Floodplain Gravel Research Articles

Zeroing of IRSL signals in cobbles surfaces from a modern river floodplain in the Manas river, Tian Shan

A newly developing method, rock surface luminescence dating, provides a novel means of constraining the burial age of fluvial gravel and unveiling the transport and exposure-burial process of fluvial bed-load. A crucial requirement for successful age determination in luminescence dating of buried rock surfaces is that a sufficiently thick surficial layer was reset to a near-zero level of signal prior to deposition and burial. However, little such effort has been made on modern fluvial gravels from various depositional environments to provide a sound justification for the use of luminescence dating in such settings. In this study, we reported an investigation of daylight bleaching in modern cobbles with different sizes and shapes at a modern river floodplain from the Manas River, Tian Shan, to test the reliability and applicability of fluvial cobble optical dating. Four multi-elevated-temperature post-infrared infrared (MET-pIRIR) stimulated luminescence signals of rock slices were measured using a modified MET-pIRIR protocol to establish residual luminescence-depth profiles. The residual does of pIRIR and MET-pIRIR signals of sub-surface rock slices were also estimated using different modified SAR protocols. The results showed that the high temperature IRSL signal could be reset to ∼2–3 mm depth into cobbles surface and flat cobbles seem easier to bleach than spherical cobbles. The residual doses of sub-surface rock slices of cobbles from modern river floodplain was ∼0.4 Gy and ∼1.1 Gy for the IR50 and the pIRIR170 signal respectively, suggesting a residual age of ∼0.1 ka and ∼0.2 ka. The residual ages of MET-pIRIR signals of sub-surface rock slices of cobble MNS2-5 were ∼0.5–1 ka at higher stimulation temperature. Our results show that the fluvial cobble optical dating techniques have great potential for providing reliable chronologies for river floodplain gravel and other fluvial depositional events.

Impact of floodplain gravel mining on landforms and processes: a study case in Orlat gravel pit (Romania)

Understanding gravel mining, a very common but aggressive activity, as a morphogenetic action is fundamental for analyzing and assessing the impact on floodplain morphology and the dynamic of riverbeds, on sediments budget and water balance assessment, but also for floodplain planning and resources management. Field observations and GIS analysis were performed in a gravel pit area from central Romania to assess the impact of gravel harvesting during the last decade (2005–2015) on floodplain landscape, landforms dynamic and fluvial processes. Field measurements, diachronic analysis on maps, channel sinuosity coefficient and braided coefficient were carried out to assess the riverbed pattern. The results indicate that the intensive harvesting of gravels and sands in floodplain area leads to doubling of pit and pit ponds surfaces, changes in floodplain morphology and landscape degradation and radical changes in land use/land cover. The channel analysis indicates that the natural conditions and gravel harvesting had an important role in riverbed mobility and reveals different patterns along the Cibin River: meandered, disentangling and sinuous. The main changes of the riverbed consist of meanders radius reduction, meander loops migration northward and downstream, increased sinuosity and decreased braided coefficient. This study facilitates a better understanding of the geomorphologic consequences of off-stream gravel harvesting, the fluvial processes variability linked to flow and bedload and point to human action as morphogenetic and morphodynamic factors. Moreover, this study may enhance the environmental significance in sustainable management of floodplain being a useful tool in applied ecology, river remediation studies and territorial planning.

Inverted topographic features, now submerged beneath the water of Lake Nasser, document a morphostratigraphic sequence of high-amplitude late-Pleistocene climate oscillation in Egyptian Nubia

