Climate and Stormwater

Regulations around stormwater are being adjusted more holistically to take into account the impacts of climate change. Stormwater practitioners use precipitation data derived from a combination of federal datasets and design standards. The most widely used dataset is NOAA Atlas 14, which provides 24-hour, 6-hour, 1-hour, etc., rainfall totals for various return intervals (e.g., 2-year, 10-year, 100-year storms).

These datasets provide analysis of historic precipitation data to inform the sizing of critical stormwater infrastructure. However, historic data is no longer representative of current and future conditions. Today’s stormwater managers are preparing for greater precipitation intensity, warmer temperatures, and rising sea levels in the Chesapeake Bay watershed compared to the past several decades

Volume 2 of Atlas 14 was updated in 2006, and includes a period of record through 2000. However, Atlas 14 used past observed data rather than projections accounting for increasing frequency and quantity in precipitation events due to climate change.

As a result, many states and municipalities are incorporating their own data into their modeling to account for gaps in Atlas 14, using locally observed rainfall records to update their design standards for stormwater practices. NOAA Atlas 15 is in development, and will incorporate climate-adjusted precipitation frequency.