BEYOND ENGINEERING - Hidden Drivers of Flood Risk

When I was involved in a flood mitigation project and risk assessment, the emphasis was largely on engineered solutions. The measures included flood gates and high-capacity pump systems to manage peak flows and tidal backflow, detention ponds for temporary stormwater storage etc. Rubber dams were also suggested to regulate river levels. Drainage systems were upgraded, and steel bridges were improved to increase hydraulic capacity and reduce debris blockages. Road designs were revised, including widening carriageways and improving turning radii, enhancing runoff management and reduce flow constrictions.

Restrictions on hillside development where uncontrolled slope development reduces natural infiltration, increases surface runoff, accelerates erosion, and raises risks of landslides and sedimentation downstream.

The discussions identified multiple causes of flooding - rapid urbanisation, inadequate drainage systems, uncontrolled land clearing, excessive surface hardening due to development, encroachment into river reserves, poor drainage maintenance, climate change-driven extreme rainfall, weak enforcement of planning controls, river sedimentation, narrowing of waterways due to unregulated structures and limited flood retention areas.

However, I was concerned that illegal logging and illegal sand mining were given far less emphasis. From a field and technical standpoint, both are significant contributors to flood risk. Illegal logging removes forest cover that serves as a natural catchment buffer, reducing infiltration, increasing surface runoff, accelerating soil erosion, and increasing sediment loads in rivers. Over time, this reduces channel capacity and raises both flood levels and frequency downstream.

Similarly, illegal sand mining alters river morphology and destabilises riverbanks, disrupting natural flow regimes. Excessive extraction creates uneven riverbeds, deepening certain sections while destabilising others, leading to increased erosion, bank collapse, and unpredictable hydraulic behaviour during heavy rainfall. Collectively, these effects significantly worsen flood vulnerability.

For more than a decade, I have advocated for Malaysia to have its very own Flood Risk Act, similar to frameworks in the UK and the US. Such legislation should go beyond infrastructure and adopt integrated floodplain management, including protection of catchment forests, strict enforcement against illegal logging and sand mining, mandatory flood risk assessments for all developments, preservation of natural retention zones, climate adaptation planning, and stronger inter-agency coordination.

It should also strengthen early warning systems, data-driven hydrological planning, community preparedness, and long-term land-use control. Most importantly, the approach must shift flood management from a reactive disaster-response model to a preventive, science-based national framework.