Permeable Pavement Cross-Section: Lateral Drainage

This simulator walks across a permeable-pavement reservoir course one column at a time instead of treating it as a single lumped tank. Each column has its own local surface clogging — worst directly beneath the two wheel paths where tyres grind fines into the paver joints — so rainfall enters unevenly across the section. What happens next is genuinely two-dimensional: stored water doesn't just sit where it lands, it spreads sideways through the open-graded stone by a real lateral-diffusion process, letting a saturated wheel-path column relieve itself into drier ground beside it before it has to pond. Drainage to the subgrade below still follows the same Darcy-limited exfiltration as any lumped model, but bypass runoff now has a visible spatial signature: watch ponding appear first exactly where the wheel-path clogging peaks, and see how a stronger lateral conductivity buys time before it does.