Gravel Sites Research Articles

Štěrky na rozvodí Dyje a Pulkau jižně od Znojma (Česko–Rakousko): nové poznatky ve srovnání s dosavadním stratigrafickým zařazením

A thin veneers of coarse gravel deposits (clast size up to > 15 cm) are preserved on many summits of the Dyje–Pulkau watershed upland on the Carpathian Foredeep surface near the Bohemian Massif in the area, where the Waitzendorf fault parallels the boundary between both the large geological units. Related rim of the latter unit is there topographically manifested by the current prominent marginal slope mostly developed in granitoids of the Dyje Massif. In the existing maps and corresponding explanatory notes the northwestern occurrences of the gravel were considered, without direct stratigraphic evidence, as marine deposits of the Lower Badenian or uppermost Karpatian age (Lower/Middle Miocene transition). This paper revises the assumed genesis and stratigraphic position of the gravel based on pebble grain size and petrography analysis, assessment of geomorphological setting, and comparison with other gravel deposits in the vicinity characterized by some similar properties. The study of pebble material on the watershed upland revealed an existence of two adjacent WNW–ESE trending gravel belts of different petrography: the southern with only dominant quartz-rich rocks and the quartz-rich northern but with a high portion of the Dyje Massif rocks. Gravel characteristics and its position above fine-grained Carpathian Foredeep sediments in the basement deposited in the Lower/Middle Miocene transition period (lower stratigraphic limit) indicate a later terrestrial origin of both the gravel belts by two adjacent streams flowing from the WNW towards the ESE and largely redeposi­ting coarse material eroded in older layers at former margin of the foredeep basin. In the southern and northern surroundings of the watershed upland a number of other gravel sites are preserved near or within the marginal slope whose coarse pebbles also overlay fine-grained basement clastic sequences of the Carpathian Foredeep. Their mutually different petrographic properties also indicate dissimilar source areas within marginal part of the basin presumably located in the WNW or NW, thus supporting quite uniform material transport direction in many subparallel traces. The general regional transport seems to be largely interrupted by a renewed activity of the Waitzendorf fault system predisposing the Bohemian Massif uplift against the current Carpathian Foredeep. A related strong stream incision into the uplifted surface included a newly created SW–NE reach of the Dyje river within the marginal slope between the Šobes meander and the town of Znojmo whose origin presumably started in the (Lower) Pliocene (higher stratigraphic limit) based on the supposed age of sedimentary remnants preserved within higher parts of the corresponding valley section. Thus the deposition of gravel at the Dyje–Pulkau watershed finished before or shortly after the uplift and the valley incision began. Genesis and stratigraphic position of the focused coarse sediments is likely different from those in the previous considerations.

Endophytic nitrogen fixation - a possible 'hidden' source of nitrogen for lodgepole pine trees growing at unreclaimed gravel mining sites.

Lodgepole pine (Pinus contorta var. latifolia) trees have been thriving on unreclaimed gravel mining sites in British Columbia, Canada, with tissue nitrogen-content and growth-rate unaffected by extremely low soil nitrogen-levels. This indicates that pine trees could be accessing a hidden nitrogen source to fulfill their nitrogen requirements - possibly via endophytic nitrogen-fixation. Endophytic bacteria originally isolated from native pine trees growing at gravel sites were selected (n = 14) for in vitro nitrogen-fixation assays and a year long greenhouse study to test the overall hypothesis that naturally occurring endophytic nitrogen-fixing bacteria sustain pine tree growth under nitrogen-limited conditions. Each of the 14 bacteria colonized the internal tissues of pine trees in the greenhouse study and fixed significant amounts of nitrogen from atmosphere (23%-53%) after one year as estimated through 15N isotope dilution assay. Bacterial inoculation also significantly enhanced the length (31%-64%) and biomass (100%-311%) of pine seedlings as compared to the non-inoculated control treatment. In addition, presence of the nifH gene was confirmed in all 14 bacteria. Our results support the possibility that pine trees associate with nitrogen-fixing bacteria, capable of endophytic colonization, to survive at unreclaimed gravel mining pits and this association could potentially be utilized for effective reclamation of highly disturbed sites in a sustainable manner.

