Caribbean Water Initiative2nd Senior Administrators’ Workshop

Flooding in the Caribbean: Improved Forecasting

Presented by:

Shawn BoyceCaribbean Institute for Meteorology & Hydrology

Husbands, St. JamesBarbados

Examples of Recent Flooding in Jamaica

Examples of Recent Flooding in Jamaica

Examples of Recent Flooding in Jamaica

Examples of Recent Flooding in Haiti

Examples of Recent Flooding in Haiti

Examples of Recent Flooding in Haiti

Examples of Recent Flooding in TCI

Examples of Recent Flooding in TCI

Examples of Recent Flooding in TCI

Flash Flooding on Barbados

Flash Flooding on Barbados

2004 Flooding in Guyana

2004 Flooding in Guyana

2004 Flooding in Guyana

Flooding Mechanisms in the Region

Functions of:Rainfall intensityRainfall durationRiverine floodingTidal InfluenceCatchment characteristics

Rainfall IntensityLocalized convective eventsRecording rain gauge dataMaximum accumulations for 5, 10, 15, 30 mins and 1, 2, 6, 12 hour durationsShort duration rainfall frequency analysisShort duration data sparse in the regionEstimate short duration maxima from 24hr data

1hr Frequency Plot

2 5 10 50 100 200 T

0

10

20

30

40

50

60

70

80

90

-2 -1 0 1 2 3 4 5 6

Reduced variate

Ann

ual m

axim

um

rain

fall

(mm

)

Barbados: August, 2008

Rainfall DurationRainfall on consecutive daysIncreased saturation levels (i < K)Surface ponding (i > K)Frequency analysis on rainfall accumulations greater than 1 day

Guyana: January, 2005

Riverine FloodingFlooding when river overflows banksFlood risk high

Fertile landsHeavily populated

Rainfall generated surface runoff + river channel routingFactors that affect runoff need to be considered

Climatic factorsCatchment characteristics

Jamaica: August, 2008

Tidal InfluenceStorm surge

Significant flooding along low lying coastlinesHurricane related

Spring tidesHigh tides + rainfall

Increases the probability of floodingContributes to flooding in Guyana

Martinique: November 1999

Catchment CharacteristicsWatershed delineation

DEM resolutionCatchment size and shape

Land use and land coverSoil and rock types

Infiltration ratesHydraulic conductivities

Characteristics can be used to determine high risk zones

Narrow, steep sided valley in Dominica

Objective:Integrate precipitation forecasts into a hydrological model

Provides an early flood warning system before the precipitation eventLead times of at least two daysForecast updates (weather radar)Water depths simulated throughout catchmentFlood extents delineated

Improved Flood Forecasting

Weather Research Forecasting model Outputs: atmospheric variables at all levels of the troposphere; the state of the atmosphere at different times in the future Forecasting tool:

Provides simulations on different spatial scalesReal-time forecasting out a fortnightCan be altered to better represent the tropical atmosphereRegional climate scenarios

HydroGeoSphere (Hydrological Model)Outputs: Water depths; SW/GW flows; GW saturations; ConcentrationsWater resources management tool

Flood forecastingSimulate impact of contaminant transportSimulate climate change scenarios scenariosReal time monitoring

The Models

Calibration and ValidationLocalized convective event in Barbados 26/08/2008, 12:00-00:00 UTC

*TMPA-RT

60.94km x 4kmWRF V3.0

1.40.25° x 0.25°TRMM 3B42*

29Point estimateRain gauge

Rainfall(mm)

ResolutionInstrument

Calibration and ValidationObserved data

Weather radar (calibrated) dataHydrometric network installationsData logging and transmission

Uncalibrated Water Depths at Arch Cot, St. Michael

Complementing InitiativesCARIWIN

Capacity BuildingCCRIF

Flood risk insurance feasibilityCarib-HYCOS

Hydrometric networks, Database management software

Italian projectHydrometric networks