Article

Temporal variability of contemporary floodplain sedimentation in the Rhine–Meuse delta, The Netherlands

Earth Surface Processes and Landforms

July 1998
23(7):595 - 609

DOI:10.1002/(SICI)1096-9837(199807)23:7<595::AID-ESP869>3.0.CO;2-Y

Authors:

Nathalie Asselman

Deltares

Hans Middelkoop

Utrecht University

It is often believed that extreme but infrequent events are most important in the development of landforms. When evaluating the overall effect of large floods on floodplain sedimentation, quantitative measurements of both high- and low-magnitude events should be considered. To analyse the role of flood magnitude on floodplain sedimentation, we measured overbank sedimentation during floods of different magnitude and duration. The measurements were carried out on two embanked floodplain sections along the rivers Rhine and Meuse in The Netherlands, using sediment traps made of artificial grass. The results showed an increase in total sediment accumulation with flood magnitude, mainly caused by enhanced accumulation of sand. At low floodplain sections the increase in sediment deposition was smaller than expected from the strong increase in suspended sediment transport in the river. Spatial variability in sediment accumulation was found to depend both on flood magnitude and duration. Deposition of sand on natural levees mainly takes place during high-magnitude floods, whilst low floods and slowly receding floods are important for the deposition of silt and clay in low-lying areas, at greater distance from the main channel. © 1998 John Wiley & Sons, Ltd.

The influence of floodplain morphology and river works on spatial patterns of overbank sediment and heavy-metal deposition

Article

Jan 2006

Floodplain deposition constitutes an important part of the sediment and contaminant budget of many large rivers throughout the world. The amount, patterns and characteristics of floodplain deposition are determined at the scale of the river branch by the channel sinuosity, floodplain and valley width, whereas factors such as morphology and flow patterns are of importance at the floodplain scale. Human influence may change these factors at both scales, but little is known about the subsequent impact of these changes on overbank deposition at the scale of the floodplain and the river branch.

Landscape reconstruction and major flood events of the River Main (Hesse, Germany) in the environs of the Roman fort at Groβkrotzenburg

Article

Aug 2018
QUATERN INT

Detailed geoarchaeological studies were conducted at the Groβkrotzenburg floodplain (Southern Hesse, Germany) in order to reconstruct the fluvial palaeogeography and search for Roman harbour installations. Another objective was to reconstruct the local flood history based on stratigraphic and geochronological data. Prospection based on electrical resistivity tomography, vibracoring and direct push electrical conductivity logging were carried out to detect and analyze subsurface stratigraphies. Altogether, 6 sediment cores, up to 7 m long, were drilled along transects along and perpendicular to the present course of the River Main. Based on sedimentological and geochemical data, we classified four sedimentary units. Vibracore data helped to detect the pre-Holocene bedrock topography and to differentiate between sedimentary facies. We present geophysical, sedimentary and geochronological evidence of a river channel right in front of the Roman fort that was probably active during Roman times. Moreover, we found another bridge pier candidate in the prolongation of a well documented Roman bridge. Our findings further indicate that the northern riverbank has shifted towards south since Roman times. However, neither sedimentary nor archaeological evidence for harbour installations could be brought to light. Nevertheless, we assume that conditions favorable of a river harbour, namely permanent water flow and sufficient water depth, were guaranteed in front of the fort where an undercut slope was probably already existing during Roman times. Several sequences of coarse-grained, sandy to gravelly river deposits were found associated with major flood events that affected the site at Groβkrotzenburg during late Medieval and modern times. At that time, central Germany was repeatedly influenced by extreme meteorological conditions and associated extreme runoff events. Based on radiocarbon data we were able to define two periods of major flooding, namely between 1435 and 1484 cal AD and 1646–1792 cal AD. These periods are contemporaneous with periods of increased flood frequency in Central Europe, derived from historical sources, namely 1430–1460 AD and 1730–1790 AD. Based on sedimentary and geo-chronostratigraphic evidence, major flood events detected at the Groβkrotzenburg alluvial plain are most probably related with the AD 1480, AD 1573 and AD 1780 events known from historical records. Our results document that few historical flood events controlled the overall development of the fluvial landscape at Groβkrotzenburg at least since Roman times until the late 19th century, namely by eroding pre-existing fluvial deposits, accumulating thick sequences of event deposits and narrowing the riverbed. Since the late 19th century, river regulation measures severely changed the hydrological conditions of the River Main.

Floodplain plant productivity is better predicted by particulate nutrients than by dissolved nutrients in floodwater

Article

May 2018
ECOL ENG

Production of suspended sediment and flood typology in areas of Algerian steppe the watershed of Wadi Saida.

Article

Full-text available

Jan 2017

This work focuses on the quantification of sediment flux and the study of the relationship between the concentration of suspended sediment C and the liquid flow rate Ql, for a hydrological event such as floods. The results of analysis (sampling campaigns from 1980 to 2010) have shown the importance of seasons in the understanding of hydrological processes in the basin. The mean of the soil erosion rate is evaluated at 55 t.km-2.an-1 varying between 2 and 276 t.km-2.an-1. The analysis of 11 floods recorded on river Saida is made from the look of graphs representing C depending Ql that draw three models of hysteresis curves: clockwise, counterclockwise and shaped eight. Of the 11 flood studied those with an hourly pace for the C-Ql relationship are maximum concentrations and generally high flows. Loops in the counterclockwise and eight-shaped direction of the relationship C-Ql characteristics of winter and spring floods present the lowest concentrations, soil conditions, and ground cover are the erosive action is diminished.

Factors controlling sediment trapping in two freshwater tidal wetlands in the Biesbosch area, The Netherlands

Article

Full-text available

Nov 2017
J SOIL SEDIMENT

Purpose A thorough understanding of mechanisms controlling sedimentation and erosion is vital for a proper assessment of the effectiveness of delta restoration. Only few field-based studies have been undertaken in freshwater tidal wetlands. Furthermore, studies that measured sediment deposition in newly created wetlands are also sparse. This paper aims to identify the factors controlling the sediment trapping of two newly created freshwater tidal wetlands. Materials and methods Two recently re-opened polder areas in the Biesbosch, The Netherlands are used as study area. Field measurements of water levels, flow velocities, and turbidity at both the in- and outlet of the areas were carried out to determine the sediment budgets and trapping efficiencies under varying conditions of river discharge, tide, and wind in the period 2014–2016. Results and discussion Short-term sediment fluxes of the two study areas varied due to river discharge, tide, and wind. A positive sediment budget and trapping efficiency was found for the first study area, which has a continuing supply of river water and sediment. Sediment was lost from the second study area which lies further from the river and had a lower sediment supply. The daily sediment budget is positively related to upstream river discharge, and in general, export takes place during ebb and import during flood. However, strong wind events overrule this pattern, and trapping efficiencies decrease for increasing wind strengths at mid-range river discharges and for the highest river discharges due to increased shear stress. Conclusions Delta restoration, based on sedimentation to compensate for sea-level rise and soil subsidence, could only be effective when there is a sufficient supply of water and sediment. Management to enhance the trapping efficiency of the incoming sediment should focus on directing sufficient river flow into the wetland, ensuring the supply of water and sediment within the system during a tidal cycle, creating sufficiently large residence time of water within the polder areas for sediment settling, and decreasing wave shear stress by the establishment of vegetation or topographic irregularities.

Lower Rhine historical flood magnitudes of the last 450 years reproduced from grain-size measurements of flood deposits using End Member Modelling

Article

Dec 2014
CATENA

Channel and flood plain response to reforestation in the Dragonja basin, southwestern Slovenia: Linking past and present

Article

Full-text available

Oct 2002

Saskia Deborah Keesstra

This paper presents the results of ongoing research concerning the effects of natural forest regeneration on the sediment budget of the 91 km 2 Dragonja drainage basin in southwestern Slovenia. Several techniques were combined to reconstruct the development of the flood plain as a result of land use changes in the last 50 years. These techniques include the use of historical records of land cover, measurements of present-day stream samples of suspended sediment load, reconstruction of the flood plain sedimentation rates with 137 Cs, as well as dating river incision and calculating erosion rates through geomorphological mapping, tree ring analysis, lichenometry and aerial photo graphic interpretation. The collected data show that because of the ongoing reforestation in the Dragonja valley the sedimentation rate on the flood plain and the suspended sediment load have decreased and the erosion rate in the river bed has increased. With the reforestation the river transports less water but even less sediment, which means there is energy to incise into the river bed.

Assessment of the effects of cyclic floodplain rejuvenation on flood levels and biodiversity along the Rhine River

Article

May 2004
RIVER RES APPL

To reduce flood risks in the Netherlands, measures to increase the flood conveyance capacity of the Rhine River will be implemented. These measures will provide more room for the river and include lowering of the floodplains and excavation of secondary channels. Moreover, these measures provide opportunities for ecological rehabilitation of the floodplains. However, it is expected that floodplain sedimentation and softwood forest development in rehabilitated floodplains will gradually reduce the conveyance capacity and the biodiversity. Therefore, a floodplain management strategy was proposed that would meet both flood protection and nature rehabilitation objectives. This strategy, Cyclic Floodplain Rejuvenation (CFR), aims at mimicking the effects of channel migration by removal of softwood forests, by lowering floodplains or by (re)constructing secondary channels. In this study, the effects of CFR measures on reducing flood levels and enhancing biodiversity along the Waal River were assessed. A one-dimensional hydraulic modelling system was applied together with rule-based models for floodplain vegetation succession and floodplain sedimentation. The model simulations demonstrated that the flood management strategy of Cyclic Floodplain Rejuvenation is able to sustain safe flood levels in the Waal River when about 15% of the total floodplain area is rejuvenated with a return period of 25 to 35 years. The rejuvenation strategy led to a diverse floodplain vegetation distribution that largely complies to the historical reference for the Waal River. Cyclic Floodplain Rejuvenation may be the appropriate answer to solve the dilemma between flood protection and nature rehabilitation in highly regulated rivers. Copyright © 2004 John Wiley & Sons, Ltd.

Large deltas, small deltas: Toward a more rigorous understanding of coastal marine deltas

Article

Oct 2022
GLOBAL PLANET CHANGE

Deltas are subaerial landforms that cap underlying deposits with subaqueous extensions that result from a river feeding sediment directly into a standing body of water at a rate that overwhelms any effective dispersal processes derived from the ambient basin. This definition encapsulates both the terrestrial surface expression and the geological focus on the entire sediment mass. Environmental studies also focus on the ecology of deltaic wetlands, their drowning history, and related sustainability issues including societal considerations, history, and culture. A mean 76 ± 16% drop in hydraulic energy occurs in all subaerial deltas regardless of size, given the break in gradients separating fluvial and deltaic surfaces, driving an ever-decreasing bed-material transport, shallowing of distributary channels and concomitant overbank flooding. A delta's sediment mass grows from the addition of new river loads but can also include aeolian and marine sediment derived from outside the delta domain, growth of peat and other biomass, and inputs from human action. Removal of sediment is via river plumes interacting with marine currents, wave-induced transport, sediment failures and gravity flows, high-tide inundation onto the delta plain, tidal channel widening and deepening, and human action (peat, clay, sand and gravel mining). A delta's trapping efficiency ranges from 0 for small-load rivers that discharge directly into an energetic ocean, to 80% for large deltas, and up to 100% for some semi-enclosed bayhead deltas, including fjords. The global (ensemble) subaerial delta aggradation rate is ~1.6 mm/y if 70% of the global sediment load exits the river mouth(s), a reminder of how much sediment can be expected to be delivered to the surfaces of global deltas at a time when the 2022 CE sea level rise is ~4 mm/y. At the planetary scale, deltas are environmentally complex given Earth's range in climate, hydrodynamics, tectonic settings, relative sea-level provinces, sediment input, redistribution processes, and human actions. Under natural conditions, the subaerial portion of deltas adapt to change by advancing, retreating, switching, aggrading, and/or drowning, whereas many modern deltas are structurally constrained by societal needs. The 89 large and mud-rich coastal marine deltas (i.e. subaerial area > 1000 km²) account for 84.3% of Earth's total deltaic area that hosts >89% of all humans occupying deltas, many living within megacities. The 885 medium-size deltas (i.e. subaerial areas 10–1000 km²) account for 15.5% of the global delta area and 10.5% of humans living on deltas, with characteristics that fall between the small and large delta categories. The 1460 small and essentially sandy deltas (1–10 km²), including all fjord deltas, are impacted less from human action (with exceptions) and most are better able to withstand climate change. Recognizing the limits of big data in capturing delta complexity, field data remains a necessary gold standard for site investigators.

Evolution de la concentration des sédiments en suspension et du débit liquide durant les crues et le phénomène d’Hystérésis dans le sous bassin de l’Oued Djdiouia (Nord-ouest algérien)Evolution of the concentration of suspended sediments and liquid flow during floods and the hysteresis phenomenon in the wadi Djdiouia sub-basin (North-West Algeria)

Article

Mar 2020

The sub-basin of the Djdiouia wadi, tributary of the left bank of the Cheliff near Oued Rhiou north of Relizane, covers 835 km². This basin is quite representative of many basins of the semi-arid northern fringe of Algeria. In this paper, we are interested in the analysis of the discharge/concentration relationship at the scale of individualized floods, which is much more oriented to the graphs that give the framework presented in the chronological order C and Q. Thus, the analysis of the evolution of the concentrations of the suspensions according to the discharge during the floods of the sub-basin of wadi Djdiouia showed three models of curves (hourly loop, anti-clockwise loop and a form of eight). The models of classes III and V are the most frequent, reflecting a high availability of sediments after a dry season when the soil is particularly weakened and the appearance of a peak discharge before the maximum concentration, reflects a net deposition of sediments in the stream. We cannot neglect the Class II model, which is also necessary. It reflects a supply of sediment even during the flood.