Invasive tunicate restructures invertebrate community on fishing grounds and a large protected area on Georges Bank

Marine invasive species can profoundly alter ecosystem processes by displacing native species and changing community structures. The invasive tunicate Didemnum vexillum was first found on the northern edge of Georges Bank in 1998. It can form encrusting colonies on gravel substrates that are also a preferred habitat for a number of other invertebrates. In this study we used data collected via HabCam, a vessel-towed underwater imaging system, to investigate the distribution of D. vexillum and its relationship to other epibenthic macroinvertebrates in a portion of Georges Bank that includes fishing grounds and an area protected from bottom-fishing. This novel technology provides imaging of epibenthic species distributions in areas of the benthic environment that were previously unobservable. We found that D. vexillum density is negatively correlated with the Atlantic sea scallop (Placopecten magellanicus), barnacles (genus Balanus), the tube anemone (genus Cerianthus), the green sea urchin (Strongylocentrotus droebachiensis), the globular sponge of the genus Polymastia, and Bryozoa. However D. vexillum is positively correlated with Cancer spp. Crabs, the tube forming polychaete, Filograna implexa, and Asterias spp. sea stars. The hypothesis that D. vexillum restructures the invertebrate community is supported by principal components analysis, revealing it as a primary driver of variation in the community when present. Additionally, there is an effect of the closed area as compared to fishing grounds on the structure of the invertebrate community and the abundance of certain species as consistent with previous studies, bottom-fishing affects invertebrate community structure. Principal components analysis revealed that bottom-fishing also appears to weaken clustering among species in the invertebrate community as compared to the community structure in the closed area. Biodiversity in high gravel sites of the epibenthic environment, as measured by the Shannon diversity index, also declined with increasing D. vexillum percent cover, while the open and closed areas were not significantly different in their level of biodiversity. D. vexillum appears to be the key driver of biodiversity decline in the epibenthos when present, rather than other processes such as direct disturbance and extraction from dredging. This research evaluates ecological responses to the presence of an invasive tunicate and suggests that this invasive species is a major force in shaping the ecological interactions in invaded areas.

Estimation of S-Wave Velocity Profiles at Lima City, Peru Using Microtremor Arrays

Microtremor exploration was performed around seismic recording stations at five sites in Lima city, Peru in order to know the site amplification at these sites. The Spatial Autocorrelation (SPAC) method was applied to determine the observed phase velocity dispersion curve, which was subsequently inverted in order to estimate the 1-D S-wave velocity structure. From these results, the theoretical amplification factor was calculated to evaluate the site effect at each site. S-wave velocity profiles at alluvial gravel sites have S-wave velocities ranging from ∼500 to ∼1500 m/s which gradually increase with depth, while Vs profiles at sites located on fine alluvial material such as sand and silt have Swave velocities that vary between ∼200 and ∼500 m/s. The site responses of all Vs profiles show relatively high amplification levels at frequencies larger than 3 Hz. The average transfer function was calculated to make a comparison with values within the existing amplification map of Lima city. These calculations agreed with the proposed site amplification ranges.

Survey of the Levels of some Heavy Metals in Roadside Dusts along Katima Mulilo Urban Road Construction, Namibia

