ISSN:0197-9337    

DOI:10.1002/esp.3290200702

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe natural habitat of geomorphologists is at play in the fields of the Lord. Picnics, not the work ethic, often motivate the most productive. As in the field, so too in the mind, creative insights derive from the play of ideas. As in much of science today, Earth scientists are called upon to ‘solve’ immediate problems, but problems whose solutions lie at the cutting edge of the research frontier. The impact of anthropogenic activities in the context of natural processes, the playground where many geomorphologists work, requires continuous reciprocal exchange between research and application. Apologies are not needed for choices of orientation, but only for destructive separat

ISSN:0197-9337    

DOI:10.1002/esp.3290200703

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper reviews some of the challenges and objectives in the application of fluvial geomorphology to improved river management in the U.K. It describes the mechanisms by which geomorphology can be applied to solve problems, including the development of design guidance, policy, management approaches, procedures and training. While it is true that geomorphology is being used increasingly, there remain a number of challenges, such as the need to promote a more professional image and to develop appropriate standards. The scientific basis on which decisions relating to the water environment are made needs to be developed further. Perhaps some of the most significant challenges for fluvial geomorphology in U.K. river management during the next decade will concern river and floodplain restoration.

ISSN:0197-9337    

DOI:10.1002/esp.3290200704

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe management of riverine environments is shown to require a knowledge and awareness of the complex interactions between fluvial and mass‐wasting processes, riparian vegetation, and channel form. Identification of the cause of instability rather than the local symptoms, and knowledge of the temporal and spatial aspects of channel adjustment are central to the application of (1) appropriate analyses to estimate future channel changes, (2) appropriate mitigation measures, and (3) the protection of river‐crossing structures and adjacent land. Conceptual models of channel evolution and bank‐slope development are particularly valuable for interpreting past and present processes, applying appropriate computational techniques to estimate future channel changes, and implementing strategies to mitigate the impacts of processes likely to dominate the channel in the future.Techniques for identification and analysis of channel instability are interdisciplinary and provide a mechanism for estimating changes in channel‐bed elevation and channel width with time. Features of channel form and associated riparian vegetation can be used as diagnostic criteria to identify channel processes, the stage of channel evolution and the magnitude and extent of instability. Changes in bed elevation with time can be represented using an exponential function; changes in channel width with time can be calculated using slope stability equations and (or) projection of a temporary angle of stability from a low‐angle surface termed the ‘slough line’ that supports re‐establishment of woody vegetation. These techniques, in combination with knowledge of the state of channel evolution, can then be used to assess the appropriateness of various mitigation measures to control on‐going channel adjustments and to protect river‐

ISSN:0197-9337    

DOI:10.1002/esp.3290200705

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper addresses the role that fluvial geomorphology might play in the management of sediment‐related river maintenance in the U.K. Sediment‐related river maintenance refers to the operational requirement of river management authorities to remove deposits of sediment or protect river boundaries from erosion, where these compromise the flood defence levels of service. Using data collected as part of a National Rivers Authority (NRA) Research and Development Project it is possible to identify the geomorphic causes of problems, and engineering responses to sediment‐related river maintenance (SRRM) in England and Wales. The Project identified the management problem as widespread and often treated in isolation from the causative processes. Geomorphological guidance is shown to be both relevant and complementary to conventional engineering practice through its ability to identify the cause of a SRRM problem. A methodology for conducting a geomorphological survey, or ‘fluvial audit’, is presented, which synthesizes historical data on the catchment land‐use and channel network, with contemporary morphological maps to present a statement of the location and type of sediment supply, transport and storage within the river basin under scrutiny. The application of geomorphology to two contrasting SRRM problems is explored using case studies from two catchments: the River Sence, a fine sediment system, and the Shelf Brook, a coarse sedi

