach adopted here provides a basis for advancing palaeoflood hydrology beyond the stage of estimating peak discharges to the next stage of estimating palaeoflood hydrographs.

The March 2021 Tyrnavos, central Greece, doublet (Μw6.3 and Mw6.0): Aftershock relocation, faulting details, coseismic slip and deformation

On 3 March 2021, the Mw6.3 Tyrnavos earthquake shook much of the Thessalia region, leading to extensive damage in many small towns and villages in the activated area. The first main shock was followed in the next day, on 4th of March 2021, by an “equivalent” main shock with Mw6.0 in the adjacent fault segment. These are the largest earthquakes to strike the northeastern part of Thessalia since the M6.3, 1941 Larissa earthquake. The main shocks triggered extensive liquefaction mainly along the banks of the Titarisios tributary where alluvial flood deposits most probably amplified the ground motions. Our seismic monitoring efforts, with the use of recordings of the regional seismological network along with a dense local network that was installed three days after the seismic excitation initiation, led to the improved understanding the geometry and kinematics of the activated faults. The aftershocks form a north–northwest–trending, east–northeast–dipping, ~40 km long distribution, encompassing the two main ruptures along with minor activated structures, consistent with the rupture length estimated from analysis of regional waveform data and InSAR modeling. The first rupture was expanded bilaterally, the second main shock nucleated at its northern tip, where from this second rupture propagated unilaterally to the north–northwest. The focal mechanisms of the two main shocks support an almost pure normal faulting, similar to the aftershocks fault plane solution determined in this study. The strong ground motion of the March 3 main shock was computed with a stochastic simulation of finite fault model. Coseismic displacements that were detected using a dense GPS / GNSS network of five permanent stations located the Thessaly region, have shown an NNE–SSW extension as expected from the nature and location of the causative fault. Coulomb stress changes due to the coseismic slip of the first main shock, revealed that the hypocentral region of the second main shock was brought closer to failure by more than 10 bars.

Olive groves around the lake. A ten-thousand-year history of a Cretan landscape (Greece) reveals the dominant role of humans in making this Mediterranean ecosystem

The reconstruction of millennial-scale interactions between ecosystems and societies can provide unique and valuable references for understanding the creation of cultural landscapes and help elucidate their value, weaknesses and legacies. Among the most emblematic forms of Mediterranean land use, olive groves and pastoralism have occupied a prominent place. Therefore, it is vital to know when, how, and with what ecological consequences these practices were established and developed. Located in the southern part of the Aegean Sea, Crete is the largest island of Greece. The island is characterised by a long human history of land use, but our understanding of past environmental changes for the entire Holocene is fragmentary. This paper presents a new investigation of Lake Kournas in Crete, where recent coring provided a 15-m sequence covering ten millennia of land cover and land-use history. The study of this new core involves the analysis of the sediment dynamics, flood deposits, pollen, diatoms, fungal and algal remains, and microcharcoals. Results show that ecosystem development near Lake Kournas was not a linear process. They reveal linkages and feedbacks between vegetation, biodiversity, fire, human impact, erosion, and climate change. A possible human occupation and agro-pastoral activities around the lake may have been detected as early as 9500 cal BP, perhaps in a transitional phase between the Mesolithic and the Neolithic. At 8500 cal BP, climatic conditions may have promoted the expansion of the evergreen oak woodland. However, human impact was probably the most important driver of ecosystem change with the establishment of an agro-system after 8000 years ago. Thereafter, the trajectory of Kournas’ lake and catchment ecosystems from the Mid to Late Holocene follow the rhythm of land-use change. Among the traditional Mediterranean land uses, olive cultivation locally played a major role in the socio-ecosystem interactions, providing economic benefits but also destabilising soils. During the last six millennia, three main phases of olive cultivation occurred during the Final Neolithic-Minoan period, the Hellenistic-Roman-Byzantine (HRB) period and Modern times. Along with the changing land use under the successive political and economic influences rules, the resilience capacities of vegetation permitted it to shift back to higher biodiversity again after decreasing phases. Forest vegetation was always able to recover until the onset of the Venetian period (13th century), when woodlands were dramatically reduced. Only during the past century has forest vegetation slightly recovered, while the flood regime had already been altered during previous centuries. During the past 100 years, biodiversity markedly declined, probably in response to the industrialization of agriculture.

