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| Titel |
Predicting the Discharge Rate Contribution of the Binuwang Watershed to the Agos River, Philippines |
| VerfasserIn |
Dakila Aquino, Eduardo Paningbatan, Alfredo Mahar Francisco Lagmay |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250099069
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| Publikation (Nr.) |
 EGU/EGU2014-14815.pdf |
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| Zusammenfassung |
| In 2004, Typhoon Winnie brought torrential rains which triggered massive landslides and
floods which devastated the provinces of Infanta, Real and General Nakar in the Philippines.
Winnie inflicted USD 111.14 million worth of damage to crops, livestock and infrastructure
and left thousands dead or homeless. The Binuwang River is a sub-tributary of the Agos
River, but the extent to which it contributes to flooding has not yet been determined. This
study measures the depth of the Binuwang River to estimate the discharge rate contribution of
the Binuwang River Watershed to the Agos River using an automatic rain gauge recorder and
water level loggers set to record at 5-minute intervals. Flood-generating rainfall events were
monitored during the onset of Typhoon Nesat (locally called “Pedring”) September
26-27, 2011. The automated rain gauge recorded 227 mm cumulative rainfall over a
6-hour and 41-minute period. It reached a peak rainfall intensity of 17.5 mm per
5-minute interval that generated a discharge height increase of 1.8 m at the monitoring
station and a total discharge volume of 99,823 m3 over a 35-hour duration. An
8.81-hour lag time from the peak rainfall to the peak discharge concentration was
recorded.
A PCRaster-based hydrologic model was used to predict the total discharge hydrograph
of the Binuwang River Watershed. A Digital Elevation Model (DEM) and soil and land use
maps were prepared to parameterize the model. The observed and predicted discharge
hydrographs were found to be highly correlated. Among the parameters used to
calibrate the model hydrologic output, most sensitive are the infiltration saturation
coefficient and Manning’s roughness coefficient. An increase in the infiltration saturation
coefficient resulted in a decreased discharge height, while an increase of Manning’s
roughness coefficient lengthened the lag time. The predicted discharge volume and
height were used to simulate the impact of reforestation and land conversion to
cultivated areas in the watershed. The results showed that by converting the brushland
and tree plantation area—which accounts for 78% of the watershed (710 ha)—to
cultivated area, the discharge height could increase by 2 m with a total discharge
volume of 218,694 m3 and shorten the lag time by 1.36 hours. On the other hand,
implementing a reforestation plan for 38% of the watershed (350 ha) covered by brushland,
bareland and grassland areas could substantially lower the discharge height by
1.2 m with a total volume of 20,663 m3 and lengthen the lag time by 8.38 hours. |
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