Sediment Mobility in the Severn Estuary and its Influence upon the Distribution of Shorebirds

1983 ◽  
Vol 40 (S1) ◽  
pp. s331-s340 ◽  
Author(s):  
Peter N. Ferns
Keyword(s):  
Intertidal Zone ◽  
Weather Conditions ◽  
Intertidal Sediment ◽  
Severn Estuary ◽  
Fine Sediments ◽  
Regional Trends ◽  
Sediment Mobility ◽  
The 1960S ◽  
Muddy Sediments ◽  
Log Linear

In December 1979, superficial muddy sediments were eroded from considerable areas of the intertidal zone of the southern shores of the Severn Estuary during a period of prolonged westerly gales. Shorebird numbers at the affected sites showed an immediate decline as a result of the depletion of their mud-dwelling invertebrate food resources, and there was a corresponding increase in the numbers of birds along the northern shores of the estuary where no such erosion had occurred. Detailed monthly counts of 14 species of shorebirds in the Severn Estuary during 1971/72 to 1975/76 were therefore examined to determine if any of the previously unexplained anomalies in their distribution coincided with weather conditions likely to have given rise to similar losses of intertidal sediment. Although the 5 yr in question were relatively calm compared with the 1960s, there were five individual months during which the mean hourly windspeeds exceeded 13 m∙s−1 on more than 25 occasions. During these periods, the average deviations in the numbers of Shelduck, Grey Plover, Dunlin, Curlew, and Redshank from those predicted by a log-linear model taking seasonal, annual, and regional trends into account, were particularly large. Furthermore, the sites which were involved in each case were those that were directly exposed to the prevailing winds during the windiest periods of the month in question. High winds, by propagating waves that mobilize fine sediments in the intertidal zone, are thus implicated as a significant factor influencing the distribution of some shorebirds.Key words: Severn Estuary, sediment mobility, shorebird distribution, wading birds, local migration

Trends and Variability of North American Cool-Season Extratropical Cyclones: 1979–2019

2021 ◽  
Author(s):  
Robert Fritzen ◽  
Victoria Lang ◽  
Vittorio A. Gensini
Keyword(s):  
North American ◽  
Research Question ◽  
Weather Conditions ◽  
Extratropical Cyclones ◽  
Mountain Range ◽  
Cool Season ◽  
The North ◽  
Primary Driver ◽  
Regional Reanalysis ◽  
Log Linear

AbstractExtratropical cyclones are the primary driver of sensible weather conditions across the mid-latitudes of North America, often generating various types of precipitation, gusty non-convective winds, and severe convective storms throughout portions of the annual cycle. Given ongoing modifications of the zonal atmospheric thermal gradient due to anthropogenic forcing, analyzing the historical characteristics of these systems presents an important research question. Using the North American Regional Reanalysis, boreal cool-season (October–April) extratropical cyclones for the period 1979–2019 were identified, tracked, and classified based on their genesis location. Additionally, bomb cyclones—extratropical cyclones that recorded a latitude normalized pressure fall of 24 hPa in 24-hr—were identified and stratified for additional analysis. Cyclone lifespan across the domain exhibits a log-linear relationship, with 99% of all cyclones tracked lasting less than 8 days. On average, ≈ 270 cyclones were tracked across the analysis domain per year, with an average of ≈ 18 year−1 being classified as bomb cyclones. The average number of cyclones in the analysis domain has decreased in the last 20 years from 290 year−1 during the period 1979–1999 to 250 year−1 during the period 2000–2019. Spatially, decreasing trends in the frequency of cyclone track counts were noted across a majority of the analysis domain, with the most significant decreases found in Canada’s Northwest Territories, Colorado, and east of the Graah mountain range. No significant interannual or spatial trends were noted with bomb cyclone frequency.

scholarly journals Bedforms in a tidally modulated ridge and runnel shoreface (Berck-Plage; North France): implications for the geological record

2018 ◽  
Vol 189 (1) ◽  
pp. 5 ◽  
Author(s):  
Romain Vaucher ◽  
Bernard Pittet ◽  
Sophie Passot ◽  
Philippe Grandjean ◽  
Thomas Humbert ◽  
...  
Keyword(s):  
Intertidal Zone ◽  
Spring Tide ◽  
Experimental Studies ◽  
Weather Condition ◽  
Weather Conditions ◽  
Field Investigation ◽  
Fair Weather ◽  
Coastal System ◽  
The North ◽  
Current Ripples