The Nile Valley between the Second Cataract at Wadi Halfa and the First Cataract at Aswan has been inundated behind two dams – the Aswan Dam, first built in 1902, and the High Dam (Sa'ad el A'ali), that blocked the flow of the Nile in 1964. The anticipated loss of archeological monuments in Lake Nasser, the reservoir behind the High Dam, initiated an international campaign to protect, move, or at least document as many of those monuments as possible.The UNESCO Campaign to Salvage the Monuments of Nubia included two projects that undertook to record the prehistoric archeology of the reservoir area; each of those projects engaged geologists to help place archeological sites in rigorous stratigraphic contexts. Thus, the Nile Valley between Wadi Halfa and Aswan was the site of an intensive investigation of late-Cenozoic geologic history.In this paper we summarize the principal stratigraphic elements of the suite of sediments and landforms that characterize the late-Cenozoic geology of Egyptian Nubia. Those elements include:1.Early Nile Gravel (ENG), a Nile flood-plain gravel deposited while humans were manufacturing Acheulean artifacts in the Nile Valley.2.Wadi Conglomerate (WCGL), a wadi-floor gravel topographically inverted to form sinuous ridges in the time after deposition of ENG.Because of the deep incision of the Nile Valley and immediately adjacent tributary wadis, the terrain close to the Nile, within the Reservoir area, preserves multiple generations of wadi inversion, a complex morphostratigraphic sequence not described from other areas in Egypt. The oldest body of WCGL was deposited at the same time as the ENG was accumulating.3.Late Nile Sediments (LNS), a section of younger (∼27,000-5000 14C yrs BP) sediment representing both local components and Nile-deposited components, that enclose a rich inventory of prehistoric cultures younger than Acheulean.Although examples of WCGL can be studied at locations remote from the Aswan Reservoir, most outcrops of ENG, WCGL, and LNS described in the field in Egyptian Nubia are now submerged under the water of the Reservoir.

Fingerprinting groundwater pollution in catchments with contrasting contaminant sources using microorganic compounds

Evaluating the occurrence of microorganics helps to understand sources and processes which may be controlling the transport and fate of emerging contaminants (ECs). A study was carried out at the contrasting instrumented environmental observatory sites at Oxford, on the peri-urban floodplain gravel aquifer of the River Thames and Boxford, in the rural valley of the River Lambourn on the chalk aquifer, in Southern England to explore the use of ECs to fingerprint contaminant sources and flow pathways in groundwater. At Oxford compounds were typical of a local waste tip plume (not only plasticisers and solvents but also barbiturates and N,N-diethyl-m-toluamide (DEET)) and of the urban area (plasticisers and mood-enhancing drugs such as carbamazepine). At Boxford the results were different with widespread occurrence of agricultural pesticides, their metabolites and the solvent trichloroethene, as well as plasticisers, caffeine, butylated food additives, DEET, parabens and trace polyaromatic hydrocarbons (PAHs). Groups of compounds used in pharmaceuticals and personal care products of different provenance in the environment could be distinguished, i) historical household and medical waste, ii) long-term household usage persistent in groundwater and iii) current usage and contamination from surface water. Co-contaminant and degradation products can also indicate the likely source of contaminants. A cocktail of contaminants can be used as tracers to provide information on catchment pathways and groundwater/surface water interactions. A prominent feature in this study is the attenuation of many EC compounds in the hyporheic zone.

Enlightenment and the GM floodplain

ABSTRACTIn the last 400 years floodplains in England and Wales have changed drastically. This has been steered by changes brought about through diverse human activities including river regulation for transport, water abstraction and power generation; mining, industrial and urban pollution; the spread of buildings and transport link construction; land drainage; minimization of flood risk through engineering; floodplain gravel extraction; and environment redesign for recreation and conservation.Adding to the evolving complexity of floodplains, a sequence of post‐Enlightenment impacts from the earliest of industrial societies provides an interesting precursor for other transforming global systems. Historical and sedimentological evidence for this history is available, despite limited quantitative monitoring data. A four‐phase floodplain transformation model is presented for the period.Novel patterns of erosion and sedimentation (in location and quality) have emerged as geomorphological processes have continued in ‘genetically‐modified’ form. Problems building up for the future are likely to rest particularly with more extreme events. Understanding the last four centuries of floodplain history can aid enlightened remedies and adaptations. Copyright © 2012 John Wiley & Sons, Ltd.

Oxbow Lakes as Indicators of River Channel Change: Leaf River, Mississippi, USA

This study uses oxbow lakes to ascertain the extent and nature of change in a river's form, focusing on the effects of post-1950s floodplain gravel extraction on the geomorphology of the Leaf River in southeastern Mississippi, USA. The river and oxbow lakes of a 5 km reach were examined for the effects of local and upstream floodplain and in-channel gravel mining. Data from 12 cross-sections suggests that the present-day river is 35% wider and 12% shallower than the cross-sectional geometry in cutoffs that pre-date 1955. Field measurements reveal that the Leaf River was relatively stable from at least 1911 to the early 1940s, but has since undergone an average of 2.65 m of degradation in the study reach. Survey data from a nearby USGS stream gage show that degradation began abruptly in the mid 1970s, most likely as a result of in-stream mining and pit avulsions on a major tributary that deprived downstream areas of bed load and created profile adjustments.

