Mapping Future Hazards in South East London Interpreting climate change models and predicting the impact of EWE’s Dr Stephen Blenkinsop [email protected].

Mapping Future Hazards in South East London

Interpreting climate change modelsand predicting the impact of EWE’s

Dr Stephen [email protected]

SWERVE (Severe Weather Events Risk and Vulnerability Estimator)

SWERVE

UKCP09data

Pluvial flooding

Fluvial flooding

Tidal flooding

Heat wavesSubsidence

Water resources

Wind

• Aim to assess current and future hazards by looking at the baseline (1961-90) 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

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 Allen

Photo copyright Martin Speck

Photo copyright John Lindsay

Photo copyright Stephen Craven

Health related heat thresholds

Subsidence9 classes of combined vulnerability

10th percentile

90th percentile

50th percentile

2020s

BSL

VERY UNLIKELY TO BE LESS THAN

CENTRAL ESTIMATE VERY UNLIKELY TO

BE MORE THAN

Heat wavesHeat 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)

BASELINE LOW CENTRAL HIGH0

0.4

0.8

1.2

1.6

2

Num

ber o

f pot

entia

lly d

amag

ing

even

ts p

er y

ear

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.

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