Vulnerability assessment to landslides and flooding along the Sta. Rosa-Silang Riverine system using LIDAR and GIS-based hydrological modeling technologies

Date

2017

Abstract

Occurrence of landslides and flooding had been increasing in the Santa Rosa-Silang sub watershed brought about by extreme weather disturbances including tropical depressions, Southwest monsoon rains, storms and typhoons. Rapid industrializations and urbanization in the past three decades in the subwatershed resulted to massive land use change involving the conversion of agricultural and agroforestry farms into built-up areas. This land use change resulted to increased impermeable soil surface altering the water balance in the subwatershed. The Santa Rosa riverine network with its headquarters from the upstream areas of Silang, Cavite passes through the city of Santa Rosa and drains into the vast Laguna de Bay [Philippines]. In this study, a GIS-based hydrological model, the Soil and Water Assessment Tool (SWAT), was used to simulate the quantities of water inflow and outflow in each of the 49 dominant hydrologic response units (HRUs) along the entire subwatershed area. Spatial information such as its digital terrain model (DTM) extracted from LIDAR and RS data, land cover map and soil map, together with its 36-year (1980 to 2015) rainfall and temperature data, were inputted in the SWAT model's platform to generate the surface flow and sediment yield during rain events in the HRUs within the subwatershed. With these outputs, the subwatershed portions and the specific HRUs vulnerable to flooding and erosion were mapped out. Simulation results showed that the low permeability of soil surface increases the occurrence of flashfloods in low-lying areas. Sloping and open surfaces in the upstream areas are however, prone to landslides. Vulnerability assessment has shown that the communities along the shoreline and riverine system are most vulnerable to flooding and landslides. These results will be useful in the development of area-specific adaptation and mitigation strategies to disasters like landslides and foods.

Language

English

Document Type

Article

Pages /Collation

210 leaves

En – AGROVOC descriptors

WATERSHED MANAGEMENT; WATERSHEDS; LAND USE; LANDSLIDES; FLOODING; SEDIMENT WATER INTERFACE; TOLERANCE; GROUNDWATER TABLE; GEOGRAPHICAL INFORMATION SYSTEMS; PHILIPPINES

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