Mapping the Impacts of Typhoon Goni inCamarines Sur
Geomatics for Environment and Development
MANILA OBSERVATORY
November 9, 2020

Summary• Low-lying municipalities (with elevation of less than 10 meters
above sea level) were flooded (flood extent was estimated to2
be 295 km ) due to rainfall exceeding 150 mm during theonslaught of Typhoon Goni.
• Roughly 200,000 people or 10% of the province’s population
were estimated to be flooded.
• Buildings in different parts of the province were damaged. Thetyphoon damaged a total of more than 10,000 houses.
2• 281 km of land for annual crops were flooded.

Low-lying Areas in Camarines Sur

Typhoon Goni (Nov. 1, 2020)

Low-lying municipalities:
Libmanan
MinalabacCalabanga
Bula
CanamanLagonoy
SirumaMagaraoTinambac
Ragay
Caramoan
Cabusao

Baao
Garchitorena
Pamplona
MilaorNabua
San Fernando
San Jose
BombonGainzaDel Gallego
Bato
Naga City

SagñayPasacaoCamaligan
Sipocot
Presentacion
BalatanTigaonLupi
Iriga CityGoa
PiliFlooded Areas in Camarines Sur

Typhoon Goni (Nov. 1, 2020)24-hour Total Rainfall
Global Precipitation Measurement (GPM)
31 Oct 8 PM – 1 Nov 8 PM
http://sharaku.eorc.jaxa.jp/GSMaP_NOW/index.htm• Highlighted in blue are the observed flooded areas
in Camarines Sur (295 km2) after >150 mm of rain
due to Typhoon Goni on Nov. 1, 2020.
• Flood extent was detected by thresholding the difference ofpixel values of Sentinel-1 SAR image taken on Nov. 1, 2020and Oct. 2, 2020 in Google Earth Engine.
• Please note that flood extent could be underestimated inurban areas due to complex backscattering over builtsurface.
• Note also that no ground validation was done for this map.

30 Flooded municipalities in Camarines Sur
Libmanan
Bula
Minalabac
Nabua
Canaman
Baao
Calabanga
Pamplona•

MilaorGainzaSanFernando
Bato
MagaraoCabusao
BombonSAR – Synthetic Aperture Radar

Iriga City
Buhi
PiliCamaligan
San Jose
Naga City
OcampoLagonoy

TinambacSagňayPasacao
TigaonGoa
Balatan
SipocotFlooded Population in Camarines Sur

Typhoon Goni (Nov. 1, 2020)

Estimated Population in FloodedMunicipalities• Roughly 200,000 people or 10% ofCamarines Sur’s population wereflooded.
• This estimation is based on thedetected flooded area and PSA’s
barangay population data of 2015.
• More than 10,000 residents wereflooded in Nabua, Calabanga, Bula,Libmanan, Milaor, Canaman,
Minalabac, and Baao.
• Please note that due to the limitationof flood detection over urban areasusing SAR images, the flooded
population in urbanized cities likeNaga City might be underestimated.
••

PSA – Philippine Statistics Authority
SAR – Synthetic Aperture RadarAffected Population in Camarines Sur as of Nov. 8, 2020Typhoon Goni (Nov. 1, 2020)• NDRRMC reported that Goni affected atotal of 159,722 persons in Camarines
Sur.
• Iriga City, Bato, Calabanga, Siruma
have the highest number of affected
population (>10,000 persons).
•NDRRMC – National Disaster Risk Reduction and Management Council

Damaged Buildings in Camarines Sur

Typhoon Goni (Nov. 1, 2020)• Highlighted in yellow are the location ofbuildings and in red the possible location ofbuilding damage due to inundation and strong
winds of Typhoon Goni.
• NDRRMC reported a total of 13,718 damaged
houses of which 3,042 were totally damaged
and 10,674 were partially damaged.
••••••••

Building locations were merged from OSM data and AI predictions
on Bing Map images from Netherlands Red Cross for typhoon
Goni.
Damaged areas were detected using synthetic aperture radar dataof Sentinel-1 of European Space Agency by ARIA-SG team of Earth
Observatory of Singapore (EOS) in collaboration with NASA-JPL andCaltech.
Please note that no ground validation was done for this data.
NDRRMC – National Disaster Risk Reduction Management Council
OSM – Open Street Map
AI – Artificial IntelligenceNASA - National Aeronautics and Space Administration
JPL – Jet Propulsion Laboratory

Damaged Buildings in Camarines SurTyphoon Goni (Nov. 1, 2020)

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Damaged Houses in Camarines Sur

Typhoon Goni (Nov. 1, 2020)• NDRRMC reported that Goni damageda total of 13,716 houses in Camarines
Sur.
• Bato, Calabanga, and Tinambac havethe highest number of damaged
houses (>1,000 houses).
•NDRRMC – National Disaster Risk Reduction and Management Council

Affected land cover in Camarines Sur

Typhoon Goni (Nov. 1, 2020)• Based on this map, flooding affected22281 km of annual cropland, 3.9 km
2of perennial cropland, and 1.5 km of
built-up area in the province.
• Note that the land cover data used was 5years old and that flood detection fromradar images tends to be underestimated.

• Aside from the agricultural damage
caused by floods, crops were also
damaged due to strong winds.

• Multi-temporal RGB composite ofSentinel 1B GRDH IW images capturedon (R) November 1, 2020, (G) October
20, 2020, and (B) August 9, 2020.
• Blue portions show the fields plantedwith rice in August that was covered
with water on Oct. 20, 2020.
• Green regions show the fields plantedwith rice in August that was flooded
on Nov. 1, 2020 due to Typhoon Rolly.
• Black – open water• Yellow• This map is not ground validated.

Calabanga

Naga
Pili

S1B_IW_GRDH_1SDV_20201101T095742_20201101T095807_024070_02DC13_74FA
S1B_IW_GRDH_1SDV_20201020T095742_20201020T095807_023895_02D69A_5CF1
S1B_IW_GRDH_1SDV_20200809T095740_20200809T095805_022845_02B5D2_98C5• RGB – Red Green Blue
• GRDH – Ground Range
Detected High Resolution(10x10 m)• IW – Interferometric WideSwath Mode• Sentinel 1 SAR images captured on August 9, 2020, October 20, 2020, and Nov. 1, 2020 to show the change in agriculturalland• Pink – potentially rice field• Blue – surface water

S1B_IW_GRDH_1SDV_20201101T095742_20201101T095807_024070_02DC13_74FA
S1B_IW_GRDH_1SDV_20201020T095742_20201020T095807_023895_02D69A_5CF1
S1B_IW_GRDH_1SDV_20200809T095740_20200809T095805_022845_02B5D2_98C5

Typhoon Goni (Nov. 1, 2020)

Typhoon Goni (Nov. 1, 2020)

Typhoon Goni (Nov. 1, 2020)

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