This post is an excerpt from the forthcoming 2nd Edition of the Bentley Press publication Stormwater Conveyance Modeling and Design
Two tools that are available to assess the impact of climate change on stormwater infrastructure are described here. IDF CC is a web-based tool for generating future IDF curves throughout Canada. SWMM-CAT is a downloadable tool used to adjust hydrologic parameters used in stormwater models in the United States.
IDF CC Hosted at www.idf-cc-uwo.ca
IDF-CC Tool is a web-based computer tool for generating Intensity-Duration-Frequency (IDF) curves and assessing the impact of climate change on the precipitation design storms. It is available for free and is hosted by the University of Western Ontario. IDF-CC Tool can be applied all across Canada. It has three components:
A library of precipitation data from over 700 Environment Canada rain stations with an option to add user supplied data for existing or additional stations. Stations can be selected via a GIS style interface. After selecting a rain station of interest, users can view information on that rain station, including the length of the data record.
A utility to calculate IDF curves for durations of 5 minutes to 24 hours and return intervals ranging from 2 to 100 years. The Gumbel distribution and the method of moments are used to estimate IDF parameters. Output is produced as data tables, plots and interpolation equations.
A tool to calculate future IDF curves utilizing user selected list of 22 Global Climate Models (GCMs) and Representative Concentration Pathways (RCPs) scenarios.
The site requires a registration to obtain an account. Results can be generated for an future time period up to the year 2100 based on 22 GCMs that simulate various climate conditions to local rainfall data and three future climate scenarios ranging from low to high severity. The IDF CC tool adopts an equidistant quantile-matching (EQM) method for updating IDF curves, developed by Srivastav et al. (2014), which can capture the distribution of changes between the projected time period and the baseline period (temporal downscaling) in addition to spatial downscaling the annual maximum precipitation derived from the GCM data and the observed sub-daily data.
To create IDF curves for future climate change conditions, users can select a 20-year projection period for any time between 2006 to 2100 using single or multiple GCM or GCM ensemble options. After selecting these options, the tool will automatically downscale GCM results and apply GCM results to the local rain station data, providing future IDF curves in table or graphical format; allowing the user to compare the impacts of multiple RCP scenarios and rainfall return periods, and to compare historical IDF curves to these updated curves.
In the example below, the total precipitation for the 2-year event as determined from the historical data is compared to the projected precipitation as determined from scenarios RCPs 2.6, 4.5 and 8.5 for durations of 5 minutes to 24 hours.
US EPA Stormwater Management Model Climate Adjustment Tool (SWMM-CAT)
Download at: www.epa.gov/water-research/storm-water-management-model-swmm
SWMM-CAT is a software tool that allows future climate change projections to be incorporated into the EPA Storm Water Management Model (SWMM). SWMM is a dynamic rainfall-runoff-routing simulation model used for single event or long-term (continuous) simulation of stormwater runoff quantity and quality from primarily urban areas. The tool can be used with commercial software packages that are based on SWMM.
SWMM-CAT provides the linkage between the EPA’s Climate Resilience Evaluation and Awareness Tool (CREAT) downscaled climate change estimates and localized monthly adjustment factors to the hydrologic parameters used by SWMM. On a monthly basis
Precipitation,
Evaporation, and
air temperature
may be adjusted according to one of three user selected climate change outcomes. SWMM-CAT automatically updates the SWMM input file.
CREAT uses statistically downscaled General Circulation Model projections from the World Climate Research Programme (WCRP) Coupled Model Intercomparison Project Phase 3 (CMIP3) archive (Meehl et al., 2007) as the source of its climate change data. SWMM-CAT provides a set of location-specific adjustments that were derived from global climate change models run as part of the World Climate Research Programme (WCRP) Coupled Model Intercomparison Project Phase 3 (CMIP3) archive. These are the same climate change simulations that helped inform the United Nations Intergovernmental Panel on Climate Change in preparing its Fourth Assessment report (IPCC, 2007).
In the figure below adjustment factors for precipitation depths (expressed as percent increase) are presented for return periods of 5 to 100 years for Wilkes-Barre, Pennsylvania.