Tidally modulated shoreface (TMS) corresponds to peculiar costal environments. The general morphology and the expressed bedforms are provided by the interplay of both waves and tides. The recognition of TMS in the fossil record still remains a difficult task. The study of one mega-tidal modern TMS in the north of France (Berck-Plage) provides new key criteria to identify this kind of coastal system in the rock record. Field investigation and digital mapping were realized at lowest tide during spring tide under fair-weather condition. The intertidal zone is characterized by a succession of several sand banks shore parallel separated by topographic lows that are defined as ridges and runnels. Seven distinct dominant bedforms are recognized: 3D current ripples, 3D asymmetrical ripples, 2D symmetrical ripples, 2D small symmetrical dunes, 2D large symmetrical dunes, 3D symmetrical dunes and plane beds. The upper stage plane bedding mainly composed the ridges while the six other bedforms are commonly found within the runnels or on the flanks of the ridges. Comparison of the bedforms of Berck-Plage with previous experimental studies on bedforms genesis proves that the necessary flow parameters for generating these bedforms belong to an oscillatory flow except for the 3D current ripples, which are formed by a unidirectional flow. This study confirms the dominance of oscillatory structures through the intertidal zone in a mega-tidal context and show that wave processes are more powerful than tide processes for bedform generation although during fair weather conditions. Based on the timing of genesis, the description and the repeated pattern of distribution of bedforms between two ridges is highlighted thus helping to propose a theoretical facies sequence for an intertidal zone characterized by ridges and runnels applicable to ancient sedimentary successions.

Formation of mud ridge and runnels in the intertidal zone of the Severn Estuary, UK

2009 ◽  
Vol 29 (16) ◽  
pp. 1913-1926 ◽  
Author(s):  
P.A. Carling ◽  
J.J. Williams ◽  
I.W. Croudace ◽  
C.L. Amos
Keyword(s):  
Intertidal Zone ◽  
Severn Estuary

Method for Identifying Factors Contributing to Driver-Injury Severity in Traffic Crashes

2000 ◽  
Vol 1717 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Wan-Hui Chen ◽  
Paul P. Jovanis
Keyword(s):  
Injury Severity ◽  
Statistical Tests ◽  
Selection Procedure ◽  
Weather Conditions ◽  
Early Morning ◽  
Influential Factors ◽  
Complex Nature ◽  
Crash Data ◽  
Late Night ◽  
Log Linear

Numerous driver, vehicle, roadway, and environmental factors contribute to crash-injury severity. In addition to main effects, interactions between factors are very likely to be significant. The large number of potentially important factors, combined with the complex nature of crash etiology and injury outcome, present significant challenges to the safety analyst, who must select from a large number of factors and specify a comprehensive but feasible set of main factors and interactions for testing in statistical models. In addition, some factors contain a relatively large number of categories (e.g., weather conditions), and the selection of cut-off points for categorization of continuous factors may not be readily obvious (e.g., driver age). It is also important that statistical tests underlying these analyses accurately address the frequent problem of data sparseness. The development and testing of a variable-selection procedure to address each of these problems is the stated objective. Bus-involved crash data for Freeway 1 in Taiwan from 1985 through 1993 were used to screen a set of 39 possible influential factors, along with interactions. The final log-linear model shows that late-night or early-morning driving increases the risk for bus drivers of being severely injured, particularly when the drivers caused the accident or when the drivers were involved in rear-end accidents. Bus accidents involving large trucks or tractor-trailers also increase the risk. An assessment of the importance of considering interactions in crash models is presented as a conclusion.

scholarly journals Transportation and Transformation of Arsenic Species at the Intertidal Sediment-Water Interface of Bohai Bay, China

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Xiaoping Yu ◽  
Yafei Guo ◽  
Qin Wang ◽  
Tianlong Deng
Keyword(s):  
Environmental Conditions ◽  
Intertidal Zone ◽  
Stable State ◽  
Arsenic Species ◽  
Intertidal Sediment ◽  
Bohai Bay ◽  
Diffusive Flux ◽  
Water Interface ◽  
Overlying Water ◽  
Vertical Distributions

Arsenic species including arsenite As(III), arsenate As(V), monomethylarsenate (MMA), dimethylarsenate (DMA), and some diagenetic constituents (Fe, Mn, and S2−) in porewaters along with the unstable arsenic species in sediments collected from a typical intertidal zone of Bohai Bay in China were measured. Their vertical distributions were subsequently obtained to reveal the transportation and transformation characteristics of arsenic at the intertidal sediment-water interface (SWI). Results show that the reduction of As(V) by microorganisms occurred in sediments, but the methylation of arsenic by microorganisms was weak in the intertidal zone. The distribution of As(V) was mainly controlled by Mn, whereas As(III) appeared to be more likely controlled by Fe. Arsenic in sediments mainly existed in a stable state, so that only little arsenic could be released from sediments when the environmental conditions at the SWI are changed. As(III) diffused from porewaters to the overlying water while the opposite was true for As(V) at that time when the samples were collected. The total diffusion direction for arsenic across the SWI was from porewaters to the overlying water with a total diffusive flux estimated at 1.23 mg·m−2·a−1.