Carbon Sequestration on Floodplains

Chapter

Jan 2021

Thomas O Hoffmann

Floodplains are a dynamic organic carbon reservoir that receive substantial amounts of sediment and organic carbon (OC). Here, a conceptual carbon budget model of river/floodplain systems and dynamics that are relevant for floodplain OC sequestration are reviewed. The focus is on sequestration rates and the time-scale of OC retention through the use of three case studies with floodplain systems that reveal different degrees of human alteration. The case studies reveal that natural systems show a high variability in OC concentration between floodplain systems and may sustain very high sequestration rates for prolonged periods of time (i.e., in the order of 10³ years). In contrast, OC sequestration rates in floodplains with strong anthropogenic pressure may exceed natural rates. However, OC residence times may strongly be reduced due to enhanced OC degradation in response to strongly altered hydrological conditions or intense agricultural land use. OC sequestrations rates reviewed range from 0.09 to 0.22 PgC a− 1, globally, representing 5–10% of the missing terrestrial carbon sink. Thus, floodplains need to be considered in the global carbon cycle. The review highlights the importance of sustainable floodplain management to preserve the natural dynamics of floodplains and to sustain their function to sequester large amounts of OC and thus mitigate climate change.

Sedimentation patterns in the Selenga River delta under changing hydroclimatic conditions

Article

Jan 2018
HYDROL PROCESS

The Selenga River delta (Russia) is a large (> 600 km2) fluvially-dominated fresh water system that transfers water and sediment from an undammed drainage basin into Lake Baikal, a UNESCO (United Nations Educational, Scientific and Cultural Organization) World Heritage Site. Through sedimentation processes, the delta and its wetlands provide important environmental services, such as storage of sediment-bound pollutants (e.g., metals), thereby reducing their input to Lake Baikal. However, in the Selenga River delta and many other deltas of the world, there is a lack of knowledge regarding impacts of potential shifts in the flow regime (e.g., due to climate change and other anthropogenic impacts) on sedimentation processes, including sediment exchanges between deltaic channels and adjacent wetlands. This study uses field measurements of water velocities and sediment characteristics in the Selenga River delta, investigating conditions of moderate discharge, which have become more frequent over the past decades (at the expense of peak flows, Q > 1350 m3 s-1). The aims are to determine if the river system under moderate flow conditions is capable of supporting sediment export from the main distributary channels of the delta to the adjacent wetlands. The results show that most of the deposited sediment outside of the deltaic channels is characterized by a large proportion of silt and clay material (i.e., < 63 μm). For example, floodplain lakes function as sinks of very fine sediment (e.g., 97% of sediment by weight < 63 μm). Additionally, bed material sediment is found to be transported outside of the channel margins during conditions of moderate and high water discharge conditions (Q ≥ 1000 m3 s-1). Submerged banks and marshlands located in the backwater zone of the delta accumulate sediment during such discharges, supporting wetland development. Thus, these regions likely sequester various metals bound to Selenga River sediment.

Floodplain aggradation caused by the high magnitude flood of 2006 in the lower Tisza region, Hungary

Article

Full-text available

Jan 2008

The area of floodplains in the Carpathian Basin was dramatically reduced as a result of river regulation works in the 19th century. Therefore, the accumulation processes were limited to the narrower floodplains. The aims of the presented study are to determine the rate of accumulation caused by a single flood event on the active, narrow floodplain of the Lower Tisza and to evaluate the relations between the aggradation, flow velocity during the peak of the flood and the canopy. The uncultivated lands in the study area cause increased roughness which decreased the velocity of the flood, influencing the rate of aggradation. The highest flow velocity was measured on points where the flood entered to the floodplain and at the foot of the levee. These points were characterised by thick (over 50 mm) and coarse sandy sediment. In the inner parts of the floodplain flood conductivity zones were formed, where the vegetational roughness was small. In the inner parts of the floodplain the rate of aggradation was influenced by the geomorphology and the vegetation density of the area.

Accretion and Vegetation Community Change in the Wax Lake Delta Following the Historic 2011 Mississippi River Flood

Article

Full-text available

May 2015

Carle, M.V.; Sasser, C.E., and Roberts, H.H., 2015. Accretion and vegetation community change in the Wax Lake Delta following the historic 2011 Mississippi River flood. During the 2011 Mississippi River flood, discharge to the lower river exceeded that of the 1927 and 1937 floods and the lower river remained above flood stage for nearly 2 months. A combination of WorldView-2 and Land Satellite 5 Thematic Mapper (Landsat 5 TM) imagery was used to assess the impact of this flood event on the Wax Lake Delta, one of few areas where the river is building new land. Vegetation community change was mapped from 2010 to 2011 and related to elevation change using plant species elevation distributions calculated from light detection and ranging (LIDAR) data. Changes in the land area in the delta were also assessed by regressing land area against water level for a series of pre- and postflood Landsat 5 TM images. The results indicate a net growth of 6.5 km2 at mean water level and 4.90 km2 at mean sea level. Areal gains were greatest at high water levels, indicating substantial vertical accretion across the subaerial delta. At least 8.7 km2, or 31.8%, of the area studied converted to a higher-elevation species. The most change occurred at low elevations with conversion from fully submerged aquatic vegetation to Potamogeton nodosus and Nelumbo lutea. Conversion to lower-elevation species occurred across 3.4 km2, or 12.8% of the study area, while 55.5% remained unchanged. The results highlight the importance of infrequent, large flood events in the maintenance of river deltas and provide a reference for estimating the impact of proposed large-scale river diversions on the Mississippi River Delta.

HULLÁMTÉR-FEJLŐDÉS VIZSGÁLATA A MAROS MAGYARORSZÁGI SZAKASZÁN

Chapter

Full-text available

Jan 2010

1 Geodezia Földmerőmérnöki es Szolgáltató Kft., orosziv@geodeziakft.hu 2 SZTE Természeti Földrajzi és Geoinformatikai Tanszék ÖSSZEFOGLALÁS A Maros XIX. század közepi szabályozásának köszönhetően a folyó alsó szakaszán jelentősen meg-változtak a felszínformálódás folyamatai. Hordalékkúpjának peremén, illetve annak előterében a jelentős mennyiségű lebegtetett hordalékot szállító áradások szemmel látható mértékű akkumulá-ciót okoztak az utóbbi évtizedekben dús vegetációval benőtt, szűk hullámtéren. Kutatásunk során a hullámtér felmagasodásának legfontosabb tényezőit, a feltöltődés mértékét, a fluviális formák eltérő akkumulációját kívántuk megismerni. Ehhez a szabályozás óta elterjedt özönnövények pollensze-meit használtuk fel, mint kormeghatározókat. A hullámtér hidraulikai érdessége 1953-2000 között a duplájára nőtt, legnagyobb mértékben az akkumulációnak fokozottan kitett, mederhez közeli terü-leteken. Két áradás akkumulációs hatásának adatai alapján az aktív medertől 300-400 m távolsá-gig exponenciálisan csökkenő üledék-felhalmozódás jellemző, ami a part menti (20-50 m széles sáv) fokozott felmagasodását (18 ill. 26 cm) idézi elő. A hullámtér mögöttes részein pedig főként a mor-fológia és a növényzet által befolyásolt, csekélyebb feltöltődés tapasztalható. A szabályozások során átvágott és mára erőteljesen feltöltődött kanyarulatokra jelenleg is kitüntetett akkumuláció a jel-lemző (2-3,5 cm/év). Alacsonyan fekvő mindenkori ártéren átlagosan 0,63 cm/év; míg az egykori, maga-sabb folyóháton 0,23 cm/év feltöltődési ütemet mértünk. Az akkumuláció mértéke a morotvák ese-tében volt a legjelentősebb (Csordajáráson 2,45 cm/év, Zugolyban 1,30 cm/év és Vetyeháton 1,80 cm/év). Mindezek a hullámtér szintkülönbségeinek kiegyenlítődése és az intenzív folyóhát képződés irányába mutatnak. 1. Bevezetés, célkitűzések A Maros a negyedik legjelentősebb víz-folyás a Kárpát-medencében vízgyűjtőte-rületét (30 332 km 2) és legnagyobb vízho-zamát (2420 m 3 /s) tekintve. A XIX. század ármentesítési munkálatai a Marost sem hagyták érintetlenül, a folyó alsó szaka-szán mind a jelenlegi hullámtéren, mind a mentett oldalon módosultak a felszínfor-máló folyamatok. A hullámtéren végbe-menő legfontosabb geomorfológiai folyamat pedig a feltöltődés lett, az ármentesítésnek köszönhetően ugyanis szűkebb területen rakódott le a Maros áradásai által szállított jelentős üledékmennyiség. A felgyorsult lerakódást a vizsgált hullámtéri szakasz hordalékkúpi helyzete és a mederrendezés is befolyásolta. Ezeket a változásokat tovább fokozhatta a megváltozott vegetáció. A fen-tiek szemmel látható eredménye a hullám-tér mélyebb területeinek (főként az egyko-ri kanyarulatoknak) és az aktív meder köz-vetlen környezetének intenzív akkumulá-ciója a ritkábban elöntött hullámtéri részek-kel szemben. Mindez az árvízi védekezés szempontjából is jelentős problémákat okoz-hat az árvízi vízszintek növelése útján.

AqBot 2004

Data

Full-text available

Feb 2014

Thomas Horvath

Floodplain deposits: A geochemical archive of flood history – A case study on the River Rhine, Germany

Article

Mar 2012
APPL GEOCHEM

Based on the correlation between discharge and carbonate content of the suspended load of the River Rhine, Germany, a systematic geochemical, mineralogical and granulometric study was carried out to verify whether this geochemical signal is transferred to floodplain deposits and in what way these sediments and their chemostratigraphic characterization can be used as a tool for the reconstruction of the river flood history. The analysis of the time resolved changes in the composition of particulate matter during a flood event revealed that the increase of carbonate content (represented by CaO, Sr) with discharge was coupled to a simultaneous decrease in the relative amount of siliciclastics (K2O, Rb). The association of these two groups of diametrical parameters with specific grain size fractions (carbonates with 40-200 μm; siliciclastics with >200 μm) were found to be slightly shifted relative to each other and showed different gradients during the surging and fading flood wave. This, together with the covariance of elements pertaining to minerals with different density (e.g., carbonate and heavy minerals) suggests a chemical response to the changes in discharge, which is controlled primarily by hydraulic equivalence rather than grain size. There is also a time lag between the amount of suspended load and discharge, with a maximum in suspended load shortly after the peak discharge, when the flood has already started to abate. The flood plain sediments have similar composition to the suspended load, suggesting the direct transfer of the geochemical flood signal to the floodplain sediments.

Assessment of cyclic floodplain rejuvenation on flood levels and biodiversity in the Rhine river

Article

Jan 2004

Floodplain Sedimentation During an Extreme Flood: the 1999 Flood on the Tar River, Eastern North Carolina

Article

Full-text available

Jul 2004

This study examines floodplain sedimentation following the largest flood in the 98-yr. record on the Tar River, North Carolina. Hurricane Floyd made landfall just 10 days after Hurricane Dennis in September 1999, bringing unprecedented rainfall (30-46 cm) and flooding to eastern North Carolina. A field survey of the lower 350 km of the river showed that this >500 yr. flood deposited very little overbank sediment (<1 mm) on most of the floodplain. We used suspended sediment concentrations measured on the Tar River from 1958-1967 to suggest that the seasonal timing and sequencing of flood events in 1999 are the most probable explanations for the minimal geomorphic impact of this extreme flood. The early autumn timing of the flood coincided with crops that were mature but not yet harvested, and when natural vegetation was very dense and effective at stabilizing channel banks, hillslopes, and floodplain soils. Hurricane Dennis may have exhausted the available sediment supply and transported this sediment to the Pamlico Sound before reaching flood stage, thereby reducing the sediment available to be transported and deposited by the flood that followed Hurricane Floyd.

Deposition and storage of fine‐grained sediment within the main channel system of the River Tweed, Scotland

Article

Nov 1999
EARTH SURF PROC LAND

This paper assesses the importance of deposition and storage of fine-grained (c. < 150 µm) sediment on the floodplains and beds of the main (non-tidal) channels of the River Tweed (4390 km2), Scotland, and two of its tributaries (River Teviot and Ettrick Water). Caesium-137 analysis of floodplain sediment cores has been used to estimate average rates of overbank sedimentation during the last 30 to 40 years. Average values for individual transects ranged from 0·16 to 2·18 kg m−2 a−1 (0·13 to 2·2 mm a−1). The mean for the 10 transects investigated was 1·29 kg m−2 a−1 (1·3 mm a−1). The total amount of fine sediment deposited was estimated to be about 44 000 t a−1. The fine-grained sediment stored in the channel bed was quantified using resuspension techniques. Average values for individual sites ranged from 0·12 to 0·96 kg m−2. The mean for the 10 sites investigated was 0·56 kg m−2. The total amount of sediment stored on the channel bed of the main channel system at the time of sampling was estimated to be about 4300 t. Comparison of these estimates of floodplain and channel storage with the estimated suspended sediment load for the River Tweed at the downstream gauging site at Norham, indicates that floodplain sedimentation and channel bed storage represent about 40 and 4 per cent, respectively, of the annual load of fine sediment delivered to the main channel system. Erosion of channel banks will reintroduce the equivalent of about 30 per cent of the floodplain-deposited sediment back into the channel. The residence time of the fine-grained sediment stored on the channel bed is probably less than one year, but that of sediment deposited on the floodplain is likely to be considerably longer. Conveyance losses associated with overbank deposition have important implications for the routing of sediment through fluvial systems and the interpretation of downstream sediment yields. Copyright © 1999 John Wiley & Sons, Ltd.

