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)