Optical dating of Yardang sediments and its implications for past flood events on the border of the Badain Jaran Desert, Northern China

The unique landscape of numerous lakes distributed in between megadunes in the Badain Jaran Desert (BJD) has attracted much research attention. The lakes are considered to be recharged by groundwater because of the absence of surface runoff and the very limited precipitation in the region. However, the source of the groundwater and recharge mechanism for the lakes is controversial. Ancient flood sediments, indicated by the residual Yardang landforms, are distributed on the southwestern fringe of the BJD, close to the Beida and Heli Mountains which form the southwestern border of the desert. At the present day, flooding between the mountains and the BJD occurs during heavy rainfall events. Ancient river courses identified on an alluvial fan by remote sensing images interpretation revealed that the floodwater originated in the Beida and Heli Mountains. In this study we conducted optically stimulated luminescence (OSL) dating of sequences of ancient flood sediments in the BJD. The results showed that in the southern border of the BJD, flood events occurred during marine isotope stage (MIS) 7, MIS 5, and in the middle Holocene. Since the gradient of groundwater flow beneath the alluvial fan is from the Beida Mountains to the BJD, and the ground-water table responds to the local rainfall, we conclude that at least part of the groundwater of the BJD is derived from ancient and modern mountain flood events and is supplied as belowground runoff beneath the alluvial fan. The rainfall triggers flooding in the southwestern mountains, which recharges the BJD groundwater and subsequently the BJD lakes.

Paleodischarge reconstruction using oxbow lake sediments complicated by shifting hydrological connectivity

Alluvial sedimentary records attract great attention for quantitative paleoflood studies because they may preserve continuous high-resolution archives in lowland floodplains that are most vulnerable to inland flooding. The coarse-grained flood deposit in oxbow lakes emerges as a promising paleoflood proxy due to its sensitivity to flood magnitude and high preservation potential. Previous work has established a coarseness-discharge correlation for the instrumental period that was subsequently used to retrodict paleodischarge of older flood deposits. However, it has not been tested whether this correlation applies to older deposits that may represent different lake hydrological connectivity due to plug-bar growth and river migration. Furthermore, overbank sedimentation is known to be episodic and may not scale with flood magnitude. Here we investigate this issue by comparing peak annual discharge and the coarseness of a two-stage infill sequence of a ~60 yr old oxbow lake in South Carolina, USA. We found that local morphology had the first-order control and was responsible for the sedimentation shift in the lake. There is a strong linear coarseness-discharge correlation in the upper section of the lake infill. However, this correlation overestimated the flood magnitude for flood deposits in the lower section. This finding suggests that oxbow lake sediments can be greatly useful for paleoflood reconstruction, but this may be complicated by shifting hydrological connectivity. Therefore, the stratigraphic context of an oxbow lake needs to be well understood to derive paleodischarge from the sediments properly.

Chronology of Missoula Flood Deposits at the Coyote Canyon Mammoth Site, Washington State, USA

Late Pleistocene outburst megafloods, mostly from glacial Lake Missoula, hydraulically ponded behind downstream constrictions in the Columbia River in southeastern Washington State, USA. Optically stimulated luminescence (OSL) ages for flood deposits from the Coyote Canyon Mammoth Site, located in a high (315–320 m asl) distal portion of the transient lake, indicate that at least seven floods ponded high enough to inundate the area during the period 20.9 ± 2.6 ka to 16.3 ± 2.8 ka. This is consistent with a radiocarbon age of about 17.4 ± 0.2 ka cal BP from the middle of the flood sequence. OSL ages from loess deposits overlying a paleosol at the top of the flood sequence range from 14.0 ± 2.3 ka to 10.9 ± 2.0 ka, suggesting a hiatus of about 2.3 thousand years. These datasets are consistent with current understanding that multiple late Pleistocene megafloods occurred between 20 ka and 14 ka and that earlier floods produced higher flood stages than later ones. The lack of flood deposits in the Coyote Canyon area younger than 16 ka supports the hypothesis that younger megafloods did not hydraulically pond in the Pasco Basin above about 230 m asl.