In situ measurement of sediment settling characteristics in floodplain using a LISST-ST

Article

Sep 2005
EARTH SURF PROC LAND

Due to a lack of data on settling velocities ( w s ) and grain size distributions (GSDs) in ﬂoodplain environments, sedimentation models often use calibrated rather than measured parameters. Since the characteristics of suspended matter differ from those of deposited sediment, it is impossible to derive the w s and GSD from the latter. Therefore, one needs to measure in situ suspended sediment concentrations (SSCs), settling velocities, effective grain sizes and sedimentation ﬂuxes. For this purpose we used the LISST‐ST, a laser particle sizer combined with a settling tube. In 2002 (twice) and 2004, we located the LISST‐ST with an optical backscatter sensor and sediment traps in two ﬂoodplains in The Netherlands: one along the unembanked IJssel River, another along the embanked Waal River. Measurements revealed that the SSC in the ﬂoodplains varied in relation to the SSC in the river channel. Smaller ﬂocs dominated the SSC, while larger ﬂocs dominated the potential sedimentation ﬂuxes. The in situ GSD in the IJssel ﬂoodplain was signiﬁcantly coarser than in the Waal ﬂoodplain, while the dispersed median grain sizes were equal for both ﬂoodplains. Therefore, the dispersed median grain size was two to ﬁve times smaller than the effective one. The in situ grain size exhibited a signiﬁcant positive relationship with w s , although the w s for the largest ﬂocs showed high variability. Consequently, the variability in sedimentation ﬂuxes was also large. In the actual sedimentation ﬂuxes, and hence in sedimentation models, in situ grain sizes up to about 20 µm can be neglected. In ﬂoodplain sedimentation models the relation between settling velocity and in situ grain size can be used instead of Stokes's law, which is only valid for dispersed grain sizes. These models should also use adequate data on ﬂow conditions as input, since these strongly inﬂuence the suspended sediment characteristics. Copyright © 2005 John Wiley & Sons, Ltd.

The impact of changes in climate and land use on soil erosion, transport and deposition of suspended sediment in the River Rhine

Article

Nov 2003
HYDROL PROCESS

The objective of this study was to estimate the potential effects of changes in climate and land use on the mobilization of fine sediment and the net transport of wash load from the upstream basin to the lower Rhine delta. For this purpose, a suite of geographical information system-embedded models was developed that simulates the production, and transport of wash load through the drainage network and deposition on floodplains along the lower river reaches. The model results indicate that if climate changes in accordance with the UKHI climate-change scenario, in combination with land use changes, erosion rates will increase in the Alps and decrease in the German part of the basin. Averaged over the entire basin, erosion will increase by about 12%. However, due to inefficient sediment delivery, increasing erosion in the Alps will have little effect on the sediment load further downstream. In the delta area, sediment loads are expected to decrease by 13%. When changes in river discharge are accounted for, it appears that, although very high discharges are expected to occur more frequently, sedimentation on floodplains tends to decrease. This is caused mainly by reduced sediment loads at discharges during which the floodplains are just inundated and trapping efficiencies are high. Copyright © 2003 John Wiley & Sons, Ltd.

Reconstruction of floodplain sedimentation rates: A combination of methods to optimize estimates

Article

Full-text available

Oct 2010
EARTH SURF PROC LAND

Reconstruction of overbank sedimentation rates over the past decades gives insight into floodplain dynamics, and thereby provides a basis for efficient and sustainable floodplain management. We compared the results of four independent reconstruction methods – optically stimulated luminescence (OSL) dating, caesium-137 (137Cs) dating, heavy metal analysis, and flood bed interpretation – applied at three embanked floodplain sites along lower Rhine River distributaries in the Netherlands. All methods indicate significant sedimentation rates on the floodplains, varying between 2–7 mm/a in the distal zones and 3–9 mm/a in the proximal zones. On a rapidly developing sand bar along a natural levee sedimentation rates of 9 to 25 mm/a were found. Except for some minor inconsistencies in 137Cs dating results, all methods show decreasing sedimentation rates with increasing distance from the river channel. Intercomparison of the results of the different dating methods revealed the potential errors associated with each method, particularly where disagreement among the results were found. Uncertainties may arise due to (1) grain-size dependent downward migration of 137Cs, (2) smoothing of the vertical heavy metal and 137Cs profiles, (3) delayed sediment-associated input of 137Cs in addition to direct atmospheric fall-out, (4) overestimation of the burial age in OSL dating due to incomplete resetting of the OSL signal, or (5) non-linear relationships between sediment deposition and flood magnitude in the count-from-the-top correlation between sediment lamination and past observed flood records. Still, taking the uncertainties associated with each method into account, the results are generally in good agreement. Using the results we indicate the optimal spatial range of application of each method, depending on sediment texture and sedimentation rate. The optimal spatial and temporal ranges differ for each method, but show significant overlap. A combination of the methods will thus provide maximum information for accurate estimation of sedimentation rates on a decadal time scale. Copyright

Fast Response of Lake Planton and Nutrients to River Inundations on Floodplain Lakes

Article

May 2008
RIVER RES APPL

Key variables in ecosystems tend to operate on widely different time-scales. These time-scales become relevant when a disturbance rocks the ecosystem. Here we try to explain the fast dynamics of plankton and nutrients in the water column of floodplain lakes after disturbances (inundations). We take advantage of natural experiments, that is occasional massive overflow of floodplain lakes with river water. We sampled 10 lakes in two floodplains along the Dutch river Waal monthly for 3 years, capturing the impact of three inundation events. The inundations reset the plankton as well as chemical composition of most lakes to largely the same state. While biologically inert macro-ion data reflected a large and long lasting impact of the river water, dynamics of nutrients, phytoplankton and zooplankton communities between lakes diverged in a few weeks to regimes characteristic for the different lakes. While one spring inundation synchronized plankton dynamics to let the subsequent clear water phase occur at the same moment in different lakes, winter inundations did not have the same effect and apparently dynamics quickly diverged. Our results showed that effects of inundations and other processes that affect the state of the ecosystem should be studied considering the level of the slow components such as the sediment nutrient pool, fish stock and macrophyte communities. Plankton communities and lake water nutrient status give a practically instantaneous reflection of the condition of these slow components. Copyright © 2008 John Wiley & Sons, Ltd.

Impact of Climate and Land Use Change on River Discharge and the Production, Transport and Deposition of Fine Sediment in the Rhine basin - a summary of recent results

Chapter

Full-text available

Jan 2008

Over the past decennia, the palaeogeographic development of the Rhine-Meuse delta in the Netherlands has been extensively studied and an extremely detailed database of the Holocene delta architecture has been established. The delta offers a unique palaeo-environment to study both palaeogeography and avulsions on a timescale of millenia, because of the relatively complete geological record, as a result of rapid aggradation during the Holocene, governed by relative sealevel rise and land subsidence. The palaeogeographic reconstruction provided many new insights in the characteristics of the fluvial system, such as period of existence of individual channel belts, avulsion frequency and the factors influencing these characteristics over time scales of centuries to millennia. In recent years, research attention also became focused on the Rhine basin, which is the main source area of the water and sediment for the delta. These studies considered a decadal to century time scale, and aimed at assessing the potential impacts of future changes in climate and land use on the river Rhine discharge regime as well as on the production of fine sediment and the net transport of wash load from the upstream basin to the lower Rhine delta. For this purpose, a suite of GIS-embedded models has been developed that simulates this sequence of processes. The results indicate that climate change may accelerate erosion rates. However, land use changes, that foresee a reduction in arable land, lead to a net reduction of erosion in the German part of the basin. Due to inefficient sediment delivery, increasing erosion in the Alps has little effect on the sediment load farther downstream. Suspended sediment loads transported into the lower delta are expected to decrease by 13 %. Due to the combined effect of increased peak flows, discharge-dependent sediment transport and trapping efficiencies of floodplains, long-term average sedimentation rates at low floodplain may decrease, while sedimentation rates at high floodplains may accelerate.

River floodplains as source or sink for fine sediment and total phosphorus export in an agricultural watershed

Article

Jun 2024

Floodplains constitute a vital and integrated component of the riverine network ensuring the connectivity and continuity of the river with the upland watershed areas. However, the sediment trapping efficiency of floodplains has not been well investigated. The purpose of this experimental study was to evaluate the functionality of floodplains to act as either sources or sinks for fine sediments and sediment‐bound nutrients (e.g., total phosphorus) during floods of various return periods. Thus, we hypothesized that (i) soil texture, in terms of topsoil erodibility and (ii) the magnitude of the incoming flood, in terms of the applied shear stress, are the two key parameters govern river floodplains' ability to store or release fine sediments and total phosphorus, during major flood conditions. Topsoil erodibility experiments were coupled with site‐specific flood inundation maps to estimate the eroded fine sediment mass and the total phosphorus release rates per unit area per unit time of each flood condition considered. Results suggested that the floodplain soils of the upstream reaches act as net sources, the floodplains of the midstream reaches have a dual functionality; during low magnitude flood events (up to 10‐year return periods), they act as net sinks, while during higher flood events, they act as sources; and the floodplains of the downstream reaches largely act as sinks. This study results are applicable for watershed managers to identify floodplain areas vulnerable to erosion and sources of nutrient pollution.

Anthropogenicchanges in sediment and nutrient retention in the Rhine delta

Chapter

Oct 2013

This volume provides a state-of-the-art summary of biogeochemical dynamics at major river-coastal interfaces for advanced students and researchers. River systems play an important role (via the carbon cycle) in the natural self-regulation of Earth's surface conditions by serving as a major sink for anthropogenic CO2. Approximately 90 percent of global carbon burial occurs in ocean margins, with the majority of this thought to be buried in large delta-front estuaries (LDEs). This book provides information on how humans have altered carbon cycling, sediment dynamics, CO2 budgets, wetland dynamics, and nutrients and trace element cycling at the land-margin interface. Many of the globally important LDEs are discussed across a range of latitudes, elevation and climate in the drainage basin, coastal oceanographic setting, and nature and degree of human alteration. It is this breadth of examination that provides the reader with a comprehensive understanding of the overarching controls on major river biogeochemistry.

The effect of woody vegetation on the geomorphology of a lowland floodplain: a study of a basin in southern England

Thesis

Jan 2002

Rich Jeffries

p>Previously published research has not explicitly investigated lateral and vertical accretion on lowland wooded floodplains. This thesis describes how these lacunae were addressed with three field campaigns undertaken along the Highland Water, a small lowland stream that is surrounded by one of the largest areas of uncleared woodland in England. Firstly, a catchment-scale survey identified the geomorphology of this lowland forested floodplain. Visual observations were made of floodplain features and channel characteristics; and the width of the channel, the area most recently flooded, and the maximum extent of the floodplain were measured. This survey provides the first inventory of geomorphological features found on a wooded lowland floodplain. The channel and floodplain were split into reaches that were observed to be geomorphologically homogeneous. The outcomes from this survey were that management and in-channel accumulations of woody debris appeared to be primarily responsible for changes in floodplain formation. A second survey, similar to the first but more focused upon lateral channel change, provided evidence to suggest that lateral accretion was frequently determined by vegetation. Rates of channel change were found to be extremely low, except in the vicinity of in-channel accumulation of debris, which caused change at the reach scale (10¹-10²m). In contrast with cleared floodplains, lateral river accretion was not focused at meander apices, but instead within zones of discrete floodplain activity directly caused by in-channel blockages of woody debris. This debris also caused significant areas of overbank flow to occur. Thirdly, reach-scale experiments into floodplain sedimentation determined that vertical accretion did occur, but the pattern and amount of sediment deposited was a direct result of floodplain vegetation, particularly trees and LWD. These controls of vegetation upon fluvial and floodplain processes also have implications for long-term landscape development and may explain the palaeoenvironmental history of many lowland floodplains. The findings from this thesis could also be used to design and implement sustainable forest floodplain management practices.</p

Incorporating alluvial hydrogeomorphic complexities into paleoflood hydrology, magnitude estimation and flood frequency analysis, Tennessee River, Alabama