Roadside dusts pollutions with heavy metals continue to attract attention as more anthropogenic activities including urban road construction impacted on the natural metal loads of the environment. This study employed analytical procedures to investigate the concentrations of arsenic, lead, chromium, cadmium, cobalt, copper, nickel, manganese, vanadium, iron and tin in the roadside dusts along Katima Mulilo urban road construction. Replicate dusts samples collected from three different areas of the road and a quiet residential area (control) were digested by EPA method 3050B followed by Inductively Coupled Plasma-Optical Emission Spectrophotometer (ICP: Perkin Elmer Optima 7000 DV) analysis. The results of levels of the heavy metals revealed that iron recorded the highest concentration of 7491.13±0.15 mg/kg along the road construction while tin recorded the lowest value (0.27±0.13 mg/kg). Similar trend was observed at the control area located 1.5 km away from the road: iron recorded the highest concentration of 2327.17±0.12 mg/kg while tin recorded the lowest concentration (0.20±0.10 mg/kg). The analysis of variance of the heavy metal concentrations across the sample locations were statistically significant (p > 0.05). However, the levels of the heavy metals recorded cross the sampling areas were less than their soil maximum permissible concentrations. There are strong positive inter-elemental correlations between the sampling areas while result of the soil enrichment factors showed significant enrichment; which are related to common and input from anthropogenically induced sources respectively. The results of single element pollution indexes of the heavy metals showed low contaminations but elevated levels of arsenic and cadmium in all the sampling areas. These could become a potential source of health concern following environmental accumulation and non-biodegradation of the heavy metals. Thus, it is recommended among others that an environmental impact assessment should be carried out on gravel sites to be used in urban road construction to limit heavy metal contaminations of roadside dusts following their usage.

Host removal as a potential control method for Phytophthora cinnamomi on severely impacted black gravel sites in the jarrah forest

SummaryRemoval of living plants from an area of Eucalyptus marginata (jarrah) forest on black gravel sites infested with Phytophthora cinnamomi significantly reduced subsequent pathogen recovery. Vegetation, including trees and annual and herbaceous perennial plants, was killed on the sites by herbicide application. To determine whether this treatment efficiently eliminated P. cinnamomi, soil samples were seasonally collected and baited to test for the presence of the pathogen. There were no recoveries on treated sites in autumn, 28 months after removal of all vegetation by herbicide application. To test whether this was the result of the complete elimination of the pathogen or whether inoculum remained, regrowth on sites was not controlled after this period leading to the re‐establishment of annual and herbaceous perennial species, some of which are hosts of P. cinnamomi. Recovery of P. cinnamomi after plant regrowth on the formerly treated sites indicated that for complete pathogen removal, sites need to remain free of vegetation for longer than 28 months. Overall, however, this study confirms that the pathogen is a weak saprophyte, and withdrawal of host material for a period of time may make eventual rehabilitation of these sites possible.

Annual and herbaceous perennial native Australian plant species are symptomless hosts of Phytophthora cinnamomi in the Eucalyptus marginata (jarrah) forest of Western Australia

Resistant annual and herbaceous perennial plant species were identified as key hosts which allow Phytophthora cinnamomi to persist on severely impacted black gravel sites within the Eucalyptus marginata (jarrah) forest of southwest Western Australia. Of the annual and herbaceous perennial plant species present on black gravel sites, 15 out of 19 species were found to be hosts of P. cinnamomi, and 10 of these were symptomless hosts. In particular, the native annual Trachymene pilosa and the two native herbaceous perennials Stylidium diuroides and Chamaescilla corymbosa were commonly found to be hosts of the pathogen. Species from 12 new genera including three from new families (Crassulaceae, Droseraceae and Primulaceae) are reported for the first time to be hosts of P. cinnamomi. The species from which P. cinnamomi was recovered were the native species: Chamaescilla corymbosa, Crassula closiana, Drosera erythrorhiza, Hydrocotyle callicarpa, Levenhookia pusilla, Paracaleana nigrita, Podotheca angustifolia, Pterochaeta paniculata, Rytidosperma caespitosum, Siloxerus multiflorus, Stylidium diuroides and Trachymene pilosa, and the introduced annual weeds Hypochaeris glabra, Lysimachia arvensis and Pentameris airoides.

Environmental Impact of Flooding in the Main (Smallwood) Reservoir of the Churchill Falls Power Plant, Labrador, Canada . III. Environmental Impact Zones and Direct and Indirect Changes.

