Large Gravel Research Articles

Anatomy of the tidal scour system at Minas Passage, Bay of Fundy, Canada

Strong currents have eroded thick Quaternary sediments to create a scour trough at Minas Passage, in the Bay of Fundy, Canada, site of Earth's largest tides. We describe this trough in the context of a larger system that comprises a range of elements, viz: 1) Scour troughs extending 170m below mean sea level are incised into thick glaciomarine sediments and have exhumed bedrock over wide areas. The flanking uneroded terrain has low relief and a winnowed surface. 2) Sets of sand banner banks off Cape D'Or and Cape Chignecto. 3) The atypical set of banner banks at Cape Split, consisting of the Scots Bay dune field and its counterpart, a large gravel bank trapped in the Minas Passage scour trough. 4) Low-relief banks with sand ribbons and barchan dunes alongside some banner banks, and termed ‘shadow banks’. 5) A large (0.8km3) sediment drift at the entrance to Minas Channel (without large bedforms). The location of troughs and banks can be correlated with tidal-current patterns: trenches are located in regions of very strong bi-directional currents; banner banks near headland-sited tidal gyres; shadow banks in areas of maximum mean bottom stress asymmetry; and the sediment drift at the entrance to Minas Channel in an area of weak bottom stress at all stages of the tides. Previous work has argued that the scour system formed after 3400 14Cyrs BP (radiocarbon years before present) following collapse of a barrier system across Minas Passage. We speculate that formation of the scour trough system may have released vast quantities of sediment that have not been accounted for in previous sediment budgets, and that much of this released sediment has been sequestered in the late-Holocene salt marshes at the head of the Bay of Fundy.

Low-frequency sound propagation in porous media: Glass spheres and pea gravel

The sound propagation properties of two air-filled granular materials: large sifted pea gravel and 10mm diameter glass spheres have been measured in an impedance tube. The experimental method was essentially the same as reported earlier [Swenson et al. Low-frequency sound wave parameter measurement in gravels. Appl Acoust 2010; 71: 45–51] for two other kinds of gravel: crushed limestone and undifferentiated pea gravel. Additional sampling and processing steps were applied to the microphone signals such that instead of tones, band-limited random noise was used as the input signal, and spectral domain complex pressures are now offered as input to the estimation algorithm. The estimation process extracts the best-fit attenuation coefficient, phase velocity, and characteristic impedance for the material over the signal frequencies, all with better precision than we previously obtained. Quadratic approximations for the acoustical parameters are given over the frequency range 25–160Hz. The media are both slightly attenuating and dispersive, having attenuation coefficients within 0.13–0.34Np/m, phase velocities smaller than those in air (180–240m/s), and characteristic impedance approximately 3–5times that for air. Pea gravel was more attenuating, and had slightly higher characteristic impedance, but lower phase velocities than the glass spheres.

Sediment budget monitoring of debris-flow and bedload transport in the Manival Torrent, SE France

Abstract. Steep mountain catchments typically experience large sediment pulses from hillslopes which are stored in headwater channels and remobilized by debris-flows or bedload transport. Event-based sediment budget monitoring in the active Manival debris-flow torrent in the French Alps during a two-year period gave insights into the catchment-scale sediment routing during moderate rainfall intensities which occur several times each year. The monitoring was based on intensive topographic resurveys of low- and high-order channels using different techniques (cross-section surveys with total station and high-resolution channel surveys with terrestrial and airborne laser scanning). Data on sediment output volumes from the main channel were obtained by a sediment trap. Two debris-flows were observed, as well as several bedload transport flow events. Sediment budget analysis of the two debris-flows revealed that most of the debris-flow volumes were supplied by channel scouring (more than 92%). Bedload transport during autumn contributed to the sediment recharge of high-order channels by the deposition of large gravel wedges. This process is recognized as being fundamental for debris-flow occurrence during the subsequent spring and summer. A time shift of scour-and-fill sequences was observed between low- and high-order channels, revealing the discontinuous sediment transfer in the catchment during common flow events. A conceptual model of sediment routing for different event magnitude is proposed.

