Storm Sewer Infrastructure Planning with Climate Change Risk: The City of Alexandria Virginia Case Study

The City of Alexandria, Virginia, has experienced repeated and increasingly frequent flooding events attributable to old infrastructure, inconsistent design criteria, and perhaps climate change. The purpose of this project is to provide a program that, over a period of up to 5 years, will analyze storm sewer capacity issues, identify problem areas, develop and prioritize solutions, and provide support for public outreach and education. The purpose of the first task was to review and propose revisions to the City's stormwater design criteria, including benchmarking of design criteria from neighboring jurisdictions, updated precipitation frequency results, evaluation of climate change risk. This paper summarizes potential changes in intensity, duration, and frequency (IDF) values, as well as sea level rise values, that were determined based on the results of general climate models paired with a range (low to high) in greenhouse gas emission scenarios. In addition, modeling of stormwater capacity under current design storm and projected storm intensity for the year 2100 are presented.