Recent land cover change in the Silang-Sta. Rosa sub-watershed of the Philippines, and implications for flood risk

We analyzed the change in vegetated and urban (impervious) area in the Silang-Santa Rosa sub-watershed of the Philippines to assess the implications related to flood risk. Our main findings were:

-The impervious area of sub-watershed increased by 54% (from 3,239 ha. to 4,988 ha.).
-The vegetated area decreased by 21% (from 8,509 ha. to 6,760 ha).
-Upstream: The impervious area increased by 102% in the upstream municipality of Silang, and also increased in upstream parts of Biñan and Santa Rosa City, causing higher runoff (more frequent and intense floods downstream).
-Downstream: The most flood-prone areas in the watershed underwent some of the most development.