Flood risk management of a small urban river using a sustainable urban drainage system: Wortley Beck, Leeds, UK

This paper explores potential flood resilience approaches for the highly urbanised Wortley Beck river basin, south west of the City of Leeds, UK. Integrated 1D and 2D hydrodynamic modelling, using the ISIS and TUFLOW has been utilised to explore potential impact of SuDS on the flood hazard for three (1:15, 1:50 and 1:100) flood events. A direct rainfall runoff modelling approach has been employed to implicitly incorporate SuDS features within the case study region. Results indicate that SuDS reduce the flood hazard in downstream for all three (1:15, 1:50 and 1:100) flood events, with the effect more pronounced for the lowest rainfall (1:15) event

Further development of The Ebbsfleet Water Management System Dynamics Model: Adjusting representation of processes and system boundaries, incentivising stakeholder re-engagement, and exploring the potential for University teaching

This is the final version. Available from WIT Press via the DOI in this record. System Dynamics Model (SDM) that explores sustainable urban water management. The model is open-source compiled using Vensim software, which is free for non-commercial use. This paper demonstrates that the current SDM and the modelling approach are open to adjustment, which is illustrated by introducing a link between water tariffs and environmental awareness. The increase in water tariffs leads not only to the obvious increase in water bills, but also to an increase in Environmental Awareness, and consequently, to increases in the use of water efficiency devices, grey water acceptability, and grey water reuse. A range of further modifications is suggested, including expanding representation of sustainable drainage systems (SuDS) to consider resultant improvements in stormwater quality as well as quantity. This would recognise the indirect benefits of improved stormwater quality on biodiversity in the River Ebbsfleet, which is the receiving watercourse. This study intends to encourage knowledge transfer, by facilitating and incentivising the use and further development of the SDM by stakeholders and a wider community of end-users, including practitioners, academics and the public. While SDM is particularly suited to analysis of indirect relations, benefits and trade-offs among system constituents, other approaches provide viable alternatives and we discuss the potential for re-implementing our findings in other interactive modelling software packages and programming languages. We also explore the scope for linking the adapted SDM to other models. Finally, we consider the utility of the Ebbsfleet SDM in teaching, learning and knowledge transfer. We conclude that students, practitioners and other stakeholders could not only enhance their understanding of urban water management complexity, but also gain valuable system modelling skills based on using the SDM to support kinaesthetic learning. Ultimately, society benefits when the level of knowledge and analytical thinking skills of its members are enhanced.Engineering and Physical Sciences Research Council (EPSRC)Engineering and Physical Sciences Research Council (EPSRC)Engineering and Physical Sciences Research Council (EPSRC

Spin Fluctuations and Unconventional Superconductivity in the Fe-based Oxypnictide Superconductor LaFeAsO_0.7 probed by 57Fe-NMR

We report $^{57}$Fe-NMR studies on the oxygen-deficient iron (Fe)-based oxypnictide superconductor LaFeAsO$_{0.7}$ ($T_{c}=$ 28 K) enriched by $^{57}$Fe isotope. In the superconducting state, the spin component of $^{57}$Fe-Knight shift $^{57}K$ decreases almost to zero at low temperatures and the nuclear spin-lattice relaxation rate $^{57}(1/T_{1})$ exhibits a $T^{3}$-like dependence without the coherence peak just below $T_{c}$, which give firm evidence of the unconventional superconducting state formed by spin-singlet Cooper pairing. All these events below $T_c$ are consistently argued in terms of the extended s$_{\pm}$-wave pairing with a sign reversal of the order parameter among Fermi surfaces. In the normal state, we found the remarkable decrease of $1/T_1T$ upon cooling for both the Fe and As sites, which originates from the decrease of low-energy spectral weight of spin fluctuations over whole ${\bm q}$ space upon cooling below room temperature. Such behavior has never been observed for other strongly correlated superconductors where an antiferromagnetic interaction plays a vital role in mediating the Cooper pairing.Comment: 4 pages, 4 figures,Accepted for publication in J. Phys. Soc. Jpn., vol.78, No.1 (2009