The Churchill Falls Hydro Project (called the ‘Upper Churchill Development’) in Labrador [CF(L)Co], was initiated in the late 1960s. At that time, in general, not much attention was paid to the impact of such development on the flooding of vegetation, especially forest stands. Both forested and un-forested terrestrial vegetation types were flooded (244,915 ha creating some 74,075 ha of Islands) in the construction of the Main (Smallwood) Reservoir. The effect of flooding and of the constructions, both above and below the Main Reservoir major dyke system, were the subject of our investigation. This paper, the third in a series, reports on the effect of building the dykes during the early phases of construction with the descriptions of the post flooded conditions below the dykes as related to vegetation. The direct disturbances were excavations, fills, and partial and /or total removal of vegetation cover from fabrication platforms and from gravel and rock extraction sites. No new vegetation cover established in the abandoned quarries and gravel pits. However camp sites and manufacturing platforms were subsequently taken over by Alder growth. The indirect disturbances were the flooding of land areas and the de-watering of sections of the original river and lowering of the water level in some lakes. The results of flooding and the de-watering of some nearby areas are illustrated with aerial photographs and figures showing the environmental impact zones and new shore line development. The flooded trees in large and small pools of stagnant water died suddenly and remain in their original place. New vegetation cover developed on the exposed shore lines of de-watered rivers and lakes.

Gravel Addition as a Habitat Restoration Technique for Tailwaters

AbstractWe assessed the efficacy of passive gravel addition at forming catostomid spawning habitat under various flow regimes in the Cheoah River, a high‐gradient tailwater river in North Carolina. The purpose was to provide a case study that included recommendations for future applications. A total of 76.3 m3 (162 tons) of washed gravel (10–50 mm) was passively dumped down the streambank and into the channel in four locations. Gravel sites differed in terms of average reach slope, bank slope, and the initial volume of gravel added, which could have influenced gravel entrainment. Maps of gravel movement under various flows suggested that large‐magnitude discharges (≥113 m3/s) caused extensive migration; however, less obvious, smaller discharges (∼28 m3/s) still caused substantial shifting, which may influence the stability of catostomid spawning substrates. Following gravel addition, the proportion of gravel in the streambed was significantly higher at all gravel sites. However, comparisons of sites to reference stream reaches suggested that sand, gravel, and cobble were still extremely deficient. Additionally, the volume of gravel was inadequate to create gravel depths that provided suitable habitat for catostomid spawning. Although periodic, passive gravel additions may take years to provide suitable spawning habitat for some fish species, we found that river chub Nocomis micropogon utilized the newly added gravel for spawning.

Fugitive Dust Emission Source Profiles and Assessment of Selected Control Strategies for Particulate Matter at Gravel Processing Sites in Taiwan

Particles emitted from gravel processing sites are one contributor to worsening air quality in Taiwan. Major pollution sources at gravel processing sites include gravel and sand piles, unpaved roads, material crushers, and bare ground. This study analyzed fugitive dust emission characteristics at each pollution source using several types of particle samplers, including total suspended particulates (TSP), suspended particulate (PM10), fine suspended particulate (PM2.5), particulate sizer, and dust-fall collectors. Furthermore, silt content and moisture in the gravel were measured to develop particulate emission factors. The results showed that TSP (<100 µm) concentrations at the boundary of gravel sites ranged from 280 to 1290 µg/m3, which clearly exceeds the Taiwan hourly air quality standard of 500 µg/m3. Moreover, PM10 concentrations, ranging from 135 to 550 µg/m3, were also above the daily air quality standard of 125 µg/m3 and approximately 1.2 and 1.5 times the PM2.5 concentrations, ranging from 105 to 470 µg/m3. The size distribution analysis reveals that mass mean diameter and geometric standard deviation ranged from 3.2 to 5.7 µm and from 2.82 to 5.51, respectively. In this study, spraying surfactant was the most effective control strategy to abate windblown dust from unpaved roads, having a control efficiency of approximately 93%, which is significantly higher than using paved road strategies with a control efficiency of approximately 45%. For paved roads, wet suppression provided the best dust control efficiencies ranging from 50 to 83%. Re-vegetation of disturbed ground had dust control efficiencies ranging from 48 to 64%.