Article

Jun 2022
J HYDROL

Extreme floods are underrepresented in stream gauge records. Sedimentological evidence of past floods (paleofloods) yields longer records, allowing extreme floods to be examined over several Holocene climate periods. This study examines the influence of hydrogeomorphic complexity (floodplain aggradation and spatially variable flood deposition) on paleoflood record “completeness” and their implications for flood magnitude estimates made with paleoflood hydrologic data. We collected two sediment cores 500 m apart from the same elevation on a natural levee along a bank of the Tennessee River near Guntersville, Alabama. We measured grain size from each core at a 1-cm resolution using a Malvern 3000 laser granulometer. Optically stimulated luminescence dating of flood deposits revealed approximate age ranges of 50 – 6500 years calibrated before present (yrs. B.P.) for the downstream 3.5 m core (i.e., BO1) and 190 – 8500 yrs. B.P. for the upstream 4.18 m core (i.e., EL2). First, a sensitivity analysis revealed adjusted floodplain elevations (AFE) for each paleoflood cross-sectional geometry to reflect floodplain aggradation over time enabled the detection of paleoflood magnitude differences, suggesting floodplain aggradation should be considered in paleoflood reconstruction within alluvial settings. Minimum paleodischarge intervals were estimated in a 1D HEC-RAS step backwater model by calculating the minimum paleoflood stage needed to transport the d90 of each paleoflood deposit. Big Oak and East Levee 2 sediment cores each contained 15 high magnitude, identifiable paleofloods. The majority of the BO1 paleofloods occurred in the last 2,000 years, while most EL2 paleofloods occurred between 2,000 and 5,000 yrs. B.P., suggesting localized geomorphic complexity produced distinct paleoflood records for the same hydrogeomorphic surface. Four paleoflood events correlate across the two cores based on their ages and grain size distributions, and we combined these four floods to create a ‘harmonized’ flood chronology for the site. The timing of these four floods corresponds with paleofloods that occurred in the last 2000 years in the middle section of the Tennessee River identified by prior paleoflood hydrologic studies. Flood frequency analysis (Bayesian Markov Chain Monte Carlo method) scenarios with ten configurations of paleoflood hydrologic data revealed differences in the number and timing of paleofloods in three paleoflood chronologies (BO1, EL2, and the harmonized) resulting from hydrogeomorphic complexities affected model distribution parameters, goodness-of-fit, and the estimated discharges of annual exceedance probabilities used to inform the design of critical flood infrastructure. As a consequence of longer records containing smaller floods, the estimated discharge of the 0.01 (100-yr), 0.001 (1000-yr), and 0.0001 (10,000-years) AEPs for EL2 were 16%, 11%, and 5% smaller, respectively, than BO1 estimates. Alluvial rivers present more challenges for reconstructing paleoflood records than bedrock, confined channel settings. The strategies presented in this paper can help integrate paleoflood hydrologic data into flood frequency analyses for alluvial rivers identifying and minimizing error stemming from hydrogeomorphic complexity. These strategies offer opportunities to expand the use of paleoflood hydrologic data in flood frequency analyses to include more rivers located in temperate environments where climate change is intensifying precipitation and a compelling need exists to anticipate and plan for changes in extreme flood occurrence.

Climate change and human influences on sediment fluxes and the sediment budget of an urban delta: the example of the lower Rhine–Meuse delta distributary network

Article

Full-text available

Jan 2021

Deltas require sufficient sediment to maintain their land area and elevation in the face of relative sea-level rise. Understanding sediment budgets can help in managing and assessing delta resilience under future conditions. Here, we make a sediment budget for the distributary channel network of the Rhine–Meuse delta (RMD), the Netherlands, home to the Port of Rotterdam. We predict the future budget and distribution of suspended sediment to indicate the possible future state of the delta in 2050 and 2085. The influence of climate and anthropogenic effects on the fluvial and coastal boundaries was calculated for climate change scenarios, and the effects of future dredging on the budget were related to port development and accommodation of larger ships in inland ports. Suspended sediment rating curves and a 1D flow model were used to estimate the distribution of suspended sediment and projected erosion and sedimentation trends for branches. We forecast a negative sediment budget (net annual loss of sediment) for the delta as a whole, varying from −8 to −16 Mt/year in 2050 and −11 to −25 Mt/year by 2085, depending on the climate scenario and accumulated error. This sediment is unfavourably distributed: most will accrete in the northern part of the system and must consequently be removed by dredging for navigation. Meanwhile, vulnerable intertidal ecosystems will receive insufficient sediment to keep up with sea-level rise, and some channels will erode, endangering bank protection. Despite increased coastal import of sediment by estuarine processes and increased river sediment supply, extensive dredging for port development will cause a sediment deficit in the future.

Bibliography

Article

Nov 2021

Paul F. Hudson

Pressure on large fluvial lowlands has increased tremendously during the past twenty years because of flood control, urbanization, and increased dependence upon floodplains and deltas for food production. This book examines human impacts on lowland rivers, and discusses how these changes affect different types of riverine environments and flood processes. Surveying a global range of large rivers, it provides a primary focus on the lower Rhine River in the Netherlands and the Lower Mississippi River in Louisiana. A particular focus of the book is on geo-engineering, which is described in a straight-forward writing style that is accessible to a broad audience of advanced students, researchers, and practitioners in global environmental change, fluvial geomorphology and sedimentology, and flood and water management.

Increased flood height driven by local factors on a regulated river with a confined floodplain, Lower Tisza, Hungary

Article

Jul 2021
GEOMORPHOLOGY

On artificially confined floodplains, various active processes influence the local peak flow level. However, these active processes are often neglected in flood management because calculations are based on static parameters. The aim of this study is to analyse the processes that contribute to rising local flood levels in a regulated channel and on an artificially confined floodplain of a lowland river. Our goals were to evaluate the role of cross-sectional channel changes, overbank floodplain aggradation, and riparian land-cover changes on local flood level increases since the late nineteenth century and early twentieth century and to assess the height changes of artificial levees. The research was performed in a low-gradient river (Lower Tisza, Hungary), which was regulated in the late nineteenth century; thus, the effects of century-long processes on flood levels could be evaluated. The results suggest that along the 92 km-long reach, the channel was narrowed by 9% and its cross-sectional area decreased by an average of 2%; however, the narrowing was over 30% in some locations. Because of these changes, flood levels increased by an average of 13 cm (maximum = 134 cm) since 1931. Because the artificial levee was constructed in the mid-nineteenth century, the mean overbank floodplain accumulation reached 1.2 m (maximum = 2.6 m), flood levels decreased by an average of 112 cm. During the same period, the land cover of the floodplain changed considerably, increasing the vegetation roughness (i.e., Manning’s n) from 0.048 to 0.11. Based on our modelled data, the higher vegetation roughness increased flood levels by 42 cm (Scenario A) or 139 cm (Scenario B), on average, based on the increased vegetation roughness (by 10% or 30%, respectively). By overlapping these data, the results showed that since the river regulation work in the late nineteenth century, the actual flood level increased by an average of 175 cm (maximum = 350 cm) in the case of Scenario A and 272 cm (maximum = 443 cm) in the case of Scenario B. The latter is more consistent with the actual flood stage measurements. As these processes are still active, further increases in the flood level could be expected. In addition, the height of artificial levees decreased by an average of 23 cm (maximum = 75 cm); thus, some levee sections became more susceptible to overtopping during record high floods, especially along the eastern levee. Based on this approach, local hydrological managers can identify the processes that contribute more to peak flow level increases at a given location and determine the correct actions at the correct locations, which could lead to decreases in peak flow levels.

Floodplain forms along the lowland Maros River, Hungary

Article

Full-text available

Mar 2020

The floodplain forms of lowland rivers act as fluvial archives, as their morphology, material and spatial characteristics refer to the hydromorphological changes of the river and (dis)connectivity of the alluvial system. The aims of the research are (1) to identify natural levees, crevasses, and point-bars on the Hungarian floodplain section of the Maros River, (2) to measure their morphometric parameters, and (3) to analyse their spatial and temporal variations in connection with various human impacts. Six genetic types of natural levees and pointbar systems developed as the result of various human impacts, thus the development of the forms terminated or became laterally limited.

The impact of large to extreme flood events on floodplain evolution of the middle and lower reaches of the Yangtze River, China

Article

May 2019
CATENA

Fluvial floodplain evolution is poorly understood despite its importance in sediment deposition, the carbon cycle, and the unique ecosystems it represents. Here we present how different magnitude and frequency of river floods contribute to floodplain evolution by analyzing three profiles of the middle and lower reaches of the Yangtze River. To investigate the formation of the Yangtze flood deposits we determine the percentage of flood events with different magnitude that can be identified from sediment cores and analyze their contribution to floodplain deposition. Our study demonstrates that magnitude of flood events strongly controls the identifiability of flood event deposition, and therefore the evolution of floodplains. Analyses show that detectability of flood layers resulted from large floods is remarkably influenced by sedimentation rates within the floodplain. High occurrence frequency of large to extreme flood events tend to correspond to high sedimentation rates, regardless of decreasing suspended sediment loads over the wet season. This implies that frequent large to extreme floods can counterbalance the decrease in suspended sediment load to maintain a high sedimentation rate in the floodplain. High flood stage is a principal factor that accounts for acceleration of floodplain sedimentation induced by large to extreme floods in the middle and lower Yangtze River. However, acceleration of sedimentation is limited by the quantity of sediment supply.

Establishing a sediment budget in the newly created “Kleine Noordwaard” wetland area in the Rhine–Meuse delta

Article

Full-text available

Mar 2018

Many deltas are threatened by accelerated soil subsidence, sea-level rise, increasing river discharge, and sediment starvation. Effective delta restoration and effective river management require a thorough understanding of the mechanisms of sediment deposition, erosion, and their controls. Sediment dynamics has been studied at floodplains and marshes, but little is known about the sediment dynamics and budget of newly created wetlands. Here we take advantage of a recently opened tidal freshwater system to study both the mechanisms and controls of sediment deposition and erosion in newly created wetlands. We quantified both the magnitude and spatial patterns of sedimentation and erosion in a former polder area in which water and sediment have been reintroduced since 2008. Based on terrestrial and bathymetric elevation data, supplemented with field observations of the location and height of cut banks and the thickness of the newly deposited layer of sediment, we determined the sediment budget of the study area for the period 2008–2015. Deposition primarily took place in channels in the central part of the former polder area, whereas channels near the inlet and outlet of the area experienced considerable erosion. In the intertidal area, sand deposition especially takes place at low-lying locations close to the channels. Mud deposition typically occurs further away from the channels, but sediment is in general uniformly distributed over the intertidal area, due to the presence of topographic irregularities and micro-topographic flow paths. Marsh erosion does not significantly contribute to the total sediment budget, because wind wave formation is limited by the length of the fetch. Consecutive measurements of channel bathymetry show a decrease in erosion and deposition rates over time, but the overall results of this study indicate that the area functions as a sediment trap. The total contemporary sediment budget of the study area amounts to 35.7×103 m3 year-1, which corresponds to a net area-averaged deposition rate of 6.1 mm year-1. This is enough to compensate for the actual rates of sea-level rise and soil subsidence in the Netherlands.

Establishing a sediment budget in the newly created Kleine Noordwaard wetland area in the Rhine-Meuse delta

Article

Full-text available

May 2017

Many deltas are threatened by accelerated soil subsidence, sea level rise, increasing river discharge, and sediment starvation. Effective delta restoration and effective river management require a thorough understanding of the mechanisms of aggradation, erosion, and their controls. Sediment dynamics has been studied at floodplains and marshes, but little is known about the sediment dynamics and budget of newly created wetlands. Here we take advantage of a recently opened tidal freshwater system to study both the mechanisms and controls of aggradation and erosion in newly created wetlands. We quantified both the magnitude and spatial patterns of aggradation and erosion in a former polder area in which water and sediment have been reintroduced since 2008. Based on terrestrial and bathymetric elevation data, supplemented with field observations of the location and height of cut banks and the thickness of the newly deposited layer of sediment, we determined the sediment budget of the study area for the period 2008–2015. Aggradation primarily took place in channels in the central part of the former polder area, whereas channels near the inlet and outlet of the area experienced considerable erosion. At the intertidal flats, sand aggradation especially takes place at low lying locations close to the channels. Mud aggradation typically occurs further away from the channels, but sediment is in general uniformly distributed over the intertidal area, due to the presence of topographic irregularities and micro topographic flow paths. Cut bank retreat does not significantly contribute to the total sediment budget, because wind wave formation is limited by the length of the fetch. Consecutive measurements of channel bathymetry show a decrease in erosion and aggradation rates over time, but the overall result of this study indicate that the area functions as a sediment trap. On average, the area traps approximately 46 % of the sediment delivered to the study area, which is approximately 3 % of the sediment load of the River Rhine at the Dutch-German border. The total sediment budget of the study area amounts to 29.7 × 10³ m³ year−1, which corresponds to a net area-averaged aggradation rate of 5.1 mm year−1. This is enough to compensate for the actual rates of sea level rise and soil subsidence in The Netherlands.

Sédiments en suspension et typologie des crues dans le bassin versant de l’oued Saïda (Hauts plateaux algériens)

Article

Jan 2016

The Wadi Saïda lies within the Mediterranean basins of northwestern Algeria and is characterized by a semi-arid climate. Rainfall is very irregular in time and space and occurs in the form of intensive showers that lead to important erosion and solid transport. This work focuses on the study of the relationship between the concentration of suspended sediment, C, and flow rate, Ql, for hydrological events such as floods. The analysis of graphs representing C as a function of Ql for 11 floods in the Wadi Saïda revealed three types of hysteresis curves: clockwise, counterclockwise and figureeight. The sediment discharge Qs for each flood is related to flow by the power relation Qs=aQbl. The floods studied with a clockwise hysteresis curve have maximum concentrations and generally high flow. Loops in the counterclockwise and figure-eight configurations for the relationship (C-Ql) are characteristic of winter and spring floods, which present the lowest concentrations of suspended solids; soil conditions and vegetation cover are such that erosive action is reduced.

