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Mapping per- and polyfluoroalkyl substances contamination in England's surface waterbodies: Urban water cycle pathways and governance challenges

2026-04-15T00:00:00Z

Title: Mapping per- and polyfluoroalkyl substances contamination in England's surface waterbodies: Urban water cycle pathways and governance challenges Authors: García Herrera, A; Iacovidou, E; Giakoumis, T Abstract: Per- and polyfluoroalkyl substances (PFAS) contamination has emerged as a major international environmental and regulatory challenge, with PFAS increasingly detected across freshwater systems worldwide. However, in countries with limited PFAS manufacturing, such as England, it remains unclear whether surface waterbodies contamination reflects diffuse consumer-driven pollution, sectoral pressures, or dominant point-source pathways of PFAS pollution, such as Wastewater Treatment Works (WWTWs). In this study, we address this gap by providing the first surface-waterbody-level characterisation of PFAS contamination across England, drawing on the Environment Agency 's 2024 national dataset. Linking PFAS detections with sectoral pressure classifications, the study makes the following contributions: 1) quantifies the associations between individual compounds and human activities, 2) assesses WWTWs as pathways for PFAS release, and 3) maps detected PFAS to sector-specific product applications. Our analysis reveals that 92% of monitored waterbodies contain at least one of thirty-four detected PFAS, with multiple compounds co-occurring (mean ∼ 6.5) and PFOS frequently exceeding its Environmental Quality Standard. Water Industry/Domestic/General Public pressures showed strong positive associations with 11 PFAS compounds, with effect sizes of 2.9–9.9 (FDR < 0.05). After adjusting for overlapping sectoral influences, significant positive associations remained for PFHxS.L, PFBS, PFHpA, PFOS..B, PFOS..L and PFOS_combined, with odds ratios between 2.0 and 3.0 (FDR < 0.05). PFAS were also routinely present in WWTWs effluents, where removal efficiencies were often low or negative, indicating that WWTWs function as chronic point sources. Persistent PFOS detections in WWTWs effluents long after its restriction reflect that PFAS are now deeply embedded within the built environment, recirculating through the urban water cycle. These findings underscore the necessity for a comprehensive, system-level governance approach for PFAS that transcends single-compound restrictions and advocates for a fair allocation of mitigation responsibilities. Description: Highlights: • PFAS contamination is widespread, detected in 92% of England's monitored waterbodies. • Water Industry/Domestic/General Public key pathways of PFAS leaching to waterbodies. • PFOS routinely present in Wastewater Treatment Works effluents despite regulatory ban. • Wastewater Treatment Works showed low or negative removal efficiencies for many PFAS. • Stronger source controls and polluter-pays governance are essential for protection.; Data availability: Data will be made available on request.; Supplementary data are available online at: https://www.sciencedirect.com/science/article/pii/S0048969726004432?via%3Dihub#s0075 .

Controls on lag time in Philippine catchments identified using rainfall–runoff modelling and a generalized additive model (GAM)

2026-03-16T00:00:00Z

Title: Controls on lag time in Philippine catchments identified using rainfall–runoff modelling and a generalized additive model (GAM) Authors: Tolentino, PLM; Hurst, MD; Williams, RD; Hoey, TB; Boothroyd, RJ Abstract: Understanding the controls upon lag time, can improve river and flood management decision-making. This study investigates the relative importance of catchment characteristics in explaining lag time variability across the Philippines. Numerically simulated 5-year return period lag times for 291 catchments were analysed using a generalized additive model (GAM) to capture non-linear relationships with location, geology, climate, topography, and land use. The 5-year return period is representative of moderate flood response, as lag time varies little across return periods. Correlation analysis and recursive feature elimination guided variable selection, while bootstrapping assessed model stability and uncertainty. Ten significant controls on lag time were identified, with relief ratio, land cover index, and catchment area most influential. The GAM achieved an R² of 0.77 and explained 84% of deviance. Land cover emerged as the only anthropogenically modifiable control, highlighting a key management lever. National hydrological observations are needed to further support model calibration. Description: Data availability: Input data and R codes are available the University of Glasgow Enlighten data repository https://researchdata.gla.ac.uk/.; Supplementary material: Supplemental data for this article can be accessed online at https://doi.org/10.5525/gla.researchdata.2197

Kinetic Energy Estimation of IMU-Equipped Sediment Particles with Gaussian Process Regression and Conformal Prediction