The Value of Comparing an Energy Management Program with Those in Other Industries

Lafarge North America, a large producer of cement and construction materials with an annual capacity of over 20 million tonnes, operates 19 cement manufacturing plants in Canada and the U.S, as well as five grinding facilities. The company's production represents over 35 percent of Canadian and 12 percent of U.S. cement industry capacity. Cement is sold primarily for the manufacturing of ready-mix concrete manufacturing and other concrete products. Lafarge's significant construction material activities include manufacture and sale of ready-mix concrete, construction aggregates, other concrete products, and asphalt and road constructions. The company has operations at more than 450 locations, and aside from cement and ready-mix plants includes quarry, sand and gravel sites, asphalt plants, and concrete plants. Energy management is an important part of the operation of Lafarge's Cement Division. This article will describe the current Lafarge energy management program by focusing on its successes, challenges, sustainability, organization, and people mobilization. It will examine Lafarge's goals for energy management and the challenges in achieving them. Finally, an analysis of the similarities of criteria for success in energy management between Lafarge, 3M, and Corning will be presented. The comparison will demonstrate the value of cross-industry comparisons and their ability to improve energy management among diverse businesses.

Allometric relationships and dendroecology of the dwarf shrubDryas integrifolianear Churchill, subarctic Manitoba

Shrubs have generally been overlooked in dendrochronology, and little information exists on allometric relationships in dwarf shrubs. Dryas integrifolia M. Vahl. has been recognized as an important species in revegetation of disturbed gravel pits in northern areas. In this study, the dimensions (mat, stem, and root) of D. integrifolia shrubs were measured in four populations having recolonized disturbed areas, and anatomical slides containing growth rings were prepared for each individual. The first objective was to compare allometric relationships among descriptors of shrub dimension and between these descriptors and shrub age. Secondary objectives included documenting maximum age and evaluation of the potential for cross-dating among shrubs. Strong, consistent allometric relationships between aboveground dimensions were observed among individuals from all sites, although growth rates varied within and between sites. This indicated that even though aboveground shrub dimensions grow proportionally to one another, these measurements cannot be used to infer age, because of differences in growth rates among D. integrifolia shrubs. However, numerous cross-sections from D. integrifolia shrubs could be successfully cross-dated, and a short chronology was developed. The radial growth – climate association was found to be similar to that of dominant tree species of the region regarding the impact of October conditions. Increased snowfall in October prior to and warm May temperature during the year of ring formation appear to restrict growth of these shrubs by altering the onset of the growing season. This study has demonstrated that it is possible to accurately date D. integrifolia shrubs, and this ability may be applied to future studies involving population dynamics and remediation of open gravel sites. Growth rings also have the potential to be used in other Arctic shrubs.

Characteristics and Emission Factor of Fugitive Dust at Gravel Processing Sites

Particles emitted from gravel processing sites have severely worsened ambient air quality. This study analyzed the fugitive dust emission characteristics at selected pollution sources using several kinds of particle samplers, including TSP, PM10, PM2.5, and dry deposition plate. It is the first attempt to modify emission factors of AP-42 with a systematical study, utilizing domestic information under dimensionless analysis at the gravel processing sites. Results showed that TSP concentrations at the boundary of gravel sites ranged from 280 to 1,290μg/m 3 . Moreover, PM10 concentrations ranged from 135 to 550μg/m 3 which were 1.2 - 1.5 times PM2.5 concentrations, which ranged from 105 to 470 μg/m 3 . Emission of unpaved roads accounted for about 45 - 55% of the total emission at the gravel processing sites. The silt and moisture content of gravel/sand/dust affected the emission rate of each emission source and ranged from 0.1 to 8.3 % for silt and from 0.6 to 14 % for moisture. After statistical analysis using the least square method, the domestic emission factors of four main emission sources were developed. Furthermore, the size coefficient of emission factors for TSP, PM10, and PM2.5 emission rate estimation equation were also determined in this study.

