Lookup NU author(s): Dr Mark Wilkinson,
Dr James Bathurst,
Professor Chris Kilsby
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A deficiency in current understanding of flood response behaviour is the way in which extremes of rainfall intensity reduce in relation both to the area covered by the storm and to the storm duration. Hydrological data from an extensive, nested hydrometric network in the unregulated, predominantly rural Upper Eden catchment in Northern England are presented for three major flood events; each resulted from different types of rainfall event (a single and a multi-day synoptic scale event and a convective event). Flood response is examined over varying scales and land uses from the upland Gais Gill catchment (1.1km2) to the outlet of the Upper Eden catchment (616km2). The Upper Eden catchment is part of the national Catchment Hydrology And Sustainable Management (CHASM) programme. Flood peak scaling is examined to the Eden outlet at Carlisle (2286km2). Flood peak analysis indicates that there is a power law relationship between the catchment area and the associated flood peak. Catchment runoff conditions indicate that runoff is generally greater in the uplands due to the thin soils and waterlogged soils compared to that in the lowlands which are well drained and have relatively deep soils. The storm lag times for each storm vary due to the antecedent catchment conditions. Variations in the rainfall patterns can be seen in the three different storm events of which "Windstorm Erwin" was the largest of these events which hit Cumbria on the 7-8th January, 2005. All storms displayed high cumulative rainfall values but these were exceptionally high in the uplands with return periods for some storms being of the order of 100 years. Rainfall undercatch due to high wind speeds has been a problem with estimating rainfall with some of the synoptic events, with some higher elevation raingauges recording lower rainfalls than the nearest lower elevation gauge. A physically based distributed model (SHETRAN) is currently being used to investigate flood peak response with improved rainfall estimates to highlight how the spatial and the temporal variability of storms are important in flood forecasting.
Author(s): Wilkinson ME, Bathurst JC, Kilsby CG
Editor(s): Eos Transactions AGU
Publication type: Conference Proceedings (inc. Abstract)
Conference Name: AGU Fall Meeting Supplement
Year of Conference: 2006
Pages: Abstract H23H-05