The influence of valley plugs in channelized streams on floodplain sedimentation dynamics over the last century

Article

Sep 2007

Channelization of alluvial systems alters the functions and processes of floodplain ecosystems. In the loess belt region of western Tennessee and northern Mississippi, channelization, the geology of the region, and past land-use practices have resulted in geomorphic readjustments of streams and the formation of valley plugs. Valley plugs completely block stream channels with sediment and debris, and can result in greater deposition rates on floodplain surfaces. We used dendrogeomorphic techniques to quantify floodplain sediment deposition rates from the last 100+ years. The data were used to determine the spatial and temporal patterns of sedimentation in floodplains affected by channelization and the subsequent formation of valley plugs and in floodplains along unchannelized streams. We measured sediment accumulation by coring trees for age determination and measuring depth to the root collar of 63 trees at unchannelized sites and 214 trees at channelized valley plug sites. Mean floodplain deposition rates were greater at valley plug sites (-x = 1.71 ± 0.08 cm/yr) compared to rates at unchannelized sites (-x = 0.31 ± 0.02 cm/yr). The formation of valley plugs in channelized streams also affected the spatial and temporal patterns of sedimentation. Increases in deposition rates at the valley plug sites occurred approximately 30 years ago and corresponds to the timing of regional activities including: channelization projects, increases in agricultural activity, and the termination of stream dredging projects.

Grain-size trends used to assess the effective discharge for floodplain sedimentation, river Waal, the Netherlands

Article

Jan 1999
J Sediment Res B Stratigr Global Stud

NEM Asselman

The importance of hoods of different magnitude on floodplain sedimentation can be estimated from sedimentation measurements carried out during a series of hoods, However, because these measurements represent sediment accumulation during the entire hood, they cannot be used to estimate the importance of individual hood stages on sediment deposition. In this study, the importance of different hood stages on floodplain sedimentation was assessed from analysis of spatial variations in grain-size distributions, which are indicative of sediment transport directions. As a secondary objective, the applicability of grain size trend analysis to fine-grained floodplain sediments was tested. The grain-size trend analyses were carried out in a Geographical Information System, and applied to sediment deposited on an embanked floodplain section along the river Waal in the Netherlands, during a large flood in December 1993, Because flow patterns at the studied floodplain section vary with flood stage, comparison of the identified sediment transport pathways with computed flow patterns indicates at which discharge most sediment is deposited. The results indicate that large discharges with a recurrence time of more than two years are most effective in depositing suspended sediment on floodplain areas enclosed by a minor river dike. On floodplain sections that directly border the main channel, moderate discharges with a recurrence time of about one year seem to be more efficient. Contrary to the results of floodplain sedimentation models, low but increasing discharges with a recurrence time of less than one year and during which only low lying areas near residual channels are inundated appear important for deposition of suspended sediment in these low-lying areas. This observation is confirmed by measurements of spatial concentration gradients and by floodplain sedimentation measurements, Comparison of the trends with additional information on sediment transport directions indicates that trends in which sediment becomes finer, better sorted, and more negatively skewed (when measured in phi units) are most suitable for defining transport pathways on river floodplains. Trends may, however, deviate up to 90 degrees from true transport directions. Flocculation does not seem to have any negative effects on the applicability of grain-size trend analysis.

The role of overbank floodplain sedimentation in catchment contaminant budgets

Chapter

Mar 2003

Overbank sedimentation on river floodplains can result in significant reduction of the suspended sediment load transported by a river and can thus represent an important component of the catchment sediment budget. Such conveyance losses will also exert an important influence on sediment-associated contaminant fluxes and budgets. This contribution reports the results of a study of sediment-associated contaminants (i.e. total-P, Cr, Cu, Pb and Zn) fluxes in the River Swale (1346 km2) and River Aire (1002 km2) in Yorkshire, U.K., aimed at quantifying the role of overbank floodplain sedimentation in the sediment-associated contaminant budgets. The catchment of the River Aire is dominated by urban and industrial land use in its middle and lower reaches, whereas the River Swale drains a largely rural catchment, although there is a legacy of metal mining in its headwaters which impacts on heavy metal transport by the river. The results for the River Swale indicate that the conveyance losses associated with the deposition of sediment-associated contaminants on the floodplains bordering the main river can be as high as 47% of the total flux through the main channel system. Equivalent values for the River Aire range up to 26%. Contrasts between the two rivers reflect both the location of the contaminant sources within the catchments and the relative magnitude of the fine sediment deposition fluxes associated with their floodplains.

Dynamics of heavy metals in reedbeds along the banks of the river Scheldt

Article

Jan 2006

Gijs Du Laing

The pollution status of recent sediment deposits in the intertidal reedbeds along the banks of the river Scheldt was assessed, to be able to predict potential metal accumulation in controlled flooding areas and new wetlands. Moreover, the most important factors that affect metal accumulation and mobility in these marshes were identified. The superficial intertidal sediment layer was found to be significantly contaminated with trace metals. The metal concentrations could be predicted from clay or organic matter concentrations. They were somewhat higher then predicted at sites within a range of a few km from specific point-sources, whereas they were lower than predicted at sites which are regularly subjected to flooding by high salinity water. In the deeper sediment layers, sulphides also seem to play an important role in the metal accumulation. An increased salinity increases the metal mobility in oxidised sediment layers in the brackish part of the estuary. This was mainly observed for Cd. It was reflected in increasing metal concentrations in the reed plants, which were however primarily related to the clay and organic matter concentrations in the sediments. The decomposition of stems and leaves of reed and willow can both increase and decrease the metal mobility in the upper sediment layer. The concentrations of most metals in the reed litter itself increased strongly during decomposition under field conditions. The hydrological regime to which metal-polluted sediments are subjected, affects the metal concentrations in the pore water to an important extent. Flooding of a calcareous sediment led to an increased mobility of Fe, Mn, Ni and Cr and a decreased mobility of Cd, Cu and Zn. Alternating hydrological conditions resulted in fluctuating metal concentrations in the pore water. Reduction and oxidation of Fe and Mn, carbonate breakdown and the formation and re-oxidation of sulphides were the main controlling processes.

Palaeoflood extremes of the Lower Rhine

Article

Apr 2012

Assessment of the magnitude of design discharges (floods with an expected recurrence of 1/1250-yr) requires knowledge on the frequency and magnitude of extreme events. The current estimate of the size of the design flood for the Lower Rhine is based on the discharge record of the last 100 years, but it is improbable that its extrapolation is optimal for prediction of the magnitude of extreme events, as larger floods than those in the observational records have not been measured. Reconstructing palaeoflood magnitudes and frequencies from sedimentary records may provide insight in the potential maximum magnitude of extreme Rhine discharges. This helps to improve the determination of the design discharge with a reduced uncertainty, especially for extreme values. We reconstructed the magnitude of a Middle-Holocene flood in the Lower Rhine valley (Germany) based on the highest slackwater deposits on elevated terrace levels and in a palaeochannel fill in a section across the valley. A Chézy-based hydraulic model was used to calculate the palaeoflood discharge out of carefully evaluated geological data; e.g., palaeochannel dimensions, Middle-Holocene natural floodplain landscape, surface roughness, and palaeostage indicators. To account for the uncertainty in the reconstructed input variables, we considered an ensemble of 10 sets of input variables. These represent a realistic range of model inputs and results. From this set we determined a 'best guess' estimate for the minimum magnitude of floods that left the highest registered slackwater deposits in the cross section. The calculated discharge is 13,250 m3s-1 with an estimated recurrence time of 1,250 to 2,500-yr. The recurrence time is based on AMS dating and palynological analysis of the organic palaeochannel fill, which occasionally contains flood event layers. The use of the calculated discharge in flood frequency analysis for the present-day situation is not straightforward, as the Middle-Holocene flood was generated in a still forested natural catchment. According to present-day records, such discharges date roughly to a recurrence time of ~1/150-yr (e.g., the 12,600 m3s-1 flood of 1926 AD). At present, discharge waves are much steeper than millennia ago, due to deforestation since prehistoric times, and a managed river network. Correcting for these human impacts, the reconstructed palaeoflood would relate to a significant larger discharge, probably matching the current design discharge of the river dikes in the Netherlands. Although geological-based calculations of palaeoflood discharges are often less accurate than modern measurements, they provide unique information to bracket magnitudes of extreme events. Instead of accurate point-data, palaeodischarge outcomes can be used to verify previous estimates on the size of extreme events, and as thresholds of minimum discharge values, which can be used to narrow down uncertainty in previous estimations.

A Lower Rhine flood chronology based on the sedimentary record of an abandoned channel fill

Article

Apr 2012

The Bienener Altrhein is an abandoned channel of the Lower Rhine (Germany). Following a late 16th century abandonment event, the channel was disconnected from the main stream and the oxbow lake gradually filled with 8 meters of flood deposits. This process still continues today. During annual floods, a limited proportion of overbank discharge is routed across the oxbow lake. Large floods produce individual flood layers, which are visually recognized in the sedimentary sequence. Based on the sedimentary characteristics of these event layers, we created a ~450-year flood chronology for the Lower Rhine. Laser-diffraction grain size measurements were used to assess relative flood magnitudes for individual flood event layers. Continuous sampling at a ~2 cm interval provided a high-resolution record, resolving the record at an annual scale. Standard descriptive techniques (e.g., mean grain size, 95th percentile, % sand) and the more advanced 'end member modelling' were applied to zoom in on the coarse particle bins in the grain size distributions, which are indicative of higher flow velocities. The most recent part of the record was equated to modern discharge measurements. This allows to establish relations between deposited grain size characteristics in the abandoned channel and flood magnitudes in the main river. This relation can also be applied on flood event layers from previous centuries, for which only water level measurements and historical descriptions exist. This makes this method relevant to expand data series used in flood frequency analysis from 100 years to more than 400 years. To date event-layers in the rapidly accumulated sequence, we created an age-depth model that uses organic content variations to tune sedimentation rates between the known basal and top ages. No suitable identifiable organic material for radiocarbon dating was found in the cores. Instead, palynological results (introduction of agricultural species) and palaeomagnetic secular variation measurements did allow to verify the initial age-depth model. Furthermore, initially modelled ages attributed to the five biggest floods were compared to hazardous events described in historical records. As these reproduce their dates within a decade, the dated flooding events are used as additional age tie-points for further improvement of the age-depth model. The refined model was in turn used to date floods of a medium magnitude, which are more common and thus more difficult to individually relate to a specific historical peak discharge. This case study demonstrates the suitability of channel fill sediment records for (palaeo)flood characterisation. Based on a network of sites (work in progress), it should be possible to provide an accurate (internally cross-validated) flood chronology for the Lower Rhine and delta. Moreover, given the preservation of filled oxbows from all periods along the Lower Rhine, it is possible to extend relative flood chronologies back to the Early Holocene using channel fill sedimentary data.

Three-Dimensional Numerical Modeling of Deltas

Chapter

Full-text available

Jan 2005

Contribution of floodplain sequestration to the sediment budget of the Waipaoa River, New Zealand

Article

Oct 1999

Rapid vertical accretion on the Waipaoa River floodplain is conditioned by the river's high suspended sediment load (30 000-40 000 mg l(-1) at flood stage). Cumulative sediment accumulation curves derived from three cores suggest an average (post-1850) rate of vertical accretion of c. 60 mm a(-1), though a 15 year lacuna in flood activity has depressed the post-1948 rate to c. 40 mm a(-1). Rates of aggradation during floods are several orders of magnitude larger than the time-averaged rate. Within a 44 km long reach, cross-section surveys indicate that 0.2-0.8 m of sediment was deposited between 1979 and 1990. Over this period floodplain storage accounted for 5% of the total suspended sediment load, and 16% of the suspended sediment load transported during events that exceeded bankfull stage. The Waipaoa Ri,er floodplain may be representative of floodplains bordering rivers with high suspended sediment loads, produced by rapid, episodic vertical accretion, on which overbank deposition occurs across the entire floodplain, and is complemented by channel aggradation. Such rivers are able to construct high banks. Thus channel capacities are greater and the incidence of overbank flows is less than in rivers where overbank deposition is slow relative to the rate of floodplain destruction by lateral migration. The difference between our time-averaged estimate for sequestration on the Waipaoa River floodplain and comparable estimates for actively meandering rivers, and meandering rivers with low sediment loads, reinforces the notion that there is a link between the sediment transport regime of a river and its sedimentary record. To elucidate this link it is necessary to view vertical accretion in the context of the flood events that generated it, rather than in the context of a time-averaged sediment budget.

The use of floodplain sedimentation measurements to evaluate the effects of river restoration works

Article

Oct 1999

Nathalie Asselman

This paper is part of the special publication No.163, Floodplains: interdisciplinary approaches (eds S.B. Marriott and J.Alexander). Over the past century, many rivers throughout Europe have been channelized. The channel of the River Rhine in the Netherlands was straightened, groynes were built, and minor river dykes were constructed to prevent inundation of parts of the embanked floodplain during minor floods. More recently, however, ecological rehabilitation of the rivers Rhine and Meuse and the reduction of flood risk have become major issues for river management in the Netherlands. Various projects for restoration of the embanked floodplains to a more natural state and for the improvement of the discharge capacity of the high-water floodway have been initiated. Proposed measures include the construction of side channels through the floodplain, lowering of the floodplain surface by several decimetres, removal of minor river dykes, and reintroduction of floodplain forests. These measures will alter floodplain sedimentation rates. The aim of this paper is to evaluate the possible effects of such river rehabilitation measures on sediment accumulation using the results of overbank sedimentation measurements. The measurements were carried out during several floods at different floodplain sections along the rivers Waal and Meuse in the Netherlands. Sediment traps made of artificial grass were used to collect the deposited sediment. By comparing amounts and patterns of sediment deposited at floodplain sections characterized by different topography, the possible effects of rehabilitation measures on floodplain sedimentation are assessed. The findings are compared with model predictions. Results indicate that removal of minor dykes and lowering of the floodplain surface will significantly enhance sedimentation, whereas the impact of changes in vegetation cover from grass to grass with clusters of trees will be small.