Projecting Cumulative Benefits of Multiple River Restoration Projects: An Example from the Sacramento-San Joaquin River System in California

Despite increasingly large investments, the potential ecological effects of river restoration programs are still small compared to the degree of human alterations to physical and ecological function. Thus, it is rarely possible to "restore" pre-disturbance conditions; rather restoration programs (even large, well-funded ones) will nearly always involve multiple small projects, each of which can make some modest change to selected ecosystem processes and habitats. At present, such projects are typically selected based on their attributes as individual projects (e.g., consistency with programmatic goals of the funders, scientific soundness, and acceptance by local communities), and ease of implementation. Projects are rarely prioritized (at least explicitly) based on how they will cumulatively affect ecosystem function over coming decades. Such projections require an understanding of the form of the restoration response curve, or at least that we assume some plausible relations and estimate cumulative effects based thereon. Drawing on our experience with the CALFED Bay-Delta Ecosystem Restoration Program in California, we consider potential cumulative system-wide benefits of a restoration activity extensively implemented in the region: isolating/filling abandoned floodplain gravel pits captured by rivers to reduce predation of outmigrating juvenile salmon by exotic warmwater species inhabiting the pits. We present a simple spreadsheet model to show how different assumptions about gravel pit bathymetry and predator behavior would affect the cumulative benefits of multiple pit-filling and isolation projects, and how these insights could help managers prioritize which pits to fill.

Effects of gravel augmentation on macroinvertebrate assemblages in a regulated California River

Enhancement projects within anadromous salmonid rivers of California have increased in recent years. Much of this work is intended as mitigation in regulated streams where salmon and steelhead spawning habitat is inaccessible or degraded due to dams, water diversions and channelization. Little research has been done to assess the benefits of spawning habitat enhancement to stream organisms other than salmon. We monitored benthic macroinvertebrates at seven spawning gravel augmentation sites in the lower Mokelumne River, a regulated stream in the Central Valley of California. Placement of cleaned floodplain gravel decreased depths and increased stream velocities. Benthic organisms colonized new gravels quickly, equalling densities and biomass of unenhanced spawning sites within 4 weeks. Macroinvertebrate species richness equalled that of unenhanced sites within 4 weeks and diversity within 2 weeks. Standing crop, as indicated by densities and dry biomass, was significantly higher in enhancement sites after 12 weeks than in unenhanced sites and remained so over the following 10 weeks. Although mobile collector/browsers initially dominated new gravels, sedentary collectors were the most common feeding category after 4 weeks, similar to unenhanced sites. These data suggest that cleaned gravels from adjacent floodplain materials, used to enhance salmonid spawning sites, are quickly incorporated into the stream ecosystem, benefiting benthic macroinvertebrate densities and dry biomass. Copyright © 2005 John Wiley & Sons, Ltd.

04/01952 Net energy analysis of solar and conventional domestic hot water systems in Melbourne, Australia: Crawford, R. H. and Treloar, G. J. Solar Energy, 2004, 76, (1–3), 159–163

The paper deals with gravels which occur near the present level of the Upper Thames, and below it in terms of selected illustrative examples, mainly of recent discovery. It covers about fifty miles of the river, from the headwaters around Cricklade, where the origin of some pebbles is discussed, to Goring gap, where it is shown that a knick-point in the present river accentuates the relative height of old marginal gravels which lie upstream.The deposits of the Summertown-Radley Terrace around Oxford consist of a lower part, with a fauna characterised by woolly rhinoceros and associated fauna, and an unconformable upper part yielding hippopotamus and associated mammalian and molluscan faunas: Acheulian implements occur. The Flood Plain gravels are now known to contain remains of Siberian mammoth and reindeer, with recently discovered contemporary molluscan fauna and flora, which are described in an Appendix. No human industry has yet been attributed to the Flood Plain gravels.Means of distinguishing between the older Summertown-Radley gravels and the younger Flood Plain deposits, in the field, are explained, and it is shown that low-lying extensions and gravel-filled channels of the former occur locally beneath the latter (as at Lechlade and Dorchester).

