Pearson, Jonathan M.

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Pearson, Jonathan M.
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Pearson, Jonathan M.

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  • Publication
    Effectiveness of Eco-retrofits in Reducing Wave Overtopping on Seawalls
    (Coastal Engineering Research Council, 2020-12-28)
    O'Sullivan, J. J. 
    ;
    Salauddin, Md 
    ;
    Abolfathi, Soroush 
    ;
    Pearson, Jonathan M. 
    Terms such as 'nature-based', 'living shoreline', 'green infrastructure' and 'ecological engineering' are increasingly being used to reflect biomimicry-based engineering measures in coastal defences. Innovative interventions for nature-based sea defences have included the retrofitting of man-made water filled depressions or 'vertipools' to existing seawalls (Hall et al., 2019; Naylor et al., 2017) and the addition of artificial drill-cored rock pools to intertidal breakwaters (Evans et al., 2016). Through their capacity to retain water, such measures serve to enhance biodiversity in the built environment (Browne and Chapman, 2014). Evans et al. (2016) for example, experimentally demonstrated that the introduction of artificial rock pools to an intertidal granite breakwater enhanced the levels of species richness compared to those observed on plain surfaces of the breakwater. Notwithstanding these biological benefits, the impetus for incorporation of ecologically friendly measures to existing defences remains low (Salauddin et al., 2020a). This situation could potentially change should it be shown that the addition of 'green' measures to sea defences could enhance wave attenuation and reduce wave overtopping as well as wave pressures on the coastal defence structures. This paper describes small-scale physical modelling investigations of seawalls and explores reductions in wave overtopping that could be realised by retrofitting sea defences with 'green' features (such as 'vertipools'). Surface protrusions of varying scale and density are used in the physical modelling to mimic 'green' features and the results from measurements of overtopping are benchmarked to reference conditions determined from tests on a plain seawall.
      143
  • Publication
    Distribution of Individual Wave Overtopping Volumes on a Sloping Structure with a Permeable Foreshore
    (Coastal Engineering Research Council, 2020-12-31)
    Salauddin, Md 
    ;
    O'Sullivan, J. J. 
    ;
    Abolfathi, Soroush 
    ;
    Dong, Shudi 
    ;
    Pearson, Jonathan M. 
    Maximum wave overtopping volumes on sea defences are an indicator for identifying risks to people and properties from wave hazards. The probability distribution of individual overtopping volumes can generally be described by a two-parameter Weibull distribution function (shape and scale parameters). Therefore, the reliable prediction of maximum individual wave overtopping volumes at coastal structures relies on an accurate estimation of the shape factor in the Weibull distribution. This study contributes to an improved understanding of the distribution of individual wave overtopping volumes at sloping structures by analysing the wave-by-wave overtopping volumes obtained from physical model experiments on a 1V:2H sloped impermeable structure with a permeable shingle foreshore of slope 1V:20H. Measurements of the permeable shingle foreshore were benchmarked against those from an identical experimental set-up with a smooth impermeable foreshore (1V:20H) of the same geometry. Results from both experimental set-ups were compared to commonly used empirical formulations, underpinned by the assumption that an impermeable foreshore exists in front of the sea structure. The effect on the shape factor in the Weibull distribution of incident wave steepness, relative crest freeboard, probability of overtopping waves and discharge are examined to determine the variation of individual overtopping volumes with respect to these key parameters. A key finding from the study is that no major differences in Weibull distribution shape parameter were observed for the tested impermeable and permeable sloped foreshores. Existing empirical formulae were also shown to predict reasonably well the Weibull distribution shape parameter, b, at sloping structures with both impermeable and permeable slopes.
      146
  • Publication
    Extreme wave overtopping at ecologically modified sea defences
    (Copernicus, 2020-05-08)
    Salauddin, Md 
    ;
    O'Sullivan, J. J. 
    ;
    Abolfathi, Soroush 
    ;
    Pearson, Jonathan M. 
    Damage to coastal structures and surrounding properties from wave overtopping in extreme events is expected to be exacerbated in future years as global sea levels continue to rise and the frequency of extreme meteorological events and storm surges increases. Approaches for protecting our coastal areas have traditionally relied on the development and ongoing maintenance of ‘hard’ defences. However, the longer-term sustainability of coastal flood management that is underpinned by such defences is increasingly being questioned both in terms of dealing with climate change and in the environmental/ ecological consequences and associated losses of biodiversity that comes with these structural defence lines in coastal areas.
      80