Spatial variability in floodplain sedimentation: the use of generalized linear mixed-e ects models

Article

Development and evaluation of a new catchment-scale model of floodplain sedimentation

Article

Oct 2006

Fine-sediment storage within floodplain systems typically represents a significant component of the catchment sediment budget and a primary control on sediment-associated nutrient and contaminant fluxes at the basin scale. However, quantitative modeling of floodplain sedimentation within whole catchments represents a significant challenge, not least because hydraulic controls on sediment transport and deposition processes operate at fine spatial scales that cannot be resolved by basin-scale models. This paper outlines a new approach to addressing this problem in order to develop a computationally efficient model of floodplain sedimentation, which retains a strong physical basis. The approach involves two stages. First, a simple theoretical model of overbank sedimentation is presented, which quantifies the relationship between floodplain geometry, overbank discharge, and total sedimentation rate. Second, the precise form that such a relationship should take is established by analysis of the output from high-resolution flow and suspended sediment transport models applied to 22 floodplain reaches along three U.K. rivers. This analysis supports a simple power law model between discharge in excess of bankfull and sedimentation rate per unit valley floor length per unit sediment concentration. The power law model is then incorporated within a sediment budget framework and implemented using a Monte Carlo approach to allow an assessment of uncertainty in the model parameterization. The relative likelihood of competing model structures is determined using estimates of mean annual floodplain sediment storage derived by analysis of the 137Cs content of floodplain sediment cores. Comparison of 137Cs-derived sedimentation rates with uncertainty-bounded model predictions highlights the potential for assessing the significance of overbank sedimentation within catchment sediment budgets using the simple power law model.

Overbank deposition along the concave side of the Red River meanders, Manitoba, and its geomorphic significance

Article

Full-text available

Dec 2005
EARTH SURF PROC LAND

Gregory R. Brooks

Slow earth sliding is pervasive along the concave side of Red River meanders that impinge on Lake Agassiz glaciolacustrine deposits. These failures form elongated, low-angled (c. 6 to 10°) landslide zones along the valleysides. Silty overbank deposits that accumulated during the 1999 spring freshet extend continuously along the landslide zones over hundreds of metres and aggraded the lower slopes over a distance 50 to 80 m from the channel margin. The aggradation is not obviously related to meander curvature or location within a meander. Along seven slope profiles surveyed in 1999 near Letellier, Manitoba, the deposits locally are up to 21 cm thick and generally thin with increasing distance from, and height above, the river. Local deposit thickness relates to distance from the channel, duration of inundation of the landslide surface, mesotopography, and variations in vegetation cover. Immediately adjacent to the river, accumulated overbank deposits are up to 4 m thick. The 1999 overbank deposits also were present along the moderately sloped (c. 23 to 27°) concave banks eroding into the floodplain, but the deposits are thinner (locally up to c. 7 cm thick) and cover a narrower area (10 to 30 m wide) than the deposits within the landslide zones. Concave overbank deposition is part of a sediment reworking process that consists of overbank aggradation on the landslide zones, subsequent gradual downslope displacement from earth sliding, and eventually reworking by the river at the toe of the landslide. The presence of the deposits dampens the outward migration of the meanders and contributes to a low rate of contemporary lateral channel migration. Concave overbank sedimentation occurs along most Red River meanders between at least Emerson and St. Adolphe, Manitoba. © Her Majesty the Queen in right of Canada.

Evidence for hydrochory and the deposition of viable seeds within winter flow-deposited sediments: The River Dove, Derbyshire, UK

Article

Jul 2003
RIVER RES APPL

Previous studies of the influence of hydrochory on plant dispersal have focused on relationships with existing vegetation patterns or litter deposits. River sediment deposition studies have assessed sediment accretion rates, particle size and quality. The link between seed and sediment transport and deposition has been overlooked and never quantified. This paper presents observations of over‐winter viable seed and sediment deposition on three river margin sites along the River Dove, England. At these sites, 105 paired artificial turf mats were installed on the river bank top, face and toe from October 1999 to March 2000 to collect river‐deposited material. From each pair, one mat was used to determine the dry weight; median particle size; percentage sand, silt, clay and organic content of deposited sediment. The other was used in germination trials to determine the number and species of deposited viable seeds. Topographic surveys and water level measurements supported the estimation of the hydrological characteristics of each mat location. Few seeds and little sediment were found on mats not inundated by river water. For these inundated, sediment characteristics varied primarily with elevation (relative to local mean river water level during the study period), with less marked between‐site contrasts. The species composition of viable seeds also varied with elevation. Detrended correspondence analysis (DCA) revealed associations between river/wetland‐related seed species and the bank toe samples. Regression analysis revealed significant relationships between seed number, sediment properties and mat elevation. Redundancy analysis (RDA) revealed associations between the species and abundance of viable seeds and elevation, sediment weight and organic matter content. These analyses suggest that sediment and seed deposition by rivers are closely related processes. The implications of these results for seed remobilization and dispersal and hydrochory within riparian zones are discussed, as are the implications of changes in sediment/seed delivery mechanisms, river flow regimes, and the hydraulic properties of river margins for seeds, sediments and riparian vegetation patterns. Copyright © 2003 John Wiley & Sons, Ltd.

Cyclical construction and destruction of flood dominated flood plains in semiarid Australia

Article

Full-text available

Mary C. Bourke

The morphostratigraphy of flood plains along unconfined reaches of the Todd River, central Australia, indicate that flood plain formation is dominated by high magnitude floods. Processes of flood plain destruction include channel widening, vertical stripping, flood channel, back channel and macroturbulent scour. Flood plain construction occurs predominantly during high magnitude floods. Overbank: aggradational sequences comprise a complex assemblage of depositional units which include channel and flood plain insets, terrace veneer sedimentation and channel fills separated from each other by erosional unconformities. The resultant sedimentary sequences within the flood plain is best described as chaotic. Mechanisms responsible for the construction and destruction of flood plains operate at three scales. These extend from the alteration of individual sedimentary layers to the complete removal of valley hottom aggradational sequences. The highly complex morphostratigraphy of flood plains in this region negates the application of conventional paleoenvironmental reconstruction techniques.

Sediment characteristics of an extreme flood: 1993 upper Mississippi River valley

Article

Full-text available

Nov 1995
GEOLOGY

The 1993 Mississippi River flood was notable for its high magnitude, long duration, summer occurrence, and low sediment discharge. A field survey of a 70-km-long reach in the vicinity of Quincy, Illinois, revealed that the event was characterized by 100 yr flood had remarkably little sedimentological or geomorphological impact on the flood plain within the study reach because the transport effectiveness of floods in large drainage basins is influenced by event sequencing in the same manner as floods in small watersheds, and the cohesive flood-plain soils were not susceptible to erosion.

Conveyance Loss of Suspended Sediment within a Floodplain System

Article

Full-text available

Jan 1986

Depositional losses of suspended sediment within a 13 km reach of the lower course of the River Culm, Devon, UK (drainage area 276 km^) have been investigated. This stretch of the river evidences a well developed flood plain which is frequently inundated by floodwater and detailed records of suspended sediment load obtained from upstream and downstream gauging stations indicate that approximately 28 percent of the upstream load may be deposited within the reach. The magnitude of the conveyance loss for individual events varies according to their characteristics. Rates of deposition have been estimated from the conveyance loss and these have been compared with data obtained from sedimentation traps and from analysis of the "'Cs content of flood plain soils. Average rates of approximately 500 gm-^ year (0.5 mm year--1) are indicated, although the •'•-''Cs data suggest that considerable spatial variation may occur. An investigation of the characteristics of the suspended sediment transported through the reach shows that conveyance losses are associated with a preferential loss of the coarser fractions, although appreciable deposition of the clay fraction also occurs.

Sediment availability and the prediction of storm-period sediment yields

Article

Full-text available

Jan 1982

The form of the suspended sediment concentration/discharge relationship or rating curve for a drainage basin reflects the overall pattern of erosion and sediment delivery operating in the upstream area. As such it may prove useful in the development of a realistic model of storm-period sediment yield. Several workers have highlighted the existence of 'exhaustion effects' in the form of the relationship and an attempt has been made to evaluate the evidence for temporal variations in sediment availability. Detailed records of suspended sediment concentration provided by continuous recording turbidity sensors installed in several basins in Devon, UK, have been used to study this feature of basin response. The implications for the development of sediment yield models are discussed.

The hysteresis effect of sediment transport system

Article

Full-text available

Aug 2008

Jim Bogen

Factors of importance to the generation of complex sediment rating curves involving hysteresis effects are discussed. Temporary storage of sediments in channels, and interaction between fluvial processes and some other sediment producing process, may be recognized as two fundamentally different situations associated with the phenomenon. An examination of sediment transport in glacierized river basins shows that variable discharge in broad shallow channels may cause temporary storage of sediments within the channel system. Implications for the sediment budget in river systems are discussed.

Particle size characteristics of fluvial suspended sediment.

Article

Jan 1982

The relationship between the particle size characteristics of source and sediment is investigated by considering data from a number of small drainage basins in the USA and from two small basins in Devon, UK. These demonstrate the importance of soil type and catchment characteristics in controlling this relationship. Temporal variations in the particle size distribution of suspended sediment are considered by highlighting the varied evidence presented in existing studies and by considering in detail data from the two small drainage basins in Devon which exhibit markedly different responses.-from Authors

Embanked floodplains in the Netherlands; geomorphological evolution over various time scales

Article

Jan 1997

Hans Middelkoop

The reliability of suspended sediment load data.

Article

The growing significance of suspended sediment load data has directed attention to the reliablility of measurement procedures and published data. The efficiency of sampling equipment and laboratory techniques has been studied by many workers, but much less attention has been given to the problems of assessing long term loads. In the absence of detailed records of suspended sediment concentration, a number of indirect methods of estimating such loads based on, interpolation and extrapolation procedures have been employed. These may lead to serious under- or overestimation of the actual loads. A detailed assessment of both the accuracy and precision of load estimates produced for the River Creedy in Devon, UK, using these procedures is presented. (A)

Holocene floodplain sedimentation and channel response of the lower River Severn, United Kingdom

Article

Sep 1987
Z GEOMORPHOL

Tony Brown

Describes upper and middle reaches characterised by meandering and lateral sedimentation and lower reaches displaying channel stability, low sinuosity and overbank sedimentation. Radiocarbon dates show different accumulation rates in different floodplain environments with maximum rates around 2-3000 BP probably due to deforestation and arable agriculture. The Severn is typical of many low-energy systems where low slope, bank resistance and relatively high suspended sediment load can produce floodplain fills dominated by vertical sedimentation associated with semi-stable straight, meandering or anastomosing channels -from Author

Sedimentation and water quality in the flood basin of the river Kyrönjoki in Finland

Article

Jan 1985
Fennia

Hannu Mansikkaniemi

The river Kyrönjoki on the west coast of Finland has a catchment area of 4920 km2 and a mean discharge of 43 m3/s, which can increase to 500 m3/s during the spring flooding season, when the water level in the river can be more than 6 m higher than during dry periods. The floodwaters frequently spread over the surrounding flat farm land and also cause considerable damage to property in years of serious flooding. The Ilmajoki flood basin studied here is practically 30 kin in length, 1–6 km wide and has a maximum water depth on the fields of almost 3 m. Sedimentation in this flood lake was measured using a total of 150 samplers of three types placed at given points on the flood plain before the rise in water level. The measurements were carried out in spring 1983 and 1984. The dry weight of the sediment collected ranged from a few grammes to over 6000 g per m2 (60,000 kg/ha). Sedimentation rates of 20,000–50,000 kg/ha were common in water of over 2 m in depth. Maximum water depth served to explain 83 % of the variance in sedimentation rate. The sediments deposited during severe flooding contained very little organic matter, usually about 6–15 %, but those deposited by floods of average proportions contained very much more, a median value of 34 %. The inorganic material deposited was of a grain size of 0.006‑0.02 min. Suspended solids were of the order of 100 mg/l at the height of the flood, but the water of the fields soon cleared after that, to give values of 10–20 mg/1. The only exceptions to this were caused by clouding of the water at the edge of the food lake due to waves whipped up by the wind. The water contained 138 mg/1 dissolved substances during the severe flooding of 1984, and 158 mg/1 during the ordinary flooding of 1983. The mean pH of the water was 5.0 in the former case and 5.6 in the latter. Large amounts of nutrients were carried in the water, the total nitrogen content being 11–14 mg/1 during normal flooding and 5–10 mg/1 even at high flood levels. Other values varied generally in the following ranges: phosphorus 0.3–0.5 mg/1, calcium 5–10 mg/1, potassium 3–7 mg/l, magnesium 2–8 mg/1, sulphates 25–70 mg/1, chlorides 5–15 mg/1, manganese 0.05–0.6 mg/l, iron 0.3–1.0 mg/1 and zinc 0.01–0.04 mg/1.

