Framework for Incorporating Downscaled Climate Output into Existing Engineering Methods: Application to Precipitation Frequency Curves

Abstract

Abstract:To improve the resiliency of designs, particularly for long-lived infrastructure, current engineering practice must be updated to incorporate a range of future climate conditions that are likely to be different from the past. However, a considerable mismatch exists between climate model outputs and the data inputs needed for engineering designs. The present work provides a framework for incorporating climate trends into design standards and applications, including: selecting the appropriate climate model source based on the intended application, understanding model performance and uncertainties, addressing differences in temporal and spatial scales, and interpreting results for engineering design. The framework is illustrated through an application to depth-duration-frequency curves, which are commonly used in stormwater design. A change factor method is used to update the curves in a case study of Pittsburgh, PA. Extreme precipitation depth is expected to increase in the future for Pittsburgh for all return periods and durations examined, requiring revised standards and designs. Doubling the return period and using historical, stationary values may enable adequate design for short duration storms; however, this method is shown to be insufficient to enable protective designs for larger duration storms.

Framework for Incorporating Downscaled Climate Output into Existing Engineering Methods: Application to Precipitation Frequency Curves

“…When it is available to choose between multiple emissions trajectories, the authors recommend analyzing at least two scenarios when possible: (a) an upper bound that will provide the most conservative estimate of future conditions for use in engineering practice, such as SRES A2 (projecting 2.0 -5.1 °C of warming by 2100) or RCP 8.5 (5-6 °C by 2100), and (b) a lower bound that is aligned to targets of the Paris agreements (Framework Convention on Climate Change 2015), similar to SRES A1B and RCP 4.5. Choosing between emissions scenarios is most relevant for infrastructure of long lifetimes (40 years or more), since many impacts across emissions scenarios generally diverge after the middle of the century (Collins et al 2013). Irrespective of the scenarios and model sources that are ultimately chosen by the engineer, it is important to document assumptions and make them available to those interpreting the findings.…”

“…Climate change has the potential to affect infrastructure systems in multiple ways, including: (i) changes in average and/or extreme temperatures; (ii) variations in frequencies, intensities, and duration of precipitation causing extreme rainfall and flooding in some regions; (iii) changes in storm tracks and severe weather; (iv) an increase in sea levels and the risk of storm surge; and (v) a decrease of water availability in some areas (Walsh et al 2014;IPCC 2014;Kilgore et al 2016).…”

Temporal and spatial evaluation of stormwater engineering standards reveals risks and priorities across the United States

“…For example, a structure designed using a 25 year depth from TP40 may be inadequate to handle increases in rainfall extremes that were observed in the later Atlas 14 data period. In addition, subsequent increases as result of climate change will further degrade the performance of under-designed structures (Guo 2006, Mailhot and Duchesne 2010, Janssen et al 2014, Cook et al 2017.…”

“…Even with the uncertainty in timing and magnitude of future rainfall patterns (Milly et al 2008, IPCC 2012, Easterling et al 2017 as well as changes in climate variability Evans 1997, Barros et al 2017), several studies have recognized that these changes must be accounted for and have estimated possible impacts of climate change on urban stormwater infrastructure design and performance in future climate conditions (Willems et al 2012, Mailhot and Duchesne 2010, Semadeni-Davies et al 2008, Arisz and Burrell 2006, Cook et al 2017.…”

Infrastructure Resilience to Climate Change

“…Moreover, although most articles are expected to be heavily technical by nature-for example, Bristow and Hay (2017), Pozzi et al (2017), and Xie et al 2017-we are also pleased to offer more qualitative contributions that discuss how formal protocols and institutional change can drive society to become more resilient, such as Zimmerman et al (2017), Douglas et al (2017), and Uda and Kennedy (2018). Finally, the most frequent hazard studied, with five contributions out of fourteen, is flooding, as it has plagued cities and regions across the United States and the world, whether from precipitation (Cook et al 2017;Pregnolato et al 2017;Wisetjindawat et al 2017) or sea-level rise (Sadler et al 2017).…”