Modelling the long-term suspended sedimentological effects on stormwater pond performance in an urban catchment

The influence of long-term suspended sediment dynamics on stormwater pond performance should not be ignored, but is often neglected in pond design and performance evaluation. This paper provides systematic simulated quantification of long-term suspended sedimentological effects on stormwater pond performance. Integrated hydrological and two-dimensional hydro-morphodynamic modelling and simulations were carried over a 32-year period (1984–2015) covering 3896 rainfall events with a wide range of rainfall volumes, durations and intensities. Three event-based hypothetical rainfall scenarios: non-flood condition (5-year), sewer design condition (30-year), and river flood condition (100-year) rainfall events with 1-h duration, were also simulated for comparison between the traditional event-based approach and the novel approach presented in this study. Simulation results show that the flood peak attenuation and delay are more pronounced for small (<5-year) and medium (<30-year) flood events. The long-term continuous simulation results indicate that the pond provides positive annual trap efficiencies varying from 2% to 69% for 31 of 32 years, providing long-term water quality benefits downstream. However, an extreme rainfall event in year 2012 flush out the accumulated sedimentation as a shock load to the downstream river, leading to a negative trap efficiency of −11%. The spatially averaged sediment deposition rate, as predicted by the model, varies with a mean (SD) of 2 (1.34) cm/year over the study period, which resulted in a 24% loss in the pond’s volume over 32 years. The impact of the loss in storage on pond flood attenuation capacity are explored at regular time intervals over the study period. The results indicate that reduction in the pond’s flood attenuation capacity is relatively more pronounced for medium (30-year) and extreme (100-year) flood events than the frequent small flood (5-year) events. The variation in annual sediment loading with rainfall quantities and patterns are also explored

Achieving urban flood resilience in an uncertain future

Preliminary results of the UK Urban Flood Resilience research consortium are presented and discussed, with the work being conducted against a background of future uncertainties with respect to changing climate and increasing urbanization. Adopting a whole systems approach, key themes include developing adaptive approaches for flexible engineering design of coupled grey and blue-green flood management assets; exploiting the resource potential of urban stormwater through rainwater harvesting, urban metabolism modelling and interoperability; and investigating the interactions between planners, developers, engineers and communities at multiple scales in managing flood risk. The work is producing new modelling tools and an extensive evidence base to support the case for multifunctional infrastructure that delivers multiple, environmental, societal and economic benefits, while enhancing urban flood resilience by bringing stormwater management and green infrastructure together.</jats:p

A participatory process to support sustainable water resources management in the Ebbsfleet Garden City

This is the author accepted manuscript. The final version is available from IAHR via the link in this recordThe present work describes the development of a participatory System Dynamics Model (SDM) aiming to explore sustainable urban water management (UWM) in a structured way and to understand where policy interventions might be best focused. The proposed multi-step process is useful for supporting decision-making at a strategic, system-wide level and for exploring the long-term consequences of alternative strategies. The strongly participatory base of the SDM allows both to include local knowledge held by relevant stakeholders, and to support a collective learning process, which should improve the effectiveness of the selected strategies. In the following sections on the SDM co-development to enhance sustainable urban water management in the Ebbsfleet Garden City are provided.Engineering and Physical Sciences Research Council (EPSRC

The blue-green path to urban flood resilience

Abstract Achieving urban flood resilience at local, regional and national levels requires a transformative change in planning, design and implementation of urban water systems. Flood risk, wastewater and stormwater management should be re-envisaged and transformed to: ensure satisfactory service delivery under flood, normal and drought conditions, and enhance and extend the useful lives of ageing grey assets by supplementing them with multi-functional Blue-Green infrastructure. The aim of the multidisciplinary Urban Flood Resilience (UFR) research project, which launched in 2016 and comprises academics from nine UK institutions, is to investigate how transformative change may be possible through a whole systems approach. UFR research outputs to date are summarised under three themes. Theme 1 investigates how Blue-Green and Grey (BG + G) systems can be co-optimised to offer maximum flood risk reduction, continuous service delivery and multiple co-benefits. Theme 2 investigates the resource capacity of urban stormwater and evaluates the potential for interoperability. Theme 3 focuses on the interfaces between planners, developers, engineers and beneficiary communities and investigates citizens’ interactions with BG + G infrastructure. Focussing on retrofit and new build case studies, UFR research demonstrates how urban flood resilience may be achieved through changes in planning practice and policy to enable widespread uptake of BG + G infrastructure.EPSR

