Influence of rainfall intensity on the production of runoff on ceramic tile roofs: laboratory experiments under simulated rainfall

Rainwater harvesting consists on the collection of runoff from low permeable surfaces, as roofs and streets. Designing these systems is often based on pluviometer data and not on pluviograph data, therefore they do not consider crucial data on the amount of rainwater available to harvesting. Laboratory experiments were conducted by simulating low, moderate and high intensity rainfall on a ceramic tile root. Results shown that rainfall intensities between 12.8 and 61.6 mm (moderate to high intensity) lead to runoff coefficients greater than 0.9, while for rainfall low intensities (lower than 1.2 mm h(-1)), the runoff coefficient drastically decreased, reaching values of zero for rainfall intensities lower than 0.25 mm h(-1). In conclusion, for the simulated experimental conditions, water absorption of the ceramic tiles is more significant on the runoff for very low rainfall intensities than the strong or moderate rainfall intensities.