Life between predators and a small space: substrate selection of an interstitial space‐dwelling stream salamander

AbstractPhysical space is a fundamental habitat constraint for interstitial space‐dwelling organisms; however, few studies have examined how physical space variation structures predator/prey interactions within such communities. Streambeds in the western Ozark Plateau are composed of Silurian/Ordovician chert gravel and contain a rich assemblage of interstitial space‐dwelling species, including macroinvertebrates, fishes and aquatic salamanders. Here, we used field and lab experiments to examine interstitial space size preference and structure of an Ozark streambed community, with emphasis on the Oklahoma salamander, Eurycea tynerensis, and its predators (crayfish) and prey (isopods and amphipods). In the field, we implemented a three by six grid of enclosures containing three distinct size classes of well‐sorted substrate (small, medium and large) that represented three categories of interstitial space size. Isopods and amphipods were the most abundant macroinvertebrates at the site, and the average size of isopods increased with substrate size. Salamanders were significantly more abundant in medium‐sized substrate enclosures, whereas isopods of consumable size and amphipods were more abundant in small and medium substrate, and crayfish were found exclusively in large substrate enclosures. Pairwise choice experiments in the lab showed that salamanders always preferred the largest gravel size (i.e. large or medium to small, and large to medium). A subsequent experiment performed with uniformly large gravel demonstrated that salamanders avoided positions near and adjacent to crayfish. We suggest that the finite interstitial space distribution of Oklahoma salamanders is limited by physical constraints of small, prey‐rich spaces, and avoidance of predators and prey scarcity in the interstitial spaces among large substrates. This study demonstrates the strong influence of interstitial space size on community structure and predator/prey interactions in chert‐bottomed Ozark streams.

Modeling flows over gravel beds by a drag force method and a modified S–A turbulence closure

A double-averaged Navier–Stokes equations (DANS) model has been developed for depth-limited open channel flows over gravels. Three test cases are used to validate the model: an open-channel flow over a densely packed gravel bed with small-scale uniform roughness (D/d50∼13, d50=median diameter of roughness elements, D=water depth), open-channel flows over large-scale sparsely distributed roughness elements (D/Δ∼2.3–8.7, Δ=roughness height) and steep slope gravel-bed river flows with D/d50∼7–25. Various methods of treatment of the gravel-induced resistance effect have been investigated. The results show that the wall function approach (WFA) is successful in simulating flows over small gravels but is not appropriate for large gravels since the vertical profile of the longitudinal velocity does not follow the logarithmic–linear relationship. The drag force method (DFM) performs better but the non-logarithmic velocity distribution generated by sparsely distributed gravels cannot be simulated accurately. Noting that the turbulence length scale within the gravel layer is governed by the gravel size, the DANS model incorporating the DFM and a modified Spalart–Allmaras (S–A) turbulence closure is proposed. The turbulence length scale parameter in the S–A model is modified to address the change in the turbulence structure within the gravel layer. The computed velocity profiles agree well with the corresponding measured profiles in all cases. Particularly, the model reproduces the S-shape velocity profile for sparsely distributed large size roughness elements. The modeling methodology is robust and can be easily integrated into the existing numerical models.

The effects of water velocity and sediment size on Acroneuria abnormis (Plecoptera: Perlidae) entrainment

We investigated the roles that velocity and substrate size play in the drift of stonefly larvae (Acroneuria abnormis). Acroneuria were introduced into an experimental flume containing homogeneous substrates of different size (small gravel, large gravel, or cobble), or a mixture of various substrate sizes. For each substrate Acroneuria were subjected to three different velocities (0.3, 0.6 and 0.9 ms−1) corresponding to base flow conditions in real streams, and the number of individuals entrained into the water column was measured. Entrainment was nearly two times higher from the smallest substrates than larger substrates and the heterogeneous mixture of substrate sizes. Higher entrainment from the small particles appeared to result from lower availability of refugia among particles and movement of particles under the higher water velocities. Entrainment generally increased with increasing discharge on small and large, but not intermediate-sized, particles. Our results suggest there may be dynamic Acroneuria entrainment under low flow conditions in streams.

