If the trees are no longer there to stop water run-offs, every drop of water goes rushing to the valleys below. Barren hills and treeless mountains are a recipe for disaster.
Flood control projects can help reduce the impacts of floods. But these projects are often band-aid solutions not to mention the fact that they are often sub-standard which means they cause more harm than good.
Imagine if those billions of pesos wasted on unnecessary and sub-standard flood control projects are used instead in reforestation projects.