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10th International Rainwater Catchment Systems Conference
"Rainwater International 2001"
Mannheim, Germany - September 2001

Section I: Rainwater Harvesting in an Urban Context

Paper 1.1

Runoff Absorption Potential of Roofing Materials

Adhityan Appan and Sim Wan Seng
Division of Environmental & Water Resources Engineering
School of Civil & Structural Engineering
Nanyang Technological University


About 48% of the land area in Singapore is being utilised as water catchment. The water abstracted is not sufficient for the increasing demands in a rapidly growing industrial society. Consequently, about 60% of the water is imported. Hence, ways and means are being looked into to harness more water from the rest of the land area in which 86% of the urban population lives in high-rise buildings. The potential catchments being looked into are the roofs of high-rise buildings wherein the water collected at the roofs is of a high order (Appan, 1997) and will also reduce considerably the energy costs. The rooftops are primarily flat and, in some cases, pitched roofs have different types of roofing tiles. Being in a sub-tropical region, where radiated heat can reach very high levels throughout the year, it is envisaged that during tropical downpours, considerable amount of the rainfall is absorbed by the roofing material resulting in a loss in the runoff. The main objectives of this paper are to:

  • to review a few absorption standards for roofing materials and study some of the roofing material used locally · to establish a relationship between heat generated by radiation and the equivalent temperature 
  • to set up an experiment  
  • to study the amount of water absorbed in different roofing materials for the worst condition of a thunderstorm and  
  • to draw conclusions and make recommendations for further research.

PDF of full document (8pp, 33kb)

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