The reliability of suspended sediment load data, erosion and sediment transport measurement

Article

Jan 1981

Investigating contemporary rates of floodplain sedimentation

Article

Jan 1992

Uses Cs-127 to estimate rates of sedimentation of floodplains. There are case studies of a 250m stretch of the River Culm floodplain near Exeter, a small part of the floodplain of the River Severn near Tewkesbury just above the junction with the Mill Avon (otherwise known as the Tewkesbury Ham), and the more rapidly accreting floodplain of the River Leira, 25 km NE of Oslo, Norway. -K.Clayton

Anti clockwise hysteresis in suspended sediment concentration during individual storms

Article

Dec 1984
CATENA

M. Klein

Analysis of the flow sediment hysteresis shape may assist in determining the sediment source area in a small basin. A clockwise hysteresis occurs when sediment is derived from the bed and banks of the channel or areas adjacent to the channel, whereas an anti-clockwise hysteresis occurs when the upper part of the slopes is the sediment source area.

Holocene sedimentation rates in overbank deposits in the Black Bottom of the Lower Ohio River, Southern Illinois

Article

May 1971

Overbank Sedimentation Rates of Fine Grained Sediments. A Study of the Recent Deposition in the Lower River Fyrisan

Article

Jan 1987

Recent overbank deposition of fine grained sediments along Swedish rivers is a rare process. Favourable conditions for overbank deposition exist, however, near the base level of low gradient rivers on the central Swedish plains. Lack of sedimentation data has inspired us to make this study which aims to estimate the present sedimentation rate and to test a field method to observe the spatial variation in deposition, by using simple sediment traps. The study area lies within the River Fyrisån drainage basin, previously investigated in several studies of fluvial geomorphology and sedimentology. The suspended sediment transport was calculated from actual discharge figures and from concentration figures obtained by water sampling and by using a "Surface Scatter Turbidimeter". The total sedimentation in the deposition area was estimated in three ways, i.e. from actual figures on sediment transport, by a sedimentation formula and by using the results from the sediment traps. The surface deposition rates varied between 8 and 240 g/m2. The accuracy of the different methods is discussed in this paper.

A sediment budget for Coon Creek basin in the Driftless Area, Wisconsin, 1853-1977

Article

May 1983

Stanley W. Trimble

Almost 50% of human-induced sediment has historically gone into flood plain storage and less than 7% has left the basin. However, some of the stored sediment is now becoming mobile, and the present sediment yield per unit area may actually be increasing downstream with the augmentation coming from storage loss. In general, sediment yield from a basin is limited by the conveyance capacity of the streams and floodplains. -from Author

Floodplain Sedimentation: A Preliminary Investigation of Contemporary Deposition within the Lower Reaches of the River Culm, Devon, UK

Article

Jan 1987

Within a 13 km reach of the lower course of the River Culm, Devon, UK, the river has a well-developed floodplain which is frequently inundated at times of high flow. Detailed records of suspended sediment load obtained from upstream and downstream gauging stations indicate that approximately 28% of the upstream load may be deposited within this reach. Direct measurements of floodplain sedimentation using 'plastic grass' sediment traps evidence both macro- and microscale spatial variations in deposition which can be related to the duration of inundation, the topography of the floodplain surface and the flow velocity of the inundating water. Rates of deposition have been estimated from conveyance losses and these have been compared with data obtained from the sediment traps. Average rates of approximately 490 g m-2 (0.49 mm year-1) are indicated. A comparison of the characteristics of storm and floodplain sediment indicated that conveyance losses are associated with a preferential loss of the coarser fractions, although appreciable deposition of the clay fraction also occurs.

Lateral Erosion and Overbank Deposition on the Mississippi River in Louisiana Caused by 1973 Flooding

Article

Sep 1974
GEOLOGY

In 1973, the Mississippi River was out of its banks for more than 2 mo from April to June. The thickness and the texture of overbank sediments were determined for a number of depositional environments on the Mississippi River flood plain in Louisiana. Average sediment thickness ranged from 53 cm along the natural levee to 1.1 cm in the back-swamp. The texture of deposits varied from natural levee sediments with 68 percent sand to backswamp sediments with 97 percent silt and clay. The amount of lateral erosion of bordering Pleistocene bluffs increased 271 percent over the previous 9 yr of record because of the flood. Using the rate of backswamp deposition during the 1973 flood, it is suggested that backswamp deposits in this area required 10,000 to 11,000 yr to accumulate.

Long and Short-term Episodic Storage and Removal of Sediment in Watersheds of Southwestern Wisconsin and Northwestern Illinois

Article

Jan 1989

James C. Knox

Average annual rates of erosion and sedimentation commonly are used to evaluate long-term movement and storage of sediment in watersheds. Use of average rates often poorly represent actual rates because changing environmental factors may dramatically alter surface runoff, flooding, and channel stability. Dating of historical, Holocene (post-glacial), and Late-Wisconsin (late glacial) hillslope and flood plain sediments in southwestern Wisconsin and northwestern Illinois indicates that rates of sediment erosion, storage, and transportation fluctuate episodically due to changing watershed environmental conditions. In the humid climate Upper Mississippi Valley, periods of sediment storage tend to be relatively slow and progressive whereas removal of sediment from storage tends to be episodic with short periods of dramatically high rates separating longer periods of relatively low rates. Historical erosion and sedimentation rates usually poorly represent long-term natural rates because of anthropogenic disturbance of land cover. The replacement of prairie and forest by agricultural land use in the Upper Mississippi Valley resulted in accelerated flood plain sedimentation that averages 30-50 cm deep on tributary flood plains and as much as 3-4 m deep on flood plains in lower reaches of main valleys near the Mississippi River. The use of lead and zinc trace metals associated with historical mining shows that decadal-scale average historical rates of overbank flood plain sedimentation range from about 0.3 cm year-1 to 4.0-5.0 cm year-1 and greatly exceed the average presettlement post-glacial flood plain vertical accretion rate of 0.02 cm year-1 that was determined for radiocarbon dated alluvial deposits.

Effects of Agriculture on Erosion and Sedimentation in the Piedmont Province, Maryland

Article

Jan 1975

JOHN E. COSTA

A study of surficial deposits in the Piedmont province of Maryland has made it possible to construct a balance equation of sediment production and deposition since erosive agricultural land use began in the 1700s. Truncated Piedmont upland soil profiles imply approximately 0.15 m of soil erosion. In Western Run, a basin 155 km2, consisting of 85 percent Chester and Manor soils, this amounts to 130 × 10-3 hm3/km2 of eroded sediment. Reservoir sedimentation rates imply that 34 percent of the eroded sediment has been carried out of the system. The rest of the sediment remains in the watershed as alluvium in the upper 1 m of flood plains and as colluvium and sheetwash deposits on hillslopes. Agricultural sediment stored in flood plains constitutes 14 percent of the estimated soil erosion. The sediment was deposited mostly by overbank deposition at rates as high as 1.6 cm/yr. The remaining 52 percent of the eroded sediment occurs as colluvium and sheetwash deposits on hillslopes and as fan-shaped colluvial-alluvial deposits at junctures of headwater tributaries. Wood from such deposits was radiocarbon dated at 290 ± 100 yr. A buried junk pile in a flood plain yielded license plates whose dates imply that after 1925 the dump was buried by overbank deposition at rates as high as those for a basin undergoing urbanization. Piedmont basins less than 26 km2 have statistically longer bankfull recurrence intervals than streams with drainage areas greater than 26 km2. This suggests that since the decline of agricultural land use in the early 1900s, small upland tributaries have adjusted to decreased sediment loads by entrenchment into and erosion of sediment deposited since the initiation of colonial agricultural land use.

Deposition Rates in Valleys Determined Using Fallout Cesium137

Article

Jan 1975

Many of man's cultural activities have accelerated the deposition of sediment in valleys, yet in most places these rates are low and difficult to measure. Sediment profiles collected in northern Mississippi had a range of deposition rates from 0.9 to 6.5 cm/yr as determined using fallout cesium-137. These deposition rates are similar to rates determined along these same ranges using the survey techniques.

An analysis of overbank deposits of a flood at Blandford-Forum, Dorset, England.

Article

Jan 1983

Tony Brown

Studies the Stour flood of December 1979 which had a maximum discharge of 313 cubic metres per second. It formed a thin veneer of sand, sand mounds and a coarse sand and gravel bar. Sediment variations are probably related to human activity (bridges, embankments, drainage etc), but the overall effects are hard to assess.-A.Scarth

Channel storage of fine-grained sediment in the Potomac River

Article

Jan 1986

Comparison of suspended sediment records from three USGS gauges suggests that storage of a sizable fraction of the suspended load of the Potomac River occurs in a reach of the channel upstream of the tidewater transition. Field studies reveal that combined channel- bottom and channel-margin storage of fine-grained sediment amount to 190 000 t (14.3% of average annual suspended load) along a 33-km reach between the Monocacy River and Seneca Dam. The distribution of channel storage is related to variations in water-surface slope, depth, and current velocity; these in turn are influenced by channel-island locations and bedrock ledges on the channel floor. Because residence times for most stored sediment are longer than one year, measured amounts of sediment storage do not account for the mass of storage and remobilization suggested by the OSGS records. Several additional sources and sinks of sediment in the study reach are identified and discussed.

Alluvial stratigraphy and radiocarbon dating along the Duck River, Tennessee: Implications regarding flood-plain origin

Article

Jan 1984

Robert Brakenridge

Four lithostratigraphic alluvial formations and eight chronostratigraphic subdivisions occur along the middle Duck River Valley. Analysis of the formations and subdivisions suggest the importance of environmental controls over fluvial systems at time scales of 10**2 to 10**4 yr. The stratigraphic information also indicates that after periods of stability and soil development and in response to altered hydrologic regimes, the Duck river forms new flood plains by lateral and vertical suspended-load accretion on channel banks and in-channel bars. At the same time, the older flood-plain surface is covered by as much as several meters of the younger alluvium and becomes a terrace. In contrast, lateral accretion of point-bar sands and gravels is not an important flood-plain-forming process along this river. Refs.

Magnitude & Frequency of Forces in Geomorphic Processes

Article

Jan 1960

The relative importance in geomorphic processes of extreme or catastrophic events and more frequent events of smaller magnitude can be measured in terms of (1) the relative amounts of "work" done on the landscape and (2) in terms of the formation of specific features of the landscape. For many processes, above the level of competence, the rate of movement of material can be expressed as a power function of some stress, as for example, shear stress. Because the frequency distributions of the magnitudes of many natural events, such as floods, rainfall, and wind speeds, approximate log-normal distributions, the product of frequency and rate, a measure of the work performed by events having different frequencies and magnitudes will attain a maximum. The frequency at which this maximum occurs provides a measure of the level at which the largest portion of the total work is accomplished. Analysis of records of sediment transported by rivers indicates that the largest portion of the total load is carried by flows which occur on the average once or twice each year. As the variability of the flow increases and hence as the size of the drainage basin decreases, a larger percentage of the total load is carried by less frequent flows. In many basins 90 per cent of the sediment is removed by storm discharges which recur at least once every five years. Transport of sand and dust by wind in general follows the same laws. The extreme velocities associated with infrequent events are compensated for by their rarity, and it is found that the greatest bulk of sediment is transported by more moderate events. Many rivers are competent to erode both bed and banks during moderate flows. Observations of natural channels suggest that the channel shape as well as the dimensions of meandering rivers appear to be associated with flows at or near the bankfull stage. The fact that the bankfull stage recurs on the average once every year or two years indicates that these features of many alluvial rivers are controlled by these more frequent flows rather than by the rarer events of catastrophic magnitude. Because the equilibrium form of wind-blown dunes and of wave-formed beaches is quite unstable, the frequency of the events responsible for their form is less clearly definable. However, dune form and orientation are determined by both wind velocity and frequency. Similarly, a hypothetical example suggests that beach slope oscillates about a mean value related in part to wave characteristics generated by winds of moderate speed. Where stresses generated by frequent events are incompetent to transport available materials, less frequent ones of greater magnitude are obviously required. Closer observation of many geomorphic processes is required before the relative importance of different processes and of events of differing magnitude and frequency in the formation of given features of the landscape can be adequately evaluated.

Cyclical construction and destruction of flood dominated flood plains in semiarid Australia

Conference Paper

Jan 1994

Mary C. Bourke

The morphostratigraphy of flood plains along unconfined reaches of the Todd River, Central Australia, indicate that flood plain formation is dominated by high magnitude floods. Processes of flood plain destruction include channel widening, vertical stripping, flood channel, back channel and macroturbulent scour. Flood plain construction occurs predominantly during high magnitude floods. Overbank aggradational sequences comprise a complex assemblage of depositional units which include channel and flood plain insets, terrace veneer sedimentation and channel fills separated from each other by erosional unconformities. The resultant sedimentary sequences within the flood plain is best described as chaotic. Mechanisms responsible for the construction and destruction of flood plains operate at three scales. These extend from the alteration of individual sedimentary layers to the complete removal of valley bottom aggradational sequences. The highly complex moprphostratigarphy of flood plains in this region negates the application of conventional paleoenvironmental reconstruction techniques.

