PROPOSED REGIONAL FLASH FLOOD WARNING SYSTEM FOR SOUTH AFRICA:

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PROPOSED REGIONAL FLASH FLOOD WARNING SYSTEM FOR
SOUTH AFRICA Enhancing the Early Warning of
Flash Floods
Eugene Poolman South African Weather Service
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OUTLINE OF PRESENTATION

• Southern Africa region of extremes
• Flash flood early warning system in South Africa
• Way forward

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SOUTHERN AFRICA REGION OF EXTREMES

• Most important natural disasters in Southern
  Africa
• Droughts,
• Floods,
• Windstorms,
• Epidemics

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Source Global Archive Map of Extreme Flood
Events since 1985 to 2002 (Dartmouth Flood
Observatory)
Flood fatalities Southern Africa in the Global
context
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Flooding events between 1985 and 2002
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Impact Of Disaster Risk In Southern Africa

• Disaster risk
• hazard x vulnerability
• coping capacity
• Of the 14 SADC countries, 9 are Least Developing
  Countries (of 49 globally)
• - Increased vulnerability
• - Reduced coping capacity Increased Disaster Risk
• Weather Services aim to reduce the RISK through
  early warning of flooding

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FLASH FLOOD EWS IN SOUTH AFRICA
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Early Warning through increased lead-time
Tools
Observations
NWP
GCM
GCM

• -Satellite
• Radar
• Synops
• Raob

• Regional
• Local
• Mesoscale
• Ensembles MOS

• Medium range models
• Ensembles
• MOS

-Ensembles -MOS
-Ensembles -MOS
-GCM Ensembles -MOS
Forecast Uncertainty
3-Month Season
Month
14 Days
7 Days
Outlook -Rainfall temperature anomalies

• Guidance
• -Potential hazardous weather events
• Rain and temperature tendencies

2 Days
Advisories -Severe weather events -Daily Weather
elements
0 2 Hours
Warnings -Severe weather -Daily weather elements
Products
Detail Warnings -Severe weather
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Meteosat 8 (MSG)

• 12 Channels
• 15 minutes
• Specialized products

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Radar Network
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Tropical Cyclone Eline January 2000
Numerical Weather Prediction

• Now upgrading to
• 12km regional model
• 5 km mesoscale in selected areas

5 km
15 km
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Ensemble Prediction
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SA Weather Early Warning System
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Warning and Advisory Coordination and
Dissemination

• Current warning for flash floods
• Areas of expected heavy rain with potential
  of flash flooding

NDMC, Media, DWAF
NFC
MDMC
RFO
PDMC
RFO
PDMC
MDMC
PDMC
RFO
RFO
PDMC
MDMC
MDMC
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Disaster Management lessons from the
Montagu-floods of March 2003

• The need for EWS integrated into DRM, improve
  warning dissemination prior and during weather
  event
• Poor communication of warnings to communities at
  risk
• Use rainfall hydro data at time of flood to
  determine areas affected

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Case study April 2005 Bredasdorp Floods

• In April 2005 a severe weather system caused
  widespread flash flood damage on the Cape South
  Coast

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According to News24.com

• Torrential rain lashed the region on Sunday
  night, causing millions of Rands damage.
• In Bredasdorp between 600 to 800 houses were
  damaged, and 3 000 people affected.
• In Mitchells Plain, Bellville, Durbanville and
  Khayelitsha heavy rains, a strong wind and
  hailstorms created havoc
• In the Joe Slovo informal settlement, hundreds of
  people were also affected by the downpour.
• ..

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Radar Imagery
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Forecasting Ensemble and NWP Guidance
Eta model 24 hour forecast
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• Forecasting Advisories and Warnings to
  Disaster Management (SMS and direct
  communications)
• 8/4 (Friday) Advisory Widespread showers
  expected Sunday along south coast and adjacent
  interior with possible heavy falls in places E of
  Still Bay
• 10/4 (Sunday) Warning Heavy falls likely today
  (Sunday), Overberg, Breede River valley, Ruens,
  Little Karoo, South Coast persisting in east
  tomorrow morning Monday
• Update1 Warnings as issued earlier, heavy fall
  will last longer along the south coast areas and
  improve during tomorrow from the west.
• Update 2 Please keep communication channels
  constantly open as in past.
• Update 3 Warnings as issued earlier, heavy falls
  will last longer and improve during tomorrow
  (Mon) from the west
• Gale force south easterly winds (35knots/65km/h)
  expected in places Between T/Bay and C/Agulhas
  today and Mon Morning
• There seems to be a well developed weather
  systems to NW of CT. If this moves across (from
  eve) we might have substantial falls in CT

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Challenges to the Early Warning Systemfor Flash
Flood Warnings

• Lack of FF decision support system prior to event
• Need to use rainfall hydro data at time of
  flood to determine areas affected
• Communication of warnings to communities at risk
  differs
• Developed regions vs
• Developing regions
• Needed increased lead-time to overcome
  communication problem to rural communities
• Rather issue a warning and be wrong, but do not
  miss the event!

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WAY FORWARDAn Integrated Flash Flood
Forecasting System

• Discussions between meteorologists, hydrologists
  (Prof Geoff Pegram) and disaster managers
• It was clear that flash flood warnings had little
  hydrological basis
• Proposed solution similar to the CAFFG
• Development a mammoth task
• Discussions with NOAA very positive

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Combine QPE, QPF with hydrological model to issue
FF guidance and warnings to Disaster Management
and communities
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How might we get Soil Moisture?Mapping
Brightness Temperature(Prof Geoff Pegram)
Related Research Activities
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Soil Moisture Liebenbergsvlei ground
temperatureat 15 minute intervals on May 30 2005
from MSG
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Combining Gauge, radar and satellite
rainfall21-22 June 2005(SAWS UKZN)
Kriged Rain Gauge Field
Radar Rain Estimate
Meteosat 8 (MSG) Rain Estimate
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Merged Sat/Radar/Gauge Rainfall Field
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The envisaged development of the FFF system

• Team to include meteorologists, hydrologists and
  disaster managers
• Develop FFF system over quaternary basins
• Hydrological information available
• QPE from rain gauges, radar, MSG
• QPF from nowcasting techniques, NWP
• Integrate with Disaster Management Centers
• Dissemination of warnings and info to DM
  structures
• Inform communities at risk, awareness raising
• Involve other countries where possible to develop
  a Southern African regional system