Integrated water quality and environmental cost-benefit modelling for the management of the River Tame

1999 ◽  
Vol 39 (4) ◽  
pp. 213-220 ◽  
Author(s):  
Bob Crabtree ◽  
Matt Hickman ◽  
Dave Martin
Keyword(s):  
Water Quality ◽  
Cost Benefit ◽  
Weather Conditions ◽  
Environmental Cost ◽  
Northern Portion ◽  
Wet Weather ◽  
The 1960S ◽  
The Uk ◽  
Water Quality Impact

In the UK, the River Tame catchment covers an area of about 1,400 km2 and forms the northern portion of the Birmingham Conurbation. In the 1960s, wet weather conditions in Birmingham could result in the total depletion of oxygen in the River Trent below the Tame confluence. Construction of a system of purification lakes at Lea Marston, below the major polluting discharges, was completed in the early 1980s. Today, the operation of the Lea Marston Lakes significantly improves the quality of the Tame. However, wet weather pollution episodes in the Tame continues to have a severe impact on water quality in the Trent and put major fisheries at risk. This paper reports on the outcome of an integrated environmental impact and cost-benefit assessment modelling study into the future strategic management of the Lea Marston Lakes. The study demonstrated that the Lea Marston Lakes provide an economically justifiable method for reducing the water quality impact of the Birmingham conurbation and as a result will continue to be operated.

Effects of Sewage Outfalls on Intertidal Ecosystems in Kuwait

1986 ◽  
Vol 18 (11) ◽  
pp. 35-45 ◽  
Author(s):  
P. Literathy ◽  
L. Nasser Ali ◽  
M. A. Zarba ◽  
K. Puskas
Keyword(s):  
Organic Matter ◽  
Particulate Organic Matter ◽  
Intertidal Zone ◽  
High Tide ◽  
Nutrient Release ◽  
Organic Load ◽  
Intertidal Sediment ◽  
Water Characteristics ◽  
Photosynthetic Productivity ◽  
Close Relationship

Kuwait City has an impact on the nearshore marine environment by discharging sewage randomly through short emergency outfalls into the intertidal zone. The effect of the discharged sewage on the biological activity and the chemical characteristics of the relevant intertidal areas, which are controlled by a dry, tropical climate, was studied. Pore water, tidal water characteristics and nutrient release and transport from the intertidal zone during tidal flushing were investigated in polluted and unpolluted areas. The accumulation of particulate organic matter in the upper, middle and lower intertidal zones was characterized. It was concluded that in addition to settling, a great deal of particulate organic matter entered into the upper tidal sediment by infiltration during high tide and was filtered out by the sediment and migrated toward the low tide zone during the falling tide. The rate of the release of the substances associated with inorganic particulates was controlled by the overall organic load and the microbial activity. Sediment core samples were taken for multistage carbon dioxide treatment, and the results showed a decrease in carbonate-bound phosphates with depth. Photosynthetic productivity observed during the spring showed a close relationship with the sewage discharges and were also controlled by the tidal current. Based on the determination of dissolved nutrients, it was concluded that the limiting nutrient for photosynthesis was nitrogen rather than phosphorous. The release of some heavy metals from the sewage-polluted intertidal sediment was significant, and beachrock development also related to the discharges. The intertidal fauna was impoverished because of the organic sludge.

Mycotoxin Contamination in Stored Maize and Groundnuts Based on Storage Practices and Conditions in Subhumid Tropical Africa: The Case of Kilosa District, Tanzania

2016 ◽  
Vol 79 (12) ◽  
pp. 2160-2166 ◽  
Author(s):  
K. S. MAGEMBE ◽  
M. W. MWATAWALA ◽  
D. P. MAMIRO
Keyword(s):  
Fumonisin B1 ◽  
Weather Conditions ◽  
Storage Conditions ◽  
The Other ◽  
High Concentration ◽  
Data Loggers ◽  
Honestly Significant Difference ◽  
Significant Difference ◽  
Using Data ◽  
Log Linear

ABSTRACTExperiments were conducted to assess the influence of storage practices on mycotoxin incidences in stored maize and groundnuts in Kilosa District, Eastern Central Tanzania. Factorial experiments were used to test the effects of processing, storage conditions, and protectants at 3-month intervals for 12 weeks. Temperature and relative humidity data were recorded by using data loggers. The differences among the treatment means were compared using Tukey's honestly significant difference test at 5% probability level. The log-linear model was used to determine the influence of weather on mycotoxin. Dried neem (Azadirachta indica) leaves significantly reduced fumonisin B1 (FB1) in stored maize. Levels of FB1 were significantly higher in maize heaped on the floor than in the other tested storage methods (P < 0.001). Similarly, aflatoxin levels were significantly higher in groundnuts stored in nylon bags than in the other tested methods (P < 0.001). The high concentration of mycotoxins at the study villages suggests that storage practices and weather conditions play major roles in mycotoxin production.

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