Spatial Variability of Floodplain Sedimentation at the Event Scale in the Rhine–Meuse Delta, the Netherlands

Article

Jun 1998
EARTH SURF PROC LAND

This article addresses spatial variability of comtemporary floodplain sedimentation at the event scale. Measurements of overbank deposition were carried out using sediment traps on 11 floodplain sections along the rivers Waal and Meuse in The Netherlands during the high-magnitude flood of December 1993. During the flood, sand sheets were locally deposited behind a natural levee. At distances greater than 50 to 100 m from the river channel the deposits consisted mainly of silt- and clay-sized material. Observed patterns of deposition were related to floodplain topography and sediment transporting mechanisms. Though at several sites patterns were observed that suggest transport by turbulent diffusion, convection seems the dominant transporting mechanism, in particular in sections that are bordered by minor embankments. The average deposition of overbank fines ranged between 1·2 and 4·0 kg m−2 along the river Waal, and between 1·0 and 2·0 kg m−2 along the river Meuse. The estimated total accumulation of overbank fines (not including sand sheets) on the entire river Waal floodplain was 0·24 Mton, which is 19 per cent of the total suspended sediment load transported through the river Waal during the flood. © 1998 John Wiley & Sons, Ltd.

Use of Fallout Pb-210 Measurements to Investigate Longer-Term Rates and Patterns of Overbank Sediment Deposition on the Floodplains of Lowland Rivers

Article

Feb 1996
EARTH SURF PROC LAND

The potential for using fallout (unsupported) Pb-210 (210Pb) measurements to estimate rates of overbank sediment deposition on the floodplains of lowland rivers is explored. A model which distinguishes the contribution from direct atmospheric fallout and the catchment-derived input associated with the deposition of suspended sediment has been developed to interpret the fallout Pb-210 inventories at floodplain sampling sites and to estimate average sediment accumulation rates over the past 100 years. The approach has been successfully used to estimate rates of overbank sedimentation on the floodplains of the Rivers Culm and Exe in Devon, U.K. A detailed investigation of the pattern of longer-term sedimentation rates within a small reach of the floodplain of the River Culm indicated a range of deposition rates between 0.07 and 0.59 g cm−2 a−1, which was in close agreement with estimates of current sedimentation rates obtained using sedimentation traps.

Controls of Variation in Suspended Sediment Concentration in the River Rother, West Sussex, England

Article

Jun 2006
SEDIMENTOLOGY

P. A. WOOD

Suspended sediment concentrations were determined for samples collected from the River Rother, West Sussex, and rating loops constructed for several hydrographs. The rating loops often exhibit hysteresis with a greater suspended sediment concentration for a given discharge occurring on the rising limb than on the falling limb. A comparison of these loops indicates that the hysteresis, and the suspended sediment concentration (for a given discharge) become progressively reduced when storm events occur in rapid succession. Various types of rating curves can be identified, and a model of suspended sediment concentration and discharge constructed. Controlling factors of suspended sediment concentration are river discharge, duration and frequency of the storm event, the length of time between successive events, and the time of year.

Floodplain Sedimentation: Quantities, Patterns and Processes

Article

Sep 1995
EARTH SURF PROC LAND

This paper presents the result of measurements of floodplain sedimentation using sediment traps. The study was carried out on two embanked floodplains along the Rivers Rhine and Meuse in The Netherlands during a 3 day flood in January 1993. Raster maps of sediment accumulation were made by interpolating the measurements from the traps using block kriging. The sediment maps show clear patterns in sediment accumulation, together with the estimated interpolation errors. Average sediment accumulation ranges between 0·57 and 1·0 kg m−2. High sediment accumulation is found on the levees (4 kg m−2 or more) and on low lying areas (1·6 kg m−2); sediment accumulation decreases with distance from the main channel. The sedimentation patterns are related to floodplain topography and sediment transporting mechanisms. Sediment transport by turbulent diffusion as well as by convection can be recognized. Also, flood duration and the process of sediment settling out in ponding water in closed depressions are important. The applied method allows comparison of the results with raster-based sedimentation models.

The Magnitude and Frequency Characteristics of Fluvial Transport in a Devon Drainage Basin and Some Geomorphological Implications

Article

Dec 1982
CATENA

Magnitude and frequency analysis of fluvial transport based on long and detailed record has been lacking for British rivers. Continuous monitoring of suspended sediment and solute concentrations for the River Creedy, Devon since October 1972 has provided an opportunity to establish the medium-term magnitude and frequency characteristics of river transport in a sizeable (262 km2) drainge basin. Results reveal the importance of solute removal, substantial variations in the relative magnitude of annual dissolved and suspended sediment yields, clear differences in the temporal distribution of sediment and solute removal, and contrasts in the magnitude and recurrence of extreme values of dissolved and suspended solids transport. Consideration of discharge levels most effective for transporting river loads in relation to a natural channel cross-section has stressed the importance of events of moderate magnitude and frequency in this drainage system.

The impact of climate change on suspended sediment transport in the river Rhine

Article

Dec 1995
Stud Environ Sci

Nathalie Asselman

Erosion, transport and deposition of fine suspended sediments are both directly and indirectly influenced by climate conditions. In this study, the suspended sediment transport regime of the river Rhine under present and future climate conditions was assessed. The impact of climate change on the sediment transport regime was investigated using sediment rating curves in combination with flow duration curves, developed using the BaU-climate scenario, and three sediment production scenarios. The results indicate that a climate change under changed land use conditions will result in a 14% increase in total annual suspended sediment load. A larger part of the yearly sediment load will be transported at discharges over 4000 m3/s. This probably results in increased floodplain sedimentation rates.

Role of the Floodplain and Riparian Zone in Suspended Matter and Nitrogen Retention in the Adour River, South-West France

Article

Mar 1994

The retention capacity of the floodplain and riparian zone for suspended matter and nitrogen has been investigated in the Adour River, a seventh order stream in south-west France. Suspended matter and nitrogen fluxes through a 25 km meandering stretch of the river were measured during two flood events and compared with the amount of sediment trapped in the riparian zone (1.1 km2) and the major floodplain (16.8 km2) of the studied area. It was estimated that the floodplain and the riparian zone together retained between 10 and 20% of the suspended matter entering the stretch under study during the two main floods (138 700 Mg). Moreover, they retained about 11% of the total particulate nitrogen fluxes (640 Mg). Although the riparian zones are 15 times smaller than the major floodplain, the total suspended matter and particulate nitrogen deposition were, 50 and 17 times, respectively, larger in the riparian zone. The results obtained on the Adour River floodplain show that large river systems should not be considered only as export systems as riparian zones can retain a significant amount of suspended organic and mineral matter during floods.

Rates and patterns of contemporary floodplain sedimentation: A case study of the River Culm, Devon, UK

Article

Jul 1989

A variety of methids have been used to document contemporary rates of overbank sedimentation along an 11 km reach of the floodplain of the River Culm in Devon, UK. These have included measurements of the conveyance loss of suspended sediment between upstream and downstream measuring stations, the use of sediment traps, and the application of caesium-137 measurements to estimate the rate of accumulation of fine sediment over the past 30 years. The resultant data point to sedimentation rates typically of the order of 1500 g m–2 year–1 or 1.5 mm year–1. Values in excess of 15000 g m–2 year–1 or 15 mm year–1 have been documented in closed depressions and in backwater embayments close to the channel, whereas minimal deposition and even scour may occur along those areas that function as secondary channels during floodplain inundation.

Anti clockwise hysteresis in suspended sediment concentration during individual storms: Holbeck Catchment; Yorkshire, England

Article

Aug 1984
CATENA

Micha Klein

Effective and Bankfull Discharges of Streams in the Yampa River Basin, Colorado and Wyoming

Article

Apr 1980
J HYDROL

Edmund D. Andrews

The effective discharge is defined as the increment of discharge that transports the largest fraction of the annual sediment load over a period of years. Increments of the average annual total sediment load transported by various discharges were calculated by the flow-duration, sediment-transport-curve method for 15 gaging stations in the Yampa River basin of Colorado and Wyoming. A total sediment-transport curve was constructed for each gaging station by adding measured instantaneous suspended-sediment discharges to bedload-sediment discharges computed by the Meyer-Peter and Mueller relation. The streamflow durations were compiled from the respective gaging-station records. The quantity of sediment transported by discharges having various frequencies may be computed by combining these two relations.The 15 gaging stations had diverse hydraulic and sediment characteristics. Contributing drainage area ranged from 51.8 to 9,960 km2, and mean-annual discharge ranged from 0.040 to 43.9 m3/s. The median diameter of bed material ranged from 0.4 to 86 mm. Mean-annual sediment load from the drainage basins studied ranged from 500 to 1.3·106 metric tons per year.The effective discharges at the 15 gaging stations were equaled or exceeded on the average of between 1.5 days per year (0.4% of the time) and 11 days per year (3.0% of the time). The recurrence interval of the effective discharges ranged from 1.18 to 3.26 yr. on the annual flood series. To compare the effective discharge with the bankfull discharge, cross-sections were surveyed in a self-formed reach of the channel in the vicinity of each gaging station. The bankfull discharge was defined as the discharge which filled the channel to the level of the floodplain. At all gaging stations, the effective discharge and the bankfull discharge were nearly equal. Thus, the stream channels appear to be adjusted to their effective discharge.

The particle size characteristics of fluvial suspended sediment: an overview

Article

Jul 1989

The particle size characteristics of suspended sediment are of fundamental importance in understanding its role in a variety of environmental processes. Existing knowledge concerning the spatial and temporal variability of the grain size composition of suspended sediment is, however, relatively limited. At the global scale, major contrasts may exist between individual rivers in the calibre of their suspended load and this may be related to a number of controls including climate, catchment geology and basin scale. Any attempt to understand the precise relationship between the grain size characteristics of suspended sediment and those of its source material must also take account of the selectivity of erosion and delivery processes. A local case study undertaken by the authors in the 1500 km2 basin of the River Exe in Devon, UK is used to illustrate the considerable spatial variability that may occur within a relatively small area and the complexity of the associated controls. Available evidence concerning the temporal variability of the grain size characteristics of suspended sediment emphasises the diverse patterns of behaviour that may exist and the complexity of the controls involved. In some rivers the sediment may become coarser as flow increases, in others it may become finer, whilst in others it may exhibit a relatively constant grain size composition. Data from the local case study in the Exe basin are again used to highlight the considerable diversity in response to changing discharge that may occur within a relatively small area. Any attempt to understand the dynamics of sediment movement through a river system must also take account of the potential contrast between the ultimate and effective particle size distribution of suspended sediment in response to aggregation. Results from the Exe basin study indicate that even in rivers with relatively low solute concentrations, almost an order of magnitude difference may exist between the median particle size associated with the ultimate and effective grain size distributions.

The Dispersal of Metal Mining Wastes in the Catchment of the River Geul (Belgium – The Netherlands)

Article

Jan 1989

H. Leenaers

This thesis is a compilation of papers previously presented at scientific meetings and articles published in or submitted to international journals. The study area covers the catchment of the transboundary River Geul which flows from northeastern Belgium into the Netherlands province of Limburg where it eventually flows into the Meuse. The fluvial dispersal of mining wastes has caused enhanced concentrations of lead, zinc and cadmium in aquatic sediments and floodplain soils in both countries. As the Geul continues to migrate across its floodplain, contaminated sediments are reworked and ultimately discharged into the River Meuse, which is an important source of drinking water in the Netherlands. The objective of this study is to investigate quantitatively the dispersal of metal mining wastes in this catchment. Eventually, the data collected and knowledge obtained may be used to compile mass balances of sediments and heavy metals in the alluvial area. -from Author

Suspended sediment concentrations during high discharge events in the River Rhine, Internal Report Interuniversitair Centrum voor Geo-ecologisch Onderzoek

Jan 1996

N E M Asselman

Asselman, N. E. M. 1996. Suspended sediment concentrations during high discharge events in the River Rhine, Internal Report Interuniversitair Centrum voor Geo-ecologisch Onderzoek, ICG 96/1.

Fluviale Erosion und Sedimentation auf landwirtschaftlich genutzten Auenböden der unteren Sieg

Jan 1993
175-192

K Heusch
J Botschek
A Skowronek

Heusch, K., Botschek, J. and Skowronek, A. 1993. 'Fluviale Erosion und Sedimentation auf landwirtschaftlich genutzten Auenböden der unteren Sieg', Berliner Geographische Arbeiten, 78, 175–192.

The dynamics of suspended solids in the tidally unaffected river Elbe as a function of flow and shipping

Apr 1994
21-25

D Spott
H Guhr

Spott, D. and Guhr, H. 1994. 'The dynamics of suspended solids in the tidally unaffected river Elbe as a function of flow and shipping', Preprints of the International Symposium on Particulate Matter in Rivers and Estuaries, Reinbek, 21–25 March 1994, 267–273.

Magnitude and frequency characteristics of suspended sediment transport in Devon rivers

Jan 1984
595-609

Floodplain Sedimentation Webb
B W Walling

© 1998 John Wiley & Sons, Ltd. Earth Surf. Process. Landforms 23, 595–609 (1998) FLOODPLAIN SEDIMENTATION Webb, B. W. and Walling, D. E. 1984. 'Magnitude and frequency characteristics of suspended sediment transport in Devon rivers', in Burt, T. P. and Walling, D. E. (Eds), Catchment Experiments in Fluvial Geomorphology, 399–415.

Particle size characteristics of fluvial suspended sediment’, Recent Developments in the Explanation and Prediction of Erosion and Sediment Yield

Jan 1982
397

Peart

Temporal variability of contemporary floodplain sedimentation in the Rhine–Meuse delta, The Netherlands

Abstract

No full-text available

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