Our decision-makers need to have a deeper understanding of the destructive force of water and its relationship with land to significantly prevent flooding in times of weather disturbances.
Residential areas in low-lying cities always fall victim when tropical storms, monsoon rains and other climate phenomena trigger heavy rainfall. Communities are submerged in stormwater, causing inconvenience to the public and putting lives and properties in peril.
This eyesore of a situation is on a continuous repeat every time the Philippines is hit by typhoons or even just on the receiving end of habagat. For some, it has become a habit to pack their belongings and be prepared to be evacuated by their local officials when the sky turns gray.
But amidst this recurring burden, the government has yet to impose a definitive solution.
“Despite the laws on disaster risk management and climate change adaptation, and the government’s adoption of programs and projects to mitigate climate-induced disasters, there is something missing from all of these efforts as deaths and destruction continue unabated. A cursory review of laws, policies, and programs on flooding shows that we do not have a national policy on stormwater management,” Nathaniel von Einsiedel, chairman and principal urban planner of Consultants for Comprehensive Environmental Planning (CONCEP) Inc., said.
Stormwater cannot assimilate into impenetrable land surfaces such as concrete, asphalt pavement and streets, parking lots, and rooftops during rainfall events. Since it cannot penetrate the ground, it simply “runs off” into waterways and low-lying areas.
However, it is a different situation in forests and open green spaces where rainwater takes time to reach a river. When impervious surfaces are added to a watershed, the water reaches rivers quickly and in large volumes.
This is why an effective watershed management plan is a must as a nature-based solution to prevent flooding.
Preventing runoff means protecting the trees and green spaces found in riparian zones. These are lands that occur along the edges of rivers, streams and other water bodies.
A 2022 case study entitled “Nature-Based Solutions for Flood Risk Management: Revitalizing Philippine Rivers to Boost Climate Resilience and Enhance Environmental Stability” said that flood conveyance solutions help increase the river’s capacity to contain high discharge during heavy rainfall. This happens when the river’s drainage is improved to enable quick release and flow of stormwater before it accumulates and floods.h
Anything that obstructs the normal flow of water will also affect the flow of stormwater.
The case study also pointed out that water retention and detention are other solutions that smoothen the flow of water during heavy rainfall. It can control the flow of stormwater since it is not sudden and does not surge unexpectedly.
Bank erosion control is another nature-based solution to consider. This aims to reduce the sediment-carrying capacity of the river by reducing its flow. This is because floodwaters in eroded riverbanks are outpouring since they are carrying sediments and debris.
Structural and non-structural flood impact reduction such as the implementation of early warning systems and flood zoning are also nature-based alternatives to prevent flooding, according to the study.
The 2022 case study centers on utilizing the functions of natural river systems to boost climate resilience at a comparatively low cost. These are simple nature-based solutions like restoring wetlands, developing water retention areas, removing obstacles and reviving old channels.