Dispersion of gold in stream sediments in the Sungai Kuli region, Sabah, Malaysia

The distribution of Au in a Au-rich tributary of the Sungai Kuamut, Sabah, Malaysia, was studied initially by the authors in 1999 prior to disturbance of the tropical rain forest by logging. That study found: (i) a strong but extremely erratic Au anomaly with median values of 230 to 690 ppb in the fine and medium sand sized fractions from both cobble and gravel sites; and (ii) Au values typically &lt;15 ppb in the −53 μm fraction. It was suggested that increased input of fine sediment into the stream after logging might substantially dilute and modify the Au anomaly. Logging of the drainage basin in 2000–2001 provided an opportunity to test this possibility. Results from sampling at gravel sites in 2001 show no dilution of Au values after logging. This is attributed to the occurrence of rainfall and flood events that counteracted dilution of the anomaly by releasing deeply buried Au and/or flushing excess fine sediment from the stream channel. It is concluded that the strength of Au anomalies in stream sediments is likely to fluctuate as a result of the interactions of rainfall events, stream discharge, and the effects of land disturbance on erosion.

Shell gravel deposits on the Åland Islands, southwestern Finland, with special reference to the molluscan assemblages

Twenty‐six shell gravel sites at elevations between 3 and 35 m a.s.l. were found on the Åland Islands. The faunal composition was determined on 14 of these locations and Mytilus edulis and Macoma balthica were found everywhere. Another common species was Hydrobia ulvae, while H. ventrosa, Littorina saxatilis and Cerastoderma glaucum were more sporadic. This species assemblage implies that the salinity of the area was about 10C when the animals lived there. The deposits on the N‐NE hilltops generally have southerly to westerly aspects, while those of the south‐central hilltops are easterly. On the basis of a 14C‐dated stratified deposit it is suggested that each deposit was formed during a relatively short period of time. As a hilltop emerged from the sea, glacial debris was flushed down. Shell‐bearing molluscs colonized the bare rock surface and were flushed down and formed the shell gravel deposit as the shoreline displacement continued. At a later stage, as the more concave part of the hilltop was subject to wave action, erosion was weaker and the shell gravel deposit was covered by beach sand. Since the hills may be of different elevation, it is concluded that trying to date ancient shorelines from shell gravel deposits is not justified, as each deposit originates from the hill with which it is associated.

Inversion of Strain-Dependent Nonlinear Characteristics of Soils Using Weak and Strong Motions Observed by Borehole Sites in Japan

During the 1995 Hyogo-ken Nanbu earthquake, strong motions with horizontal peak ground accelerations of 507 cm/sec 2 or more, 187 cm/sec 2 , and 126 cm/sec 2 were observed at surface stations of borehole sites at Amagasaki, Takasago, and Nanko in Japan, respectively. We showed qualitative evidence of nonlinear soil response during strong motions at Amgasaki and Takasago, but not at Nanko, using cross correlation and spectral ratio analyses of weak and strong motions. We evaluated soil nonlinearity by inversion for S -wave velocities and frequency-dependent damping factors. The strain-dependence of shear modulus ratios inverted for gravel is larger than that for clay, which is consistent with laboratory test results. In the shear-strain range from about 10 –4 to 10 –3 , the strain dependence of shear modulus ratios inverted for clay and gravel at Amagasaki and Takasago is consistent with empirical relations based on laboratory test results for clay and gravel, respectively. These results support using laboratory estimates of shear modulus ratios to simulate strong motions at clay and gravel sites. The damping factors for gravel inverted from the mainshock at Amagasaki are the largest among the others, but the strain dependence of damping factors are not as significant as that of shear modulus ratios. The reason why the strain dependence of damping factors is not so significant may be because scattering attenuation is relatively dominated in the low-strain range.

