Urban pluvial flood forecasting- rainfall data processing- experimental site in Redbridge

Prof. Čedo Maksimović, Dr. Christian Onof, Li-Pen WangDept. Civil and Environmental Engineering, Imperial College LondonVisitors from University of Iowa, 28/05/2010 @ ICL

A more reliable flooding forecast could be implemented if a high-resolution rainfall prediction with longer lead time is carried out

TimeNow

Rainfall Depth

Observed Predicted

ResolutionLead time

Runoff Modelling

Surface Flooding Forecast / Warning

Sewer Simulation

RAINFALL DATA PROCESSING

Aim to carry out high-resolution rainfall forecasting with longer lead time

Numerical Weather Prediction: UM/MM510 km

1 km

C-Band

Meteorological Radar

X-Band1 km

100 m

Ground Raingauge Network

CALIBRATION

T = Future

T = Current i

t

NOWCASTING

1 kmSTATISTICALLYDOWNSCALING

i i

tTemporal

Spatial

Possible improvements in Nowcasting, Calibration & Downscaling

• Information based upon NWP outputs– Advection of rainfields– Larger-scale weather variations

• Enhanced radar observations– X-Band radar and ground raingauge data– Super-resolution techniques to improve the spatial

resolution• Statistically-based space-time downscaling

techniques– Cascade-based spatial disaggregation method– Temporal correlation between successive rainfields

Generalised Linear Models (GLMs)

Poisson cluster based methods

Cascade-based Methods: scale-invariance

Cascade-based methods: mapping to rainfall sequences

1

Level (L):

0

1

2

g

h

p11 p2

1 p31 pb

1

p11p1

2 pb1pb

2

p11p1

2... p1g p2

1p22... p2

g pi1pi

2... pig pb

1pb2... pb

gpb-11... pb-1

g

p11p1

2... p1h

pb1pb

2... pbh pb

1pb2... pb

hpi1pi

2... pih

pi1pi

2

5-min Rainfall

hourly Rainfall• Rainfall volume observed • No rainfall volume observed

time (1-hr)

time (5-min)

Intensity (mm/hr)

EXPERIMENTAL SITE

Cran Brook catchment in the London borough of Redbridge

Redbridge catchment and Roding river

#*

#*

!(

Redbridge

High Ongar

0 7.5 153.75Kilometers

LegendRiver flow gauging stationsCran Brook catchmentSeven Kings catchmentRoding catchment

#*Cran Brook CatchmentThe drainage area is approximately 910 ha.

Radars surrounding the Redbridge area

Three real-time accessible tipping bucket raingauges over the Redbridge catchment (frequency: 1 – 5 min)

Real-time access to 30+ weather monitoring systems in each London Borough (frequency: 30 min)

One pressure sensor for Roding river (frequency: 5-10 min)

Two sensors for water depth measurement in sewers (frequency: 5/10 min)

One sensors for water depth measurement in open channels (frequency: 5-10 min)

Thank you for your attention

Li-Pen Wangli-pen.wang08@imperial.ac.uk