On-site prediction of ephemeral gully erosion

CER84-85CRT2.July 1984

Direct observation of charge inversion by multivalent ions as a universal electrostatic phenomenon

We have directly observed reversal of the polarity of charged surfaces in water upon the addition of tri- and quadrivalent ions using atomic force microscopy. The bulk concentration of multivalent ions at which charge inversion reversibly occurs depends only very weakly on the chemical composition, surface structure, size and lipophilicity of the ions, but is dominated by their valence. These results support the theoretical proposal that spatial correlations between ions are the driving mechanism behind charge inversion.Comment: submitted to PRL, 26-04-2004 Changed the presentation of the theory at the end of the paper. Changed small error in estimate of prefactor ("w" in first version) of equation

Flood risk management through a resilience lens

To prevent floods from becoming disasters, social vulnerability must be integrated into flood risk management. We advocate complementing conventional risk analysis by adopting a resilience lens in which the welfare of different societal groups is considered by adding recovery capacity, impacts of beyond design events, and distributional impacts

Being explicit about aspects of mathematics pedagogy

It is conventional wisdom that contextualising mathematics tasks can make them more meaningful for students, and that open-ended questions create opportunities for student engagement. Yet concerns are emerging that strategies such as these may exacerbate the disadvantage of some. We report data from a project that seeks to address such concerns by encouraging teachers to be explicit about aspects of their pedagogy. Men teachers were explicit about aspects of the pedagogy, the students responded in the direction intended.<br /

Methods of assessing flood resilience of critical buildings

An overview is presented of recent advances in the assessment methods and mitigation solutions for the performance of critical buildings during flood events. This draws on research focusing on critical urban infrastructure, which is defined as assets that are essential for the continuity of economic activities in cities and for the basic living needs of the urban population. These assets include networks as well as buildings, the latter (termed ‘critical buildings’) having an important role in protecting equipment and personnel associated with the networks. Examples include power stations, transport control centres, communication hubs, fire stations, shelters and hospitals. Unlike domestic constructions, due to their specificity, these buildings cannot easily be categorised in terms of type of construction or age, and have to be treated as individual buildings. Three methods are presented as a framework with a logical progression for the assessment of building flood vulnerability and the identification of improvement measures: the ‘quick scan’ method, the ‘selection and evaluation tools for flood proofing of buildings’ and the ‘individual building flood damage tool’ (IBT). It is expected that building owners, insurance companies, local authorities and agencies with urban flood management responsibilities will benefit from the application of the framework and tools presented

Modelling the spatial distribution of DEM Error

Assessment of a DEM’s quality is usually undertaken by deriving a measure of DEM accuracy – how close the DEM’s elevation values are to the true elevation. Measures such as Root Mean Squared Error and standard deviation of the error are frequently used. These measures summarise elevation errors in a DEM as a single value. A more detailed description of DEM accuracy would allow better understanding of DEM quality and the consequent uncertainty associated with using DEMs in analytical applications. The research presented addresses the limitations of using a single root mean squared error (RMSE) value to represent the uncertainty associated with a DEM by developing a new technique for creating a spatially distributed model of DEM quality – an accuracy surface. The technique is based on the hypothesis that the distribution and scale of elevation error within a DEM are at least partly related to morphometric characteristics of the terrain. The technique involves generating a set of terrain parameters to characterise terrain morphometry and developing regression models to define the relationship between DEM error and morphometric character. The regression models form the basis for creating standard deviation surfaces to represent DEM accuracy. The hypothesis is shown to be true and reliable accuracy surfaces are successfully created. These accuracy surfaces provide more detailed information about DEM accuracy than a single global estimate of RMSE