292 research outputs found
Assessing the importance of river bank erosion for fine sediment delivery to Bassenthwaite Lake
No full textAvailable evidence from lake sediment core records and short-term sediment flux sampling programs has suggested increased fine sediment deposition and suspended sediment transfers to Bassenthwaite Lake, Cumbria, U.K over recent decades. This increase in sedimentation has been associated with a decline in water quality in the lake which is thought to have had serious consequences for the population of the vendace (Coregonu albula), which also declined markedly during the 1990ร and into the 21 St Century. Recent studies of sediment delivery risk in the catchment have suggested that there are potentially large sediment sources in the lowland river network, especially the River Derwent between Derwent Water and Bassenthwaite Lake. The aim of this research is to describe the characteristics of fluvial suspended sediment transfers to Bassenthwaite Lake through direct monitoring of the River Dement and Newlands Beck (at the head of Bassenthwaite Lake) in order to assess the potential contribution of river bank erosion on the lowland River Derwent to fine sediment delivery. Three suspended sediment monitoring stations at Portinscale and Low Stock Bndge on the River Derwent and at Newlands Beck Bridge are used to assess changes in sediment transport along these important river reaches. The potential contribution of river bank erosion to fluvial sediment delivery was assessed by river bank mapping and surveying of erosion features on the 5.7km reach of the River Derwent between Derwent Water and Bassenthwaite Lake, along with a detailed study of morphological change on three river banks near Low Stock Bridge using a terrestrial laser scanner. The main findings of this project suggest that the River Derwent dominates suspended sediment transfers to Bassenthwaite Lake. The fine sediment load transported on the Derwent is over five times greater than that of Newlands Beck and the mean suspended sediment concentration on the lower Derwent is 56% higher than that on Newlands Beck. Specific catchment sediment yields for the River Derwent and Newlands Beck, based on effective drainage area, are 50.871 km(^2) a(^-1) and 35.721 km2 a(^-1) respectively. A high proportion of all suspended sediment transfers in the lowland Bassenthwaite Lake catchment were observed to occur in high-magnitude, low-frequency flow events, with approximately two- thirds of total suspended sediment transport occurring in just over 10% of the time. There is also direct evidence for increased fine sediment supply on the lowland River Derwent, as an estimated 1,158 ta(^-1) increase in the overall sediment load was observed on the 3.7 km reach of the Derwent between Portinscale and Low stock Bridge. Hysteresis analysis and analysis of suspended sediment transfers during high flow events on the Derwent support this hypothesis. Overall, 21.1% of all river banks on the River Derwent were assessed as eroded, with 9.4% of banks undergoing active river bank erosion. Therefore, it is suggested that river bank erosion is a significant fine sediment source in the lowland Bassenthwaite catchment, and that it is responsible for a large proportion of sediment inputs on the lowland River Derwent (c. 18.9%), and ultimately to Bassenthwaite Lake
Rev. Derwent Coleridge, ca. 1860\u27s
No full textRev. Derwent Coleridge, ca. 1860\u27s, col. Derwent was a child of Samuel Taylor Coleridge. distinguished scholar and author. In 1864 he accepted from Bishop Tait the rectory of Hanwell. Finding the parish church a long way from the population, he set to work to build a new one in the midst of them, and it was consecrated on the last day of 1879, when he was in his eightieth year.https://mds.marshall.edu/marshall_regional_photograph_collection/1423/thumbnail.jp
The floods of the Lake District - Part I
No full textThis report summarises the annual rainfall of the River Derwent catchment area and examines the floods of 1931 and 1932. The author uses data from the Meteorological Office to examine if the floods were extraordinary and takes into account local lakes in reducing the magnitude of the flood. Areas that are presented in more detail are Bassenthwaite Lake, Thirlmere, Cockermouth, Keswick, Newlands and Coledale Beck. (PDF contains 38 pages
Role of convection in determining the budget of odd hydrogen in the upper troposphere
No full textThis paper presents a model study of the changes in upper tropospheric HOx ( = OH + HO2) due to upward convective transport of surface pollutants. The model used is a three-dimensional global Lagrangian tropospheric chemistry transport model of 70 chemical species and 150 reactions including nonmethane hydrocarbon chemistry. It is driven by meteorological data from the U.K. Meterological Office with a 6 hour time resolution. We find that the effect of convection is to increase upper tropospheric (300–200 hPa) HOx globally by over 50%. The effect is greatest over the tropical continents where convection and VOC emissions from vegetation are colocated. The convection of isoprene, and hydroperoxides has the greatest effect. Convecting formaldehyde and acetone has a lesser effect. The contribution from isoprene depends more on the convection of its degradation products than the convection of isoprene itself. The upper tropospheric HOx budget is shown to be very sensitive to the model implementation of convective wet deposition
Reservoir compensation releases and the ecology of the River Derwent, Northumberland.
No full textRiver regulation is commonplace in England and much of the UK. Regulation for the purposes of public water supply causes flows downstream of a reservoir to be attenuated and the flow regime of the channel to be altered. The impact of channel impoundment on a small, upland UK river, has been assessed and methods for mitigation of ecological impacts explored. The method utilised a unique macroinvertebrate data set for pre- and post-impoundment periods to quantify the impact of Derwent Reservoir and the steady, continuous compensation release into the River Derwent, Northumberland. Impacts on the hydrological regime were also investigated and links drawn between changes in flow regime and changes in macroinvertebrate richness and diversity as a result of impoundment. In response to the claim that the impoundment has caused a change in flow regime and had deleterious effects on fish and macroinvertebrates, a compensation redesign tool (CRAB: Compensation Release Assessment at the Broad scale) was employed to design new compensation release regimes from the reservoir which account for the seasonal flow requirements of a number of key fish species. The impact of impoundment on the current flow regime was modelled and the impacts of predicted new regimes were predicted, using a 1D hydrodynamic model (HEC-RAS), as part of a modelling process known as CRAM (Compensation Release Assessment at the Meso-scale). Depth and velocity were the foci of the analysis as they are the two habitat requirements most well documented for the fish species in question, they could be modelled using HEC-RAS and they can act as surrogates for other habitat parameters such as temperature and substrate. The suitability of the depth and velocity combinations predicted using the HEC-RAS model were assessed using fuzzy rule-based modelling, which allowed the habitat quality of a given parameter combination to be quantified.
Based on the results of the investigation it was concluded that there has been a change in flow regime and in ecological community structure since impoundment. The flow regime of the River Derwent has become less flashy with fewer extreme events, while macroinvertebrate richness and diversity have increased. The new flow regimes that were designed by CRAB, based on the depth and velocity requirements of brown trout, grayling and Atlantic salmon were predicted through CRAM to have minimal benefits for the fish populations of the River Derwent and it was concluded that no changes to flow regime should be made based solely on the assessment of habitat for fish. Impacts for the macroinvertebrate communities must also be considered as well as the impacts on other aspects of fish habitat including temperature, substrate and cover. A more detailed, micro-scale investigation into the effects of changing flow regime would be required to warrant a change in compensation release regime from Derwent Reservoir
Ozone formation downwind of an industrial source of hydrocarbons under European conditions
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A Computer Modelling Study of the Relationship between Urban Exposure to Nitrogen Dioxide and Motor Vehicle Exhaust Emissions During the Summer Months
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