Percorrer por autor "Horsburgh, Nicola"
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- Parameterised barrier morphological evolution for future storm impact assessmentPublication . Loureiro, Carlos; Horsburgh, Nicola; Ferreira, ÓscarCoastal storm impacts are mainly determined by the interaction of extreme water levels with barrier morphology, particularly the height of the foredune. While future projections of storm hydrodynamic forcing, integrating sea level rise, tides, waves and storm surges, are readily available, predicting future barrier morphology at a decadal scale remains a challenge due to uncertainties in modeling morphodynamic processes. This study proposes a simplified model to predict future foredune morphology at decadal scale and determine storm impacts on coastal barriers, focusing on the critical role of foredune morphology. The model identifies three morphological behavior modes based on the nature of the sediment budget and associated shoreline dynamics, distinguishing between: “keep-up mode” for accreting barriers, “catch-up mode” for stable to mildly accreting barriers, and “give-up mode” for eroding barriers. Application to the Portuguese coast, specifically the eroding barrier of Torrão do Lameiro, demonstrates that even with rising sea level and higher total water levels, storm impacts remain within the same regime by 2050. This simplified model offers a practical approach for considering an evolving foredune morphology, which can support first-order assessments of future storm impacts in changing climate.
- Storm impact assessment for Scotland’s wave-dominated sedimentary coastsPublication . Horsburgh, Nicola; Loureiro, Carlos; Hurst, Martin; Rennie, Alistair; Tyler, AndrewAlong wave-dominated sedimentary coasts, risks posed by chronic coastal erosion and rising sea levels during this century have received much atten-tion. However, extreme wave runup during large storms are still poorly charac-terised at large spatial scales, and can contribute significantly to coastal flooding and erosion. This creates an important challenge for coastal management and adaptation planning. This work presents a national-scale storm impact assessment for Scotland’s wave-dominated sand and gravel coasts. It uses readily available national and European datasets to model extreme total water levels that include storm wave runup, tides, storm surge and changes in mean sea level. Future impacts are assessed by integrating likely climate-driven changes to storm forcing and coastal morphology. Outputs estimate the likely storm impact regime at 50 m alongshore transects in Scotland’s natural sand and gravel coasts for the present day, 2050 and 2100, considering climate change scenarios RCP4.5 and RCP8.5. Results indicate 65%, 11% and 4% of transects currently experience collision, overwash and inundation as the most severe storm impact. Towards 2100, tran-sects in overwash and inundation increase to 20% (22%) for RCP4.5 (RCP8.5), but local increases vary considerably between coastal cells. This study contributes to a strategic, national scale understanding of coastal risk that supports the spatial prioritisation of areas in need of proactive adaptation solutions.
- Wave-driven storm impacts on Scotland's sedimentary barriers intensify with climate changePublication . Horsburgh, Nicola; Loureiro, Carlos; Rennie, Alistair; Hurst, Martin; Naylor, Larissa A.; Tyler, AndrewBeaches and dunes form vital natural barriers, protecting coastal communities from extreme sea levels. To support coastal management, a geomorphologically-informed understanding of how barriers may be impacted by storm-induced coastal hazards is essential. While storm wave runup can contribute significantly to local extreme sea levels and drive dramatic short- and near-term morphological change to sedimentary coasts, it remains only partly characterised in existing national and regional assessments. This study investigates wave-driven storm impacts at large spatial scales (100–1000 km), at a resolution sufficient to inform local decision making. Using higher resolution national and European datasets, established empirical parameterisations and a simplified barrier morphological evolution model, we predict extreme wave runup and storm impacts on Scotland's wavedominated sedimentary coasts, at 50 m alongshore resolution. We consider a synthetic storm comprised of 25- year return levels of tides and storm surge, and the 1% exceedance of wave height and period, and predict storm impacts for the present-day, mid- and end-century, under RCP4.5 and RCP8.5. Results show that wave runup contributes on average 38% to extreme sea levels, and over 50% in the most exposed locations under present conditions. Nationally, 416 km (65% of the assessed coast) experience barrier erosion during the synthetic storm event, while 72 km (11%) and 27 km (4%) undergo overwash and inundation, respectively. By 2100 the predicted length of inundated coast approximately doubles to 46 km (7%) under RCP4.5, and 59 km (9%) under RCP8.5. Results reveal strong sub-national variability in storm impacts, identifying clear hotspots with the potential for erosion-enhanced flooding.