Riparian vegetation and island formation along the gravel-bed Fiume Tagliamento, Italy

After more than 300 years of river management, scientific knowledge of European river systems has evolved with limited empirical knowledge of truly natural systems. In particular, little is known of the mechanisms supporting the evolution and maintenance of islands and secondary channels. The dynamic, gravel-bed Fiume Tagliamento, Italy, provides an opportunity to acquire baseline data from a river where the level of direct engineering intervention along the main stem is remarkably small. Against a background of a strong alpine to mediterranean climatic and hydrological gradient, this paper explores relationships between topography, sediment and vegetation at eight sites along the active zone of the Tagliamento. A conceptual model of island development is proposed which integrates the interactions between large woody debris and vegetation, geomorphic features, sediment calibre and hydrological regime. Islands may develop on bare gravel sites or be dissected from the floodplain by channel avulsion. Depositional and erosional processes result in different island types and developmental stages. Differences in the apparent trajectories of island development are identified for each of the eight study sites along the river. The management implications of the model and associated observations of the role of riparian vegetation in island development are considered. In particular, the potential impacts of woody debris removal, riparian tree management, regulation of river flow and sediment regimes, and changes in riparian tree species' distribution are discussed.

1993 Student Professional Paper: Graduate Division: Processes and Rates of Shoreline Bluff Recession at Lake Sharpe, South Dakota

Lake Sharpe is the center of three reservoirs formed by dams built by the U. S. Army Corps of Engineers on the Missouri River in South Dakota in the early 1960's. The design service life of the reservoir is 400 to 700 yr based on the expected rate of shoreline erosion to the boundary of the Federally purchased land. In only 30 yr however, this buffer zone has already been eroded and the shoreline continues to retreat into private land at some locations. Processes of shoreline erosion at Lake Sharpe were observed in the field and correlated to bank geology. Active processes of erosion observed included: slump, block slide, debris flow, toppling, slaking, and gullying. Each process was unique to a single bank material. Long term rates of erosion were measured at representative sites from historical profile surveys conducted by the U. S. Army Corps of Engineers. Total shoreline retreat at each site is not related to bank material or retreat process. Total shoreline losses varied from 28 ft to 622 ft since the filling of the reservoir. This makes an average rate of retreat of 1 to 22 ft/yr. Most sites had a generally constant retreat rate after an initial high rate except the gravel sites where retreat is decreasing in rate. The factor causing the extreme erosion is the ease of erosion of the bank materials and their tendency to stay in suspension until they reach deep water. Because the fine-grained bank materials are carried away in suspension rather than be deposited to form a protective beach, the toe of the bluff is continuously subjected to wave action and retreat continues. Only at the shorelines where there is a significant sand or gravel layer does a protective beach develop to slow the retreat rate.

Microhabitat Variables Influencing Nest‐Site Selection by Tundra Birds

Studies were performed to determine what types of microhabitat characteristics attract the most common bird species to nest at particular sites on tundra habitats in the Prudhoe Bay oil field. Microhabitat variables of 2 x 2 m plots centered on bird nests were measured and compared with those of plots centered on random points. Results indicated differences in amount of microrelief, graminoid and shrub/forb cover, roughness of topography, and presence of water among species. These differences have implications for management of abandoned gravel sites as oil production declines in the Prudhoe Bay oil field. The amount and variability of microrelief plays an important role in influencing nest—site selection. Birds do not require total coverage by graminoid and shrub/forb plant species at nest sites. Water plays an important role by influencing plant growth at disturbed gravel sites.

Management of Northern Gravel Sites for Successful Reclamation: A Review

In the Arctic and Subarctic, roads and other construction projects require large amounts of gravel to provide well-insulated, stable surfaces. Gravel pits create large disturbed, terrestrial areas and produce significant on-site and off-site impacts, at least some of which are long lasting or even permanent. Gravel substrates are difficult to revegetate since they typically have low moisture- and nutrient-holding capacities. There are several possible approaches to maximize the likelihood of successfully reclaiming northern gravel sites: (1) Minimize their areal extent and visual impact; (2) improve the substrate characteristics for plant growth by such measures as erosion control and reuse of topsoil; (3) select adapted biological materials; and (4) proper siting of gravel pits to enhance reinvasion of native plant species. The extreme conditions of most arctic and subarctic sites require site specific approaches. These conditions also increase the need to use native plant species and to utilize their successional strategies to develop appropriate reclamation plans for gravel sites.