Why are surface drains more common than subsurface drains on newly reclaimed tropical land?

On newly reclaimed tropical land, surface drains are more common than subsurface drains primarily because specific soil and environmental conditions often make subsurface improvements impractical.1

The effectiveness of subsurface drainage relies heavily on the permeability of the soil, which determines how efficiently water can be transmitted to underground conduits. In many tropical regions, the soil characteristics and high rainfall patterns combine to limit the viability of subsurface systems. When soils have low permeability—a common trait in clay-heavy environments—excess water must be removed via surface flow.21

Additionally, newly reclaimed tropical land requires a period of soil stabilization, during which drainage systems often need special attention and reconstruction. While surface drains are installed in uniform patterns and require land grading to function, they remain the most feasible method for managing water in areas where the soil cannot adequately transmit water to subsurface tile lines.132