The first record of “spelaeoid” bears in Arctic Siberia

For a long time, “spelaeoid” (cave-bear-like) bears, Ursus ( Spelearctos) spp., were believed to be almost purely European animals. Their geographic range has recently been extended to the east, in southern Siberia, Transbaikalia, Kirghizia, Mongolia and Korea. Two unexpected new findings, presented here in detail, significantly change existing views on the distribution of cave bears; both were found in North-Eastern Siberia, far beyond the Arctic Circle, more than 1500 km to the north-east of the previously accepted range. One of the fossils is a mandible, found near the town of Cherskiy at 68.73°N, 161.38°E. The analysis of local geology and accompanying mammal fossils suggests that it comes from the Olyorian Fauna (Early to early Middle Pleistocene). Morphologically, the Cherskiy mandible is closest to Ursus savini, a small middle Pleistocene cave bear from the British Cromer Forest-bed Formation, but differs in having a slightly more advanced dentition, and thus it is described as a new subspecies Ursus savini nordostensis. Another newly recognized fossil of the “spelaeoid” bear is an astragalus found at the Oskhordokh site at 67.54°N, 135.67°E, on a large gravel bar on the right bank of the Adycha River. This specimen is attributed to Ursus cf . deningeri. The paper also presents an interesting example of the interaction between classical and “molecular” palaeontology. The new finds significantly change existing ideas on the ecology and evolution of cave bears, some of the most remarkable members of the extinct Pleistocene megafauna.

Channel adjustments and vegetation cover dynamics in a large gravel bed river over the last 200 years

The timing and extent of the morphological changes that occurred in the last 200 years in a large gravel bed river (the Piave River, eastern Italian Alps) that was heavily impacted by human activities (training structures, hydropower schemes, and gravel mining) have been analyzed by historical maps, aerial photos, repeated topographic measurements, and geomorphological surveys. Results show that the channel underwent a strong narrowing during the twentieth century, but with a faster pace during the 1970s–1990s and with an associated shift from a dominant braided pattern to a wandering morphology. Bed incision up to 2 m — mostly from gravel mining — has been documented for this period. Large areas of the former active channel were colonized by riparian forests, both as islands and as marginal woodlands. The ceasing of gravel extraction in the late 1990s seems to have determined a reversal in the evolutionary trend, with evidence of vegetation erosion/channel widening even though a significant aggradation phase is not present. We conclude that alteration of sediment regime has played a major role on the long-term channel evolution. However, only relevant flood events ( RI > 10–15 years) appear to determine substantial island erosion, and therefore the proportion of island vs. channel area fluctuates depending on flood history.

The importance of anchors

Recently my son and I were fishing our favorite “local” river, which is actually six hours away from home. The fishing was spectacular and the day very beautiful. We were standing on a large gravel bar, where the water was sweeping almost directly toward the middle of the river from an eddy next

Life-History Attributes of the Imperiled Frecklebelly Madtom,Noturus munitus(Siluriformes: Ictaluridae), in the Cahaba River System, Alabama

Noturus munitus (Frecklebelly Madtom) is a diminutive catfish with a disjunct distribution across the southeastern United States in large rivers and tributaries of the Mobile Basin and Pearl River drainage. Its distribution has contracted since extensive river modification began throughout its range in the 1960s, and it is likely extirpated from the Alabama River. We collected 242 specimens of N. munitus from a gravel island in the Cahaba River on the Coastal Plain in Alabama from May 2005 to March 2007 to examine life-history characteristics. Adults were associated with fast flow over large gravel at depths of 0.5–1.0 m. Young (<23 mm) were found at water depths of 0.4–0.5 m. Gonad development indicated a reproductive season from May to August, with collection of young-of-the-year in June and July supporting a mid- to late-summer spawn. Stomach content analysis revealed a diet similar to other Noturus species and dominated in volume by Baetidae nymphs (31.2%), Hydropsychidae larvae (20.3%), and Simuliidae larvae (19.7%). Some seasonal and sex differences in diet were apparent. Relative fecundity data indicate that N. munitus is one of the most fecund madtoms of the subgenus Rabida (mean of 30.6 mature oocytes) studied thus far. Few males were found in riffles during summer, and no young were found in riffles outside summer, indicating potential sex and size differences in seasonal habitat use. This knowledge is important for conservation of the species.

