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

ABSTRACT 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 roof. Results shown that rainfall intensities between 12.8 and 61.6 mm h-1 (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.

摘要：雨水收集（Rainwater harvesting）指收集屋顶、街道等低渗透表面产生的径流。此类系统的设计通常基于雨量计（pluviometer）数据，而非自记雨量计（pluviograph）数据，因此未能纳入影响可收集雨水量的关键数据。本研究通过在陶瓷瓦屋顶上模拟低、中、高三种强度的降雨，开展了室内实验。实验结果显示，当降雨强度介于12.8至61.6 mm·h⁻¹（中至高降雨强度）时，径流系数（runoff coefficient）大于0.9；而当降雨强度较低（低于1.2 mm·h⁻¹）时，径流系数会大幅下降，当降雨强度低于0.25 mm·h⁻¹时，径流系数甚至降至0。综上，在本次模拟实验条件下，相较于中高强度降雨，陶瓷瓦的吸水率对极低降雨强度下的径流影响更为显著。