Dr Charlotte Lyddon BSc, MSc, PhD

Twenty million people living near UK estuaries are at risk from the compound effect of storm surge heights and fluvial discharge. This research has designed new methods fit-for-purpose to evaluate climate flooding hazards in UK estuaries and analyse compound flooding events across different spatial and temporal scales. Outcomes from this research include i) improved assessments of the spatial variability of compound flooding hazards in estuaries across the UK; ii) identifying site-specific thresholds for tidal, fluvial, and compound flooding in the Conwy Estuary, N-Wales using instrumental data, historic records of flooding, and model simulations using Caesar-LISFLOOD; and iii) analysing UKCP18 climate projections to identify potential changes in the magnitude, timing, and likelihood of drivers of compound flooding in the Dyfi Estuary, W-Wales.

This research applied coupled regional models to address coastal flood risk management needs in hypertidal estuaries. The research aimed to understand how tide-surge-wind-waves combine to increase flood and wave hazard at the coast, using the Severn Estuary, SW-England and S-Wales as an extreme example and location where key energy infrastructure is located. Delft3D-FLOW-WAVE was used to identify optimum model setups for simulating coastal flood hazard, which includes incorporating local atmospheric forcing and representing two-way interaction between waves and current. Key sources of coastal hazard uncertainty were identified, e.g. the importance of storm surge timing relative to tidal high water and sensitivity of wave propagation to winds speeds. Utilising optimal model setups and accounting for uncertainty can help to increase confidence in model results to more accurately know who or what is in a flood or wave hazard zone.

Numerical modelling tools can be used to better understand drivers and impacts of coastal change that operate on event timescales, from minutes to hours. High tides, storm surges, or wave events can cause rapid change in coastal and estuarine zones. I have applied models to answer questions about the influence of hydrodynamic on specific coastal phenomena. For example, XBeach was used to quantify the influence of changes in intertidal morphology on wave runup at Camber Sand, SE-England. Delft3D-FLOW-WAQ was used to explore the dispersal and distribution of macroplastics under monsoon conditions in the Savu Sea region of Indonesia.