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Title: Rainfall-runoff and other modelling for ungauged/low-benefit locations
Author: R. J. Moore
Author: V. A. Bell
Author: S. J. Cole
Author: D. A. Jones
Author: Environment Agency
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_1251, Representation ID: 414, Object ID: 2462
This report provides an overview of approaches for modelling at ungauged locations to guide operational practice both now and in the future. The emphasis is on the types of modelling problem commonly encountered and the general approaches that can be considered when addressing them. Whilst rainfall-runoff models are the main focus of attention, broader discussion encompasses hydrological channel flow routing models and hydrodynamic river models; simpler empirical models including level-to-level correlation methods are also considered. Even for specific rainfall-runoff model types, it is unusual for a methodology to be sufficiently well established for its application to be routine for ungauged forecasting purposes. The overview first focuses on the nature of the ungauged problem and the modelling approaches available when considered at a generic level. Subsequent discussions of specific model types serve to illustrate how some of these approaches have been applied and their shortcomings. Possible opportunities for improvement are identified. An important aspect of ungauged modelling is the ability to utilise digital spatial datasets on properties of the terrain, land cover, soil and geology that will influence the hydrological response. The more useful datasets for use in modelling are identified. Although not a natural choice for application to ungauged locations, the scope for using purely statistical (empirical) modelling approaches, such as level-to-level and structure function methods, is considered. Similarly, the application of real-time updating techniques at ungauged locations is not immediately obvious, but a number of methods of transferred-error updating are considered as deserving of future attention. More broadly, the opportunities for improved flood warning for ungauged locations relating to advances in monitoring and uncertain triggers for warning are considered. Topics addressed encompass improved methods of areal rainfall estimation, remotesensing of land surface properties and river height and width, stage-discharge curve derivation, and flood warning trigger mechanisms incorporating uncertainty and costs of alternative actions. The report closes with an overview of the operational guidelines for modelling at ungauged locations, providing a convenient synthesis of the main issues and approaches. It also provides, through reference to a more detailed appendix, case study illustrations of selected methods of model transfer to ungauged locations. A set of specific conclusions and recommendations are then identified. Some closing remarks highlight ongoing national and international research activities of relevance to flood forecasting and warning for ungauged locations.
Publisher: Environment Agency
Subject Keywords: ForecastingRiversFloodingHydrological processesRunoffFlow rateRainfallModellingFreshwater ecology
Extent: 264
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