3.1.1. Tidal Fluvial Flooding

In the present day, there are currently 1000 properties shown as "at risk" to an extreme (1 in 200-year Return Period (RP) or 0.5% Annual Exceedance Probability (AEP)) tidal event in Bristol. The future number of properties at risk rises to 3700 in the eventuality of an extreme (1 in 200-year RP or 0.5% AEP) tidal event in Bristol becoming apparent in the future (2115) when considering the predicted effects of sea-level rise.

The increase in predicted flood extents over the coming decades is illustrated in Figures 4–6. The flow of the River Avon through central Bristol is from East to West, discharging in the Severn Estuary. The tidal influences already cause flooding from the River Avon and Bristol Floating Harbour during exceptional high spring tides and sea-level rise will exacerbate this problem in the future.

**Figure 4.** Flood depths and extent for a 0.5% AEP tidal flood event for the 2010–2044 scenario.

**Figure 5.** Flood depths and extent for a 0.5% AEP tidal flood event for the 2044–2079 scenario.

**Figure 6.** Flood depths and extent for a 0.5% AEP tidal flood event for the 2079–2115 scenario.

In respect of flood hazard mapping, it is evident that the potential impact of climate change (primarily sea-level rise) will have huge implications for properties at risk and for the continuity of city services. Figure 7a,b displays this.

The DeFRA methodology for assessing flood hazard is accepted for application in the UK, applicable to Bristol. Flood hazards posing a danger to people have also been assessed, however, through other means in the works conducted by Martinez-Gomariz E et al. (2016), Chanson H and Brown R (2015), Russo B et al. (2013), Arrighi C et al. (2017) that could be more applicable at other localities [40–43].

**Figure 7.** Hazard mapping for the 0.5% AEP tidal/fluvial event in (**a**) Present day (left) (**b**) 2115 (inclusive of climate change) (right).
