American Society of Civil Engineers

Rainwater Harvesting and Green Roof Irrigation Design for a Peaked Roof: A Graduate Directed Study

by Cheryl A. Smith, P.E., (Graduate student, Department of Civil Engineering, Lawrence Technological University, Southfield, MI. E-mail: and Edmund E. Yuen, Ph.D., P.E., M.ASCE, (Assoc. Prof. of Civil Engineering; Chair, Department of Civil Engineering, Lawrence Technological University, 21000 West Ten Mile Road, Southfield, MI 48075-1058. E-mail:
Section: Watersheds, pp. 4370-4378, (doi:

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Document type: Conference Proceeding Paper
Part of: World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability
Abstract: This design is for a rainwater harvesting/green roof irrigation system for a facility located in a temperate climate. The peaked building roof is composed of metal on the southern elevation, and an extensive green roof on the northern elevation. The rainwater harvesting system was designed using EPA software, Storm Water Management Model (SWMM) 5.0. The rainfall data input was generated using intensity-duration-frequency (IDF) equations for Oakland County, Michigan. Rainfall hyetographs for a 1-hour storm duration for 1-, 5-, and 10-year design storms, were synthetically generated using the Alternating Block method. Rainwater volumes of 58.3 ft3 (1.65 m3), 117.7 ft3 (3.33 m3), and 132.9 ft3 (3.76 m3) were modeled based on the 1-year, 5-year and 10-year storms, from the 978 ft2 (90.9 m2) metal section of the roof. The green roof irrigation system was modeled using EPANET 2.0. Based on seasonal rainfall data, and specified pump operation, a 15-minute watering of the 1387 ft2 (129 m2) green roof, with overall flow of 21.76 gpm (82.37 lpm) is achievable once every 5 –6 days.

ASCE Subject Headings:
Green buildings