Mapping spatial distributions and uncertainty of water and sediment flux in a large gravel bed river reach using an acoustic Doppler current profiler

Spatial distributions of depth‐averaged water velocity, shear velocity, and apparent bed load velocity are mapped for the first time in a long reach of a wandering gravel bed river, lower Fraser River, British Columbia. Spatially intensive acoustic Doppler current profiler (aDcp) measurements were collected on the falling limbs of two freshets. Flow in the first year was near the threshold of motion, whereas in the second year discharge exceeded bankfull. Spatial distributions are interpolated from the point data using kriging. Joint density functions for shear velocity and flow depth throughout the reach are presented; marginal densities for shear velocity were near normally distributed but depth distributions were positively skewed by deep pools. The uncertainty of the spatial distributions is also assessed based on modeled temporal variability of the flow and bed load transport, measured aDcp error velocities, and calculated interpolation errors. The resulting maps are remarkably coherent, with maximum depth‐averaged velocity, shear velocity, and apparent bed load velocity following the thalweg. Largest values occur in channel bends at zones of flow convergence where the thalweg flow accelerates toward the bank. However, in the lower flow year the highest apparent bed load velocity was observed outside the thalweg in a deep pool downstream of a rapidly eroding cut bank. Erosion at this site was related to a flow confluence with relatively low shear but highly turbulent, strongly three‐dimensional separated flow.

The spatial structure of local surficial sediment characteristics on Georges Bank, USA

Georges Bank is one of the world’s most productive marine ecosystems, but the lack of accurate broad-scale sediment maps presently limits habitat assessments and spatial fisheries management. From 1999 to 2009 we surveyed 36,669 km 2 of Georges Bank using 2.8 and 0.6 m 2 quadrats viewed with live underwater video (video quadrats). The sediment types observed in 61,604 quadrats were used to map and evaluate spatial structure of local surficial sediment coarseness, dominance, heterogeneity, and maximum size characteristics at a 1 km 2 spatial resolution. Sand dominated sediment covered 62% of the study area, and there was a logarithmic decline in coverage by larger, coarser and more heterogeneous sediments. Gravel dominated sediments covered 38% of the study area and were more than twice as abundant as previously estimated. A 12,890 km 2 swath of gravel dominated seabed stretched from Cape Cod to northeastern Georges Bank consistent with estimates of prehistoric glacial extent. Within the swath there were 14 large gravel outcrops (15–2743 km 2) . This work increases the spatial resolution of sediment information available for habitat assessments and spatial fisheries management on Georges Bank by two orders of magnitude. The four sediment characteristics we evaluated support further detailed investigations of the Bank’s benthos, including the influences of surficial sediment characteristics on species and community distributions, and more spatially accurate estimates of seabed roughness. Finally, this work demonstrates the use of video quadrats as an alternative to traditional grab sampling and modern acoustic sampling for continental shelf-scale mapping.

Changes with Growth in Feeding Habits and Gravel Turning Behavior of the Wrasse, Coris gaimard

Ontogenetic changes in the diet and foraging behavior of the wrasse, Coris gaimard, were studied on shallow reefs at Kuchierabu-jima Island, southern Japan. C. gaimard selected larger prey with growth, smaller individuals feeding on small crustaceans (e.g., gammarideans) and larger ones feeding on larger molluscs (i.e., pelecypods, gastropods and chitons) and crabs. Although C. gaimard usualIy took prey from the surface of the substrate, individuals of 5 cm TL and over also foraged for prey under gravel by turning over the latter. The relative frequency of gravel turning and size of gravel turned over increased with growth, larger fish being able to take correspondingly larger prey (e.g., molluscs and crabs) hiding under larger gravel

The Occurrence and Persistence of MTBE in Groundwater in Windham, Maine, USA

A study was conducted from July 1998 through November 2007 on the occurrence and distribution of the fuel oxygenate methyl tert‐butyl ether (MTBE) in a large sand and gravel aquifer located in southern Maine. MTBE was detected in 44% of 129 water samples collected from monitoring wells in concentrations up to 38.7 µg/L (reporting limit = 0.1 µg/L). The number of wells with detectable quantities of MTBE declined slightly between 1999 and 2007, but in general MTBE persisted throughout the period of study. Overall, MTBE was detected more frequently in the shallow and more transmissive parts of the aquifer. There was a statistically significant difference (p &lt; 0.001) for MTBE concentrations relative to nearby land uses. MTBE was detected in 83% of the samples collected from wells in low‐density residential areas, in 50% of samples from urban areas, and in 60% of samples from undeveloped areas. The concentrations of MTBE in the test wells were compared across the sample dates for trends and seven wells had a positive trend (Mann–Kendall statistic), but none was significant at p &lt; 0.05. Nine wells had a negative trend, but only one was significant at p &lt; 0.05. Three wells had no trend. The absence of strong or even consistent trends indicates that MTBE persists in shallow groundwater, even after gasoline formulations were changed to reduce or eliminate MTBE.