Radionuclide contamination in flood sediment deposits in the coastal rivers draining the main radioactive pollution plume of Fukushima Prefecture, Japan (2011–2020)

Abstract. Artificial radionuclides including radiocesium (134Cs and 137Cs) and radiosilver (110mAg) were released into the environment following the Fukushima Dai-ichi nuclear power plant accident in March 2011. These particle-bound substances deposited on soils of north-eastern Japan, located predominantly within a ∼3000 km2 radioactive fallout plume and drained by several coastal rivers to the Pacific Ocean. The current dataset (Evrard et al., 2021), which can be accessed at https://doi.org/10.1594/PANGAEA.928594, compiles gamma-emitting artificial radionuclide activities measured in 782 sediment samples collected from 27 to 71 locations across catchments draining ∼6450 km2 during 16 fieldwork campaigns. These campaigns were conducted in Japan between November 2011 and November 2020 in river catchments draining the main radioactive plume. This database may be useful to evaluate and anticipate the post-accidental redistribution of radionuclides in the environment and for the spatial validation of models simulating the transfer of radiocesium across continental landscapes.

Study on the Horizontal Distribution Law of Flood Water and Sediment Factors under the Effect of Vegetation on a Curved Beach

The sediment-laden floodplain flood is affected by beach vegetation and the shape of curved compound channels. The laws of water and sediment exchange and deposition distribution in beach troughs are very complex and play a significant role in the formation and development of secondary suspended rivers, the adjustment of beach horizontal gradients, and even the evolution of flood control situations. This study used a combination of experimental simulations and theoretical research to carry out a generalized model test of floodplain flood evolution, analyzing the transverse distribution characteristics of sediment-laden flow and sediment factors in a curved compound channel under the conditions of beach vegetation, proposing a theoretical model of transverse distribution of velocity and sediment concentration that is based on the momentum equation considering the inertial force of the lateral secondary flow and river curvature. The results showed the following: (1) The model test results for floodplain flood in the compound channel with curved vegetation showed that the main stream was not only concentrated in the main channel but also appeared near the foot of the left and right bank levees and formed flood discharge along the embankment, as the beach siltation was mainly concentrated in the beach lip; (2) The arrangement of full vegetation on the beach had a uniform effect on the velocity distribution of the beach, which can reduce the phenomenon of excessive velocity at the foot of the beach and increase the velocity effect in the main channel; and (3) Through five numerical examples, the lateral velocity distribution model of a curved compound channel with beach vegetation was tested and, in general, the analysis model was consistent with the experimental results. The research results will provide a theoretical basis for river management and have great significance for enriching the basic theory of water and sediment movement and promoting the integration of hydraulics, river dynamics, and ecology.

Lithofacies characteristics and sedimentary model of a gravelly braided river-dominated fan: a case study of modern Poplar River alluvial fan (northwest Junggar Basin, China)

