I am working with a company which is involved in Green Building consultancy in Chennai. As part of our work, we are involved in certification of buildings for LEED- Green Building category. One of the criteria for getting certification involves effective stormwater management. The requirement statement is phrased as follows,

"Implement a stormwater management plan that infiltrates, collects and reuses runoff or evapotranspirates runoff from at least 15% of the precipitation falling on the whole project site both for an average weather year and for the two year, 24-hour design storm"

Currently I am working on two project for Chennai. Here are the problems we are facing

1. What is a "Two year, 24- Hour design storm and how can it be determined?
2. What is the difference between "Average weather year" and " 2 year-24 hour design storm"
3. What would be the intensity of rainfall in mm/hr for Chennai for both "average weather year" and " 2 year-24 hour storm"?
4. Should the detention facilities have sufficient capacity to hold a 24 hour storm run-off?
5. How should the relevant rainwater harvesting structures be designed?

Krithikha Muthukrishnan
m.krithikha@gmail.com