Climate Adaptation Engineering Bulletin 2
Engineers now accept that what was once assumed to be unchanging (i.e. “stationary”) is now fluid – literally, due to ongoing climate changes associated with a warming world. As these trends will continue, rainfall intensities will change, as is already being seen in the United States.
“Predicting Future Precipitation Intensity, Duration and Frequency,” edited by Dan Walker, Ph.D., and Craig Musselman, P.E., discusses the current state of available data and the ability to forecast changes as a result. The primary source of estimates has been a dataset first released by the National Weather Service 25 years ago known as Atlas 14, which presents data to date but does not project future changes. Next year, the weather service is expected to release Atlas 15 in two volumes with up-to-date datasets and projections through 2100. What can engineers expect and how might it change engineering practice? Read Climate Adaptation Engineering Bulletin 2. Below is the paper’s opening.
Climate Adaptation Engineering Bulletin 2
Predicting Future Precipitation Intensity, Duration and Frequency
The intensity, duration and frequency (IDF) of expected precipitation at a given location is a critical design input in m.any aspects of civil engineering. As an example, hydraulic structures are typically designed for the rainfall amount expected during an event of a given duration (in hours) and of a given probability expressed as an annual exceedance probability (AEP) or recurrence interval in years (e.g., 0.04 AEP or 25 years for simple projects where overflowing roadways is acceptable or 0.002 AEP or 500 years for major buildings or bridges). There are many civil engineering applications of future rainfall IDF estimates, including both high intensity events and drought occurrence.
Most civil engineering applications have, until recently, assumed climate conditions to be statistically “stationary” (i.e. a constant, unchanged over time). It is now recognized that climate conditions exhibit “non-stationarity” reflecting long-term (30 years or longer) statistical changes associated with a warming world, and those trends are expected to continue, or in some cases accelerate, into the foreseeable future. In a nonstationary climate, rainfall intensities will change - most in the United States will increase. Accounting for such changes in civil engineering projects that have service lives of 50 to 100 years is critical going forward, requiring new estimates that account for projected changes in climate that are in development by NOAA's Office of Water Prediction (a part of the National Weather Service [NWS]).
Read the bulletin in its entirety, then share your perspectives in the ongoing discussion in the Committee on Adaptation to a Changing Climate online community in ASCE Collaborate.
Read Climate Adaptation Engineering Bulletin 1: How updated federal sea level rise projections apply to your projects.