Conglomerate reservoirs in alluvial fans commonly contain economic crude oil, but it is challenging to depict the distribution of conglomerate reservoirs or to summarise the sedimentary model in alluvial fans deposits owing to their complex lithofacies changes and variable hydrodynamic conditions. This paper focuses on the Poplar River alluvial fan in the northwest Junggar Basin, China, as a special case to analyse its sedimentary processes and to build a sedimentary model through detailed outcrop mapping and grainsize analysis. The Poplar River alluvial fan is a braided river-dominated fan with the characteristics of a large fan size (approximate 327.6 km2), gentle slope (∼<0.04–0.07°), coarse sediments (mainly cobbles or finer pebbles) and rare fine-mud sediments deposited from floods. In this alluvial fan, 15 lithofacies are identified that mainly formed in five hydrodynamic environments: (i) debris-flow deposits; (ii) high-flow traction current deposits; (iii) low-flow traction current deposits; (iv) still-water deposits; and (v) eolian deposits. Moreover, the sedimentary processes on the Poplar River alluvial fan can be divided into flood and interflood periods. During flood periods, sediment deposition plays a major role on the alluvial fan. From the proximal to distal parts, six lithofacies associations can be identified: feeder-channel and sheet-flow deposits in the proximal part, sheet flood and braided-stream deposits in the intermediate part, and channel deposits and wetland deposits in the distal fan areas. During the interflood periods, sediment reworking is the most important function, and three lithofacies associations are identified: main-channel deposits in the proximal fan, braided-trench deposits in the intermediate fan and wetland deposits in the distal area. The braided-stream deposits, braided-trench deposits and sheet-flood deposits have the best potential for high-quality aquifers or oil reservoirs based on their moderately well-sorted grains and high primary permeable intervals. KEY POINTS Fifteen lithofacies and eight lithofacies associations are identified in the Poplar River braided river-dominated alluvial fan. The aggradation process of the studied alluvial fan can be divided into flood and interflood periods. The flood-period braided-fluvial deposits, interflood main-channel and braided-trench channel deposits are the facies with best reservoir potential.

The sedimentology of high-energy outburst flood deposits: an overview

The sedimentology of high-energy outburst flood deposits: an overview

Quantifying Debris Flood Deposits in an Alaskan Fjord Using Multitemporal Digital Elevation Models.

Six DEMs over a 10-year period were used to estimate flood-related sedimentation in the Japanese Creek drainage located in Seward, Alaska. We analyze two existing LiDAR DEMs and one GNSS-derived DEM along with three additional DEMs that we generated using differential Global Navigation Satellite System (dGNSS) and Structure from Motion (SfM) techniques. Uncertainties in each DEM were accounted for, and a DEMs of Difference (DoD) technique was used to quantify the amount and pattern of sediment introduced, redistributed, or exiting the system. Through correlating the changes in sediment budget with rainfall data and flood events, the study demonstrates that the major flood events in 2006 and 2012—the 7th and 5th highest precipitation events on record—resulted in an increased sedimentation in the drainage as a whole. At a minimum the 2006 and 2012 events increased the sediment in the lower reaches by 70,100 and 53,900 cubic meters, respectively. The study shows that the DoD method and using multiple technologies to create DEMs is effective in quantifying the volumetric change and general spatial patterns of sediment redistribution between the acquisition of DEMs.

Influences of sea level on depositional environment during the last 1000 years in the southwestern Bengal delta, Bangladesh

This study illustrates the influences of sea-level on the depositional process during the last 1000 years of the southwestern delta, Bangladesh. Sediments of eight litho-sections from landward in upper delta plain to seaward in lower delta plain along the Rupsa-Pasur river were studied. Sedimentary facies, total organic carbon, total nitrogen, δ13C value, diatom assemblages, and radiocarbon dating of deposits were carried out to determine the paleoenvironments that were influenced by the relative sea-level (RSL) change over time. During the 850–1300 AD, RSL was reached up to +80 cm higher than the present level where tidal-influenced bioturbated light yellow to gray mud deposited in the upper delta plain area. RSL was dropped up to −110 cm during 1300–1850 AD, organic-rich bluish-gray mud, mangrove peat, and terrestrial influenced yellowish-gray mud were deposited successively in the lower delta plain area, and the terrace was formed at landward due to the lowering of the base level. RSL started to rise after the period 1850 AD where tidal-influenced sediments gradually increased and deposited in the upper part at seaward and terrestrial flood sediment deposited over the erosional surface at the landward part. The estimated average sedimentation rate (1.96–2.89 mm/year) is not enough to offset the effect of subsidence and present sea-level rise over the study area. The rising trend of the sea creates inundation in the lower delta plain area, also hinders upstream water flow. For that, terrestrial flood sediments settle over the erosional surface in landward, and tidal-influenced sediment gradually onlap upon it from seaward.