2026-03-24T00:00:00Z

Title: Kinetic Energy Estimation of IMU-Equipped Sediment Particles with Gaussian Process Regression and Conformal Prediction Authors: Maniatis, G; Tuhtan, J; Toming, G; Curley, E; Gadd, C; Williams, R; Hoey, T Abstract: Direct particle-scale sediment measurements remain difficult in turbid, high-energy rivers where optical methods fail. We present an integration-free IMU workflow that maps short windows to projected speed and kinetic energy using physics-aware preprocessing, orientation-invariant Hankel embeddings, Gaussian process regression (GPR), and split conformal prediction. On event-disjoint hold-out tests, the selected GPR model (m = 10) achieves R² = 0.628, RMSE = 0.168ms⁻¹, and MAE = 0.096ms⁻¹. A four-model benchmark on identical event-grouped folds (GPR, LSTM, SVR-RBF, LSBoost) gives the lowest RMSE for LSBoost (0.158ms⁻¹); GPR is within 0.001ms⁻¹ of the strongest non-GPR comparator (LSBoost), and paired RMSE differences are non-significant (p = 0.812). Empirical conformal coverage is 87.6%/93.7%/97.9% for nominal 90%/95%/99% targets. River Calder deployments show peak kinetic energies up to 0.168 J. The framework provides uncertainty-aware kinematics and energetics for autonomous sediment-transport monitoring.

An assessment of the unintended consequences of structural coastal flood protection

2026-01-01T00:00:00Z

Title: An assessment of the unintended consequences of structural coastal flood protection Authors: Breen, Morgan James Abstract: This thesis investigates the unintended socio-hydrological consequences of structural coastal flood protections (SCFPs) and assesses the implications for coastal flood risk management strategy in the UK. Climate change, and the continued urban development of flood exposed areas can exacerbate coastal flood risk, and thus flood risk management authorities often tend towards structural coastal flood protection measures to minimise losses. However, these structurally proactive measures can lead to infrastructural lock-ins, whereby the decrease in flood probability from the defence can lead to increased urban development and population, ultimately leading to higher losses due to an inundation event. This process has been referred to as the Safe Development Paradox (SDP), a cross-cutting science-practice-policy challenge that requires a systematic understanding in the context of increased uncertainty associated with climate change and the United Nations Sustainable Development Goals. However, literature of the phenomena is limited, compounded by a lack of consistent terminology, limited geographic distribution, and a skewed emphasis on fluvial flooding. Moreover, despite being an island nation, the UK, to date, has had very little research conducted into these unintended consequences of structural flood protection. This thesis developed and applied a methodology that captures these coupled human-flood processes, by integrating well-established methods from other spheres of flood risk assessment in a novel way to explore the currently poorly understood phenomena in coastal settings. The study contributes to addressing this knowledge gap based on insights from three contrasting UK case studies: Portsmouth, Weston-super-Mare, and Southport. Differential analysis of historic LiDAR Digital Surface Models (DSMs) was used to identify temporal changes in the urban landscape to create a DSM of Difference (DoD), representing elevation change between two locations over time. Geostatistical testing, specifically t-tests, were then used to infer statistical significance of changes in urban development. The results reveal a consistent pattern: following completion or improvement of large-scale SCFPs, there is subsequent, and statistically significant, increases in coastal population and urban development within/near flood-exposed areas in all case studies, contrary to the limited flood-exposed development in neighbouring settlements, with no comparable defences constructed, or upgraded, during the same period. On average, new urban development occurs approximately 2 years after the completion of coastal flood defence projects. These data were then inputted into a newly developed agent-based model (ABM) that simulates futures changes under different climate scenarios. The results demonstrate that each SCFP project led to an initial decrease in Affected Population (AfP) following implementation, confirming the intended immediate benefits of flood risk reduction. However, long-term projections revealed significant unintended consequences under the scenarios where SCFPs were exceeded by Extreme Coastal Water Levels (ECWLs). For Southport and Weston-super-Mare, the ABM output shows a dramatic increase in AfP once ECWL surpassed the SCFP crest height, affecting a larger population than those initially protected, primarily due to the increased population growth behind the defences and the larger flood extent. Portsmouth, however, exhibited a more limited increase in AfP, attributed to its high urban density and limited room for further development behind the defences. This highlights how pre-existing land-use and population density can act as brakes on the unintended consequences of SCFPs. The thesis concludes with a recommendation for future flood risk managers and policymakers to be aware of these unintended socio-hydrological consequences. SCFPs are crucial assets, and their construction and maintenance will continue to play an integral role in coastal adaptation to climate change, particularly in highly developed urban settlements. This thesis does not attempt to provide a comprehensive predictive modelling tool for planning, nor a detailed analysis of real estate markets, but instead focuses on socio-hydrological interactions of population change and SCFP. However, new SCFP design and implementation need to account for their long-term unintended consequences on communities and climate adaptation planning. In the short-term, flood risk communication provides a means of tackling these risks, improving flood memory, awareness, and preparedness. Furthermore, in the longer term a more holistic cost-benefit analysis and spatial planning strategy, internalising these factors should be utilised in order to create more sustainable and resilient coastal communities in the UK. Description: This thesis was submitted for the award of Master of Philosophy and was awarded by Brunel University London