River response to recent environmental change in the Yorkshire Ouse basin, northern England

This study examines historical variations in flood frequency and magnitude in the Yorkshire Ouse basin, northern England, over the last 900 years. The causes of temporal and spatial variations in flooding are evaluated through investigation o f climatic and land-use controls. Documentary evidence o f flooding and climate suggests that a series of large floods between 1263 and 1360 were associated with climatic deterioration from the Medieval Optimum. A shift to generally milder conditions between 1361 and 1549 resulted in no floods being documented in the Ouse basin The frequency o f large magnitude floods increased dramatically between 1550 and 1680, as a result o f low temperatures, increased surface wetness, more frequent snowfall and a southward shift of prevailing storm tracks over middle latitudes, associated with the onset of the "Little Ice Age’. In contrast, during a wanner phase of the Little Ice Age, between 1681 and 1763, the frequency of localised summer flooding increased in the Ouse basin due to more frequent high intensity, short duration convective storms. Extensive lowland flooding became more common between 1764 and 1799 due to an increase in heavy rainfall, followed by a 50-year period characterised by relatively moderate flood frequencies and magnitudes. The later half of the nineteenth century experienced high flood frequencies and magnitudes, particularly in the 1870s and early-1880s, coinciding with high rainfall totals and a high incidence of cyclonic flood generation. Gauged flood and climate data, and land-use records indicate that the period between 1900 and 1916 was characterised by very low flood frequencies and magnitudes, associated with low rainfall, warm temperatures, and an increase in westerly flood generation. Between 1916 and 1943 there were marked variations in flood magnitude between the rural northern rivers and southern industrialised rivers. Magnitudes generally increased on northern rivers, whilst on some southern tributaries of the Ouse, flood magnitudes declined as a result of widespread channel improvement and flood defence schemes. Around 1944 a marked and sustained increase in flood frequency on northern rivers was associated with an increase in the incidence of heavy daily rainfall, greater westerly flood generation and large-scale upland and lowland drainage. Very low flood frequencies and magnitudes between 1969'and 1977 resulted from extremely low rainfall totals. Whereas the most recent period, between 1978 and 1996 has experienced some of the highest flood frequencies and magnitudes on record, associated with an increase in the frequency of floods generated under cyclonic and south-westerly synoptic situations, and a number of land-use changes promoting more rapid runoff including, large increases in upland livestock numbers, an increase in the area under winter-cereals and the cumulative effects of moorland gripping

Modelling non-stationary flood frequency in England and Wales using physical covariates

Non-stationary methods of flood frequency analysis are widespread in research but rarely implemented by practitioners. One reason may be that research papers on non-stationary statistical models tend to focus on model fitting rather than extracting the sort of results needed by designers and decision makers. It can be difficult to extract useful results from non-stationary models that include stochastic covariates for which the value in any future year is unknown. We explore the motivation for including such covariates, whether on their own or in addition to a covariate based on time. We set out a method for expressing the results of non-stationary models as an integrated flow estimate, which removes the dependence on the covariates. This can be defined either for a particular year or over a longer period of time. The methods are illustrated by application to a set of 375 river gauges across England and Wales. We find annual rainfall to be a useful covariate at many gauges, sometimes in conjunction with a time-based covariate. For estimating flood frequency in future conditions, we advocate exploring hybrid approaches that combine the best attributes of non-stationary statistical models and simulation models that can represent changes in climate and river catchments

Incorporating sedimentological data in UK flood frequency estimation

This study presents a new analytical framework for combining historical flood data derived from sedimentological records with instrumental river flow data to increase the reliability of flood risk assessments. Historical flood records were established for two catchments through re-analysis of sedimentological records; the Nant Cwm-du, a small, steep upland catchment in the Cambrian Mountains of Wales, and a piedmont reach of the River Severn in mid Wales. The proposed framework is based on maximum likelihood and least-square estimation methods in combination with a Generalised Logistic distribution; this enables the sedimentological data to be combined effectively with existing instrumental river flow data. The results from this study are compared to results obtained using existing industry standard methods based solely on instrumental data. The comparison shows that inclusion of sedimentological data can have an important impact on flood risk estimates, and that the methods are sensitive to assumptions made in the conversion of the sedimentological records into flood flow data. As current industry standard methods for flood risk analysis are known to be highly uncertain, the ability to include additional evidence of past flood events derived from sedimentological records as demonstrated in this study can have a significant impact on flood risk assessments

Experiments on Transuranium Compounds with X-Ray Resonant Exchange Scattering.

Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe

The future of flood hydrology in the UK

A ‘roadmap’ for the future of UK flood hydrology over the next 25 years has been published, based on a wide-ranging and inclusive co-creation process involving more than 270 individuals and 50 organisations from different sectors and disciplines. This paper highlights key features of the roadmap and its development as a community-owned initiative. The roadmap's relationship with hydrological research and practice is discussed, as is its context within the wider flood risk management innovation landscape, including funding. While the paper has a focus on UK flood hydrology, reflecting the scope of the roadmap, it is also considered in the context of advances in hydrology internationally