Large floods and climatic change during the Holocene on the Ara River, Central Japan

A reconstruction of part of the Holocene large flood record for the Ara River in central Japan is presented. Maximum intermediate gravel-size dimensions of terrace and modern floodplain gravels were measured along an 18-km reach of the river and were used in tractive force equations to estimate minimum competent flood depths. Results suggest that the magnitudes of large floods on the Ara River have varied in a non-random fashion since the end of the last glacial period. Large floods with greater magnitudes occurred during the warming period of the post-glacial and the warmer early to middle Holocene (to ∼5500 years BP). A shift in the magnitudes of large floods occurred ∼5500–5000 years BP. From this time, during the cooler middle to late Holocene, large floods generally had lower magnitudes. In the modern period, large flood magnitudes are the largest in the data set. As typhoons are the main cause of large floods on the Ara River in the modern record, the variation in large flood magnitudes suggests that the incidence of typhoon visits to the central Japan changed as the climate changed during the Holocene. Further, significant dates in the large flood record on the Ara River correspond to significant dates in Europe and the USA.

Inundated floodplain gravels in a stream with an unstable bed: Temporary shelter or true invertebrate refugium?

At near‐peak flow of a large flood in a New Zealand stream, we took 10 Surber samples in calm, shallow areas of an inundated flood plain. The next day, when discharge was still high enough to cause bed movement in the main channel but the flood plain had dried out again, we collected 10 sediment samples in the dry flood plain. Invertebrate taxon richness in during‐flood samples was 83% of that found in the main channel after a period of stable flow, and total invertebrate densities were 10% of densities during stable conditions. Taxon richness, total densities, and densities of the four taxa most common in the benthos of the river were significantly lower in the dry flood plain than in during‐flood samples, implying that many invertebrates left these patches during drying. Nevertheless, mean total invertebrate densities in the dry flood plain were still 37% of during‐flood values. We conclude that inundated floodplain gravels provided temporary shelter for lotic invertebrates during the flood, but several animals were trapped as the flood plain dried, and those that managed to return to the baseflow channel were still exposed to bed‐moving shear stresses. We doubt that floodplain gravels can act as true invertebrate refugia in our study river, primarily because of the unstable nature of its sediments.

Groundwater resources in the Quaternary deposits and Lower Palaeozoic bedrock of the Rheidol catchment, west Wales

Abstract An assessment of the groundwater potential of the River Rheidol catchment in west Wales is presented, a region where groundwater is an important source of water to Aberystwyth. An alternative approach to a conventional well inventory was undertaken based on the manipulation of data within a geographic information system (GIS). The GIS application revealed that, in the lower reaches of the catchment, 25% of the total recorded abstractions fall on the boundaries between different geological units and, of these, two-thirds relate to the contact between Quaternary deposits and bedrock. These abstractions are typically correlated with spring sources and represent small domestic supplies from shallow, brick-lined pits dug into the valley sides. Simple catchment water balance calculations showed that groundwater abstractions are minor in comparison to total combined surface and groundwater runoff. Compared with the weathered and fractured bedrock, the floodplain gravel aquifer is of greater significance and is further enhanced by an unquantified amount of induced recharge from the River Rheidol. However, the resource contained in the Quaternary gravels is vulnerable to mainly agricultural contaminants derived either from direct leaching through the thin unsaturated zone, especially on the floodplain, or from induced recharge from the River Rheidol.

Patchy surface stone movement during disturbance in a New Zealand stream and its potential significance for the fauna

