Mapping Future Hazards in South East London Interpreting climate change models and predicting the impact of EWE’s Dr Stephen Blenkinsop SWERVE (Severe Weather Events Risk and Vulnerability Estimator)

SWERVE UKCP09 data Pluvial flooding Fluvial flooding Tidal flooding Heat waves Subsidence Water resources Wind Aim to assess current and future hazards by looking at the baseline ( ) and the 2020s and 2050s. SWERVE only considered the medium emissions scenario.

The South East London Resilience Zone (SELRZ) The challenge: Climate model output is provided at 25 km grid squares. UKCP09 weather generator provides outputs at 5km.

The challenge: UKCP09 provides many representations of future climate. This raises issues of: – Practicality – Usability Probabilistic climate change scenarios

Climate variableHazardDefinition Flooding Urban flooding Flood depth and frequency based on critical thresholds and a new hazard number index combining information on maximum and average flood depth and flood extent. Subsidence Clay-related soil subsidence A 9-point vulnerability score based on the combination of soil and climate data, ranging from ‘Extremely Low’ to ‘Extremely High’. Temperature/heat Heat waves Vulnerability & risk indices Heat wave frequency based on sequences of London specific temperature thresholds (32°C- 18°C-32°C). Indices based on current and future population projections. Water resources Disruption to water supply Frequencies of a range of interventions from public awareness campaigns to hosepipe bans and rationing. Wind Risk of damage to buildingsMaximum gust speeds of at least 35 ms -1. Risk of damage to buildings and pedestrians Critical depth thresholds and a new hazard number index Disruption to water supply A 9-point vulnerability score Photo copyright Kenneth AllenPhoto copyright Martin Speck Photo copyright John Lindsay Photo copyright Stephen Craven Health related heat thresholds

Subsidence 9 classes of combined vulnerability 10 th percentile 90 th percentile 50 th percentile 2020s BSL VERY UNLIKELY TO BE LESS THAN CENTRAL ESTIMATE VERY UNLIKELY TO BE MORE THAN

Heat waves Heat wave (5km) hazard (32°C - 18°C - 32°C) Vulnerability information Risk maps

Hourly, 5km 15minute, 2km Flooding High Low Medium UKCP09 sample applied to rainfall model and Urban Inundation Model

Max HN Baseline 9 Max HN 2050s

Water Resources Rainfall series : baseline, 2020s and 2050s Associated river flows Environment Agency’s London Water Resource Zone model (AQUATOR). Level of service Action 1 (1 in 5 y) Media campaigns, additional water efficiency activities 2 (1 in 10y) Enhanced media campaign, customer choice/voluntary constraint, sprinkler ban 3 (1 in 20y) Hosepipe ban, non-essential use ban, drought order 4 (never) Severe water rationing e.g. rota cuts, stand pipes

Future demand saving day levels (climate change only)

Total demand saving days: 2050s (climate change & demand)

Damaging winds Baseline ‘Low’ climate projection ‘High’ climate projection ‘Central estimate’ climate projection

Future heat wave risk is greatest in high-density residential areas in the centre and the east of London. 2020s and 2050s see localised increased flooding hazard when compared with the baseline. Increased subsidence vulnerability in Croydon and North Downs. A combination of demand management and new water supply options need to be considered for the Thames. Headlines