Interplay between magnetism and superconductivity and appearance of a second superconducting transition in alpha-FeSe at high pressure

We synthesized tetragonal alpha-FeSe by melting a powder mixture of iron and selenium at high pressure. Subsequent annealing at normal pressure results in removing traces of hexagonal beta- FeSe, formation of a rather sharp transition to superconducting state at Tc ~ 7 K, and the appearance of a magnetic transition near Tm = 120 K. Resistivity and ac-susceptibility were measured on the annealed sample at hydrostatic pressure up to 4.5 GPa. A magnetic transition visible in ac-susceptibility shifts down under pressure and the resistive anomaly typical for a spin density wave (SDW) antiferromagnetic transition develops near the susceptibility anomaly. Tc determined by the appearance of a diamagnetic response in susceptibility, increases linearly under pressure at a rate dTc/dP = 3.5 K/GPa. Below 1.5 GPa, the resistive superconducting transition is sharp; the width of transition does not change with pressure; and, Tc determined by a peak in drho/dT increases at a rate ~ 3.5 K/GPa. At higher pressure, a giant broadening of the resistive transition develops. This effect cannot be explained by possible pressure gradients in the sample and is inherent to alpha-FeSe. The dependences drho(T)/dT show a signature for a second peak above 3 GPa which is indicative of the appearance of another superconducting state in alpha-FeSe at high pressure. We argue that this second superconducting phase coexists with SDW antiferromagnetism in a partial volume fraction and originates from pairing of charge carriers from other sheets of the Fermi surface

High temperature superconductivity (Tc onset at 34K) in the high pressure orthorhombic phase of FeSe

We have studied the structural and superconducting properties of tetragonal FeSe under pressures up to 26GPa using synchrotron radiation and diamond anvil cells. The bulk modulus of the tetragonal phase is 28.5(3)GPa, much smaller than the rest of Fe based superconductors. At 12GPa we observe a phase transition from the tetragonal to an orthorhombic symmetry. The high pressure orthorhombic phase has a higher Tc reaching 34K at 22GPa.Comment: 15 pages, 4 figure

Specific Heat Discontinuity, deltaC, at Tc in BaFe2(As0.7P0.3)2 - Consistent with Unconventional Superconductivity

We report the specific heat discontinuity, deltaC/Tc, at Tc = 28.2 K of a collage of single crystals of BaFe2(As0.7P0.3)2 and compare the measured value of 38.5 mJ/molK**2 with other iron pnictide and iron chalcogenide (FePn/Ch) superconductors. This value agrees well with the trend established by Bud'ko, Ni and Canfield who found that deltaC/Tc ~ a*Tc**2 for 14 examples of doped Ba1-xKxFe2As2 and BaFe2-xTMxAs2, where the transition metal TM=Co and Ni. We extend their analysis to include all the FePn/Ch superconductors for which deltaC/Tc is currently known and find deltaC/Tc ~ a*Tc**1.9 and a=0.083 mJ/molK**4. A comparison with the elemental superconductors with Tc>1 K and with A-15 superconductors shows that, contrary to the FePn/Ch superconductors, electron-phonon-coupled conventional superconductors exhibit a significantly different dependence of deltaC on Tc, namely deltaC/Tc ~ Tc**0.9. However deltaC/gamma*Tc appears to be comparable in all three classes (FePn/Ch, elemental and A-15) of superconductors with, e. g., deltaC/gamma*Tc=2.4 for BaFe2(As0.7P0.3)2. A discussion of the possible implications of these phenomenological comparisons for the unconventional superconductivity believed to exist in the FePn/Ch is given.Comment: some disagreement in reference and footnote numbering with the published versio