A patchy movement of surface stones during disturbance in streams has been proposed from field observations, but few attempts have been made to quantify this phenomenon. If spates produce a mosaic of stable and disturbed areas, the former could serve as refugia for benthic invertebrates. We monitored the stability of surface stones at three geomorphically contrasting sites in a river with an unstable bed during three spates and one large flood. Stones were marked in situ by drilling holes in them or by scraping them with a chisel. For each stone, we determined visible surface area, embeddedness in the substratum, water depth, size of surrounding stones, and presence or absence of large stones upstream. During the first monitoring period, which covered one spate and the large flood, we marked 400 stones at each 20‐m‐long site in a systematic grid with 40 to 60 cm between stones. Stones were relocated after each disturbance, but each stone set was used to monitor both subsequent events. After the large flood, few marked stones were left. Therefore, additional sets of 200 stones were marked for a second monitoring period covering the remaining two spates; these stones were located at the same sites, but the distance between transects was doubled. Patchy bed movement occurred during all four disturbances, especially during the three smaller ones, which moved only 33 to 72% of marked stones. Stability of individual stones was mainly influenced by their size and embeddedness and sometimes by the water depth above the stone. Larger‐scale parameters (e.g., the position of the stone across the transect) were less important. Whole‐site stability differed little among sites. During the three smaller events, many stable surface stones were available as potential invertebrate refugia. In contrast, invertebrate refugia may have been restricted to the hyporheic zone and inundated flood‐plain gravels during the large flood. Because patchy stone movement was observed in a river with an unstable bed, it is likely to be a feature of most rivers. Therefore, small‐scale experiments may be able to simulate the effects of disturbance on the benthic community more effectively than previously thought.

Remediation of hydrocarbon leakage from a service station at Wansford, Cambridgeshire, UK

Abstract Two service stations have been built at the location of the present Nene Service Station on the A47 Trunk Road at Wansford, Cambridgeshire, UK; one replacing the other. Both have been affected by ground movements resulting from the reactivation of a periglacial landslip. During the investigation of these ground movements, hydrocarbon contamination was found in the flood plain gravels adjacent to the River Nene, which is downslope of the present service station. The paper describes the investigation work undertaken, with emphasis on soil vapour monitoring to map the contaminant plume. Remedial measures carried out included pump-and-treat of contaminated groundwater from a recovery pit, together with removal of LNAPL phase petroleum by means of absorbent pads.

PROFILE: Hungry Water: Effects of Dams and Gravel Mining on River Channels

/ Rivers transport sediment from eroding uplands to depositional areas near sea level. If the continuity of sediment transport is interrupted by dams or removal of sediment from the channel by gravel mining, the flow may become sediment-starved (hungry water) and prone to erode the channel bed and banks, producing channel incision (downcutting), coarsening of bed material, and loss of spawning gravels for salmon and trout (as smaller gravels are transported without replacement from upstream). Gravel is artificially added to the River Rhine to prevent further incision and to many other rivers in attempts to restore spawning habitat. It is possible to pass incoming sediment through some small reservoirs, thereby maintaining the continuity of sediment transport through the system. Damming and mining have reduced sediment delivery from rivers to many coastal areas, leading to accelerated beach erosion. Sand and gravel are mined for construction aggregate from river channel and floodplains. In-channel mining commonly causes incision, which may propagate up- and downstream of the mine, undermining bridges, inducing channel instability, and lowering alluvial water tables. Floodplain gravel pits have the potential to become wildlife habitat upon reclamation, but may be captured by the active channel and thereby become instream pits. Management of sand and gravel in rivers must be done on a regional basis, restoring the continuity of sediment transport where possible and encouraging alternatives to river-derived aggregate sources.KEY WORDS: Dams; Aquatic habitat; Sediment transport; Erosion; Sedimentation; Gravel mining

Characterization of grain size distributions in Thames floodplain gravels

Grain size distributions in samples of fluvial gravel from the River Thames floodplain near Oxford, England are mainly bimodal, with modes near −3φ and 1φ. A mixture of a hyperbolic and a normal probability density function (pdf) is shown to give a better description of these distributions than a mixture of two normal PDF's.

Interrelationships of Channel Processes, Changes and Sediments in a Proglacial Braided River

Spatial and temporal variations in channel morphology, velocity and shear stress, bedload transport rate, and bedload and bed material size distribution were measured over five summer weeks in the braided Lyngsdalselva in Arctic Norway. Velocities and shear stresses reflected streamwise convergence and divergence of flow, and in turn influenced bedload transport rates although these depended also on the availability at the surface of appropriate-sized sediment. Large and small particles had almost equal mobility, so transport rate increased rapidly with shear stress as coarse sediment began to move and in so doing exposed finer particles. Size-selective transport is nevertheless indicated by down-reach and down-bar fining. The spatial patterns of shear stress and bedload transport rate within one divided-single-divided channel cycle changed with discharge, as did the resulting channel changes. In high meltwater flows, with a peak transport rate of 0.3 kg m-1 s-1, erosion was localised at two zones of flow convergence and tended to maintain the non-uniform channel geometry. During a higher rain-flood, with transport rates up to 3 kg m-1 s-1 a downstream fall in shear stress in the main distributary led to medial deposition and consequent lateral erosion, creating a wider, shallower, more uniform channel. Grain size distributions of bedload at high and low shear stresses match fairly well those of floodplain gravels and falling stage flood deposits respectively.