ISSN:0197-9337    

DOI:10.1002/esp.3290200706

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractAll river engineering schemes require flood discharge estimates as part of the design and appraisal process. Unfortunately, continuous measurement of flood discharges is limited to those river sites with instrumented gauging stations, which constitute only a small proportion of channel reaches where information is required. Therefore, considerable research effort has been devoted to the development of reliable indirect techniques of flood discharge estimation. Research on the interrelationship of stream channel geometry and river discharge has provided the basis for an indirect method of flood estimation – the channel‐geometry method – which employs river channel dimensions alone to estimate discharge characteristics at ungauged river sites. Channel‐geometry equations are developed empirically by relating streamflow data from gauging stations and channel dimensions measured from natural river reaches in the vicinity of the gauge, and take the form of power function relations. Once regional channel‐geometry equations have been defined, a channel width or channel capacity measurement is the only variable needed to estimate the flood flow characteristics at a specified river site. The method is useful as an alternative to traditional catchment‐based approaches or as a rapid reconnaissance technique. In addition to the application for flood discharge prediction, channel‐geometry equations could prove helpful in the management of river channels, first, by providing a basis for assessing local deviations in the channel form–discharge relation, deviations which could be employed as indicators of the sensitivity of particular stretches of river channel to change, and secondly, in the computation of natural channel dimensions for use in river channel design and ri

ISSN:0197-9337    

DOI:10.1002/esp.3290200707

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractDifferent mathematical models of river planform changes exist or are being developed. They are reviewed here by discussing a two‐dimensional depth‐averaged model, various meander models and a model for the braided Brahmaputra‐Jamuna River in Bangladesh. Much emphasis is placed on topics where further research is needed. It is concluded that the models help in understanding the underlying processes, but cannot yet be considered generally valid and easy‐to‐use software packages. In the hands of experienced geomorphologists or river engineers, however, some of the models do already form valuable tools which allow better predictions of future river

ISSN:0197-9337    

DOI:10.1002/esp.3290200708

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe Spey Bay coastline and the estuary of the River Spey exhibit a rapidly evolving planform. They provide an opportunity to study geomorphological changes in a coupled coastal/estuarine system which can be measured over hours and days rather than the years and decades associated with more slowly evolving landscape features. Attempting to understand coastal and estuarine geomorphology provides engineers and earth scientists with an exciting intellectual challenge. This is not, however, simply an academic challenge because the successful management of coastal and estuarine environments depends on improving this understanding. The impetus behind our work in this area is the protection of land‐use interests. It is in this context that Babtie Dobbie Limited have been employed in studying the River Spey since 1962. This paper is based on a practical case study performed for coastal and river engineering purposes between 1990 and 1992. The case study was formulated using the results and conclusions of earlier geomorphological studies of the area undertaken over the past 32 years. Knowledge gained from previous studies was crucial in designing the detailed methods and techniques employed in the 1990–1992 geomorphological study. Methods used included historical analyses, photogrammetry, numerical modelling, geographic information systems (GIS) and interpretation of the complex processes which drive landform changes in the estuary and along the adjacent shoreline. The improved understanding of geomorphological processes that has been achieved has enabled engineers to formulate a new management strategy. Central to this strategy are engineering solutions to river and coastal stability and flooding problems which are in sympathy with the environment and which take maximum advantage of our understanding of geomorphological proces

ISSN:0197-9337    

DOI:10.1002/esp.3290200709

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractRiver channels respond not only to natural external controls, and natural controls internal to individual drainage basins, but also to the influence of human activity. Although many site‐specific instances of change have been documented, the complexity of the process interactions means that very little is known about the general nature of different styles of adjustment, or their relative sensitivity to drainage basin controls. Data obtained from the Thames Basin, southeast England, are used in a probabilistic approach to differentiate between four styles of river channel adjustment and a variety of drainage basin characteristics. Adopting a probabilistic approach quantifies the degree of confidence attributable to any prediction of river channel adjustment while acknowledging that certainties are difficult to obtain in studies of the natural environment. This approach could thus allow environmental planning decisions to be made with a quantified degree of uncertainty.Four multivariate logistic regression models are described which use a combination of continuous and categorical variables to associate drainage basin characteristics with four styles of river channel adjustment derived from a reconnaissance evaluation survey. In comparison, it is shown that laterally migrating river channels are the most common ‘natural’ channel type in the Thames Basin, and their probability of occurrence rises to 71 per cent in sand/gravel environments. In channels regulated by low weirs, deposition is the most likely channel activity where gradients are lower than 0·0040, whilst above this threshold the majority of channels are morphologically inactive. In urban channels, many of which are also lined by concrete, the likelihood of obtaining a stable channel is mostly in excess of 80 per cent. In channels straightened during this century, deposition is most likely in gradients below 0·0050, whereas erosional enlargement is most probable above this value. In channels which were initially channelized prior to this century, deposition gives way to stability at a threshold gradient of

ISSN:0197-9337    

DOI:10.1002/esp.3290200710

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290200711

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY