The effect of modeling choices on updating intensity-duration-frequency curves and stormwater infrastructure designs for climate change

Abstract

Intensity-duration-frequency (IDF) curves, commonly used in stormwater infrastructure design to represent characteristics of extreme rainfall, are gradually being updated to reflect expected changes in rainfall under climate change. The modeling choices used for updating lead to large uncertainties; however, it is unclear how much these uncertainties affect the design and cost of stormwater systems. This study investigates how the choice of spatial resolution of the regional climate model (RCM) ensemble and the spatial adjustment technique affect climatecorrected IDF curves and resulting stormwater infrastructure designs in 34 US cities for the period 2020 to 2099. In most cities, IDF values are significantly different between three spatial adjustment techniques and two RCM spatial resolutions. These differences have the potential to alter the size of stormwater systems designed using these choices and affect the results of climate impact modeling more broadly. The largest change in the engineering decision results when the design storm is selected from the upper bounds of the uncertainty distribution of the IDF curve, which changes the stormwater pipe design size by five increments in some cases, nearly doubling the cost. State and local agencies can help reduce some of this variability by setting guidelines, such as avoiding the use of the upper bound of the future uncertainty range as a design storm and instead accounting for uncertainty by tracking infrastructure performance over time and preparing for adaptation using a resilience plan.

Uncertainties in Future U.S. Extreme Precipitation From Downscaled Climate Projections

“…Many stakeholders incorporate future climate conditions into their planning and analyses by using downscaled global climate model (GCM) output to inform hydrologic models or update current engineering design standards (Forsee & Ahmad, ; Kuo et al, ). Although the downscaling process is necessary to match the spatial and temporal resolution to the required resolution by the specific application (Cook et al, ), different downscaling methods and resolutions can potentially give different results (Arnbjerg‐Nielsen et al, ; Cook et al, ; Onof & Arnbjerg‐Nielsen, ; Sunyer et al, ; Wu et al, ). For the Contiguous United States (CONUS), there are several downscaled climate projection data sets covering at least the late 20th century and the 21st century (Abatzoglou & Brown, ; Mearns et al, ; Maraun et al, ; Pierce et al, ) (see Table and Figure S2 and Tables S1 to S3 in the supporting information).…”

Next-Generation Intensity-Duration-Frequency Curves for Climate-Resilient Infrastructure Design: Advances and Opportunities

“…(C) Developing nonstationary PREC-IDF and NG-IDF curves following the top-down approach. (Milly et al, 2008;Mailhot and Duchesne, 2010;Arnbjerg-Nielsen et al, 2013;Chester et al, 2020;Cook et al, 2020).…”

Past and Present Design Practices and Uncertainty in Climate Projections are Challenges for Designing Infrastructure to Future Conditions

“…These choices are often made by climate modelers, by determining which scenarios and models to focus model output. In addition, engineers, researchers, and other stakeholders interpreting climate projections for design process inputs also make these choices, which implicitly project risk preferences and can affect the resulting size and cost of resilient infrastructure (Cook et al 2020). As a result, traditional risk-based methods may currently be more useful than nonstationary approaches (Serinaldi and Kilsby 2015).…”