Interrelationships of Channel Processes, Changes and Sediments in a Proglacial Braided River

Spatial and temporal variations in channel morphology, velocity and shear stress, bedload transport rate, and bedload and bed material size distribution were measured over five summer weeks in the braided Lyngsdalselva in Arctic Norway. Velocities and shear stresses reflected streamwise convergence and divergence of flow, and in turn influenced bedload transport rates although these depended also on the availability at the surface of appropriate-sized sediment. Large and small particles had almost equal mobility, so transport rate increased rapidly with shear stress as coarse sediment began to move and in so doing exposed finer particles. Size-selective transport is nevertheless indicated by down-reach and down-bar fining. The spatial patterns of shear stress and bedload transport rate within one divided-single-divided channel cycle changed with discharge, as did the resulting channel changes. In high meltwater flows, with a peak transport rate of 0.3 kg m-1 s-1, erosion was localised at two zones of flow convergence and tended to maintain the non-uniform channel geometry. During a higher rain-flood, with transport rates up to 3 kg m-1 s-1 a downstream fall in shear stress in the main distributary led to medial deposition and consequent lateral erosion, creating a wider, shallower, more uniform channel. Grain size distributions of bedload at high and low shear stresses match fairly well those of floodplain gravels and falling stage flood deposits respectively.

Late Devensian river deposits beneath the Floodplain Terrace of the River Thames at Abingdon, Berkshire, England

An organic channel-fill deposit in gravel and sand exposed at Thrupp House Farm quarry is described. The gravels and sands were laid down in a bed-load dominated river under a cold climate regime. Two radiocarbon dates of 13,260 ± 180 BP and 13,580 ± 120 BP were obtained and indicate that the deposit accumulated during the Late Devensian substage. However, the abundance of certain members of the insect fauna, particularly Pycnoglypta lurida and Olophrum assimile suggest that the deposits may date from the latter half of the Windermere Interstadial, i.e. the C14 dates may be 1000 yr. too old. The discrepancy is attributed to inwashed, older carbonaceous material. This is supported by the find of Pinus bark, radiocarbon-dated at ℂ q 2 . The organic deposit accumulated in a floodplain channel with a variable water level. Initially, shallow water supported a rich aquatic and marsh vegetation with a diverse beetle fauna. Later, fluctuating water level led to a decline in species diversity, meadow vegetation invaded the pool and was occasionally damaged by fire. Finally, slightly higher water levels returned and semi-aquatic vegetation colonised the pool area with a range of beetle species present. Little can be judged of the regional vegetation. New Devensian plant records include Sagittaria natans Pall., Apium inundatum (L) Reichb. F., Naumburgia ( Lysimachia ) thyrsiflora (L) and Ranunculus platanifolius L. The climate is thought to have deteriorated during deposition of the organic bed. The relation of the sediments to those previously described from the Floodplain gravels of the Upper Thames Valley is discussed and their significance in dating the terrace aggradation within the Thames Valley as a whole is considered.

Extraction, reclamation and after use at gravel quarries near Canterbury, Kent

A study of the extraction, reclamation and after use of flood plain gravel quarries between Bagham and Thannington, south west of Canterbury in Kent, South-east England, was made, based on a review of the literature and field work. The area represents a linear extension of the urban fringe of Canterbury. Gravel production has been the most significant industry in terms of environmental impact over the last thirty years, and the result of such activity has been the creation of an extensive area of lakes and wetland habitats. Present and future gravel production will more than double the existing lakes and wetlands areas. It is suggested that, in terms of land use, this man-made environment is best suited for water-based recreation and that three zones should be recognised for an amenity park, angling and wildlife respectively. Further mineral production between Ashford and Bagham may mean a reappraisal of the proposed water resource use, particularly for wildlife. As a result of this study, attention is drawn to the spatial relationships between recreational demand groups and flood plain location with respect to the urban centre and to each other.