Substrate choice of territorial male Topeka shiners (Notropis topeka) in the absence of sunfish (Lepomissp.)

Abstract – Topeka shiners (Notropis topeka), an endangered minnow species, typically spawn on or around breedingLepomissunfish (Centrarchidae) nests. Why spawning Topeka shiners are attracted to these nests is unclear, but having the nesting sunfish provide shiner eggs with improved aeration, a lessening of siltation, and protection from egg predators are possibilities. We tested the substrate utilisation of Topeka shiners in outdoor tanks in the absence of sunfish to determine the shiner’s fundamental choice. Shiners were provided with substrate patches of cleaned sand, small gravel, large gravel, and small cobble, and the bare floor of the tank. The substrate above which a male shiner established his territory was used as evidence of choice. A statistically significant choice for sand substrates was demonstrated. This fundamental choice might influence which sunfish nests Topeka shiners use, given that nest substrate characteristics differ both between sunfish species and within species by spawning site location.

Toxicity of Chromium on Nitrogen and Biodegradable Compound Removal in Vertical Flow Constructed Wetlands

The objective of this study is to investigate the removal efficiencies of Chromium (Cr), Nitrogen and biodegradable organic compounds, as well as its interference of each other in vertical flow constructed wetlands with different bed media. Four laboratory-scale vertical flow constructed wetland (CW) units, each with dimensions of 750 x 635 m (diameter x height), were installed with different bed media: CWc2 with 200 100, lOOand 150 mm of charcoal, sand, small gravel and large gravel; CWci with 100, 200,100 and 150 mm of charcoal, sand, small gravel and large gravel; CWco and CWControl with 200, 200 and 150mm of sand, small gravel and large gravel. Typha Angustifolia (Cattails) were planted at initial density of 50 shoots./m2 in CWci, CWc2 and CWco units and fed with domestic wastewater spiked with Cr at the concentrations ranging from 10 to 100 mg/L at the Hydraulic Retention Time (HRT) of 4 days. Samples from CW units were taken once in 3 days throughout 115 days of operation for analysis of total Cr, nitrogen, pH. In addition, N accumulated in the plant biomass (roots and shoots) were analysed to identify the Cr toxicity for plant uptake of Nitrogen. For influent concentrations up to 30 mg/L, it was found that Cr mass removal efficiencies for all CW units were 99-100 %, resulting effluent concentrations below the industrial effluent standard which is 2 mg/L. Beyond 30 mg/L influent Cr concentrations, it was apparent that the CW unit with thick charcoal layer met the industrial effluent standard, even at an influent Cr concentration of 100 mg/L. Experimental data revealed that the CW units with charcoal layers could result in COD and N removals of 82 - 92 % and 57 - 87%, respectively. Possibly due to the inhibitory effect of Cr on N plant uptake, the N removal in CW units were decreased rapidly with increasing Cr loading. On the contrary, the increase in Cr loading did not affect the COD removal efficiencies in CW units.

Facies and ground‐penetrating radar characteristics of coarse‐grained beach deposits of the uppermost Pleistocene glacial Lake Algonquin, Ontario, Canada

