Watershed Response from Design and Threshold Rainfalls Leading to Cascading Effects of Landslide

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Andrian A. Caisip, Fibor J. Tan


Mountainous watersheds are prone to earthquakes and extreme precipitation events causing slope failures leading to
landslides and landslide dams. These events negatively affect the river channels and the water storage capacity of streams and
reservoirs. With the increasing water demand, sustainable development on water sufficiency has been receiving a lot of attention,
and acquiring a comprehensive watershed runoff is necessary. The main objective of this research is to determine the watershed
response in Antamok River using different designs and threshold rainfalls through hydrologic modeling. The hydrologic modeling
process utilized the Hydrologic Engineering Center – Hydrologic Modelling System (HEC-HMS) software. The watershed
response from the rainfall event that triggers landslide is quantified as 509.931 m3/s which is, as expected based on the intensities far below the flows from the design storms which are as follows; 1645.744 m3/s for 5-year, 2028.355 m3/s for 10-year, 2511.654 m3/s for 25-year, 2869.767 m3/s for 50-year, and 3224.789 m3/s for 100-year.

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