855773644-LEED-v5-BD-C-Reference-Guide-Launch-Edition - Page 134
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beyond the immediate building site boundary and encompasses the entire watershed area associated with the project.
Managing runoff Projects using this option must retain or manage runoff per the regional/local rainfall percentiles. Percentile calculations help determine how rare or common a particular rainfall event is by comparing it to historical data. By analyzing rainfall percentiles, projects can implement appropriate strategies for water storage, distribution, and retainment.
Table 2 provides a sample list of options that meet the requirements for LID and GI measures. [55]
Table 2. LID/GI measures
| LID/GI measure | Description and additional details |
|---|---|
| Rain gardens and Bioretention gardens | These are decorative gardens which have plants and soil that filter runoff water and encourage infiltration. This practice is ideal for collecting runoff from rooftops, sidewalks, roads, and small parking lots. |
| Green roofs | Green roofs include plants and soil media that capture and filter water that would have previously been considered runoff. |
| Rainwater harvesting | Ideal for collecting rooftop runoff, a rainwater cistern captures and stores (e.g., harvests) runoff for later use. Common uses of collected rainwater are for irrigation or for indoor plumbing fixture flushing. Project teams that use any rainwater harvesting strategies with the intent of reuse will earn additional points. |
| Vegetated swales | The shallow, open channels are ideal for collecting sheet flow runoff from roads, highways, and from subdivisions. |
| Permeable pavement | Permeable pavement allows stormwater to pass through and into gravel layers, allowing stormwater to soak into the soil. This practice is ideal for developed areas, such as parking lots and driveways. |
| Exfiltration trenches | Surface runoff collected through drainage inlets and directed into the trench via subsurface perforated pipes. The runoff infiltrates into the ground through the trench’s gravel bed, which filters the pollutants. |
Rainfall event calculations The percentile of rainfall events measures the precipitation depth accumulated over 24 hours, typically defined as 12:00:00 a.m. to 11:59:59 p.m., and it relies on the range of all daily event occurrences during the period of record.
Projects in the U.S. may use percentile rainfall events as determined by the National Climatic Data Center. International projects can use the Global Precipitation Climatology Project (GPCP) Daily Precipitation Analysis, provided by the National Centers for Environmental Information (NCEI). [56]
55 Martin-Mikle, C. J., de Beurs, K. M., Julian, J. P., & Mayer, P. M. (2015), Identifying Priority Sites for Low Impact Development (LID) in a Mixed-use Watershed, sciencedirect.com/science/article/pii/S016920461500078X. 56 National Centers for Environmental Information, (n.d.), Climate Data Records: Global Precipitation Climatology Project (GPCP) – Daily.
U.S. Green Building Council LEED v5 Reference Guide for Building Design and Construction, April 2025 Launch Edition 124