AbstractThe lithofacies of the uppermost Pleistocene (ca 11 800 to 10 400 14C yr bp), cold‐temperate, coarse‐grained beach deposits of Lake Algonquin, the precursor of the present Lake Huron of North America, have been studied and interpreted based on analogous features of modern beaches from the same region. Ice foot and ice‐cementation develop during winter but, unlike Arctic beaches, ice‐related sedimentary features are seldom, if ever, preserved in the Pleistocene and recent deposits of the Great Lakes. Instead, the deposits retain the typical characteristics of wave‐dominated, pure gravel and mixed sand and gravel beaches, there including the classical subdivision of infill zone, swash zone/sand run, imbricated zone, coarse flat‐clast zone and coastal dunes. These zones form a regular succession on the surface of many modern beaches; however, they seldom occur as quasi‐complete vertical successions in older deposits. In the studied uppermost Pleistocene deposits, the various components are separated vertically by erosional contacts (bounding surfaces) readily recognizable on working faces of large sand and gravel pits and mappable in the subsurface by ground‐penetrating radar. The lithofacies are sufficiently diagnostic to allow recognition of depositional settings, and the lithofacies architecture allows the deciphering of important geological events, such as: (i) local input of fluvial material onto the shoreface, where it was partially reworked by waves and moved onto the beachface; (ii) occurrence of major storm events; and (iii) repeated rapid transgressions and regressions typical of the glacial‐lake precursors of the modern Great Lakes.

Do parafluvial zones have an impact in regulating river pollution? Spatial and temporal dynamics of nutrients, carbon, and bacteria in a large gravel bar of the Doubs River (France)

The changes in both physical and chemical properties of interstitial water were investigated within a large gravel bar to determine if the parafluvial zone was a hotspot for nutrient transformations in a lowland eutrophic river, the Doubs (Eastern France). Interstitial water was sampled in 30 piezometers along five transects across the gravel bar, surface water was sampled in main and chute channels. Five campaigns of sampling were performed among summer and winter. In both interstitial and surface samples, water chemistry (electrical conductivity, pH, chloride, dissolved oxygen concentrations—DO) and nutrient concentrations (nitrate—NO3 −, ammonium—NH4 +, soluble reactive phosphorus—SRP, dissolved organic carbon—DOC) were measured. Moreover, temperature, water level, sediment grain size distribution and total bacterial abundance were assessed along a flowpath through a lateral gravel bar of the Doubs River. Measurements of water table elevation in the bar, main and chute channels indicated that the parafluvial flowpath was perpendicular to the main channel. Very low changes in chloride concentration and electrical conductivity showed minor groundwater input along the flowpath. The parafluvial zone was 0.9 m thick under the mean piezometric level, hydraulic gradients along the flowpath were 0.3%, and the discharge of interstitial water through the bar calculated at low flow was 40.6 m3 day−1. Most changes in interstitial nutrients occurred during the warm season, suggesting that biotic mechanisms occurred. Along the flowpath, DO, DOC, and bacterial abundance declined, while phosphate increased. Temporal trends of nitrate were less clear, exhibiting a slight increase during spring (organic matter biodegradation) and a decrease during summer (denitrification). Using the parafluvial discharge and nutrient concentrations of water infiltrating into and seeping from the gravel bar, the retention capacity of the bar was 171 gC day−1 for DOC and 48.3 gN day−1 for nitrate. Phosphate production ranged from 0.65 to 2.3 gP day−1. These values were low compared to the nutrient fluxes in the river Doubs, suggesting a minimal local impact of the parafluvial zone in regulating of river pollution.

Movements by Adult Coho Salmon in the Lower Elwha River, Washington

Abstract The Elwha and Glines Canyon dams caused a dramatic decline in the numbers of all species of native Pacific salmonids (Oncorhynchus spp.) in the Elwha River. During the fall of 2005 and 2006, we radiotagged 49 adult coho salmon (O. kisutch) and tracked their movements between the Elwha River mouth and Elwha Dam (7.3 rkms). Half of all tagged fish were never relocated, likely due to emigration from the river. The remainder tended to migrate quickly and directly to one or two areas saturated with large woody debris and gravel, known to be high quality spawning habitat, and remain there. However, 7 of the 13 tagged fish in 2005 made multiple upstream and downstream movements prior to spawning. No tagged fish in either year migrated farther upstream than a rock weir approximately 4.9 km from the river mouth and 2.4 km downstream from the Elwha Dam, possibly indicating a migration barrier for coho salmon. We did not detect qualitative differences in migration behavior between hatchery and unknown-origi...

Cardiopulmonary Bypass and Bronchoscopy for Removal of Large Gravel in the Bronchial Tree

Freemyer, Ryan MD; Mclean, Susan MD, FACS; Tyroch, Alan MD, FACS; Santoscoy, Robert MD, FACS Author Information